Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. Rev e@de follows > CIRCULAR No. 106 MARCH, 1930 UNITED STATES DEPARTMENT OF AGRICULTURE WASHINGTON, D. C. TREE HOPPERS AND THEIR CONTROL IN THE ORCHARDS OF THE PACIFIC NORTHWEST By M. A. Yorurrs, Associate Entomologist, Division of Deciduous Fruit Insects, Bureau of Entomology CONTENTS Page Page RTRD TO CUCU OTS yc atte etn SA eT a i IL 1 | Life history of tree hoppers—Continued. Reds OL tree: NOP PCESs es es erica aay ae 1 GUE Stage aad: sean Ae aS Teo ee 10 PTS CIDE GTO Wee Mees a ee AN Ot aI 2 OVP OSUETO Taras Wa ai eR a Rea 10 TBRADD SY (0 Ua 0 01D Och eens ean RP PCD LAE ea 2 Ei bernaviours Geet CI. sae eee ee 12 Hood-and oviposition plantss2=—-2 = = ssa e es Absa Natural @neMiies.cs aloe ae es eee ee 12 General description of tree hoppers--_--------- 5 | Preventive and control measures___-_________- 12 Pte historysottreeshopperseess- 2 eee eee 8 Gleanveultivationms-s eee se ee ee eee 12 LAG CMI PTONE LES se ene ee eae ele eee 8 Pruning and collecting: 222s sues. aes 13 INivphalistages. 2 seas ee ee 9 SHO ees Tal aes Sai phe a ae ree 13 INTRODUCTION * For many years there has been, in different parts of the country, a peculiar injury to the young wood of fruit trees caused by sever al species of insects commonly known as“ tree hoppers.” In the Pacific Northwest this injury has been especially common in orchards in which alfalfa is grown as a cover crop, and has become serious enough to require control measures for its suppression. Alfalfa is a favorite food plant of these insects, and they are more or less numerous wherever it is grown in orchards. Injury also often occurs along the edge of fruit-tree nurseries which are adjacent to fields of alfalfa, and throughout newly planted orchards which have been set out in land previously occupied by alfalfa and in which occasional alfalfa plants still persist. Though the nature of the injury is such that the loss can not be easily given a monetary value, the damage is nevertheless considerable. KINDS OF TREE HOPPERS ‘Until quite recently tree hoppers in orchards in the Pacific North- west have been referred to indiscriminately by both entomologists und orchardists as “the buffalo tree hopper.” Investigation has shown, however, that about 15? different species are present in the orchards, and several additional species have been found in other 1 The field observations and experiments upon which this circular is based were made, for the most part, at Yakima, Wash., at various times and incidental to other work during the years from 1923 to 1926, inclusive. 2Ceresa albidosparsa Stal. C. basalis Walk., C. borealis Fairm., C. bubalus Fab.. @. femorata Fairm., C. taurina Fitch, Stictocephala gillettet Godg., S. inermis Fab., S. pacifica Van D., SV. wickhami Van D., Campylenchia latipes Say, Glossonotus unwittatus Harr., FHeliria "rubidella Ball, Publilia modesta Uhler, and Telamona barbata Van D 89747—30 2 . CIRCULAR 106, U. S. DEPARTMENT OF AGRICULTURE places. Of this number, however, only the buffalo tree hopper (Ceresa bubalus) (fig. 1, A), the green-clover tree hopper (Stzcto- cephalainermis) (fig. 1, B), the basal or dark-colored tree hopper (C. basalis) (fig. 1, C), are thus far recognized as common enough to he considered of economic importance in that area, although the crested brown-mottled tree hopper (Heliria rubidella) has been found in considerable numbers on apple trees in the Wenatchee district ° and rarely in the Yakima Valley, Wash., and in southern Idaho. Another species, Stictocephala gillettet, which has no common name, is an important species in Utah,* but this species is unknown in the Yakima Valley . As all these different kinds of tree hoppers have so many points in common they are here treated for the most part as one group, although any important differences among the three most common species are pointed out. eo DISTRIBUTION The several species of tree hoppers considered here are found in a number of the Canadian Provinces and in most of the States except those in the extreme South, though one species® is found in Florida. In the Pacific Northwest their distribution is generally coincidental with the use of alfalfa as a cover crop in orchards. NATURE OF INJURY The injury caused by the tree hoppers is due to the weakening effects of their oviposition wounds on the fruit-tree twigs rather than to their feeding, which causes comparatively little damage. Most of the oviposition scars are found on the uvper surfaces of the twigs growing from the lower branches, especially on those which hang down into or toward the alfalfa. Very rarely is injury found more than 6 or 7 feet above the ground. The three more harmful species cause rather distinctive types of injury. which are discussed in the order of their importance in the Northwest. A much roughened, ragged appearance (fig. 2) is given to the twigs by the scars caused by the green-clover tree hopper. The incisions are cut well into the bark, but there are numerous shallow, supple- mentary cuts near by, which cause the bark to curl away from the main incision. This injury hinders the proper functioning of the bark, and retards the growth of the twig. The green-clover tree hopper lays its eggs entirely in 1-year wood and the oldest of the current season’s growth. Oviposition wounds in the form of deep, distinct, clean-cut longi- tudinal slits (fig. 3), a few of which are sufficient to cause the termi- nal portion of the twigs to die (fig. 4), are made by the basal, or dark-colored tree hopper. This tree hopper oviposits in the wood formed during the current season, sometimes well out toward the tips. Often the injury by this species begins where that caused by 3 YOTHERS, M. A., WEBSTER, R. L., and SPULER, A. HELERIA RUBIDELLA BALL. COM- PARATIVELY UNKNOWN MEMBRACID BECOMES ABUNDANT AND PROBABLY INJURIOUS IN OR- EaRe DS IN THE WENATCHEE, WASH., DISTRICT. (Scientific Note) Jour. Econ. Ent. 22: 269. zt é 4 SORENSON, C. J. TREEHOPPER- INJURY IN-UTAH: ORCHARDS. Utah Agr. Expt. Sta. Bul. 206208) pS illus. 21928: 5 Stictocephala inermis. TREE HOPPERS AND THEIR CONTROL 3 the others leaves off. Both types of wounds are shown intermingled on the same twigs in Figure 5, A. The buffalo tree hopper places its eggs in pairs of more or less parallel longitudinal cuts. L 3% FIGURE 1.—A, Buffalo tree hopper, side and front views; B, g C, basal or dark-colored tree hopper. xX reen-clover tree hopper ; Oviposition wounds by tree hoppers furnish suitable entrance for the woolly apple aphid,° many colonies of which find lodgment in them. (Fig. 5, B.) Overwintering eggs of the apple*aphid’ are also often present. Occasionally the oviposition scars so weaken ee __t. ® Hriosoma lanigerum (Hausm.). 7 Aphis pomi DeG. 4 CIRCULAR 106, U. S. DEPARTMENT OF AGRICULTURE the twigs that they subsequently break, with the weight of the fruit out beyond them. ) FOOD AND OVIPOSITION PLANTS in the orchards of the Pacific Northwest the tree hoppers feed al- most exclusively upon. alfalfa, though occasionally upon sweet clover. FIGURE 2.—Apple twigs showing the characteristic shaggy, roughened appearance Oue to the oviposition wounds of the green-clover tree hopper: A, Natural size; Pe Src: They are known, however, to feed upon grass, red clover, and other forage plants. In rare cases the newly hatched nymphs have been seen feeding upon apple and pear buds, wild mustard, and dande- By # TREE HOPPERS AND THEIR CONTROL 5 lion. Nightshade placed in a rearing cage was so girdled that the top of the stems died beyond the scar. The tree hoppers have been found to deposit eggs in the following trees: Apple, pear, peach, willow, locust, and poplar. (Fig. 6.) Cherry and prune trees appear to be nearly immune. In a num- FIGURE 3.—Apple twig showing leaf clusters nearest the tip and a number of ovipo- ancy Nounds of the dark-colored tree hopper in the live wood below the foliage. atural size ber of instances cherry and prune trees growing in the oldest of seriously infested apple orchards in alfalfa cover crop showed no oviposition scars. GENERAL DESCRIPTION OF TREE HOPPERS These insects are from 7 to 10 millimeters (one-fourth to three- eighth inch) in length and from 3 to 6 millimeters in width, more IRCULAR 106, U. S. DEPARTMENT OF AGRICULTURE ay wv tion wounds (a) of the dark- size iposi Three-fourths natural FIGURE 4.—Terminals of apple twigs killed by ov colored tree hopper. ; { TREE HOPPERS AND THEIR CONTROL 76 or less triangular in shape, whether viewed dorsally or ventrally, or from the side, and with their greatest height and width at the thorax and tapering gradually backward. (Fig. 1; fig. 9,G and H.) The upper covering of the tree hoppers is composed of membranous wings and a hard shell, the pronotum. Viewed from in front they b Figure 5.—A, Intermingling of oviposition wounds of the green-clover tree hopper (a) and the dark-colored tree hopper (0b), slightly enlarged; B, colonies of the woolly apple aphid in an old oviposition scar (a) and in a new scar (0), natural size have an odd angular appearance whether they have the pronotal horns (fig. 1, A and C) or no horns (fig. 1, B). The pronounced horns projecting from either side of the pronotum are the charac- teristics which give the buffalo tree hopper its name owing to its fancied resemblance to the bison or buffalo. 8 CIRCULAR 106, U. S. DEPARTMENT OF AGRICULTURE The three species most common in orchards of the Pacific North- west may be distinguished as follows: The buffalo tree hopper, Ceresa bubalus (fig. 1, A) is the largest of the three and has projecting pronotal horns. The dark-colored tree hopper, C. basalis (fig. 1, C), is the smallest of the three species and also has pronounced pronotal horns, but it is darker generally and black ventrally, with FIGURE 6.—Oviposition wounds of the dark-colored tree hopper: A, In pear; B, in willow; C, in peach; D, in locust; E, in apple. Natural size short hairs on the pronotum, especially in front. The green-clover tree hopper, Stictocephala inermis (fig. 1, B), has no pronotal horns. LIFE HISTORY OF TREE HOPPERS HATCHING OF EGGS Hatching starts in early April for most species and continues until early May. The eggs of the dark-colored tree hopper (fig. TREE HOPPERS AND THEIR CONTROL 9 7. a, b) hatch later than those of other species, beginning to hatch in early May about the time those of the green- clover species (fig. 7, c) and the buffalo tree hopper are through hatching. Most hatching takes place on warm, humid mornings, few young - nymphs emerging in the afternoon and none at any time when the tempera- ture is below 50° F. On warm mornings, during the hatching period, thousands of the tiny, white nymphs are often seen emerging from their eggshells in the scars in the bark of twigs (fig. 8, Me water sprouts, and 1-year-old trees. Upon hatching ‘they fall almost im- mediately to the ground or upon whatever plants are present in the orchard. After the eggs have hatched numerous empty, white egg- shells remain protruding from the scars. (Fig. 8, B.) FIGURE 7.—Wgg pouches of the tree hoppers: a, Pouch of the dark-colored tree hopper ; b, a pouch of the same with the bark removed to show the eggs; c, egg pouch of the green-clover tree hopper. XxX 3 NYMPHAL STAGES After falling to the alfalfa or other plants in the orchard, the young nymphs feed upon these plants, pass through five nymphal “stages (fig. 9), and become adult in late June or early July. Throughout the nymphal stages they live by sucking the juices from these plants. They are rarely observed during these stages, since they hide themselves at the very base of the plant upon which they are feeding. They prefer the semidark humid conditions prevailing in the center of alfalfa crowns. Fifty days and ninety days have been recorded as the two extremes for the length of the combined nymphal stages. The average length of time is ‘probably from about 60 to 80 days. During the nymphal stages the insects are of the same general shape as they are in the adult stage, but instead of the 10 CIRCULAR 106, U. S. DEPARTMENT OF AGRICULTURE hard shell covering they have many bristly spines decorating their backs and many small hairs covering their bodies. (Fig. 9, Tea They are of a creamy white to dark-brown color, and have a more or less mottled greenish appearance. ADULT STAGE Adults (fig. 1; fig. 9, G@ and H) make their appearance in late June and in July ‘and are present until the last of September, although few are seen after the middle of September. The insects as; fj = | fl ot q FIGURE 8.—A, Tree hoppers (Stictocephala inermis) hatching from eggs deposited in wounds in apple twig; B, empty eggshells protruding from the egg pouches or Oviposition wounds. xX 2 ; live about two months in the adult stage. During this time they feed to a limited extent upon the alfalfa or other cover crop, but their feeding is apparently of so little consequence, as is the case with the nymph, that no injury is attributed to it. The adults fly somewhat, especially when disturbed, and in this way become disseminated over the orchard and from one orchard or alfalfa field to another. . OVIPOSITION The adults spend most of the daytime on the fruit-tree twigs in which the females lay their eggs. Eggs are deposited from late in TREE HOPPERS AND THEIR CONTROL asi Wb Figure 9.—Life-history stages of the green-clover tree hopper, which is fairly characteristic of most of the species mentioned: A, Egg, * 15; B—F, first to fifth mymphalsstages (BB; << 202C x 4 Dy x12 BY xO S79) ix G, adult, front view,