630.7 I£6b no. 773 cop. 8 UNIVERSITY OF f ILLINOIS LIBRARY AT URBANA-CHAMPAIGN AGRICULTURE The person charging this material is re- sponsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutllotlon, and underlining of bocks or. rea.oni lor disciplinary action and may result In dismissal from the University. To renew call Telephone Center, 333-8400 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN Betisrri The "" ,T-.rv 3'.: Libfr,fy Ms i Foa lor s^cti Last Bex rials! is $50.00 L161— O-1096 Identification and Management in Illinois Marcos Kogan Donald E. Kuhlman Bulletin 773 Agricultural Experiment Station College of Agriculture University of Illinois at Urbana-Champaign February, 1982 Urbana, Illinois Publications in the bulletin series report the results of investigations made or sponsored by the Experiment Station. The Illinois Agricultural Experiment Station provides equal opportunities in programs and employment. Cover photo by Michael Jeffords. Bean leaf beetle. Tf*C3**/-t4-C!« Identification and .SCCtS* Management in Illinois Marcos Kogan Donald E. Kuhlman Bulletin 773 Agricultural Experiment Station College of Agriculture University of Illinois at Urbana-Champaign Acknowledgments The research upon which these guidelines are based was supported by the Illinois Natural History Survey, the niinois Agricultural Experiment Station, College of Agriculture, University of Illinois, and by several grants. The grants were from the National Science Foundation and the U.S. Environmental Protection Agency (through the University of California, Berkeley, NSF-GB-34918), from the U.S. Environmental Protection Agency (through Texas A & M University, CR-806277-02-0), and from the State Agricultural Experiment Stations, Regional Project S-74 (IL. 12-0320 Arthropod Pests of Soybeans). This bulletin was supported in part by a grant from the Illinois Soybean Program Operating Board. We are grateful to the Board for its support and to the soybean producers of Illinois whom the Board represents. Many people have provided technical support. We wish to acknowledge the assistance of Charles Helm, Assistant Scientist; Michael Jeffords, Field Entomologist; and Jenny Kogan, Research Librarian, Soybean Insect Research Information Center. Sandra McGary typed the manuscript. John Sherrod made the original drawings, and Marisa Rubenking Meador designed the publication and directed the graphics. Photographs other than those supplied by the authors are credited to Michael Jeffords, Sue Post, and James Steinberg, University of Illinois; Merle Sheppard, Clemson University; and Larry Pedigo, Iowa State University. The authors wish to express a special word of appreciation to William H. Luckmann, Head, Section of Economic Entomology, Illinois Natural History Survey, the Office of Agricultural Entomology, College of Agri- culture. Dr. Luckmann was the coauthor of an earlier version of these guidelines. His encouragement led to this publication, which is an expansion of the original work. Contents Introduction 1 Soybean Growth 4 Injury to Soybean 6 Identification and Biology of Insects 15 Coleopterous Pests 22 Bean Leaf Beetle, Blister Beetles, Clover Root Curculio, Dectes Stem Borer, Grape Colaspis, Japanese Beetle, Mexican Bean Beetle, Rootworm Beetles, Soybean Leafminer, White Grubs, Wireworms Hemipterous Pests 29 Green Stink Bug, Tarnished Plant Bug Lepidopterous Pests 31 Alfalfa Caterpillar, Black Cutworm, Corn Earworm, European Corn Borer, Fall Armyworm, Green Cloverworm, Painted Lady Caterpillar, Webworms, Yellowstriped Armyworm, Yellow Woollybear Orthopterous Pests 36 Grasshoppers Other Pests 37 Potato Leafhopper, Seedcorn Maggot, Soybean Nodule Fly, Soybean Thrips, Whiteflies, Spider Mites Biological Control Agents 41 Crop Growth and Pest Occurrence 44 Pest Management Program 46 Implementing the Pest Management Program 56 Implementation in Steps 57 Illinois Soybean Cropping System 58 Abstract Key words: Control decisions, cropping system, economic thresholds, host plant resistance, illustrated keys, insect pests, life cycle, natural enemies, pest management, plant injury, sampling methods, soybean A program for managing soybean insect pests is presented. This program requires identification of pests and their natural enemies and methods for measuring pest populations and injury. Illustrated keys aid in identifying symptoms of plant injury and the associated pests. Descriptions of the pests and their life cycles follow the keys. Life cycles of the main pests are presented in relation to the growth cycle of the crop. Sampling procedures for the main pests are described. The program is based on estimates of economic damage thresholds at various stages of plant growth. Decision charts outline appropriate management practices in relation to thresholds. Steps for implementing the program and integrating it into a total cropping system are summarized. Marcos Kogan is Entomologist, Illinois Natural History Survey, and Professor of Agricultural Entomology, College of Agriculture, University of Illinois at Urbana-Champaign. Donald E. Kuhlman is Associate Professor of Agricultural Entomology and Extension Entomologist, College of Agriculture, University of Illinois at Urbana-Champaign, and the Illinois Natural History Survey. Introduction Soybean production in Illinois has climbed steadily from 1.4 million bushels in 1924 to almost 369 million bushels in 1979. This increase resulted from a threefold improvement in yields and an 85-fold expansion in the acreage planted. Today, soybean is a mainstay of Illinois's economy, accounting for a third of the total cash farm income. With roughly 40 percent of the farmland planted to soybean, the crop may be found over much of the state's 56,400 square miles (Fig. 1). A relatively long state (382 miles), Illinois covers a wide range of latitudes with noticeable differences in climate, soil type, topography, and natural plant cover. Soybean growing conditions vary accordingly from one part of the state to the next. Fig. 1. Soybean production in Illinois. One dot equals 200,000 bushels. The nature and severity of soybean insect problems also vary from region to region. As a whole, however, these problems are less severe than in other growing regions of the world. During a normal year in Illinois the soybean acreage treated against insects is only 0.5 to 1 percent of the total soybean acreage. On occasion, however, localized outbreaks of certain pests have led to wide- spread spraying with insecti- cides. For sound ecological and eco- nomic reasons, insecticide use on soybean should be restricted to situations where treatment is absolutely necessary. Modem pesticides are a powerful weapon at the disposal of soybean growers, but maximum benefit is derived only from judicious use. Misuse may result in many undesirable side effects. How can we best estimate if and when to spray a soybean field? The most reasonable course to follow is to adopt management practices derived from a knowl- edge of soybean pests and their effect on the crop. These practices form the basis of an integrated pest management program for controlling pests in Illinois. Integrated pest management (IPM) is the selection of practices that will assure favorable economic, environ- mental, and social conse- quences through the use of appropriate cultural, biologi- cal, and chemical control measures. We have organized these guide- lines to help growers, Extension advisers, pesticide dealers and applicators, pest management consultants, and farm managers in developing effective pest manage- ment practices. Such practices should result in economic benefits to farmers without upsetting the ecological balance that seems to exist in Illinois soybean fields. The guidelines are divided into eight major sections: • Description of soybean growth stages. • Symptoms of plant injury and the related insect pests. Three keys appear in this section as an aid to identification. • Identification of insect pests and information about their biology. Four keys, drawings, and many color photographs are presented in this section. • Discussion of parasites, preda- tors, and diseases that provide natural control of soybean insect pests. • Maps and a chart indicating areas at risk for outbreaks of major pests. • Components of the pest manage- ment program, including scouting methods, forecasting, control tactics, and decision charts for selecting appropriate control actions. • Personnel who help implement the pest management program. • Eleven steps for implemention and a planning calendar. These guidelines should be used in conjunction with other infor- mation provided by the Illinois Cooperative Extension Service. In particular, insecticide use should be based on recommendations in Circular 899, "Insect Pest Manage- ment Guide: Field and Forage Crops," which is revised annually by Extension entomologists. Insect Injury and Plant Development Many harmful as well as beneficial species of insects and mites inhabit soybean fields. Some species that are adapted to feed on particular parts of the soybean plant may cause considerable damage (Fig. 2). Other species prey on the plant eaters and are there- fore beneficial because they help keep pest populations under control. The nature of the damage caused by plant-eating species depends on the part attacked and when attack occurs during the plant's growth cycle. Insects can injure soybean by defoliating the plant, sucking sap from leaves and stems, debranching or breaking entire plants as a result of stem feeding, destroying blossoms, boring or piercing the pods, and destroying seeds. Other less evident types of injury result from feeding on roots and nodules; piercing and sucking green seeds, thereby causing seed malformation and consequent reduction of quality; transmitting disease organisms; and injecting toxins. Fortunately, not all pest species appear in a field at the same time. By studying the dynamics of their life cycle, you will see that each species appears only during par- ticular phases of crop develop- ment (Fig. 3). The sections that follow describe the developmental stages of the crop, how it grows in Illinois, and the types of injury affecting different parts of the plant at each stage of its growth. First, however, we must introduce some concepts related to the economics of pest management. Bean leaf beetle Fall armyworm Green cloverworm Leafhoppers Mexican bean beetle Spider Mites Yellow woollybear Bean leaf beetle Grasshoppers Brown stink bug Green stink bug Black cutworm Bean leaf beetle (larvae) Bean nodule fly Fig. 2. Insect pests that are adapted to feed on particular parts of the soybean plant. Economics of Pest Management An insect or mite species becomes a pest when the amount of crop loss it causes equals or exceeds the cost of preventing the loss. This relationship between the amount of damage prevented and the cost of prevention is an expression of the economic injury level. Economic injury level is the level at which a pest population is capable of causing enough injury to justify the cost of applying an insecticide to prevent the injury. In practice, however, the rate of population increase should be estimated before the pest reaches the economic injury level to allow time for applying the insecti- cide. The turning point is usually defined for soybean defoliators as the economic damage threshold. Economic damage threshold is the combination of certain damage and population levels at which chemical controls should be applied to prevent the pest population from reach- ing the economic injury level. Economic injury levels and damage thresholds depend on the stage of plant development and whether the pests are defoliators or pod feeders. Thresholds have been established for only a few soybean pest species. The known thresholds will be presented in some detail in the section on "Injury to Soybean." V5 Bean leaf beetle Blister beetles Green cloverworm Mexican bean beetle Spider mites V8-R2 V10-R5 R8 Bean leaf beetle Bean leaf beetle Bean leaf beetle D/abrotica spp. Corn earworm Grasshoppers Grasshoppers Grasshoppers Green cloverworm Stink bugs Mexican bean beetle Yellow woollybear Spider mites Tarnished plant bug Thrips Yellow woollybear Fig. 3. At each growth stage the crop is attacked by a different complex of insect pests. Stages of growth: VE-V3 = seedling; V5 = early vege- tative growth; R2 = full bloom; R5 = beginning seed; R8 = full maturity. VE-V3 Bean leaf beetle Cutworms Leafhoppers Mexican bean beetle Seedcorn maggot Soybean thrips Soybean Growth A plant's susceptibility to injury varies from the prebloom through the bloom, pod-set, and pod-fill stages. A numbering system has been devised to identify these different stages of plant growth. The system is described here and will be referred to farther on in these guidelines. We have also included a description of other plant and crop characteristics that have a direct bearing on pest control in soybean. Growth Stages Nodes are the points at which leaf petioles or branches are attached to the main stem (Fig. 4). The number of nodes is used to describe the vegetative stages, which are designated by the letter V. The reproductive stages — bloom, pod set, and pod fill — are designated by the letter R. Emerging seedlings are at stage VE, and seedlings with open cotyledons are at stage VC. After the VC stage, the appearance of one unifoliolate node signals stage VI, followed by a second node with an open trifoliolate leaf at stage V2, a third node at V3, and so on. The reproductive stages go from Rl to R8, that is, from early flower- ing through pod maturity (Table 1). In Figure 3 a series of growth stages is identified according to the V-R system. (For a detailed descrip- tion of the system, see Iowa Co- operative Extension Service Special Report No. 80, 1977.) Table 1. Growth Stages of Soybean Stages Stage name Description Vegetative VE Emergence Cotyledons above the soil surface VC Cotyledon Unifoliolate leaves unrolled enough so that leaf edges are not touching V1 First-node Fully developed leaves at unifoliolate nodes V2 Second-node Fully developed trifoliolate leaf at node above unifoliolate nodes V3 Third-node Three nodes on main stem with fully developed leaves beginning with unifoliolate nodes V(n) nth-node n number of nodes on main stem with fully developed leaves be- ginning with unifoliolate nodes; n can be any number, beginning with 1 for first-node stage (V1) Reproductive" R1 Beginning bloom One open flower at any node on main stem R2 Full bloom Open flower at one of two uppermost nodes on main stem with fully developed leaf R3 Beginning pod Pod 5 mm long at one of four uppermost nodes on main stem with fully developed leaf R4 Full pod Pod 2 cm long at one of four uppermost nodes on main stem with fully developed leaf R5 Beginning seed Seed 3 mm long in pod at one of four uppermost nodes on main stem with fully developed leaf R6 Full seed Pod containing a green seed that fills pod cavity at one of four uppermost nodes on main stem with fully developed leaf R7 Beginning maturity One normal pod with mature pod color on main stem R8 Full maturity Ninety-five percent of pods with mature pod color; five to ten days of drying weather usually required after R8 before soybeans dry to less than 15 percent moisture " The designation for a plant at a reproductive stage should include both the V and the R stages. For example, at full bloom a plant with 11 fully developed trifoliolates above the unifoliolate nodes would be at stage V12R2 because the unifoliolate nodes are counted as one. Adapted from: low a Cooperative Extension Service Special Report No 80, 1977. Stand Establishment Effective pest management starts with seed of superior quality. Healthy seed planted at the appro- priate depth in a well prepared seedbed according to agronomic recommendations is the best guar- antee for a good stand. Anything that delays germination, such as prolonged, cool soil temperature after sowing, increases the chance Growing point that insects and diseases will attack the germinating seeds or seedlings and thereby reduce the stand. Rapidly emerging plants are less susceptible to attack from diseases and soil-dwelling insects. Of course, growers cannot control soil moisture and temperature, but the factors they can control should be carefully managed to minimize pest problems. Trifoliolate leaf Axillary buds Unifoliolate leaf Fig. 4. Soybean seedling. Crop Phenology in Illinois Phenology is the relationship between events in the crop's cycle and seasonal, climatic factors. To ensure rapid germination and emer- gence, planting is customarily done after the risk of frost is past and when soil temperature and moisture are adequate. For single- cropped soybean in Illinois, planting usually starts after May 10 and may extend to the end of June. On the average, though, about half of the crop is in the ground by May 25 (Fig. 5). Between July 10 and 20 half of the crop is in full bloom (stage R2), and pods begin to appear. By the end of the month half of the state acreage is in the pod-setting stages (R3 and R4). Harvesting may start as early as the first week of September. Normally it is at the halfway mark by September 30 and completed by the end of October (Fig. 5). In double cropping, soybean is planted sometime after June 20 as soon as small grains are harvested. Consequently, all stages of growth are somewhat delayed. Double cropping has special pest prob- lems, but we are just beginning to understand its effect on pests. Fig. 5. Crop phenology in Illinois. Injury to Soybean If you visit a soybean field every week to ten days, you'll see that different types of pests appear as the plants change from one growth stage to the next. Figure 3 lists the pests likely to be present at various times in the crop cycle. Each pest may injure one or more parts of the plant, but seldom the entire plant. Figure 2 lists some pests and the plant parts preferentially attacked. Injury to Germinating Seeds and Seedlings Bean leaf beetle adults Cutworms Mexican bean beetle Potato leafhopper Seedcorn maggot Soybean thrips Nature of injury Early season pests attack germi- nating seeds in the soil or seedlings immediately after emergence. In either case, the result is a reduced stand. Seedcorn maggots feed on cotyledons and embryos while they are still below ground. Potato leafhoppers, soybean thrips, and adults of bean leaf beetles and Mexican bean beetles are often found on seedlings shortly after emergence. Potato leafhoppers have piercing mouthparts with which they suck the sap. Although populations may be abundant, they seldom cause economic damage to most of the common commercial varieties. Soybean thrips have rasping mouthparts. As a result of their feeding, the leaflets take on a silvery appearance, injured tissue turns yellow, and the leaflets finally die. Bean leaf beetles, Mexican bean beetles, and cutworms have chew- ing mouthparts that can injure cotyledons, leaves, and stems. Bean leaf beetles cut small round holes in leaves (Fig. 6) or may sever the hypocotyl arch, thereby kill- ing the plant. Mexican bean beetles produce lacelike damage to the leaves. Some cutworms gnaw the seedling off just above the surface of the soil (Fig. 7). Although they may not eat much of the plant, they do eat enough to make it fall over. & J 3N4?-^, ^7t* Fig. 6. Injury to seedlings by bean leaf beetles. J^'": ^--v-:,, Tj/./^yS^w, . -•• . .VT.V.,-: >>_•*;; -x~ •;.';:, 7*. -i«» >•' ^ • / *U' "' iS:,^^ffl ; * ' ' "'Ay- : -;:' '•'•''• ' >W. -.'twp-^1.- - VK? "y>x, •! - ^'^-r ; ;..;" ^^,^A;. • :;(rr^*r'>^ v ^•i^^BMHBlBVHBBMI Fig. 7. Seedlings destroyed by black cutworms. Economic damage thresholds Except for the bean leaf beetle, no thresholds have been estab- lished for insects that feed on germinating seeds and seedlings. The main effect of this group of insects is reduction of the stand. To produce good plant stands, growers should maintain the optimal stands that are currently recommended: Row width, inches 40 30 20 10 Plants per foot of row 10 to 12 6 to 8 4 to 6 3 to 4 Reduction of plant density may result in some yield loss (Table 2). But insecticide treatments are justified only if the stand is reduced to less than two-thirds of the rates indicated above, or if irregular open spaces begin to show in the stand. If a field has a good stand despite severe initial attack, plants will recover under normal growing conditions with no observable effect on yield (Table 3). The capacity of plants to recover from damage inflicted this early in development is remarkable. In most cases, plants can tolerate severe injury at the seedling stage if other growing conditions, particularly moisture and tem- perature, are adequate. Injury to Roots and Nodules Bean leaf beetle larvae Clover root curculio larvae Grape colaspis larvae Rive Ilia bean fly White grubs Wireworms Nature of injury This group includes pests that inhabit the soil and feed on sub- terranean plant parts during germination. Later as the plants grow, these pests destroy roots and the nitrogen-fixing bacterial nodules (Fig. 8). The effect of insect feeding on soybean roots and nodules is not well known. White grubs can be very damaging in certain areas of the state. According to the findings from experiments using garden beans, the feeding of bean leaf beetle larvae on roots and nodules can affect yields. Root feeding may also lead to premature lodging. Economic damage thresholds No thresholds have been estab- lished for pests that feed on roots and nodules. Under normal growing conditions in Illinois, plants usually compensate for moderate levels of root injury or reduction in plant stand. The failure of seedlings to emerge or yellowing after emergence may indicate damage by underground pests. Some replanting may occasionally be necessary. Fig. 8. Injury to nodules by bean leaf beetle larvae. Table 2. Ability of Soybean to Compensate for Reduction of Plant Density, Urbana, Illinois Stand within Percent of Yield, rows 20 feet long original stand bu/A Six plants per foot of row 100 50 Three 40-inch gaps 50 41 Five 24-inch gaps 50 44 Three plants per foot of row 50 50 Four plants per foot of row 66 51 Five plants per foot of row 80 50 Adapted from: Illinois Agronomy Handbook 1979-80. Circular 1165. University of Illinois, College of Agriculture. TableS. Yield Reduction After Injury to Soybean Cotyledons and Leaves Early in Season Type of injury Yield reduction, percent 1 cotyledon removed after seedling emergence 2 cotyledons removed after seedling emergence 2 cotyledons removed with first unifoliolate expanded 2 unifoliolates removed after expansion 2 unifoliolates and 2 cotyledons removed after unifoliolate expansion Seedling cut below unifoliolates after expansion 0 1.0 0 2.8 7.3 16.1 Adapted from: Crop Science 6:25-27, 1966. Injury to Foliage Frequently damaging Bean leaf beetle Green cloverworm Grasshoppers Twospotted spider mite Occasionally damaging Blister beetles Japanese beetle Yellow woollybear Rarely damaging Alfalfa caterpillar Clover root curculio Corn earworm Legume leafminer Mexican bean beetle Painted lady Potato leafhopper Soybean thrips Webworms Whiteflies Fig. 10. Foliage injury by green clover- worm. • Nature of injury Most of the foliage-feeding species listed here have chewing mouthparts that can cause con- siderable injury (Fig. 9). A single green cloverworm, for example, can cut about 18.6 square inches of leaf area during its larval period. The method of feeding and the feeding patterns found on a plant are characteristic of each species. Thus the green cloverworm makes indentations along the margins or cuts large holes in the leaf blade. The bean leaf beetle cuts small holes. The Mexican bean beetle crushes the leaf tissues, which dry out and form a lacy net- work resembling windrows (Fig. 10, 11, 12). Wind and hail magnify the damage from chewing insects by causing the leaf blades to tear between the larger veins. Thrips, leafhoppers, and mites have either rasping or sucking mouthparts. They do not remove pieces of leaves, but the feeding areas become chlorotic (yellow- ish), dry out, and turn brown (Fig. 13). Intense sucking of mites or thrips in particular may cause leaves to become dry and fall off. Regardless of the species, the end results of these different types of foliage feeding are very similar. The total leaf area capable of photosynthesizing is reduced, and consequently the plant lacks enough photosynthate for growth and seed production. If insect populations are very large, plants may be completely stripped of leaves. Fig. 11. Foliage injury by bean leaf beetle. | Fig. 12. Foliage injury by Mexican bean beetle larva. Fig. 9. Woollybear larva feeding on soybean leaf. 8 Economic damage thresholds Soybean can tolerate consider- able defoliation without yield reduction. Tolerance varies with the stage of plant growth, overall plant vigor, and the adequacy of growing conditions such as moisture, temperature, and soil fertility. The relationship between defoliation at four growth stages and the probable yield reduction is shown graphically in Figure 14. The four stages are: vegetative growth (VO to beginning of Rl), blossom development (Rl to R2), Fig. 13. Typical foliage injury by spider mites. pod development (R3 to R5), and seed maturation (R6 to R8). While the plants are still grow- ing and producing new leaves, and again after the seeds are completely filled, soybean can tolerate considerable defoliation without yield loss. But during the early part of the reproductive stage, the plants become increas- ingly sensitive to defoliation. They are most sensitive during the period of pod development. Even at this stage (R4 to R6), however, soybean plants can normally lose 20 percent of their leaf area before any effect on yield occurs. Correct estimates of defoliation and the pest population respon- sible are essential to establishing the economic damage thresholds for foliage-feeding insects. Methods for estimating defoliation and measuring pest populations are discussed in the section on the pest management program. The thresholds currently available for soybean defoliators are summarized in Table 4. CD £ c: 0) Q s. Adults feed on soybean foliage JAN FEB MAR APR MAY JUN JUL AUG Planting Emergenc • Larvae overwinter in cells in the soil SEP OCT NOV DEC Fig. 24. Annual cycle of the grape colaspis in Illinois. 24 Seasonal life history. The grape colaspis overwinters as larvae in cells in the soil. In spring as the temperature rises, they move upward to feed on small roots and the lower parts of the main stem. There is one generation per year. A summary of the annual cycle is shown in Figure 24. Grape colaspis adult. 5X. Japanese beetle Popillia japonica Description and habits. The beetle is Vs to ¥2 inch long. It is a shiny metallic green or greenish- bronze with reddish wing covers and two white spots at the tip of the abdomen. A row of smaller white spots is located along each side of the abdomen. The larvae or grubs are white, but may appear gray from ingested soil. They have a row of V-shaped spines on the underside of the tip of the abdomen; the bottom of the V points toward the head. The spines can be seen easily with a hand lens. Seasonal life history. Having a one-year life cycle, Japanese beetles spend about 10 months as grubs in the soil. They overwinter as partly grown grubs and com- plete their growth during June, when they transform into pupae. The first adults emerge during late June. They are present during July and August, and a few can still be found in early September. In rural areas they are present mainly on the foliage of smart- weed, soybean, wild grapes, and corn silks. In urban areas the beetles feed on foliage and on the fruits of many trees, shrubs, and flowering plants. From late June until early September, the beetles deposit eggs 2 to 6 inches deep in the soil. The newly hatched grubs feed first on decaying vegetable matter and later on the roots of grasses and other plants. When the soil cools in late October and early November, the grubs become inactive and do not feed until the following spring. They are seldom a problem in soybean fields, but the adults may cause severe defoliation in some Illinois counties. Japanese beetles. 2X. 25 Mexican bean beetle Epilachna varivestis Description and habits. Al- though found in garden beans throughout the state, Mexican bean beetles seldom attack soybean in Illinois. However, beetles of a soybean-feeding strain are a serious pest in parts of Indiana and some eastern states. Their occur- rence on soybean in Illinois should therefore be carefully monitored. Resembling lady beetles, the adults are yellow to copper-colored and are V* to Vs inch long. Each wing cover has eight black spots in three rows across the body. The fully grown larvae are a brighter yellow than the adults and are Va inch long. Each body segment has six branched spines. Larvae chew the leaves, deposit- ing lacelike windrows of crushed tissue from which the juices have been extracted. Adult beetles eat holes in the leaves and make superficial scars on the pods. They attack seedlings early in the season, and increased populations in July and August cause considerable defoliation. Mexican bean beetle eggs. 5X. Seasonal life history. Adult beetles hibernate in woodland areas, and come out of hibernation in the spring. Invasion of soybean fields occurs as soon as plants emerge. Females lay clusters of yellow, elongated eggs on the underside of leaves. Larvae emerge within 5 to 14 days, depending on the weather, and are fully grown in 3 to 5 weeks. They pupate attached to leaves, the adults emerging about 10 days after pupation. There are probably three generations per year in Illinois. Mexican bean beetle larva. 4X. Mexican bean beetle pupa. 4X Rootworm beetles Diabrotica spp. Description and habits. Adults of the northern com rootworm (D. longicornis) are green to yellow beetles about V* inch long. The small, white, globular eggs are found in the soil around cornstalks. The larvae, which damage the roots, are threadlike white worms about V2 inch long when fully grown. The pupae are short, white, and stout, and are found in an earthen cell. Adults of the southern corn rootworm (D. undecimpunctata howardi), also known as the spotted cucumber beetle, are about 3/s inch long, are yellow to green, and have eleven black spots on the wing covers. The eggs, larvae, and pupae resemble those of the northern corn rootworm. Southern corn rootworm beetle. 6X. Mexican bean beetle adult. 4X. 26 Adults of the western corn root- worm (D. virgifera) are pale yellow-green beetles about V4 inch long with black stripes on the wing covers. The eggs, larvae, and pupae are similar in appear- ance and habit to the northern species. The western adults are very active and will fly at the slightest disturbance. Conse- quently, they are more difficult to capture than either the northern or the southern corn rootworm adults. Primarily pests of corn, adults of the western species may be found feeding on soybean foliage and blossoms. Western corn rootworm beetle. 7X. Northern corn rootworm beetle. 6X. Soybean leafminer Odontota horni Description and habits. The adults are small beetles about ¥4 inch long and Vs inch wide. They are brick-red with a black head and a black line along the middle of the wing covers. The flat eggs are laid mainly on the underside of leaves. The larvae are a bright orange and are a little over ¥4 inch long when fully grown. They have three pairs of legs and a series of pointed expansions on both sides of each body segment. Pupation occurs in the mined space between the upper and lower epidermis of leaves. Adults feed on soybean foliage, leaving scars that resemble those from the feeding of Mexican bean beetles. After emerging from their eggs, the larvae penetrate the leaf tissue, where they form a rounded, irregular mine. The epidermis of mined areas dries out, and dry spots similar to those caused by some foliar diseases remain. The beetles, which may have two generations a year in Illinois, probably overwinter as adults. Soybean leafminer larva. 6X Soybean leafminer adult. 3.5X. 27 White grubs Phyllophaga spp. and Cyclocephala spp. Description and habits. White grubs, which are the larvae of June beetles and several species of chafers, have a C-shaped body, a brown head, and three pairs of legs. The body is white and soft; the tip of the abdomen is shiny and transparent. True white grubs (Phyllophaga) are distinguished from annual white grubs (Cyclo- cephala) by the patterns on the ventral surface of the last abdomi- nal segment (see keys in Figure 22). The adults of both genera are light tan to black beetles Vz to 3A inch long. They deposit pearl- white, spherical eggs singly in the soil. Larvae feed on roots, and extensive feeding may kill soybean plants or severely stunt them. True white grubs may have a life cycle of 2 to 4 years, but a three-year cycle is most common. Annual white grubs, as the name indicates, have a one-year life cycle. White grub. 2.5X. Beetle of white grub. 1.5X. 28 Wireworms Larvae of Limonius, Melanotus, Conoderus, and other genera of Elateridae or the click beetles Description and habits. Several species of wireworms, all quite similar in appearance, attack the roots of many crops. When young, the cream-colored worms are about V4 inch long and less than Vie inch in diameter. When mature, they are \lk to iVz inches long and about Vs inch in diam- eter. Adults are click beetles: when placed on their backs, they flip into the air with an audible Wireworm beetle. 2X. snap and then land on their feet. The eggs are tiny white globules laid in the soil. The larvae drill holes in the underground part of soybean stems and roots, and may also destroy seeds before germination. Wireworm larvae may live from 2 to 6 years in the soil, feeding on the roots of weeds, grasses, and crop plants. The pupal stage, which lasts perhaps 2 weeks, is spent in a cell in the soil. With such a long life cycle, one genera- tion may require 6 or 7 years for completion. Wireworm. 1.5X. Hemipterous Pests: Stink Bugs, Flower Bugs Green stink bug Acrosternum hilare Description and habits. Adults are large (about 5/8 inch long), light green bugs that are tri- angularly shaped. They have slender antennae with five seg- ments each. The female lays egg masses averaging 30 eggs. Barrel- shaped and closely packed to- gether, the eggs are initially pale green, turning yellow, pinkish, and finally bright pink as they approach hatching. Small, round, reddish-brown nymphs hatch in about 12 days, depending on weather conditions. The nymphs remain aggregated on or near the egg mass without feeding. They molt in 5 to 7 days, and the second instar nymphs begin to feed. Undergoing three additional molts, they grow and acquire a varied color pattern with black, green, and yellow or red areas. Fifth instar nymphs are about Viz inch long and have clearly defined wing pads. The entire nymphal period from egg hatch to adult emergence lasts about 45 days. The life cycle of the green stink bug is shown in Figure 25. Both adults and nymphs have sucking mouthparts and feed on plant juices. Older nymphs and adults prefer feeding on fruiting Newly emerged nymphs of the green stink bug. 3.5X. - Fig. 25. Life cycle of a typical stink bug. 29 structures. Much of the stink bug damage to soybean is due to feeding on seeds. Young seeds usually abort, and older ones may be discolored or malformed in varying degrees. If a bug punctures the embryo, the seed will not germinate. Stink bugs also trans- mit the organism that causes yeast spot disease. Seasonal life history. Green stink bugs seem to overwinter as adults in woods. Early summer adults feed on berries in trees, especially dogwoods. Invasion of soybean fields normally occurs after pods begin to set towards mid or late August. Usually there is one generation of green stink bugs on soybean; the bulk of the over- wintering population is probably from this generation. A diagram of the seasonal life history of the green stink bug in Illinois is shown in Figure 26. Other species of stink bug are similar in feeding habits and biology to the green stink bug. One of these species, the brown stink bug (Euschistus servus), should not be confused with the beneficial spined soldier bug (Podisus maculiventris) (Fig. 42). You can tell them apart rather easily: in Euschistus the beak is slender and embedded between the lateral parts of the head; in Podisus the base of the beak is stout and free from the lateral parts. Podisus has a dark round spot centered on the underside of the abdomen. In the southern and eastern states, the southern green stink bug (Nezara viridula) causes more damage to soybean than do other stink bugs. It is rarely found in Illinois, however. Fifth instar nymph of the green stink bug. 2.5X. Green stink bug adult. 2.5X. Green stink bug > Bugs feed on dogwood and fruit trees i Adults probably migrate northward from overwintering sites JANiFEB MARJAPR MAY JUN > Nymphs and adults feed on soybean pods • Egg masses and young nymphs are present on soybean foliage JUL • Stink bugs do not seem to survive winter in Illinois SEP OCT NOV DEC Fig. 26. Annual cycle of the green stink bug in Illinois. 30 Tarnished plant bug Lygus lineolaris Description and habits. Adults of the tarnished plant bug are about lk inch long and % inch wide. They are brown, mottled with white, yellow, and black. The nymphs, resembling adults in body contour, are green with five tiny black dots on the back. Having sucking mouthparts, the adults and nymphs feed on many species of cultivated and wild plants and are usually very abundant in alfalfa fields. When on soybean, they prefer the blossoms and very young seeds, but the extent of damage, if any, is not well known. Tarnished plant bugs over- winter as adults in the debris of legume fields, fencerows, wooded areas, and ditch banks. In early spring these bugs leave their hibernating quarters to begin feeding. The females deposit eggs in the stems, leaf midribs, and petioles of flowers of various herbaceous plants. Nymphs hatch, feed, and mature in 3 to 4 weeks. There are three to five generations each year. Tarnished plant bug. 4X. Lepidopterous Pests: Caterpillars of Moths and Butterflies Alfalfa caterpillar Colias eury theme Description and habits. The larvae of this yellow butterfly are primarily pests of alfalfa, but they are also commonly found feed- ing on soybean leaves. The fully grown larvae are iVz inches long. Each side of the dark gray-green body has a thin white stripe through which runs a very fine red line. They pupate on plants without spinning a cocoon and overwinter as pupae. Illinois probably has two or three generations per year. Butterfly of the alfalfa caterpillar. 1X. Black cutworm Agrotis ipsilon Description and habits. Fully grown larvae are ll/z inches long. Light gray to almost black, they can be distinguished from other cutworms by the isolated skin granules on the body. These granules are convex, shiny, and very large. The pupae are brown and spindle-shaped. The moths, which are nocturnal, are difficult to distinguish from several other species of cutworm moths. The females lay their ribbed, globular, white eggs in clusters of 10 to 30 near a supply of larval food. Cutworms remain hidden in the soil during the day, but may feed below the soil surface. Since their color blends with the soil, they can be easily overlooked. To find them, carefully examine the soil for about 3 inches on each side of a freshly cut plant and 3 inches below the soil surface. Small soybean seedling grown on fields that were covered with weeds early in the spring are sometimes cut by these worms at ground level. Black cutworms probably do not overwinter in significant numbers in Illinois, but rather migrate here from the South. Usually appearing in late March and early April, the moths seem to prefer laying their eggs in low, muddy spots in fields and overflow ground. Development from egg to adult requires more than 45 days. This cycle continues until frost, three or four generations being produced each year. Moth of the black cutworm. 2X. Black cutworm larva. 1X. 31 Corn earworm Heliothis zea Description and habits. Corn earworm larvae vary greatly in color, ranging from light green or pink to dark brown or nearly black. Full-grown larvae are about 1V2 inches long. They are marked with alternating light and dark stripes running the entire length of the body. These stripes are not always the same from one larva to the next, but usually a dark double line runs down the back. The adults are moths having a wing spread of about IVz inches. The front wings are light brown to tan, marked with dark irregular lines and a dark area near the tip of the wings. The females lay small, pearly white eggs singly on the host plants. Corn earworms do not over- winter in Illinois, but migrate northward as moths in May and June. In Illinois, the earworms prefer corn. In the southern states, however, they are considered one of the most serious pests of soybean, feeding on both foliage and pods. Moth of the corn earworm. 1.5X. European corn borer Ostrinia nubilalis Description and habits. Euro- pean corn borers are typically a pest of corn, but the larvae may occasionally bore soybean stems. The caterpillars are Vz to 1 inch long. The body is flesh-colored, with small round spots that are a pale brown. Pupation occurs inside bored stems. The adults are small moths. Females are yellowish brown with dark bands running in wavy lines across the wings; males are darker than females. We have no record of economic infestations of soybean in Illinois. European corn borer. 2X. Fall armyworm Spodoptera frugiperda Description and habits. Full- grown larvae are 1V2 inches long and vary from light tan to nearly black. They have three yellowish- white hairlines down the back from head to tail. On the sides and next to the yellow lines is a wider, dark stripe, and next to it an equally wide, somewhat wavy, yellow stripe splotched with red. These worms resemble the true armyworm and corn earworm, but can be distinguished from them by the prominent inverted Y on the front of the head. Fall armyworm moths are about 3/4 inch long and are a dark gray, mottled with light and dark splotches and with a noticeable white spot near the extreme tip of the front wings. The spherical gray eggs are laid in clusters of about 150, usually on leaves of host plants, and are covered with a coating of body scales and hairs. The fall armyworm spends the winter in the southern states. It flies into Dlinois every year, arriving from midsummer on. Populations may become very abundant by late August or early September. Although the larvae are primarily a pest of corn, occa- sionally they attack the foliage of soybean in Illinois. Fall armyworm. 1.2X. 32 Green cloverwonn Plathypena scabra Description and habits. Like all butterflies and moths, the green cloverworm goes through four distinct stages: egg, larva, pupa, and adult. There are usually six larval instars (Fig. 27). The worms are a light green with two thin white stripes along each side of the body. When fully grown, these slender worms are about 1 inch to lJ/2 inches long. They have only three pairs of prolegs on the abdomen, not counting the pair on the tip. Cloverworms move by arching their body. If disturbed, they wriggle violently from side to side. Green cloverworm. 2X. Moth of the green cloverworm. 2.5X. The small green eggs are laid on the underside of leaves. Young larvae are very difficult to see, but in heavy infestations if you look against a bright sky, you can see the tiny larvae hanging by fine threads from the underside of leaves. Young larvae scrape the leaf tissues so that the transparent skin of the leaves resembles irregular, shiny windows on the surface. Older larvae eat holes in the leaves, which then become ragged as the wind tears the edges around the holes. Active at dusk, the adults are dark brown moths with black spots and a wing span of about I1/* inches. Fig. 27. Life cycle of the green cloverworm. I I I I Green cloverworm Larvae: southern Illinois Larvae: northern Illinois i Adults migrate northward and oviposit on alfalfa > Adults survive winter in warmer southern regions > Larvae feed on soybean foliage i Adults oviposit on soybean JAN FEB MAR APR MAY JUN AUG SEP OCT NOV DEC • Larvae feed on alfalfa i Most adults die during winter in northern regions Fig. 28. Annual cycle of the green cloverworm in Illinois. 33 Seasonal life history. Green cloverworms are not likely to over- winter in central and northern Illinois. Instead, they probably fly northward from breeding sites in the South each spring. The adults then oviposit here on soybean and alfalfa. Two peaks of larval populations can be observed in southern Illinois during the second half of July and the middle of August. As a rule, generations overlap in central and northern Illinois. One major peak is usually detected early in August in the central part of the state and late in the month farther to the north. Figure 28 shows the annual cycle of the green cloverworm in Illinois. Painted lady caterpillar Cynthia cardui Description and habits. The painted lady is a nearly cosmo- politan butterfly, breeding in the southern regions of the United States, then migrating northward in the spring. The butterfly has beautifully mottled red, dark brown, and white wings about 1% inches in width. The larva, a mottled yellowish green and black with a lateral yellow stripe, is covered with yellowish spines. It lives singly in a nest of leaves woven together by silken threads and feeds mainly on thistles. But sometimes the migrating butterflies oviposit on young soybean plants, which are attacked by the hatched larvae. Occasional infestations have been observed in Iowa and Illinois. Painted lady larva. 1 .5X. Painted lady butterfly. 2X. 34 Webworms Loxostege spp. Description and habits. Garden and alfalfa webworms are about 1 inch long and are green to yellow- green with three black spots on the side of each body segment. One to three bristlelike hairs pro- ject from these spots. The moths have a wingspread of 3A inch and are buff colored with irregular markings of light and dark gray. They lay their eggs in masses on plants. Webworms overwinter in the soil as pupae. Early in the spring the moths emerge and lay their eggs on host plants. Protected by a fine web, the larvae feed on the underside of leaves. After becom- ing full grown in about 4 weeks, the webworms then pupate in the soil. One generation requires about 6 weeks, and there are usually three to five generations each year. Webworm, adult 2.5X and larva 2X. Yellowstriped armyworm Spodoptera ornithogalli Description and habits. Yellow- striped armyworm larvae are velvety brown or black with a bright yellow stripe along each side of the body. When fully grown, the larvae are 3/4 inch to \l/i inches long. They feed on the foliage of many plants, including soy- bean. The adults, which are gray moths with distinct markings on the wings, lay their eggs on stems or leaves. They do not seem to overwinter in Illinois, but migrate northward from breeding sites in the South. Yellowstriped armyworm. 1X. Yellow woollybear Diacrisia virginica Description and habits. The adult woollybear, a white-winged moth with a wing span of IVi to 2 inches, lays clusters of round white eggs on leaves. The ex- tremely hairy larvae are white when young, but turn dark brown or reddish as they grow older. Although all instars feed vora- ciously on soybean leaves, the larvae are found on many other cultivated and wild plants as well. Woollybears overwinter as pupae inside silken cocoons heavily covered with interwoven hairs from the body of the caterpillar. Usually there are two genera- tions a year in Illinois. Heavy infestation commonly occurs late in the season, but quite often the dense populations are decimated by a disease caused by a fungus of the genus Entomophthora. Yellow woollybear larva. 1.2X. 35 Orthopterous Pests: Grasshoppers Grasshoppers Melanoplus femurrubrum and M. differentialis Description and habits. Several species of grasshopper invade soybean fields in Illinois. The most common are the redlegged grass- hopper and the differential grass- hopper. Young nymphs look like adults, but are much smaller and wingless. In 40 to 60 days they become adults. Strong fliers, the adults have stiff outer wings that cover clear, membranous flying wings, which fold like a fan under the outer pair. Both adults and nymphs feed vora- ciously on the foliage of soybean and other plants, and also on green soybean pods. Seasonal life history. Eggs are laid in the soil in batches of 20 to 30 early in the fall. Until the first frost, each female may lay up to 20 batches. The eggs do not hatch until the following spring. Nymphs feed mainly on plants in ditch banks and fencerows and then invade the border rows of soybean fields as the noncrop food plants are mowed or dry out. Grasshoppers usually invade soy- bean fields in the second half of the growing season. The life cycle and the annual cycle are shown in Figures 29 and 30. Differential grasshopper. 1.3X. Fig. 29. Life cycle of a grasshopper. Grasshoppers Adults and Nymphs Adults and nymphs move into soybean fields • Nymphs feed on plants in fencerows and ditch banks JUN JUL AUG SEP Planting Emergen Fig. 30. Annual cycle of grasshoppers in Illinois. 36 Other Pests Potato leafhopper Empoasca fabae Description and habits. Adults of the potato leafhopper are small (about Vs inch long), wedge- shaped, and pale green with very small white spots on the head and thorax. Nymphs are similar to adults in color and shape but are wingless. Leafhoppers feed on the underside of leaves, and if dis- turbed move sideways to the opposite side of the feeding area. When populations are abundant, their sap sucking can cause a condition known as hopperbum. Seasonal life history. Potato leafhoppers overwinter primarily on alfalfa and other legumes in fairly permanent breeding areas in the Gulf States. These pests appear in large numbers on alfalfa and soybean as soon as the crops begin to grow in the spring and early summer. Eggs are laid singly, embedded in plant tissues. De- velopment of nymphs during the summer may take only 10 to 15 days; thus, several generations are possible each season on soybean. A summary of the annual cycle is shown in Figure 31. Other species of leafhopper also inhabit soy- bean fields. Potato leafhopper nymph. 10X. Potato leafhopper adult. 10X. Potato leafhopper Adults and Nymphs • Adults colonize soybean fields • Leafhoppers overwinter in breeding sites in southern regions > Adults migrate northward and colonize alfalfa fields > Local populations die out with first frost JAN FEB MARiAPR MAY JUN JUL j AUG [ SEP OCT NOV DEC Fig. 31. Annual cycle of the potato leafhopper in Illinois. 37 Seedcorn maggot Delia platura Description and habits. The yellowish-white maggots are about a/4 inch long, cylindrical, narrow in front, and legless. When fully grown, they turn into reddish-brown puparia, from which emerge grayish-brown flies similar to house flies but smaller and thinner. Feeding on seeds that may not have germinated or on weak seedlings, the maggots are especially damaging when air and soil temperatures are cool. Seasonal life history. The flies are active in the spring after over- wintering as pupae inside puparia in the soil or as maggots in manure. Developing at any tem- perature above 52°F, the maggots complete development in about 3 weeks. They are present in soybean fields early in the season. The annual cycle is summarized in Figure 32. Seedcorn maggots attacking a germi- nating seed. 5.5X. Seedcorn maggot adults (two views), puparium, and maggot. 5X. Seedcorn maggot • Puparia ir soil • Maggots feed on seed • Several generations develop on other crops > Puparia in soil N FEB MAR APR MAY | JUN | JUL JAUG | SEP |OCT NOViDEC Fig. 32. Annual cycle of the seedcorn maggot in Illinois. 38 Soybean nodule fly Rivellia quadrifasciata Description and habits. Adult flies are about ^16 inch long with a russet head, black thorax, and reddish-yellow abdomen. Their wings are marked with four black bands; the lower parts of the legs are yellow. The flies lay small, chalky to creamy white eggs in the soil. After emerging, the larvae or maggots bore holes in soybean nodules and consume the con- tents. When fully grown, the larvae are about XA inch long. Although these flies are present in Illinois, the amount of nodule damage they produce is probably insignificant. Maggot of the soybean nodule fly. 5X. Soybean nodule fly. 4.5X. Soybean thrips Main species: Sericothrips variabilis Description and habits. Thrips insert their eggs into plant tissue. The hatched, orange-red larvae remain on the plant through the second instar, then drop to the soil, where the prepupae and pupae stay until adult emergence. The tiny adults (0.04 inch) are banded transversely and have wings that are typically fringed with long bristles. Both nymphs and adults feed actively on soybean. Seasonal life history. Soybean thrips do not overwinter in Illinois, but are carried northward on warm airstreams from breeding sites in the South. Thrips colonize soybean as soon as the plants emerge. Generations overlap each other because the life cycle is completed in about 15 days. A summary of the annual cycle in Illinois is shown in Figure 33. Soybean thrips larva. 35X Soybean thrips adult. 40X. Soybean thrips I Larvae I Adults • Adults breed in southern regions • Adults colonize soybean fields . Adults migrate northward and colonize alfalfa fields JAN FEB MAR APR MAY JUN JUL AUG | SEP [OCT NOV DEC > Local populations die out with first frost Fig. 33. Annual cycle of the soybean thrips in Illinois. Whiteflies Trialeurodes spp. Description and habits. Tiny (Vie inch long) but very lively, the adult whitefly has a yellowish body and four wings covered with a powdery wax. The small eggs are attached to the leaf surface by a short stalk. Emerging nymphs settle on nearby leaves, feeding actively on plant juices until reaching the adult stage. The nymphal stage lasts about 30 days. Whitefly injury results in a yellow speckling of leaves, and when injury is heavy, the leaves become dry. Occasional field infestations are found in Illinois, particularly in the southwestern part of the state. Whiteflies. 5.5X. 39 Spider mites Tetranychus spp. Description and habits. The most common mite species found on soybean in Dlinois is the two- spotted spider mite, T. urticae. These tiny mites (0.002 inch) are four-legged, red arthropods, more closely related to spiders than to insects. Stages of growth and development include egg, larva, protonymph, deutonymph, and adult (Fig. 34). The life cycle is completed in 10 to 20 days, depending on weather conditions. Mites are passively dispersed into fields by wind, animals, farm equipment, or workers, but may also crawl from weedy hosts to soybean plants. Thus infesta- tions often start along the borders of fields or in spots within fields. When populations are large, mites produce webbing that helps them spread from one plant to another. Initial injury results in a yellow speckling of the leaves (Fig. 13); heavy infestations cause leaves to wilt and become dry. Occurring by mid to late season, most out- breaks of spider mites in Illinois are usually associated with prolonged drought. Spider mites. 6X. Fig. 34. Life cycle of the twospotted spider mite. 40 Biological Control Agents Most soybean insect pests in Illinois are attacked by natural enemies, or biological control agents. These agents are preda- ceous and parasitic insects, spiders, insect-eating birds, toads, and insect diseases. The most effective of these agents in Illinois soybean fields are the beneficial insects and insect diseases, which usually help to keep pest populations well below the economic injury level. It is important that you recog- nize the presence of these agents. If they are destroyed by unneces- sary or ill-timed chemical applica- tions, considerable harm may be done. The worst problems arise from triggering a secondary pest explosion or from a resurgence of the target pest. Most parasitic insects of soybean pests are small wasps and flies whose identification requires the help of a specialist. However, pest managers should be able to detect the presence of beneficial insects. The Illinois pest manage- ment program is designed to pre- serve these agents and to take advantage of the natural control they provide. Parasites The most visible parasites are those found on lepidopterous caterpillars. At least eleven species of parasitic wasps and flies attack green cloverworms in the Midwest. The most important parasites are larvae of the wasp Apanteles marginiventris (Fig. 35) and maggots of a tachinid fly that lays small white eggs easily seen behind the head of the larvae. Late in the season, mummified caterpillars that look like small cigars can be found at- tached to soybean leaves. These shells are the skins of cloverworm larvae eaten inside by the parasitic wasp Rogas nolophanae (Fig. 36). Bean leaf beetles are attacked by the parasitic fly Celatoria diabroticae. Parasitized beetles are not easy to detect, but one way to do so is to collect a dozen or two in a jar and add food. After a few days some of the beetles are likely to die. If the parasite is present, you will see small gray flies similar to house flies emerge from the bodies. Green stink bugs are also hosts to several parasitic insects, the most important of which is the fly Trichopoda pennipes. The eggs of this fly can often be seen on the top of the bug's prothorax. Fig. 35. Cocoon of Apanteles marginiven- tris, parasite of green cloverworms. 6X. Fig. 36. Pupal case of Rogas nolophanae, parasite of green cloverworms. 4X. Predators The most common predators found in Illinois soybean fields are lady beetles (Fig. 37 A, B), lacewings (Fig. 38 A, B), and several bugs, notably Orius insidiosus (Fig. 39), Nabis spp. (Fig. 40), Geocoris sp. (Fig. 41), and Podisus maculiventris, the spined soldier bug (Fig. 42). Several species of predaceous ground beetles are also found in soybean (Fig. 43). Other common predators that prey indiscriminately on small insects are spiders (Fig. 44), praying mantises (Fig. 45), and some wasps (Fig. 46). Several species of predatory thrips and mites are efficient biological control agents of small, plant- feeding insects, mites, and their eggs. Fig. 37 A. Lady beetle. 5X. Fig. 37 B. Lady beetle larva. 4X. 41 Fig. 41. Geocoris adult. 10X Fig. 38 A. Lacewing adult. 4X Fig. 38 B. Lacewing larva. 4X Fig. 40. Nabis adult. 4X Fig. 42. Spined soldier bug preying on caterpillar. 3X. Fig. 39. Or/us insidiosus. 12X Fig. 43. Ground beetle. 5X. 42 Fig. 45. Praying mantis. 0.8X. Fig. 46. Predaceous wasp. 1 .5X. Diseases Several disease organisms com- monly infect soybean pests. Per- haps the most important natural control agent of the green clover- worm in Illinois is the fungus Nomuraea rileyi (Fig. 47). Lepidopterous caterpillars are infected by the spores of this fungus, and upon germination the mycelium completely fills the body cavity, killing the larva. The body becomes hard and mummi- fied and is covered with a white layer of external conidiophores. Under hot, humid conditions the fungus sporulates, encasing the cadaver in powdery, light green spores. Detection of the disease may signal the decline of the pest population. It is therefore important that you recognize the presence and spread of the disease when surveying pest populations in soybean fields. Fig. 47. Green cloverworm infected with Nomuraea rileyi. 1 .8X. Other diseases also infect many soybean pests. For instance, grasshoppers and woollybear caterpillars are frequently killed by fungi of the genus Ento- mophthora (Fig. 48). Certain diseases caused by microsporid- ians infest green stink bugs and bean leaf beetles. Because the effects are slower and less evident than those caused by fungi, these diseases may go undetected. However, they can be responsible for the death of hibernating indi- viduals, thus reducing the size of colonizing generations the following year. Fig. 48. Yellow woollybear larva infected with Entomophthora. 1X. 43 Crop Growth and Pest Occurrence We now have information on the phenology (development and life history) of the most important soybean insect pests in Illinois and the annual cycle of the soybean crop. By superimposing one set of information on the other, we produced the chart in Figure 49. The annual cycle of four major pest species — stink bugs, green cloverworm, bean leaf beetle, and grasshoppers — are included in the chart. The three latter pests, plus sporadically occurring spider mites, account for nearly 85 percent of all the insecticide spraying that is done on soybean in Illinois. Stink bugs are potentially damaging in the southern half of the state. This chart should serve as a general guide for timing the operations in your pest management program. However, the curves are only averages; departures from the general trends are to be expected. Since these curves are based on information collected in central Illinois, populations may peak one to two weeks earlier farther to the south, or one to two weeks later to the north. Depending on summer temperatures, there will also be annual fluctuations in the time of peak pest occurrence. A cool summer will cause a delay, represented by a shift to the right in the curves; a warmer than normal summer will result in a shift to the left. Furthermore, the probability of outbreaks varies among regions within the state. From records of the past ten years we mapped the areas at risk for outbreaks of green cloverworm, bean leaf beetle, grasshoppers, spider mites, green stink bug, and Japanese beetle (Fig. 50). Most other pests occur only sporadically throughout Illinois. Dales °SSSS"S£SSS±22 omotnouiotnoinotnomom CM CM PS _'-'-eMCMCO_^-*-WCSI« < 1 a Planting Flowering Maturation Fig. 49. Seasonal occurrence of some common soybean insects in Illinois. Warning: The information in Figures 49 and 50 is merely a guide. Both timing and loca- tion of possible outbreaks may vary from year to year. It is therefore essential that you monitor pest occurrence in individual fields. Refer to the recommendations in these guidelines for efficient pest management. 44 Green cloverworm rFH-N Spider mites j— in^-L , Bean leaf beetle Green stink bug j L./ V-L, r-T ) i A.M-T rr; Japanese beetle j_ _ ; ^ '-•^" \ Fig. 50. Areas of Illinois at risk for occurrence of major soybean insect pests. 45 Pest Management Program The pest management program for soybean in Dlinois requires field data for measuring insect pest populations, estimating the level of injury already caused by the pests, and evaluating natural controls in a field. With these data the program can provide criteria for helping you decide on control actions. If needed, controls consist mainly of selecting insecticides and applying them at dosages that are the most effective for given pests but least detrimental to beneficial parasites and predators. The key factor in the pest management program is the correct measurement of pest populations. Sampling the populations, evalu- ating the biological control agents, and estimating plant injury are parts of the operation known as scouting. The three major com- ponents of the soybean pest management program are: • Scouting • Deciding on control actions • Applying controls Scouting Insect pests invade soybean fields at different stages in the crop's growth cycle. To help you save time when scouting, we com- bined information about the soybean growth cycle in Illinois and the expected peak of occur- rence of the main soybean pests in the state (Fig. 49). Soybean fields should be visited at least once after plant emergence and at least two or three times between the middle of July and the end of August. During this latter period, plants are extremely sensitive to defoliation, and most potential pests, particularly green clover- worm, bean leaf beetle, and grasshoppers, are expected to reach maximum levels. Assessing insect populations Various methods can be used for sampling insect populations. Because no single method is effec- tive for all insect species or through- out the entire growing season, we compromised and used the ground cloth method, which is generally reliable and easy to adopt. The method is unsuitable, however, when surveying plants up to the V4 stage or when crops are planted at row widths of 15 inches or less. Construction and use of the ground cloth are illustrated in Figures 51 and 52. After collecting the insects, count the ones that are predominant during that particular stage of plant growth. Record the number, because control recommendations are based on the number of insects per foot of row. Also look for predators, and note the number of caterpillars killed by disease. Since samples are collected from 6 feet of row (3 feet on both sides of the ground cloth), five samples represent the insect population in 30 feet of row, or multiples of six if more samples are taken. To obtain the count per linear foot, the total number of insects collected in all samples is divided by the number of samples taken per field, times 6 (the number of row feet per sample). Thus: Insects/foot of row = no. insects in all samples -J- no. samples x 6 The ground cloth should not be used until after the stand is well established (V4 stage). Before then, fields should simply be scanned to detect gaps in the stand. If gaps are observed, try to determine if insects are the cause. Several early season pests cut young plants at the hook or destroy seeds in the ground (see pages 6-7). Use direct counts if foliage feeding, probably by bean leaf beetles, is observed early in the season. Direct count or direct observation is recommended while soybean plants are small (up to 46 stage V4). For this procedure, mark off a distance of 3 to 9 feet on the ground with the heel of your shoe. Then walk along the row between the two marks. Slowly turn the leaves upside down and unfurl the growing tips to locate any hidden beetles. It is also useful to tap the plants to dislodge beetles onto the ground. Count all beetles. To determine the insect popula- tion per linear unit of row, divide the number of insects by the number of feet measured on the ground. If done carefully, direct counts provide good estimates. Fig. 51. Ground cloth construction. Use two 4-foot lengths of 1-inch dowel and piece of white canvas 3 feet by at least 3Vz feet. Roll 3-foot side of canvas once around each stick and fasten with heavy- duty staples. Leave 6-inch handles at both ends of sticks. Fig. 52. Sampling procedure. (A) Keep cloth rolled up while slowly approaching sampling site. Walk along row space next to chosen site to avoid disturbing the insects. (B) Carefully move to face site. Put cloth, still rolled, between two rows. Quickly unroll cloth and hold sticks in place with knees. (C) Shake plants from each row over cloth. Release plants and quickly look for caterpillars or beetles clinging to fallen leaves. 47 Sweepnet sampling is recom- mended for soybean planted at row spacings too narrow for the ground cloth to be used properly. Construction of a sweepnet is illustrated in Figure 53; the nets are also available commercially. Sam- pling results obtained with the sweepnet are often difficult to interpret because they give only a relative estimate of a population. However, if you always sample carefully in the same way, you'll learn to interpret the results so that relative counts can be con- verted to absolute estimates. -47 in. I in. I Fold line •• B Fig. 53. Sweepnet construction. Use white canvas or muslin for net, No. 6 to No. 8 gauge wire for hoop, and light but strong wood for handle. Net (A) Sew two triangles together along side edges. Fold and sew band around top of net. A gap of about 2 inches should be left between ends of band for inserting hoop (C). Allow Vi inch for all seams. Hoop (B) Shape hoop as indicated, making one stem 1/z inch longer than the other. Handle (C) On opposite sides of handle make grooves for stems. Thread hoop through band of net, press stems of hoop into grooves and fasten securely with hose clamp. In narrow-row or solid plantings of soybean we recommend the use of the "sweeps across" method, which is explained in Figure 54. Each swing of the net is counted as one sweep, and each sampling unit should consist of at least 20 sweeps. Twenty sweeps cover about 40 feet of row, but in most cases you'll collect only 30 to 40 percent of the actual population, and even less if plants are badly lodged. Thus the counts must be adjusted accordingly. If the field is in 7-inch row widths, the hoop of the net, which covers a swath of about 15 inches, will include four or five rows with each stroke. Adjustments for these factors are included in the conversion of number of bugs per 20 sweeps to number of bugs per foot of row as follows for 7-inch rows: no. insects/foot of row = no. insects/20 sweeps x 0.02 Or for 15-inch rows: no. insects/foot of row = no. insects/20 sweeps x 0.04 The optimal number of samples per field varies with the character- istics of the insect species, population density, sampling procedure, and size of the field. As a rule of thumb, however, it suffices to take one ground cloth sample or one set of direct counts (3 to 9 feet of row) for every 10 acres, but never less than five samples per field. Location of sam- pling sites in fields of various shapes is shown in Figure 55. The best method, known as the sequential sampling plan, allows you to adjust the number of samples according to the four variables mentioned above (insect species, population density, and so forth). 48 *' «* Fig. 54. "Sweeps across" method. While walking along row, swing net from side to side with pendulum-like motion. Top three frames show one sweep and bottom frame a second sweep. 49 Evaluating biological control agents Predatory bugs, lady beetles, and lacewing larvae are among the most common predators of soy- bean pests. In addition to these rather large insects, there are many species of predatory thrips and mites, as well as a multitude of parasitic wasps and flies that are not easily detected by the un- trained observer. Many of these beneficial insects are present in numbers capable of keeping pest populations below the economic injury level. Pest management programs are designed to protect these predators and parasites and to gain maxi- mum benefit from their activities. Scouts and growers should learn how to distinguish the beneficial from the harmful insects. Some of the most common species are pictured on pages 41 to 43. Fungal diseases are very effec- tive natural controls. The fungus Scout B f *' JT* Scout A Nomuraea rileyi, for example, provides perhaps the most effi- cient control of green cloverworms in outbreak years. Use the ground cloth method to detect diseased larvae. Look for either white, conidiophore-filled cadavers (Fig. 47) or sluggish larvae that, unlike healthy ones, do not twitch when dropping to the ground. Record the number of diseased larvae separately from the number of apparently healthy ones. These records are important in the detection of disease outbreaks. On many occasions, green cloverworm populations that were nearing the economic injury level have been completely wiped out by this fungal disease. If the fungus is spreading, an insecticide application may be saved. The presence of predators, and par- ticularly a spreading fungal dis- ease, should be taken into account in the decision-making phase of the pest management program. Scout B picked up by Scout A Scout B parks vehicle and enters field Scout A exits field and drives vehicle to pick up Scout B Measuring injury Sampling the populations and evaluating the biological control agents are the first two sets of observations to be noted when scouting soybean fields. The third set of observations is the amount of plant injury already present. Described in the section on "Injury to Soybean," the types of measurable damage used in the IPM program are seedling destruc- tion, defoliation, and pod and seed injury. Seedling destruction and re- duction of the stand are easily identified. But keep in mind that moderate seedling injury causing growth retardation can be over- estimated. In general, if growing conditions are favorable, plants will compensate for injury early in the season unless cotyledons and unifoliolates are completely destroyed. A careful examination of plants at the seedling stage is necessary for making correct Scout A enters field s exit field park vehicle enter field Fig. 55. Efficient procedures for scouting large fields. 50 control decisions. Defoliation may result from hail, wind, and diseases, which often substantially reduce the functional leaf area of the crop. Insects produce direct defoliation or aggravate the effect of other defoliating factors. For instance, a leaf with a hole is more likely to tear under the force of the wind than a leaf with an unblemished surface. For the IPM system you 5% 20% 30% 40% 50% Fig. 56. Levels of defoliation of soybean leaflets eaten by a green cloverworm larva. This figure should be used to help calibrate estimates of defoliation. need to estimate the overall level of defoliation regardless of cause, because the various types of defoliation are essentially additive. To estimate defoliation, sur- veyors and scouts need to learn how to scan the plants from top to bottom while walking through a field. Inexperienced scouts tend initially to overestimate defolia- tion. In training sessions it is useful to allow individuals within groups of trainees to make their own estimates and then compare estimates of the entire group. With adequate guidance from more experienced scouts, a person can learn to estimate defoliation with reasonable ease. Another, although more time- consuming, way is to "calibrate" estimates. The method includes three steps: 1. Without looking at the plants, stretch out your arm and collect at random 20 leaflets each from the top, middle, and bottom thirds of scattered plants in the field, for a total of 60 leaflets. 2. Compare the leaflets with the set in Figure 56, which illus- trates insect-produced defoliation at six increments. 3. Record your estimates of the percent defoliation for each of the 60 leaflets and take the mean (add up the estimates and divide the total by 60). The result is the overall defoliation level in the field. Pod and seed injury is measured by harvesting 100 pods from various parts of plants in scattered areas of the field. The number of injured pods is tallied, thus providing the percent injury for the entire field. Grasshopper feeding and scars caused by bean leaf beetles are very easy to detect, but moderate injury by stink bugs may go undetected. There- fore, decisions on stink bug control are based solely on counts of adults and large nymphs. 51 Forecasting Scouting fields is the surest way to monitor the status of pests. However, insect pests on soybean are sporadic in most parts of Illinois. In some years few if any insects injure the crop. When this is the case, the effort and expense of scouting could be saved if we were able to predict early in the season whether an outbreak in a given region is likely to occur. Forecasting pest outbreaks is not easy. We are, however, build- ing into the IPM program a forecasting capability for bean leaf beetle, green cloverworm, and grasshoppers. The capability is based on having entomologists take samples early in key areas of the state. These data are then used in computerized simulation models, along with actual weather data from the various crop- reporting districts. The information derived from the models will be passed on to the Cooperative Extension Service for delivery to the farming com- munity. We suggest that you subscribe to the "Insect, Weed & Plant Disease Survey Bulletin," published weekly by the Illinois Cooperative Extension Service, and tune in to radio and TV programs of agricultural news in your area. Use this information advisedly, because biological phenomena can be predicted only within certain margins of probability. Control Tactics The central idea in IPM is to take maximum advantage of all available control methods. An IPM program aims at combining vari- ous methods or tactics into a regionally suitable control strategy. The main tactics used are biologi- cal control, cultural control, plant resistance, and chemical control. Biological control Biological control is the manipu- lation of parasites, predators, and diseases in a manner that helps these natural agents keep pest populations below the economic threshold. Most soybean insect pests in Illinois have efficient natural enemies that need no manipulation. Our main concern is not to disturb them by the misuse of insecticides. We therefore recommend the careful selection of insecticides that are least likely to disrupt biological control agents. Cultural control Every grower must take into account the possible effect of agricultural practices on pests. Special cultural procedures have been designed specifically for the control of damaging insects, but we are interested here in the effects of normal farming operations on pests. Tillage usually exposes many soil-dwelling insects, such as white grubs and wireworms, to birds and other predators. But the effect that minimum or no tillage may have on these pests is not well known. You should be aware of potential problems and carefully monitor changes in the incidence of the pests after adopting reduced tillage practices. Crop rotation is recommended for sound economic and agronomic reasons. Planting soybean con- tinuously seems to have little effect on insect pests, but the practice does lead to increasingly serious problems with diseases and nematodes. For good inte- grated pest management, crop rotation should be practiced in accordance with university agronomic recommendations. Planting dates are dictated by climatic conditions. We do not recommend changes in established planting dates to control insects. But bear in mind that early plant- ing favors the bean leaf beetle and that double cropping, by Fig. 57. Clark soybeans in foreground are hairless and are susceptible to the potato leafhopper; plants in the middle have curly hairs and are moderately susceptible; those in background have normal hairs and are resistant. 52 extending the growing cycle of plants in certain regions, may result in greater pod and seed damage by stink bugs, grass- hoppers, and the bean leaf beetle. Careful scouting of a late maturing crop is therefore necessary. Plant resistance Most soybean varieties recom- mended in Illinois are highly resistant to the potato leafhopper, mainly because the plants are hairy. Glabrous (hairless) lines are severely stunted by the leafhopper (Fig. 57). Considerable resistance to the most common diseases has been incorporated into practi- cally all of the recently developed varieties, and some are now being bred for greater resistance to nematodes and defoliating insects. Eventually the IPM program will add newly developed varieties that combine high yields with increased pest resistance. Chemical control If pest populations reach the economic threshold, the only remedial tactic in IPM for soybean is the well timed application of selective insecticides. Scouting provides the information needed to arrive at decisions about control and timing. Selectivity is obtained with carefully chosen insecticides and rates of application. According to the research, most soybean pests can be adequately controlled with lower dosages than those previously recom- mended by the university or the manufacturer. The lower dosages are less detrimental to biological control agents. The rates recom- mended in 1973 and 1977 in most soybean-producing states are shown in Table 6. We have not included insecti- cide control recommendations in these guidelines, because insecti- cides and dosages may change from year to year. For annually revised recommendations, consult the current issue of Circular 899, "Insect Pest Management Guide: Field and Forage Crops," pub- lished by the Illinois Cooperative Extension Service. Always follow label directions when using an insecticide, and always have in hand a copy of the "Illinois Pesticide Applicator Study Guide," also published by the Cooperative Extension Service. Table 6. Insecticide Dosages Recommended for Control of Soybean Pests, 1973 and 1977 Recommended rate, Iba i./acre Species Insecticides 1973 1977 Bean leaf beetle Carbaryl Methyl parathion Azinphosmethyl 1.50 0.50 0.25 0.50 0.25 0.125 Green cloverworm Carbaryl Methyl parathion Bacillus thuringiensis 1.50 0.50 0.50 0.25 0.25-0.50 Stink bugs Carbaryl Methyl parathion 1.50 0.50 0.25-0.50 Adapted from: D. L. Newsom et at. 1980. New Technology in p. 89. New York: John Wiley & Sons. Pest Control, ed. C. H. Huffaker, 53 Decision Charts Information gathered through scouting is used in deciding whether to spray and when. The stage of crop growth and general condition of the field should also be taken into account. Early in the season, insecticide applications for bean leaf beetles and baits for cutworms may be required. No specific preventive use of soil insecticides is rec- ommended for soybean. Control decisions for bean leaf beetle are shown in Table 7. If the stand is reduced below the tolerable levels presented in Tables 2 and 3, some replanting may be necessary. In case insects such as white grubs, wireworms, or cutworms are responsible for the damage, you may need to apply soil insecticides or insecti- cide baits in the areas to be re- planted. Mid-season pests are mainly defoliators such as green clover- worms and bean leaf beetles. Control decisions for green cloverworm are shown in Table 8. Seldom is it necessary to spray solely for control of bean leaf beetles, although their feeding may contribute to the overall level of defoliation. Spraying for green cloverworms will probably take care of any concurrent infestation of bean leaf beetles. Late season pests are pod feeders, especially bean leaf beetles, grasshoppers, and stink bugs. For stink bug control, follow the economic thresholds in Table 5. For decisions about bean leaf beetle control during the stages of seed maturation see Table 9. Table 7. Decision Chart for Control of Bean Leaf Beetle on Soybean at Seedling Stage Through Early Vege- tative Growth (VE to V3)a Injury level No. of beetles per foot of row Less than 4 4 to 6 More than 6 Cotyledons slightly injured; less than 30 percent injury to unifoliolate and open trifoliolates At least one cotyledon com- pletely destroyed; 30 to 40 percent injury to unifoliolate and open trifoliolates Two cotyledons destroyed; more than 40 percent defoliation Sample again by late July Sample again within 1 week Sample again in 3 days Sample again in 3 days Spray (correct time); no loss expected Spray (overdue) Sample in 3 days; if plants are dying, some replanting may be needed Spray; if plants are dying some re- planting may be needed Spray; if plants are dying, some re- planting may be needed • To use this table, first sample the field to determine the pest population level and the injury level. Use direct counts on 3 feet of row to sample bean leaf beetles on seedlings (see pages 46-47). 54 Table 8. Decision Chart for Control of Green Cloverworm on Soybean After Full Bloom and Before Seed Maturation (R1 to R5)a Defoliation, percent No. of cloverworms'1 (more than 1/2 in. long) per foot of row Less than 8 8 to 12 More than 12 Oto20 20 to 30 Over 30 Continue sampling at regular intervals (10 to 12 days) Continue sampling at closer intervals (3 to 5 days) Spray (preventive); low probability of loss Continue sampling at closer intervals (3 to 5 days) Spray (correct time); no loss Spray (overdue); prob- ability of minor loss Continue sampling at closer intervals; prob- ability of loss but population in decline Spray (overdue); probability of loss Spray (much overdue) probability of major loss • To use this table, first sample the field to determine the pest population level and the percent defoliation. See pages 46 to 48 for sampling procedures. "The amount of injury caused by one green Cloverworm is approximately equal to that produced by two bean leaf beetles or Vi grasshopper. Thus, to compute thresholds for bean leaf beetles, multiply the level in the above footnote by 2; to compute thresholds for grasshoppers divide the levels above by 2. Table 9. Decision Chart for Control of Bean Leaf Beetle on Soybean at Stage of Seed Maturation Through Harvest Maturity (R6 to R7)a Pod injury, percent No. of beetles per foot of row Less than 8 8 to 10 More than 10 0 to 8 8 to 12 Over 12 Discontinue sampling Sample again in 5 days Spray (preventive if pods are still green) Sample again in 5 days Spray if pods are still green or beginning to yellow Spray if pods are be- ginning to yellow Spray if pods are still yellow and beetles are present Spray unless pods are completely dry Spray unless pods are completely dry • To use this table, first sample the field to determine the pest population level and the percent pod injury. Use a ground cloth to sample the beetles (see pages 46-47). Collect 20 pods at random in 5 different locations in the field to obtain the percent pod injury. 55 Implementing the Pest Management Program The pest management program is referred to as integrated because various control tactics are coor- dinated into a control strategy that is economically and ecologi- cally sound. To develop IPM, however, we also need an integra- tion of efforts. If IMP is to be successful, everyone interested in either the public or the private aspects of agricultural production must communicate and work together as an integrated team. This team is composed of the grower, county Extension adviser, pest management consultant and scouts, and Extension and research entomologists. Each member of the team has an important role. Growers Growers are the ultimate deci- sion makers and users of IPM and hence should be the primary beneficiaries of the program. After having adopted IPM, they do their own scouting or decide to hire a pest manager or professional scouts. With the IPM guidelines, growers will be able to scout their fields more efficiently, avoid unnecessary insecticide applica- tions, and profit from the better timing of those applications that are needed. County Extension Advisers Extension advisers play a dual role in IPM. First, they alert growers to the benefits of using IPM, explain the techniques, and offer help in making IPM deci- sions. Second, the advisers com- municate to Extension and research entomologists the success and failures of IPM procedures. Their collection of data on insecticide use in each county is essential in helping to plot long-range pest trends. Because IPM is dynamic, its improvement requires constant feedback. County Extension advisers are in a unique position to promote interaction between growers and other members of the team. Pest Management Consultants Well trained consultants can serve the farming community by moni- toring the pest situation and level of injury and by assisting in the task of making control decisions. As the IPM program becomes more sophisticated and complex, the role of professional consultants will become increasingly impor- tant. Feedback from their field experiences to the professional entomologists in Extension and research is essential for the con- tinued improvement of the program. Extension and Research Entomologists Research and Extension entomol- ogists work together to identify pest problems, evaluate the effects of various pests, and define economic thresholds. The ento- mologists also monitor pest trends for the forecasting program and design improved control tech- niques. As farming systems change, updating of IPM programs is necessary. For instance, switch- ing to narrower row spacings requires a suitable method for sampling pest populations. Re- searchers are responsible for developing the appropriate technology. But the entire research effort is worthless if the findings are not effectively communicated to po- tential users, namely, growers, advisers, and consultants. Thus research and Extension must cooperate to guarantee an uninter- rupted flow of information. 56 Implementation in Steps The first seven sections of these guidelines contain information on the main soybean insect pests in Illinois, methods for measuring pest populations and injury levels, and charts and economic thresh- olds to help you decide if and when to apply insecticides. The section that follows summarizes the steps for implementing the integrated pest management program. Plant quality seed at the proper depth and adequate density for the selected row spacing. Avoid problems of plant injury from herbicides that carry over or from herbicides and insecticides that are incompatible. Scout fields early in the season for bean leaf beetles, cutworms, and seedcom maggots (see pages 22-23, 31, and 38). Refer to Tables 2 and 3 for injury tolerances and to Table 7 for control decisions. Follow the weekly pest predictions in the "Insect, Weed & Plant Disease Survey Bulletin" and the recommendations of Extension specialists in Circular 899, "Insect Pest Management Guide: Field and Forage Crops." After July 1 be on the alert for radio and TV warnings about outbreaks of green cloverworms, bean leaf beetles, or grasshoppers in your region. If warnings are given, scout your fields to estimate pest populations (see pages 46-50) and to evaluate the presence of natural enemies, especially the fungal diseases (see page 50). Estimate defoliation levels and determine the growth stage of your crop (see Table 1 and pages 50-51). Refer to the decision chart in Tables 4 and 9 for economic thresholds. If fields go through a droughty period for 18 to 21 days during July and August, check for spider mite outbreaks (see page 40), particularly in western and south- western Illinois. If patches of plants are being killed in the field, follow the current control recommenda- tions in Circular 899. If no special pest warnings are issued for your region, check your fields once during late July or early August for first-generation bean leaf beetles, green cloverworms, and grasshoppers (see pages 22-23, 33-34, and 36). 8 If populations and defoliation levels approach the economic threshold (Tables 4 and 8), be prepared to apply an insecticide spray. Refer to Circular 899 for dosages and precautions. In late August and September beware of second-generation bean leaf beetles, stink bugs, and grass- hoppers feeding on pods (pages 22-23, 29-30, and 36). Refer to Table 5 for economic thresholds, to Table 9 for control decisions, and to Circular 899 for insecticide recommendations . 10 Integrated pest management is a global strategy for controlling weeds and diseases as well as insects. Although we stress insects in these guidelines, the calendar on page 58 serves as a preliminary guide for a broader crop manage- ment program. Expand on this scheme to meet the needs of your fanning operation. 11 Use these guidelines frequently to identify less common insects and to distinguish beneficial natural enemies from pest species. Help us improve the guidelines by informing state Extension and research entomologists about new pest problems and about the results of the IPM program in your region. 57 Illinois Soybean Cropping System Crop Management Schedule Agronomic practices Insect control Weed control Nematode control Disease control Pre- season activities Jan Feb Mar Apr Planting plans Acreage Field selection Variety selection Fertilizers Pesticides Equipment Rotation Resistant varieties Insecticides" Rotation Herbicides" Rotation Resistant varieties Nematicides" Rotation Resistant varieties D isease-f ree seed Fungicides" Planting Growing season Harvesting May So Cor tic R F 1 preparation Herb cides Nema applic ticide :ation ven- Mini- nal mum or No-till r i Pre- P re- plant emerg. 1 i Planting ow spacing 'ertilization i Jun Stand lishr [Repla estab- nent nting] Scot If early season present, spray insecticide (se 7 for economic iting pests are recommended 3 Tables 4 and thresholds) Rotary hoeing Weed survey Post- Culti- emerg. vation herbi- cide l J SCOL If mid-season [ ent, spray with insecticide (sei 8 for economic ting >ests are pres- recommended 3 Tables 4 and thresholds) Row cu [Hand w tivation eeding] Disease monitoring If mid-season diseases are present, start spray schedule Jul Aug T Scouting If late season pests are pres- ent, spray with recommended insecticide (see Tables 5 and 9 for economic thresholds) We map ed ping " r " Disease monitoring If late season diseases are present, apply fungicides Soil si jrveys Sep Harvesting Storage Oct Fall N plow- ti ing D- II Post- season activities Nov Dec Marketing Maintenance of equipment Planning Rotation Herbicides Cultural practices Planning Rotation Resist, var. Nematicides 58 • For insecticide recommendations see Circular 899. " Consult Illinois Cooperative Extension Service publications for pesticide recommendations. BKBB UNIVERSITY OF ILLINOIS-URBAN* Q 630 7IL6B CDD8 BULLETIN URBANA *"* 7731982 30112019531224