Hélène Doughty

Toxicity, Feeding Preference, and Repellency Associated with Selected Organic Insecticides Against Acrosternum hilare, and Euschistus servus, (Hemiptera: Pentatomidae)

ARSTRACT Experiments were conducted to evaluate the toxicity, feeding preference, repellency, and field efficacy associated with the organic insecticides azadirachtin, pyrethrins, and spinosad against two stink bug species, Acrosternum hilare, (Say) and Euschistus servus, (Say) (Hemiptera: Pentatomidae). Laboratory toxicity bioassays were conducted using treated green bean pods. The conventional pyrethroid &lgr;-cyhalothrin was included for comparison. A. hilare, adults and nymphs were most susceptible to &lgr;-cyhalothrin and to tank mixes of pyrethrins + spinosad. E. servus, adults were susceptible to &lgr;-cyhalothrin, spinosad, and all tank mixes, whereas E. servus, nymphs were susceptible to &lgr;-cyhalothrin only. Feeding preference tests were conducted using insecticide-treated tomatoes and counting the number of feeding stylet sheaths on fruit after 24 h. All tomatoes treated with either azadirachtin, pyrethrins, or tank mixes resulted in fewer numbers of stylet sheaths than the untreated control, whereas treatment with spinosad alone did not. In filter paper repellency tests, both E. servus, and A. hilare, were repelled by pyrethrins and exhibited no response to azadirachtin. E. servus, was attracted to spinosad in comparison with a water-treated control; however, A. hilare, displayed no response. In field efficacy trials, each of the organic insecticides reduced the number of stink bugs in soybean, Glycine max, (L.) Merr., for up to 2 d after treatment; however, none of the insecticides reduced stink bug damage to fruit in tomatoes even after multiple applications. Implications for organic growers and integrated pest management programs are discussed.

Host Plant Preference of Harlequin Bug (Hemiptera: Pentatomidae), and Evaluation of a Trap Cropping Strategy for its Control in Collard

ABSTRACT Harlequin bug, Murgantiahistrionica (Hahn) (Hemiptera: Pentatomidae),is a piercingsucking pest of cole crops, causing cosmetic damage in low populations, while heavy pest pressure can kill plants or entire fields. Field studies were conducted to evaluate a trap crop for control of harlequin bug in collard. Field-cage choice tests found that potential trap crop plant species, mustard (Brassica juncea ‘Southern Giant Curled’), rapeseed (B. napus ‘Athena’), rapini (B. rapa), and arugula (Eruca sativa) attracted more harlequin bugs than collard (B. ohraeea ‘Champion’) and a nonbrassica control, bean (Phaseolus vulgaris ‘Bronco’). Mustard was the most consistently selected by harlequin bug over collard in choice tests, and was found to be an effective trap crop for reducing feeding injury on collard at two experimental sites. Augmentation of the mustard trap crop with a systemic, neonicotinoid insecticide provided no added control of harlequin bug for the 10 wk duration in the spring season.

Regional pest suppression associated with widespread Bt maize adoption benefits vegetable growers

Significance Area-wide Bacillus thuringiensis (Bt) adoption suppresses pests regionally, with declines expanding beyond the planted Bt crops into other non-Bt crop fields. The offsite benefits to vegetable crops from such pest suppression have not been documented. We show that widespread Bt field corn adoption is strongly associated with marked decreases in the number of recommended insecticidal applications, insecticides applied, and damage to vegetable crops in the United States. These positive impacts to growers, including organic producers, in the agricultural landscape expands on known ecological effects of Bt adoption. Transgenic crops containing the bacterium Bacillus thuringiensis (Bt) genes reduce pests and insecticide usage, promote biocontrol services, and economically benefit growers. Area-wide Bt adoption suppresses pests regionally, with declines expanding beyond the planted Bt crops into other non-Bt crop fields. However, the offsite benefits to growers of other crops from such regional suppression remain uncertain. With data spanning 1976–2016, we demonstrate that vegetable growers benefit via decreased crop damage and insecticide applications in relation to pest suppression in the Mid-Atlantic United States. We provide evidence for the regional suppression of Ostrinia nubilalis (Hübner), European corn borer, and Helicoverpa zea (Boddie), corn earworm, populations in association with widespread Bt maize adoption (1996–2016) and decreased economic levels for injury in vegetable crops [peppers (Capsicum annuum L.), green beans (Phaseolus vulgaris L.), and sweet corn (Zea mays L., convar. saccharata)] compared with the pre-Bt period (1976–1995). Moth populations of both species significantly declined in association with widespread Bt maize (field corn) adoption, even as increased temperatures buffered the population reduction. We show marked decreases in the number of recommended insecticidal applications, insecticides applied, and O. nubilalis damage in vegetable crops in association with widespread Bt maize adoption. These offsite benefits to vegetable growers in the agricultural landscape have not been previously documented, and the positive impacts identified here expand on the reported ecological effects of Bt adoption. Our results also underscore the need to account for offsite economic benefits of pest suppression, in addition to the direct economic benefits of Bt crops.