s ^MONTANA DEPARTMENT OF NATURAL 77 RESOURCES AND CONSERVATION ■ DIVISION OF FORESTRY INSECT AND DISEASE REPORT Montana State Library Missoula, Montana 59801 Report 77-1 3 0864 1006 4762 0 942.49 February 1977 GROUND APPLICATION OF FOUR INSECTICIDES ON DOUGLASFIR TUSSOCK MOTH AND WESTERN SPRUCE BUDWORM POPULATIONS IN MONTANA By Steve Kohler, Entomologist Cooperative Forest Management Division of Forestry SUMMARY Four insecticides (Sevin, Orthene, Pyrocide Growers Spray and Dimilin) were tested against Douglasfir tussock moth larvae, Orgyia pseudotsugata (McDunnough) , and western spruce budworm larvae, Choristoneura occidentalis Freeman, on Douglasfir near St. Ignatius, Montana, in June, 19 76. Hydraulic spray equipment was used to treat four groups of five trees each. All treatments were highly success- ful, with corrected percent control of 100 for Douglasfir tussock moth and from 86 to 100 for western spruce budworm. INTRODUCTION The importance of damage to western forests by outbreaks of Douglas- fir tussock moth, Orgyia pseudotsugata (McDunnough) and western spruce budworm, Choristoneura occidentalis Freeman, has been well documented (Tunnock, 1973; Johnson and Denton, 1975) . Loss of or damage to high-value trees in homeowner's yards, trailer courts, cemeteries, camp and picnic grounds, etc., need not be tolerated. The objectives of this test were? 1. To test and compare the effectiveness of ground applications of four chemical insecticides in reducing Douglasfir tussock moth and western spruce budworm larval populations on individual trees. 2. To provide data for registration by the manufacturer of one or more chemical insecticides which may be used by homeowners and land managers to protect individual high-value trees under attack by Douglasfir tussock moth or western spruce budworm. MATERIALS AND FORMULATION After consultation with the USDA Douglasfir Tussock Moth Research and Development Program, the USDA Forest Service Insecticide Evalu- ation Project, and the USDA Forest Service Methods Application Group, the following materials and formulations were selected from several candidates: Sevin (carbaryl) - Sevin SOW (50 percent wettable powder) was pro- vided by Union Carbide Corporation and was applied at a dosage rate of 1 pound a.i. per 100 gallons of water. Orthene - Orthene 75S (75 percent soluble powder) was provided by Chevron Chemical Company a#d was applied at a dosage rate of .5 pound a.i. per 100 gallons of water. Stabilized Pyrethrins - Pyrocide Growers Spray 7083 (1.4 percent liquid concentrate) was provided by McLaughlin Gormley King Company and was applied at a dosage rate of .1 pound a.i. per 100 gallons of water . Dimilin - Dimilin W-25 (T-H 6040) (25 percent wettable powder) was provided by Thompson Hayward Chemical Company and was applied at a dosage rate of 2 ounces a.i. per 100 gallons of water. TEST DESIGN Each treatment, including the check, consisted of one open-grown Douglasfir tree 20-50 feet tall. The treatments were replicated five times, so that a group of five trees was treated with each of - 2 - the four insecticides and a group of five trees served as checks. Tree groups were separated sufficiently to minimize spray drift be- tween groups. Insecticides were applied June 25, 1976. Application was timed so that Douglasfir tussock moth egg hatch was completed and the larvae had migrated to the foliage and begun feeding. Lar- val development for the two species on the day previous to spraying was as follows: Douglasfir Tussock Moth Larval Instar Percent First 84 Second 16 Western Spruce Budworm Larval Instar Percent Second 4 Third 14 Fourth 26 Fifth 29 Sixth 27 Larval populations were sampled the day before spraying and 4 days after treatment with Orthene and Pyrocide Growers Spray, 4 and 8 days after treatment with Sevin, and 8 and 14 days after treatment with Dimilin. Larval populations for each period were sampled by clipping eight 15-inch branches from mid-crown of each treatment tree with an extendable pole pruner equipped with catch basket. Larvae on the sample branches were counted in the field and ex- pressed as number per 1,000 square inches of foliage. Four categor- ies of larvae were recorded: (1) Douglasfir tussock moth, (2) west- ern spruce budworm, (3) sawflies (Neodiprion sp.), and (4) other lepidopterous larvae (mainly Geometridae and Dioryctria sp.) Spray was applied using a Division of Forestry fire pumper equipped with a 200 gallon fiberglass tank and a centrifugal four-stage WGC-4-SP Pacific pump. The nozzle used was an Elkhart Select-O-Flow, adjustable from 10 to 30 gallons flow per minute. All sprays were applied to the point of run-off. An average of 5 to 10 gallons of spray was applied per tree. RESULTS Test results were highly successful and indicated that any of the four materials would be suitable for control of Douglasfir tussock moth or western spruce budworm on high-value trees by private home- owners and land managers. Although the test sprays were applied with equipment that developed up to 200 p.s.i. pressure and was capable of reaching to heights of 50 feet and more, any of a variety of conventional sprayers available to private landowners would be sufficient to apply the material. The important consideration with non-persistent sprays is to insure that the entire tree crown is fully covered. Results of the tests are summarized in the following tables? Douglasfir Tussock Moth Prespray Density!/ Postspray Density— 2/ Percent Reduction-' Treatment 4 day 8 day 14 day 4 day 5 8 day 8 14 day Check 3.62 3.39 3.34 2.73 25 Sevin 7.99 0.32 0.00 96 100 — Orthene 6.79 0.00 — — 100 — — Pyrocide 7.83 0.00 — — 100 — — Dim'ilin 5.03 — 0.60 0.00 — 87 100 Western Spruce Budworm Treatment Prespray Density!/ Postspray Density- 4 day 8 day 14 day 2/ Percent Reduction- 4 day 8 day 14 day Check 21.15 18.19 22.18 16.70 14 0 21 Sevin 23.72 0.95 0.31 — 95 99 — Orthene 12.73 0.00 — — 100 — — Pyrocide 6.71 0.28 — — 95 — — Dimilin 17.06 — 7.79 1.90 — 62 86 1/ Larvae per 1000 in. foliage surface. 2/ Percent control was corrected according to Abbott's formula - 4 - Sawfh'es (Neodiprion sp.) Treatment Prespray Densityl/ Postspray Density- 4 day 8 day 14 day Percent Reduction— 4 day 8 day 14 day Check 3.90 5.55 2.13 1.82 0 45 53 Sevin 3.73 0.00 — — 100 — — Orthene 6.23 0.00 — — 100 — — Pyrocide 19.58 0.00 — — 100 — — Dimilin 16.78 2.10 0.00 — 76 100 Other lepidopterous larvae (Chiefly Geometridae and Dioryctria sp.) Treatment Prespray Density!/ Postspray Density— 4 day 8 day 14 day 2/ Percent Reduction— 4 day 8 day 14 day Check Sevin Orthene Pyrocide Dimilin 3.62 2.13 1.98 1.12 0.84 2.77 0.32 0.31 0.00 4.56 0.31 3.64 1.20 0.00 23 0 81 85 80 — 100 _-_ 100 1/ Larvae per 1000 in. foliage surface. 2/ Percent control was corrected according to Abbott's formula, - 5 - REFERENCES Johnson, P. C, and R. E. Denton, 1975. Outbreaks of the western budworm in the American Northern Rocky Mountain area from 1922 through 1971. USDA Forest Service, Gen, Tech. Rep. INT-20. Tunnock, S. 1973. The Douglasfir tussock moth in the Northern Region a cartographic history of outbreaks from 1928 to 1973. USDA Forest Service, Northern Region, Division of State and Private Forestry, Rept. No. 73-27. Test materials were contributed by the following companies: Chevron Chemical Company McLaughlin Gormley King Company Thompson Hayward Chemical Company Union Carbide Corporation The work leading to this publication was funded in part by a U. S. Department of Agriculture sponsored program titled "Expanded Douglasfir Tussock Moth Research and Development Program" . 6 -