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Refuge crop performance as part of the B t resistance management strategy for H elicoverpa spp. ( L epidoptera: N octuidae) in A ustralian cotton production systems
Author(s) -
Baker Geoff H,
Tann Colin R
Publication year - 2014
Publication title -
austral entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.502
H-Index - 39
eISSN - 2052-1758
pISSN - 2052-174X
DOI - 10.1111/aen.12072
Subject(s) - bt cotton , biology , noctuidae , agronomy , helicoverpa , crop , resistance (ecology) , pest analysis , horticulture
The emergence of B t resistance among key insect pests (especially N octuidae) is a major threat to the deployment of transgenic ( B t) cotton crops, used to combat these pests, worldwide. Refuge crops are, therefore, commonly grown in association with B t cotton to generate large numbers of B t‐susceptible insects, thus reducing the risk of B t resistance. In A ustralian B t cotton production systems, where the primary pests are H elicoverpa moths, refuge crops are mandatory, and pigeon pea and non‐ B t cotton are the refuge options available to growers. When B t cotton was first deployed (in the mid 1990s), pigeon pea was assessed as having twice the capacity to produce H elicoverpa moths as unsprayed, non‐ B t cotton. Only half the amount (in area) of pigeon pea was, therefore, required to be grown as a refuge compared with unsprayed, non‐ B t cotton. The agronomy, insecticide use, varieties of B t cotton (now based on two B t genes ( B ollgard II ®), compared with the original single gene ( I ngard®) varieties) and farmer profit margins have, however, changed radically since then. This has led to questioning of the continued relativities and best management practices involving these refuge crops. This paper assesses the performance records of pigeon pea and non‐ B t cotton refuges in the cotton production systems of eastern A ustralia since 1996. Pupae abundance is used as a surrogate for moth production. Pigeon pea has maintained its substantial superiority over unsprayed, non‐ B t cotton as a refuge generator of H elicoverpa throughout both the I ngard and B ollgard II eras. This is supported by field counts of both live pupae and empty pupal cases left behind in the soil when moths have emerged. There was some evidence that H elicoverpa production has decreased in time in both pigeon pea and cotton refuges. The incidence of parasitism of pupae has increased from the I ngard to the B ollgard II era. This latter change may, at least in part, explain a reduction in H elicoverpa productivity from refuges in recent years. There was no evidence to support a difference in parasitism of H elicoverpa between the two refuge crop types, but a temporal shift in parasite community ( T achinidae becoming more common) was apparent.