Beresford L. Cadogan

Evaluation of Tebufenozide Carry-Over and Residual Effects on Spruce Budworm (Lepidoptera: Tortricidae)

Abstract Laboratory and field studies investigated carry-over effects of tebufenozide on spruce budworm, Choristoneura fumiferana (Clemens). In the laboratory, third and fourth instars were fed either sublethal doses of tebufenozide (10 ppm) or water on Abies balsamea (L.) Mill. needles, reared to adulthood and allowed to oviposit on laying surfaces 1 or 14 d after being sprayed with water or tebufenozide concentrations of 17.5, 35.0, and 70.0 g/liter. Percentage adult emergence and sex ratio were not affected by larval ingestion of the tebufenozide. Also, the mean number of eggs laid on untreated wax paper by moths reared from tebufenozide-treated larvae was similar to the controls. Hence, tebufenozide did not inhibit carry-over effects on treated larvae. Oviposition on tebufenozide-treated wax paper by moths reared from untreated larvae was affected by both the substrate concentration and the age of the treatment residue. When offered treated and untreated laying surfaces simultaneously, C. fumiferana did not show a preference. However, significantly fewer eggs were laid on both laying surfaces by fewer females than when tebufenozide was absent. Residual tebufenozide on wax paper did not affect egg hatch but topical applications were toxic to eggs. Field studies appear to corroborate laboratory results and suggest that although the ingestion of tebufenozide by larval spruce budworm might not impair adult reproduction, the insecticide’s presence in the environment could inhibit oviposition. This inhibition was considered to be a primary factor in tebufenozide’s multi-year effects against spruce budworm populations.

Experimental aerial application of Matacil flowable insecticide to control spruce budworm (Lepidoptera: Tortricidae)

Abstract Matacil® (aminocarb)_180F flowable insecticide mixed in both water and insectide diluent ID585 and Matacil 1 · 8D oil-soluble concentrate (OSC) mixed in ID585 were sprayed aerially at 70 g a.i./1 · 51 of spray mix/ha in two applications to control spruce budworm, Choristoneura fumiferana (Clem.). The spray droplet density on Kromekote cards, the spray volume recovered on glass slides, larval population reductions and host tree defoliation were compared. The data indicate that Matacil 180F was as effective in controlling budworm populations and protecting the foliage of host trees as Matacil 1 · 8D and that the aqueous mix was as efficacious as the ID585 mix.

Deposition of aerially applied tebufenozide (RH5992) on balsam fir (Abies balsamea) and its control of spruce budworm (Choristoneura fumiferana (Clem.))

A field trial was conducted in 1994 to determine the foliar deposit of tebufenozide (RH5992), applied aerially, and its efficacy against spruce budworm, Choristoneura fumferana (Clem.). A commercial 240 g litre -1 formulation of the insecticide (Mimic 240LV) was mixed with water, dyed with a tracer dye (Rhodamine WT) and sprayed with a light fixed-wing aircraft. Six application strategies were tested. Five used 70 g AI ha -1 in a spray volume of 1 or 2 litre ha -1 with single or double applications; the sixth was an unsprayed control. Results show that the spectra of the spray applications were, with one exception, fairly uniform. Volume and number median diameters ranged from 100 to 130 μm and 27 to 72 μm, respectively. Mean number of drops cm -2 on Kromekote cards were <2.0 for strategies where either 1 or 2 litre ha -1 were sprayed. Nevertheless no one strategy produced droplet densities that were significantly different (P < 0.05) from the other strategies. Tebufenozide recovered from foliage averaged 2.5 to 5.9 μg g foliage -1 when 1 litre ha -1 was sprayed and 5.8 to 6.8 μg g foliage -1 after 2 litre ha -1 were sprayed. When a single application was the strategy used, the mean number of droplets cm -2 and μg tebufenozide g foliage -1 ranged from 1.2 to 1.4 and 2.5 to 5.9, respectively. With double applications, the same response parameters ranged from 0.3 to 1.9 and 2.5 to 6.8, respectively. Budworm population reductions (%) and the number of larvae that survived tebufenozide treatments were significantly different (P < 0.05) from the controls. After strategies that used 1 litre spray ha -1 , mean percentage population reductions ranged from 61.4 to 93.6 whereas populations were reduced by 85.6 to 98.3% when 2 litre ha -1 were sprayed. After double applications the mean percentage population reductions ranged from 93.6 to 98.3, but single application strategies resulted in mean reductions of 61 to 86%. Mean population reductions in the controls were 61%. The mean number of larvae per branch that survived spray strategies of 1 litre ha -1 ranged from 1.3 to 7.4, and from 0.4 to 1.3 when 2 litre ha -1 was the spray volume. In the controls an average of 10.2 larvae survived. With one exception, mean percentage defoliation in the treated areas was also significantly less (P < 0.05) than that in the control. Mean defoliation in trees sprayed at 1 litre spray ha -1 ranged from 40 to 62.8% whereas those treated at 2 litre ha -1 had mean defoliation levels from 31.5 to 62.8%. In contrast, average defoliation in the controls was 92.1%. When a single application was the spray strategy, mean defoliation ranged from 31.5 to 62.8%. These data imply that a double application of tebufenozide at 70 g in 2 litre ha -1 was the most efficacious strategy. However, analyses of the data also show that the primary influence on deposits and defoliation was interactions between number of applications and spray. Nevertheless the two independent variables acted without significant interactions when influencing percentage reductions of spruce budworm populations.

Control of spruce budworm (Lepidoptera: Tortricidae) with Bacillus thuringiensis applications timed to conserve a larval parasitoid

Abstract Field trials conducted in 1990 and 1991 demonstrated that commercial formulations of Bacillus thuringiensis var. kurstaki Berliner applied late to fifth and sixth instar spruce budworm Choristoneura fumiferana (Clemens) expressly to avoid affecting the larval parasitoid Apanteles fumiferanae Viereck were as efficacious in controlling spruce budworm populations as a regularly timed spray that was targeted against third and fourth instars. In 1990, with high budworm populations (50 to 70 larvae per 45 cm branch), the corrected budworm population reduction after the early spray (34.6%) was less but not significantly different (p > 0.05) from that in the late treatment (55.3%). Defoliation of balsam fir Abies balsamea (L.) Miller in the early and late spray treatments was also not significantly different [87.5 ± 8.8% and 70.3 ± 12.8% ( x ± s.d. ), respectively]from that in the control plots (87.1 ± 9.2%), but was considered unacceptably high. In 1991, with moderately high budworm populations (16–45 larvae per branch) the corrected budworm population reductions resulting from the early and late treatments (76.7 and 92.8%, respectively) were not significantly different (p > 0.05). The percentage defoliation in the late treatment (28.6 ± 12.3%) was significantly higher statistically than that in the early treatment (18.7 ± 7.6%) but was biologically acceptable. Both levels were significantly less than the defoliation observed in the check plots (42.2 ± 14.8%), which was unacceptably high. These results suggest that commercial formulations of Bt applied undiluted to moderately high budworm populations at 30 billion (109) international units (BIU) ha−1 can be judiciously delayed to conserve the survival of A. fumiferanae and still be efficacious.

Development and evaluation of a method for the design of spray applications: aerial tebufenozide applications to control the eastern spruce budworm, Choristoneura fumiferana (Clem.)

Abstract A novel approach to the design of insecticide spray applications was developed and evaluated in field trials to assess the efficacy of the insect moulting hormone analog tebufenozide (Mimic ® ) against the eastern spruce budworm, Choristoneura fumiferana (Clem.). The pest biology, and habitat and pesticide characteristics were used as a basis to derive the required active ingredient (a.i.) and deposit density. Ingestion is the primary exposure route; an LD 95 acquisition through foliage consumption by fourthinstar larvae was used to establish a target dose of 15 ng a.i. cm −2 in one drop per needle (2.5 cm −2 ). A range of a.i. and volume application rates were selected based on the required densities, canopy leaf area index and projected spray losses to the understorey and by drift; application rates of 35, 70 and 140 g a.i. 1 ha −1 were employed, with volume application rates of 1, 2 and 4 L ha −1 . Coniferous forest plots were aerially treated, resulting in average deposit densities (droplets cm −2 ) on artificial foliage between 0.8 and 3.7, with averge volumetric deposits between 7 and 30% of volume application rates. Population control was satisfactory, except for those applications at 35 g a.i. in 2 L and 70 g in 4 L ha −1 for which low deposit densities were observed. This approach to spray application design was found to be of scientific value and is adaptable to other insecticide applications.

Efficacy of tebufenozide applied by aircraft using only upwind atomizers to control spruce budworm (Lepidoptera: Tortricidae)

Abstract The efficacy of an aerial spray technique that used only two atomizers on the upwind wing to reduce drift was evaluated by comparing it with a conventional spray application that used two atomizers on each wing. The techniques were field tested in 1995 using double applications of tebufenozide at 70 g in 2 L ha −1 to suppress populations of spruce budworm Choristoneura fumiferana (Clem.) on balsam fir, Abies balsamea . The ‘upwind only’ technique emitted 35–69% of the flow rates (L min −1 ) and dosages (g AI ha −1 ) prescribed for and achieved by the conventional spray techniques. Nevertheless, spray deposit (drops cm −2 ) on kromekote cards did not differ significantly between the two application methods; but significantly more ( P P > 0.05) between the spray treatments but both were significantly better ( P