Western-spruce budworm

Western spruce budworm, Christoneura occidentalis, sixth instar stage Arsenic trioxide pestiferous species Dietary levels of 99.5 mg/kg FW killed 10%, 2250 mg/kg 7... 

Patterns in Defensive Natural Product Chemistry Douglas Fir and Western Spruce Budworm Interactions... 

Our objective Is to examine some aspects of current plant herbivore theory using Douglas-flr (Pseudotsuga menzlesll) and western spruce budworm (Chorlstoneura occldentalls). Both plant and herbivore are widespread In western North America. Natural hosts of the budworm Include Douglas-flr, species of Abies, and, on occasion, other conifers (9). Variation In budworm density occurs on both a geographic and local scale. We have frequently observed differential defoliation In trees having overlapping crowns at sites In Montana, Idaho, and New Mexico. 

Our focus was upon natural and experimental studies that were designed to Investigate various aspects of the current plant-herblvore theory using the Douglas-flr/western spruce budworm system. Specifically, we wished to test whether there are chemical characteristics In the young needle tissue of Douglas-flr that reduce the growth, survival, and adult fecundity of the western spruce budworm. Secondly, we were Interested In... 

Redak, R. "A Determination of the Resistance-Susceptibility Characteristics In Douglas-flr to the Western Spruce Budworm" MS Thesis, Unlv. of New Mexico, Albuquerque, NM, 1982, pp 1-74. 

The salts of fatty acids (not naturally occurring) have long been known to have insecticidal properties. The most effective potassium salts center around oleate in the monounsaturated and saturated series, although potassium caprate (Cio) was especially active against Choristoneura occidentalis (Western spruce budworm) and Acleris gloverana (Western blackheaded budworm) (117). 

Figure 1. Comparison of average number of western spruce budworm egg masses in treated and untreated areas,...

Himel and Moore (8), observed mostly small drops on western spruce budworm larvae. They used a fluorescent particle tracer in the mexacarbate spray. The question following their study was whether the drops from other pesticide tank mixes would behave in a similar manner. Was the deposition of drops on larvae influenced by physical properties of the tank mix, application technique, or other factors These and other questions provided the basis for investigations. In 1971 the FS initiated studies on an opportunity basis, to pursue the question of drop deposition on coniferous foliage. 

One study (18) showed that aerially applied pigmented mexacarbate particles observed on western spruce budworm larvae and Douglas-fir needles were minute (Table VII). Eighty-seven percent of the particles found on western spruce budworm larvae were less than 16 pm in diameter while 87 percent of the particles found on Douglas-fir needles were less than 11 ym in diameter. It is noteworthy that 76 percent of the particles observed on the larvae were 6 to 15 ym in diameter. We assune that the particle size distribution in the field was similar to the particle size distribution measured in the laboratory. 

Categories (um) Size distribution ( ) Impaction plates Western spruce budworm larvae Douglas-fir needles... 

Pheromone Purity. An intriguing challenge concerns chemical purity of disruptant formulations. For disruption purposes, is it necessary to treat with the precise blend of pheromone iscmers and secondary components or is only the major pheromone chemical necessary The answer to this question could be different for different pests, but in most cases it could influence treatment costs. Our experience with the western spruce budworm, Choristoneura occidentalis. Freeman, suggests that only the major component of that pheromone is necessary for disruption. Conversely, some recent work on an orchard pest (9) indicates that a complete pheromone-blend disruption treatment is more effective. 

Between-Year Population Variation in Resistance of Douglas-fir to the Western Spruce Budworm... 

WILSON, J.S., ISAAC, E.S., GARA, R.I., Impacts of mountain pine beetle Dendroctonus ponderosae) (Col., Scolytidae) infestation on future landscape susceptibility to the western spruce budworm Choristoneura occidentalis) (Lep., Tortricidae) in north central Washington, J. Appl. Entomol, 1998, 122, 239-245. 

Our efforts on western spruce budworm have thus far been limited to survey applications. Specifically, we have been attempting to correlate moth captures (in pheromone-baited traps) with larval densities and/or defoliation on a series of test plots. We would like to expand this effort in the future, and also explore use of the budworm attractant for control purposes. 

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