Biology, ecology and management of the green mirid, Creontiades dilutus (Stål) in Australia
Cotton Catchment Communities CRC, Locked Bag 1001, Narrabri, NSW 2390 and School of Rural Science & Agriculture, University of New England, Armidale NSW 2351, Australia
Correspondence: peter.gregg@cotton.crc.org.au
The genus Lygus does not occur in Australia. Its nearest analogue, in terms of biology, ecology and pest management, is the green mirid Creontiades dilutus (Stål) (GM). Other papers dealing with the damage, economic thresholds, chemical control and pheromones of GM will be presented at this conference. The aim to this paper is to provide an overview of the biology, ecology and management of the species as background to these presentations. C. dilutus is one of two significant Australian pest species in the genus Creontiades Distant, the other being the brown mirid, C. pacificus (Stål). These species attack lucerne, various grain legumes, peanuts and stone fruit, as well as a range of introduced weeds and native host plants. The most important crop affected is cotton, and C. dilutus is the most widespread and common of the two species on cotton. Prior to the late 1990's GM was regarded as a minor pest, but with the introduction of single gene transgenic cotton (Ingard®) in 1996, followed by two-gene Bt cotton (Bollgard II®) in 2004, it has become increasingly important. Transgenic Bt varieties now account for about 80% of the Australian cotton crop. Insecticide use against lepidopteran pests, notably Helicoverpa spp., has been reduced to about 15% of that on conventional cotton. These insecticides previously reduced numbers of GM, so the species is now emerging as a serious pest, and as an obstacle to IPM in cotton. License costs for transgenic varieties are high, so growers seek to protect their investment and thus economic thresholds for GM are low. Insecticides used against GM are cheap but relatively non-selective, and can flare secondary pests like aphids, mites and whitefly. Knowledge of the biology and ecology of GM is limited, reflecting its recent elevation in pest status. Questions such as whether overwintering reproductive diapause exists, and whether GM is a long-range migrant from inland Australia (as some other cotton pests are) remain unanswered, although some research is in progress. Natural enemies of GM have been identified using ELISA. Spiders, damsel bugs and ladybirds are important generalist predators, but no specific parasites have yet been identified. IPM strategies for GM have been largely limited to the use of lucerne (a highly preferred host) as a trap crop, combined with low rate insecticide/salt mixtures and efforts to promote higher economic thresholds. Current research on biopesticides and semiochemicals may increase the options for IPM. A morphologically similar mirid has recently been reported damaging cotton in southern Texas. It was previously described as C. dilutus, but recent molecular, pheromone and morphological evidence indicates that it is probably another, presumably endemic, Creontiades species.