Insects (2020) 11 (7 - 431)

Fernando R. da Silva, Dario Trujillo, Oderlei Bernardi, Jose Carlos Verle Rodrigues, Woodward D. Bailey, Todd M. Gilligan and Daniel Carrillo (2020)
Comparative toxicity of Helicoverpa armigera and Helicoverpa zea (Lepidoptera: Noctuidae) to selected insecticides
Insects 11 (7 - 431)
Abstract: Until recently, the Old World bollworm (OWB) Helicoverpa armigera (Hübner) and the corn earworm Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) were geographically isolated. Both species are major pests of agricultural commodities that are known to develop insecticide resistance, and they now coexist in areas where H. armigera invaded the Americas. This is the first study to compare the susceptibility of the two species to conventional insecticides. The susceptibility of third instar H. armigera and H. zea larvae to indoxacarb, methomyl, spinetoram, and spinosad was determined using a diet-overlay bioassay in a quarantine laboratory in Puerto Rico. Mortality was assessed at 48 h after exposure for up to eight concentrations per insecticide. Spinetoram exhibited the highest acute toxicity against H. armigera, with a median lethal concentration (LC50) of 0.11 µg a.i./cm², followed by indoxacarb and spinosad (0.17 µg a.i./cm² for both) and methomyl (0.32 µg a.i./cm²). Spinetoram was also the most toxic to H. zea (LC50 of 0.08 µg a.i./cm²), followed by spinosad (0.17 µg a.i./cm²) and methomyl (0.18 µg a.i./cm²). Indoxacarb was the least toxic to H. zea, with an LC50 of 0.21 µg a.i./cm². These findings could serve as a comparative reference for monitoring the susceptibility of H. armigera and H. zea to indoxacarb, methomyl, spinetoram, and spinosad in Puerto Rico, and may facilitate the detection of field-selected resistance for these two species and their potential hybrids in areas recently invaded by H. armigera.
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Database assignments for author(s): Oderlei Bernardi, José C.V. Rodrigues, Daniel Carrillo

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Helicoverpa armigera	Soybean (Glycine max)	Brazil (NW)
	Helicoverpa zea	Pigeonpea (Cajanus cajan)	Puerto Rico