THE EFFECTS OF ZECTRAN ON THE PARASITOIDS OF THE SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE)

Abstract

Can. Ent. 106: 545-554 (1974) Where the insecticide Zectran was used to protect foliage from feeding of the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae), the per cent parasitism of dipteran parasitoids (Tachinidae) showed a statistically significant lower value. In treated areas, the per cent parasitism of the hymenopteran Ephialtes ontario (Cresson) (Ichneumonidae) was lower;Meteorus trachynotus Viereck was about the same; Apanteles fumiferanae Viereck, Glypta fumiferanae (Viereck) (Braconidae), and Trichogramma minutum Riley (Trichogrammatidae) were greater. None of these differences was statistically significant. Results were consistent for the 2 years of study with the exception of E. ontario which showed a significant lower percentage parasitism in areas treated 1 year. Absolute population numbers of parasitoids were lower than is suggested by comparisons of apparent parasitism levels. The lowest absolute numbers were found in tachinids and E. ontario. Parasitic hymenopterans and dipterans were among the adult insects killed by the aerial application of Zectran but none of the species collected was a major spruce budworm parasitoid. 545

LONG-TERM EFFECTS OF AERIAL APPLICATIONS OF VIRUS–FENITROTHION COMBINATIONS AGAINST THE SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE)

“…Egg parasitism by Trichogramma minutum Riley was 2to 7-fold higher in the treated plots than in the untreated check in the year of application. These observations compare favourably with reports by Jaynes and Drooz (1952), Thomas (1966), and Leonard and Simmons (1974) that T. minutum incidence increased in plots treated with Zectran and DDT. Kettela and Varty (1972), however, found no gross differences in T .…”

“…The dramatic increased incidence of parasitism in the chemical insecticide-alone plot is enigmatic but apparently not unique. Macdonald (1959), Williams et al (1969), and Leonard and Simmons (1974) have observed higher densities of the spruce budworm larval parasite Apanteles fumiferanae Viereck in areas treated with DDT and Zectran. Macdonald considered it possible that parasitized larvae were less active and less likely to contact residual deposits of the insecticide.…”

THE NORTH AMERICAN SPECIES OF THE GENUS ACHRYSOCHAROIDES (HYMENOPTERA: EULOPHIDAE)

“…These observations compare favourably with reports by Jaynes and Drooz (1952), Thomas (1966), and Leonard and Simmons (1974) that T. minutum incidence increased in plots treated with Zectran and DDT. These observations compare favourably with reports by Jaynes and Drooz (1952), Thomas (1966), and Leonard and Simmons (1974) that T. minutum incidence increased in plots treated with Zectran and DDT.…”

THE EFFECTS OF BACILLUS THURINGIENSIS ON PARASITOIDS OF THE WESTERN SPRUCE BUDWORM, CHORISTONEURA OCCIDENTALS (LEPIDOPTERA: TORTRICIDAE), AND THE SPRUCE CONEWORM, DIORYCTRIA RENICULELLOIDES (LEPIDOPTERA: PYRALIDAE), IN MONTANA

“…on the parasitoids per se; rather, they are a function of host response prior to and after spraying. Similar results have been reported by other investigators (Leonard and Simmons 1974;MacDonald 1959;and Williams et al 1969) when the materials Zectrann and DDT were applied. Kettela and Varty (1972) noted that parasitism is an important factor, but not a key one, in the dynamics of epidemic budworm populations.…”