The advent of Bt-cotton led to a dramatic decline in insecticide use against Helicoverpa spp. in the Australian cotton industry. Though this had significant benefits to the industry a downside was that some pest species formerly controlled by insecticides applied against Helicoverpa spp., and which were not affected by the Bt proteins, were no longer controlled. Several species have increased in significance in Bt-cotton, including the green mirid and green vegetable bug. In addition, silverleaf whitefly (SLW) has gradually achieved pest status in central and southern regions. It became a major problem in the Lower Namoi, Mungindi, and Gwydir regions in 2008-09, and has since reached pest status in cotton in other regions as well (Upper Namoi, Macquarie and Goondiwindi). In combination these emergent pests challenge the IPM systems developed for cotton because many of the control options used are detrimental to beneficial species.

This project built on a series of projects focusing on developing and enhancing integrated pest management (IPM) in cotton, especially in Bt-cotton systems. This was done by providing key information about the ecology and management of pests and beneficials and developing that information into a format suitable for use by industry. The project aimed to maintain capacity to respond to emerging pest problems (e.g. broad mites), to address key pest management challenges, such as management of mirids, GVB and SLW and maintain core entomology skills essential given the changing pest management environment (BGII and the advent of BGIII). The project also provided key support for (1) the project of Dr Grant Herron, NSW DPI (DAN197) investigating resistance to pesticides in mites and aphids (2) the project of Murray Sharman, QDAFF (DAQ1201) which had an objective to understand alternatives hosts for cotton bunchy top disease (CBT), and (3) also interacted with Dr Robert Mensah in evaluation of the efficacy and non-target effects of some novel biopesticides and semiochemicals.

This project supported the ongoing development of IPM in cotton by targeting emerging pest issues, and inappropriate management which may threaten IPM. Key outcomes were:

a. Populations of silverleaf whitefly (SLW) were maintained throughout the year on non-cultivated hosts. Key winter hosts for nymphs were sowthistle, bladder ketmia and blackberry nightshade. Sowthistle is an important indicator host of potential SLW abundance.

b. Life history studies with silverleaf whitefly showed that survival of eggs is generally between 50-80% while survival of nymphs declined from 50% in December to 10% in March. A range of SLW predators were identified.

c. System experiments for SLW management found (i) no evidence that SLW are worse on Bt-cotton than non-Bt-cotton (ii) okra leaf shape offers resistance to SLW (iii) broad-spectrum sprays led to much higher populations of SLW

d. Investigation of the fate of honeydew on bolls showed (i) breakdown by sunlight occurs slowly (ii) rainfall substantially reduces contamination (iii) a non-linear relationship was found between % honeydew removed and rainfall.

e. Green vegetable bug (GVB) abundance increased when the drought broke and there were abundant weed hosts. Parasitism by the tachinid, Trichopoda giacomellii, also increased probably reflecting higher, consistent availability of GVB as hosts

f. Sequential host use studies showed GVB prefer to feed and oviposit in legume crops such as mungbean, pigeon pea, soybean and lucerne. Some legumes may have potential to draw GVB away from cotton.

g. Results confirm that sorghum is a potential host for GVB but only during the flowering and early seed maturation period.

h. Twelve additional hosts were identified for cotton bunchy top disease (CBT) predominantly from Malvaceae, but also from the Euphorbiaceae, Lamiaceae, Fabaceae and Aizoaceae.

i. Neonicotinoid seed treatments on cotton significantly reduced transmission of CBT by neonicotinoid-susceptible aphids. Foliar applications of an aphicide were only effective at reducing primary transmission if timed just before or just after aphids colonised the crop.

j. The IPM fit of nine new compounds was evaluated. Two recently registered compounds will be added to the „Impact of insecticides and miticides on beneficials‟ table for 2014/15.

k. Information was provided to industry to assist in management of spur-throated locusts and cluster caterpillars (2010-11) and broad mites (2011-12)

l. Simone Heimoana‟s Phd thesis „The effects of aphids (Aphis gossypii) Glover on photosynthesis in cotton (Gossypium hirsutum)‟ was awarded.

m. Contributions were made to the TIMS Committee, TIMS Insecticide and Bt Technical Panels, to REFCOM and the Industry Bio-security Committee.

This project provides new information to improve management of emerging pests. Outcomes have been delivered to industry through presentations, published resources and the WWW.