Roger D. Scharbach

Electrophysiological Response and Attraction of Emerald Ash Borer to Green Leaf Volatiles (GLVs) Emitted by Host Foliage

Green leaf volatiles (GLVs) function as host attractants, pheromone synergists, or sexual kairomones for a number of coleopteran folivores. Hence, we focused on host GLVs to determine if they were attractive to adults of the emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae), which feeds on ash (Fraxinus) foliage. Eight GLVs were identified by chromatography-electroantennogram (GC) and GC-mass spectrometry in foliar headspace volatiles collected in traps containing Super-Q from white ash, Fraxinus americana, and green ash, Fraxinus pennsylvanica, trees. GLVs in the aeration extracts elicited antennal responses from both male and female adults in gas chromatography-electroantennogram detection bioassays. Male antennae were more responsive than female antennae and showed the strongest response to (Z)-3-hexenol. Six field experiments were conducted in Canada and the USA from 2004 to 2006 to evaluate the attractiveness of candidate GLVs, in various lure combinations and dosages. Field experiments demonstrated that lures containing (Z)-3-hexenol were the most effective in increasing trap catch when placed on purple traps in open areas or along the edges of woodlots containing ash. Lures with (Z)-3-hexenol were more attractive to males than females, and dosage may be a factor determining its effectiveness.

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.

Host selection by Agrilus planipennis (Coleoptera: Buprestidae): inferences from sticky-band trapping

Abstract Sticky-band trapping experiments were undertaken in 2003–2006 to examine the host-seeking behaviour of the emerald ash borer, Agrilus planipennis Fairmaire, in woodlots in southwestern Ontario, Canada. The female proportion of A. plannipennis emerging from host logs ranged from 0.414 to 0.582. Landings on sticky-band traps varied more with the female proportion, ranging from 0.392 to 0.889, with the majority in the upper range, suggesting behavioural differences between the sexes. Correlations between landing density and tree size measured as diameter at breast height were positive or showed no relationship. In some locations more beetles were captured on the south side of the tree than on the north side; however, there was no difference between these cardinal directions at other locations. Numbers of captured beetles were never significantly greater on the north side of boles. We observed greater landing densities of adults of both sexes on traps on trees along the edges of woodlots than on trees within the woodlots. When given a choice under natural conditions, beetles landed almost exclusively on host trees (Fraxinus pennsylvanica Marsh. (Oleaceae)) rather than on other common trees species (Carya ovata (Mill.) K. Koch (Juglandaceae), Tilia americana L. (Tiliaceae), and species of Acer L. (Aceraceae)) found in the same woodlots. Our data suggest that A. planipennis make host-selection decisions while in flight rather than landing randomly. Implications for monitoring A. plannipennis using sticky-band traps and understanding its host-seeking behaviour are discussed.

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.

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