Seasonal and geographical toxicity of Indoxacarb against Helicoverpa armigera and influence of different host plants against Indoxacarb in India, 2005–2007

Abstract Indoxacarb, an oxadiazine insecticide, was evaluated for its effectiveness against Helicoverpa armigera collected from selected locations in India. Determination of Indoxacarb efficacy was done using a log‐dose probit (LDP) bioassay against third instars collected from cotton (Gossypium arborium) fields near Akola, India. Monthly levels of toxicity of Indoxacarb were determined from July 2005 to March 2007. The maximum tolerance level of Indoxacarb was reported for the Amaravati strain (5.09 p.p.m.) and the minimum tolerance level for the Fatehbad strain (0.22 p.p.m.). Seasonal monitoring of Indoxacarb toxicity revealed an increased trend in tolerance from July 2005 to February 2006, which decreased from March 2006. The LC50 of Indoxacarb was 2.71 p.p.m. in July 2005 and 17.14 p.p.m. in February 2006. During 2006–2007, the LC50 was 3.84 p.p.m. at the start of the season and in March 2007 it was 13.51 p.p.m. The minimum LC50 of Indoxacarb was reported for H. armigera larvae fed on Legasca spp. (1.62 p.p.m.) and the maximum LC50 was reported for H. armigera reared on chickpea (Cicer arietium) (8.45 p.p.m.). LC50 of 2.73 and 4.56 p.p.m. were reported for H. armigera fed on cotton (Gossypium arborium) and pigeonpea (Cajanus cajan), respectively.