Michael P. Hoffmann

Pheromone blends of green stink bugs and possible parasitoid selection.

It is confirmed from a literature review and new research that different pheromone strains exist in Nezara viridula from different geographical regions and that males from the sister genus Acrosternum emit bouquets of distinctive ratios of the same sesquiterpenes as in N. viridula. Many tachinid parasitoids use heteropteran pheromones as kairomones, and it is suggested that the chemical similarity of pheromones of N. viridula and Acrosternum has facilitated the adoption of N. viridula as a host by tachinids in the New World.

Determining parasitoid species composition in a host population: a molecular approach.

Abstract Larvae of closely related parasitoid taxa often lack morphological differences that can be used for species level identification. Determining the parasitoid species present in a host population may require rearing, often a time-consuming process. To monitor field parasitism rates by several species of Peristenus wasps (Hymenoptera: Braconidae) that are natural enemies of Lygus (Heteroptera: Miridae), we have developed a two-step molecular approach. Polymerase chain reaction (PCR) of the COI gene with wasp-targeting primers is performed on DNA extracted from a Lygus nymph and the parasitoid larva (if any) therein. A positive reaction indicates parasitoid presence. A restriction digest of the PCR product then indicates which parasitoid species is present among known alternatives, and a diagnosis is achieved in days rather than weeks or months.

Inoculative releases of Trichogramma ostriniae for suppression of Ostrinia nubilalis (European corn borer) in sweet corn: field biology and population dynamics

Abstract The effectiveness of inoculative releases of Trichogramma ostriniae Pang and Chen for suppression of Ostrinia nubilalis (Hubner) in sweet corn was assessed. Early-season, low-density (75,000 females ha −1 ) releases were made, and establishment, levels of parasitism and sex ratios of emerging T. ostriniae quantified. T. ostriniae established effectively for each season that they were released, but appeared to be unable to overwinter. Parasitism levels tracked egg mass numbers closely, and T. ostriniae persisted in fields even where insecticides were applied. Parasitism by indigenous Trichogramma species was ∼3%. Field populations of T. ostriniae were distinctly female biased (∼78%), with males produced in the majority of broods. Numbers of males did not increase linearly with number of O. nubilalis eggs parasitized, but appeared to remain constant above an egg mass size of about 20 eggs. A Type-I functional response to increasing egg and egg mass density was found under field conditions, where the proportion of egg masses parasitized remained constant with increasing egg mass density. A relatively consistent percentage of eggs per egg mass was parasitized, with a linear increase in number of eggs parasitized with increasing number of eggs per egg mass. These results show that T. ostriniae established viable reproductive populations in sweet corn following inoculative release, with the potential to contribute to reduced dependence on insecticides for the control of O. nubilalis in an integrated pest management program.

Life Table Studies of European Corn Borer (Lepidoptera: Crambidae) with and without Inoculative Releases of Trichogramma ostriniae (Hymenoptera: Trichogrammatidae)

Abstract Life table studies of European corn borer, Ostrinia nubilalis (Hübner), populations with and without inoculative releases of Trichogramma ostriniae (Peng & Chen) were conducted in sweet corn and field corn. Inoculative releases of T. ostriniae (at 72,000 females per hectare) provided relatively high parasitism of European corn borer eggs (≈37%) throughout the season. The increase in egg parasitism was not offset by compensatory changes in other mortality rates such as egg predation, eggs not hatching, and death of early instars after egg hatch. Early instar disappearance was a key mortality factor accounting for >70% of total mortality from egg deposition to established larvae. Egg parasitism by T. ostriniae was also a key mortality factor. Releases of T. ostriniae increased total egg and larval mortality of O. nubilalis from 61 to 92% in sweet corn and from 80 to 93% in field corn.

Novel Chitinolytic Enzymes with Biological Activity Against Herbivorous Insects

The soil bacteria, Streptomyces albidoflavus, secretes endochitinases and chitobiosidases that are active over a broad range of pH (4–10). Ingestion of this mixture of chitinolytic enzymes significantly reduced the growth and development of Trichoplusia ni and significantly reduced survival of Myzus persicae, Bemisia argentifolii, and Hypothenemus hampei. Perfusion chromatography was used to separate endochitinases from chitobiosidases. The endochitinases had significantly greater biological activity against Bemisia argentifolii than the chitobiosidases. The utility of chitinolytic enzymes as regulators of populations of herbivorous insects is discussed.

Control of corn flea beetle and Stewart's wilt in sweet corn with imidacloprid and thiamethoxam seed treatments.

Abstract Two field-plot experiments were conducted in western and central New York to evaluate imidacloprid and thiamethoxam seed treatments for control of corn flea beetle, Chaetocnema pulicaria Melsheimer, and Stewarts bacterial wilt in three varieties of sweet corn. Seed treatments significantly reduced flea beetle feeding injury to leaves in all varieties and reduced disease incidence 37–83% in the susceptible variety ‘Sprint’. Seed treatments did not control Stewarts wilt as effectively as genetic resistance. Disease incidence in the resistant varieties ‘Dynamo’ and ‘Bonus’ was relatively low (⩽5%) with or without a seed treatment. Additional on-farm evaluations conducted in western New York confirmed the results obtained from our field plots with incidence of Stewarts wilt ≈88% lower in imidacloprid-treated fields compared with non-treated fields. Laboratory germination tests indicated that seed treatments with imidacloprid may have some phytotoxic effects, depending on sweet corn variety and vigor of the seed lot. A general recommendation is that only high quality seed lots should be treated with imidacloprid and that carry-over seed should not be used.

Using Comparative Feedback to Influence Workplace Energy Conservation: A Case Study of a University Campaign

Although research suggests that feedback on energy usage can generate savings in residential and organizational settings, investigations into the effectiveness of comparative feedback efforts have been fragmented and the findings inconclusive. To help fill this gap, we present research on the effectiveness of a comparative feedback campaign in promoting energy conservation at a university. Surveys were administered in 2009 (n = 2,112) and 2012 (n = 1,601) to measure the extent to which a comparative feedback campaign influenced behavioral determinants, such as conservation-related subjective norms, perceived behavioral control, and attitudes, as well as self-reported behaviors. Results indicate that respondents in participating buildings increased their energy conservation behaviors and perceptions of descriptive norms. Furthermore, participating buildings reduced their energy consumption (kWh/ft2) by 6.5%, whereas non-participating buildings increased energy consumption by 2.4%. Our results show promise for comparative feedback-based campaigns as effective pro-environmental interventions within organizations and provide direction for future research and practice.

A Male-Produced Aggregation Pheromone Facilitating Acalymma vittatum [F.] (Coleoptera: Chrysomelidae) Early-Season Host Plant Colonization

We conducted field studies to investigate the involvement of volatile cues in early-season host plant colonization by striped cucumber beetle, Acalymma vittatum (F.) (Coleoptera: Chrysomelidae). Wind-directed traps were baited with male or female A. vittatum, potted cucumber (Cucumis sativus) seedlings that were of near-isogenic lines which either contained or lacked cucurbitacin, or combinations of male or female A. vittatum feeding on one or the other cucumber variety. We found no response to undamaged plants of either cucumber variety or plants that were actively being fed upon by A. vittatum females, whereas the response to volatiles associated with male A. vittatum was strong. Both male and female conspecifics and totals of up to sevenfold the number of males in the trap lures were caught overnight. Feeding males attracted more than double the number of conspecifics that responded to nonfeeding males. Active consumption of cucurbitacin in the plant on which the males were feeding, however, had no effect on attraction. A shift in sex ratio from a male to a female bias during field colonization season also supports the hypothesis that host finding is initiated by “pioneer” males. The importance of this aggregation pheromone in early-season host plant colonization and the evolutionary and adaptive significance of this pheromone are discussed.

Application of synthetic sex pheromone for management of diamondback moth, Plutella xylostella, in cabbage

Over a 2‐year period field trials were conducted to assess the potential to disrupt mating ofPlutella xylostella (L.) using a commercial rope formulation of a 70:30 mixture of (Z)‐11‐hexadecenal and (Z)‐11‐hexadecenyl acetate, two components of the sex pheromone of the female. Screened field cages were placed into blocks of cabbage which were either treated with the pheromone or left untreated. Different densities of P. xylostella pupae were placed into each cage and then larval and pupal counts were made of the subsequent generation. In addition, sentinel females at mating stations were placed in each cage to assess the influence of the pheromone on the ability of males to locate and mate with females. Likewise, we used pheromone traps to assess whether the pheromone treatment influenced the ability of males to locate a pheromone source. In both years larval and pupal populations, produced as a result of the original inoculation, did not differ between pheromone‐treated and untreated fields. The effect of pheromone treatment on larval and pupal numbers did not change with changes in inoculated P. xylostella density, however, the density of P. xylostella released caused significant differences in the density of the subsequent generation. No significant differences were detected between the number of sentinel female adult P. xylostella that successfully mated in pheromone‐treated fields compared with untreated fields. Significant differences in the numbers of male P. xylostella caught in pheromone‐baited traps occurred between pheromone‐treated and untreated fields in the first trial of 1993, and in the first trial in 1994 but not in the second trial. Such differences are often thought of as indications of mating disruption, although our other data presented in this study and reports from other studies indicate this is not always the case. Previous studies on mating disruption of P. xylostella in larger scale field tests have been performed but the results have been variable and often ambiguous. Overall, our results indicate that mating disruption of P. xylostella with the present technology does not appear to work even under the very controlled situations which we utilized to eliminate insect movement between plots.

Host color preferences and short-range searching behavior of the egg parasitoid Trichogramma ostriniae

The color of lepidopteran eggs often varies by species or egg condition, and parasitoids that attack lepidopteran eggs could therefore potentially use color to obtain information about host identity or quality. The objective of our study was to determine whether females of the egg parasitoid Trichogramma ostriniae Pang & Chen (Hymenoptera: Trichogrammatidae) showed differential responses to egg color when searching for hosts over short distances and when evaluating the suitability of encountered eggs. We examined the wasps’ host‐selection behavior in a Petri dish arena using white, yellow, green, and black clay beads as egg models presented against a green background (to mimic leaf color). In no‐choice tests, bead color had a significant effect on the proportion of tested wasps that accepted a bead for further examination, on the time it took wasps to find and begin examining a bead, and on the time that wasps spent examining the beads. However, bead color had only a marginally significant effect on the proportion of wasps attempting to drill into a bead with their ovipositors, and no significant effect on the amount of time they spent drilling. The wasps also showed significant color preferences when given a choice between two adjacent beads of different colors. The results of the no‐choice and choice trials taken together indicated a color preference ranking of yellow > white > green > black. The wasps’ higher preference for the yellow and white egg models generally corresponds to the white or yellowish‐white egg color of T. ostriniaes target host, the European corn borer moth, Ostrinia nubilalis Hübner (Lepidoptera: Crambidae). The wasps’ strong rejection of black egg models is likely to be an adaptive response that reflects the fact that eggs that are wholly or partially black are often unsuitable for parasitization due to advanced caterpillar development, damage to the egg, or previous parasitization.