Discovery and development of a new semiochemical biopesticide for cotton pest management: assessment of extract effects on the cotton pestHelicoverpaspp.

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Abstract

The Australian cotton production system is dominated by transgenic Bt (Bollgard II®) cotton varieties, Gossypium hirsutum L. (Malvaceae). These provide good control of lepidopteran pests (Helicoverpa spp.; Noctuidae) but are not effective against sucking pests. Recent trends in the frequency of resistance alleles in Helicoverpa spp. indicate the threat of pest resistance. Therefore, new technologies are required to manage the development of resistance and the resurgence of sucking pests. Consequently, the study was aimed to develop a semiochemical product able to deter feeding and oviposition of Helicoverpa spp., as well as cause direct mortality to the pest on transgenic and non-transgenic crops. Plants including sorghum, sweet corn, pigeon pea, and lucerne (used as refuge crops in cotton), various cotton genotypes (MHR11, Lumein, and Sicala VII), and the native plant Clitoria ternatea L. (Fabaceae) were cultivated within cotton crops and in cages, and assessed for the occurrence of oviposition by Helicoverpa spp. and survival of the pest larvae. The results indicated that pigeon pea, cotton, sorghum, and sweet corn were most preferred for Helicoverpa spp. oviposition and feeding, whereas C. ternatea was least preferred. We used a solid phase extraction technique to obtain six fractions of an extract of C. ternatea, which we assessed for bioactivity against Helicoverpa spp. We found that fractions 2, 3, 4, and 6 had oviposition and feeding deterrence as well as direct toxicity to Helicoverpa spp. Clitoria ternatea fractions 2, 3, 4, and 6 have been developed into a product (Sero-X®) that is effective against Helicoverpa spp. and sucking pests, and is in an advanced stage of commercialisation.

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