Improved management strategies for silverleaf whitefly in vegetable crops (VX02016)

This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

CSIRO Entomology identified the need to introduce an effective parasitoid of silverleaf whitefly after determining that existing parasitoids were less effective than required to contribute significantly to management. Based on joint research with the USDA, they decided to import Eretmocerus hayati as it had been used successfully against SLW in the Lower Rio Grande Valley in south Texas, an area very similar climatically to coastal and Central Highland areas of Queensland.

Host range studies for E. hayati showed E. hayati posed no significant threat to non-target species. Based on these results the Australian Government Departments of Environment and Heritage, and Agriculture, Fisheries and Forestry (AQIS) granted permission for the release of E. hayati.

Releases of E. hayati commenced in late October 2004 and continued through until May 2005 in selected cropping areas in Queensland. Approximately 617,000 parasitoids were released with breeding populations becoming established at sites in the Lockyer, Bundaberg/Childers and Emerald areas. Field surveys have indicated that E. hayati was highly dispersive and able to locate and parasitise SLW over a wide range of crop and non-crop hosts. The status of populations in the Bowen and Ayr regions remain undetermined.

DPIF had shown that all imidacloprid soil treatments resulted in significant decreases in SLW in tomato, zucchini, eggplant and melon. In general application of imidalcoprid as a plant hole drench delivered the best control in terms of reduced whitefly numbers and increased quantities of marketable fruit. Control of SLW in capsicum was regarded as unnecessary as first instars rarely survived beyond this stage. Four different insecticide management regimes, imidalcoprid (Confidor) as a plant hole drench, pyriproxyfen (Admiral) early in the crop life, pyriproxyfen (Admiral) late in the crop life, and a standard treatment (bifenthrin, imidacloprid, D-C-Tron) were evaluated in controlling SLW on melons. Imidalcoprid as a plant hole drench provided the best control giving approximately five weeks protection. The other treatments provided reasonable control, although Admiral applied early provided poor control late in the crop’s life. Bifenthrin gave little control of adults. There were no differences between treatments in measures of fruit number, weight or brix.