220 Research Article Received: 2 April 2010 Revised: 20 July 2010 Accepted: 30 July 2010 Published online in Wiley Online Library: 8 November 2010 (wileyonlinelibrary.com) DOI 10.1002/ps.2055 Mortality and reproductive effects of ingested spinosad on adult bollworms Juan D L ´ opez, Jr, Mohamed A Latheef and Wesley C Hoffmann * Abstract BACKGROUND: Upon emergence from their pupal cells, bollworm, Helicoverpa zea (Boddie), adults actively seek and feed on plant exudates before they disperse and reproduce on suitable host plants. This nocturnal behavior of the bollworm may be exploited as a pest management strategy for suppression of the insect by using an attractant/stimulant mixed with an insecticide to induce feeding to cause adult mortality or reproductive reduction/inhibition. This study aimed to determine in the laboratory whether or not spinosad when mixed with sucrose solution as a feeding stimulant and ingested by bollworm could influence mortality and reproduction of the insect. RESULTS: Sublethal concentrations of spinosad fed to laboratory-reared females confined with males significantly reduced percentage hatch of eggs at 0.1 mg L -1 , and it was reduced to near zero at 2.5 mg L -1 when compared with females fed 2.5 M sucrose solutions only. The lethal concentration (LC 99 ) for males captured from the field in sex-pheromone-baited traps was 73 mg L -1 for 24 h response. Proboscis extension response was not inhibited significantly even at 10 g L -1 . In spite of a 137-fold increase in lethal dose concentration, spinosad did not inhibit feeding. CONCLUSION: A detailed study of laboratory-reared and field-collected bollworm adults relative to mortality and reproduction after ingestion of spinosad indicates that spinosad would be useful in an attract-and-kill strategy to control the insect when mixed with a feeding attractant/stimulant. Field validation of the data is warranted. Published 2010 by John Wiley & Sons, Ltd. Keywords: spinosad; attract-and-kill; Helicoverpa zea; bollworm; corn earworm; adult control 1 INTRODUCTION Spinosad, a metabolite of Saccharopolyspora spinosa Mertz and Yao, is the active ingredient in Tracer  , a ‘Naturalyte’ insect control product that comprises two macrocyclic compounds, spinosyn A and spinosyn D. 1 It is both a contact and stomach poison for many caterpillar species and was registered in the United States in 1997 for use on cotton. Spinosad has low mammalian and environmen- tal toxicity, with reduced risk to wildlife compared with traditional insecticides. 2,3 It has also been formulated as Entrust  for use in organic production (Dow AgroSciences). In a season-long study, it was reported that cotton treated with spinosad was found to have fewer damaging larvae and higher numbers of beneficial insects compared with cotton treated with conventional pesticides. 4 The nocturnal and the post-emergence behavior of the bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), is to seek food as soon as it emerges from its pupal cells. 5 This nocturnal behavior of the adult could be utilized by developing a feeding attractant that could be used to attract adults to an area treated with a feeding stimulant and toxicant mixture. The adults would be induced to feed and thus cause mortality of the insect. Several authors have identified a number of feeding attractants for several noctuid species of Lepidoptera in the United States. 6–10 Recently, researchers have developed an attracticide for old-world bollworm, Helicovera armigera (H ¨ ubner), moths in Australia that is based on plant volatile compounds. 11,12 In a field study, H. zea suffered major mortality upon emergence when they fed on thiodicarb-baited sorghum–water mixture banded around corn. 13 In the Coastal Plains of Texas, it is estimated that a million H. zea moths would be killed in corn fields by treating one row width approximating 1 ha area with 20 g methomyl using 190 L of a sucrose-syrup-based feeding stimulant. 14 In a laboratory study, sublethal concentrations of emamectin benzoate mixed with 2.5 M sucrose solutions ingested by female H. zea moths significantly reduced larval hatch of eggs and significantly impacted upon the survival of larvae to the pupal stage, and killed the adults at higher concentrations. 15 The objective of the research reported here was to evaluate spinosad as the toxicant in a feeding stimulant formulation. The authors sought to characterize the effect of spinosad on toxicity, proboscis extension, gustation, reproduction and survival of the progeny when it is provided in a feeding stimulant solution to the adult bollworm. 2 MATERIALS AND METHODS 2.1 Test solutions Samples of spinosad 480 g L −1 SC (Tracer  ) were obtained from Dow AgroSciences, Indianapolis, Indiana. The appropriate amount ∗ Correspondence to: Wesley C Hoffmann, USDA-ARS, SPA, 2771 F & B Road, College Station, TX 77845, USA. E-mail: clint.hoffmann@ars.usda.gov USDA-ARS, SPA, Southern Plains Agricultural Research Center, Areawide Pest Management Research Unit, College Station, TX, USA Pest Manag Sci 2011; 67: 220–225 www.soci.org This article is a US Government work and is in the public domain in the USA