Whitefly management system underway

03 December, 2002

A study tour of Silver Leaf Whitefly problems in the United States cotton industry has provided valuable pointers to prevention and control mechanisms suitable for implementation in the Australian cotton industry. p. __Cotton Seed Distributors extension and development agronomists John Marshall and Greg Kauter were members of a 12-person delegation which recently visited Texas, Arizona and California to study Whitefly management.

The study tour was sponsored by the CRDC, CSD and Cotton Grower Associations from the Central Highlands, Theodore and Biloela in Queensland.

Pictured Left to Right: SLW Study Tour members Duane Evans, Greg Jensen, Professor Tim Dennehy (University of Arizona), Brett Austin, Hamish Millar, Simon Struss, David Kelly, Richard Sequeria, Wayne Reeves, David Parlato, John Marshall and Paul Grundy. Greg Kauter was behind the camera.

The Central Highlands cotton growing region around Emerald, which annually plants around 22,000 hectares of irrigated cotton, experienced the first major outbreak of SLW in the Australian cotton industry last season.

The study tour delegation spoke with US growers, consultants, researchers, extension agents and aerial operators, to gain an insight and understanding of SLW and its management, increasing the delegation’s knowledge of the pest, and of the tools available to manage it.

Greg Kauter, said area wide integrated pest management was a “must” to avoid this pest becoming an annual problem for growers.

“In the US situation we found examples of additional costs of US$100 to US$200 per acre in extra insecticide, as well as yield losses of at least one bale per acre, plus significant quality discounts from stickiness.

“ Ginners said they could not handle the resulting sticky honey dew cotton, with some arguing that heavily affected bales were unsaleable,” Greg Kauter said.

He said quality discounts were still being applied to some areas in the US, despite a significant reduction in the severity of the problem, with the discounts applied more due to perception than to reality.

Greg Kauter noted that smooth leaf in particular, and also the okra leaf characteristics, have an important role in non-chemical reduction of SLW numbers on cotton plants.

“Although the Insect Growth Regulators insecticide group have been an important ingredient of management mechanisms in the US, the two major products used there are not yet registered for use on cotton in Australia, and both are in the ‘very expensive’ category,” he said.

__CRDC extension and development officer, Bruce Pyke, said the industry had applied to the NRA for permits for their use this season, and a decision was expected in early September. He said at least three IGR’s could be available this season, with more in the permit pipeline.

Pictured left: Brett Austin sampling leaves in Arizona.

John Marshall said the industry had to develop strategies that reduce the incidence of SLW to levels that do not have the potential to flare annually.

“This involves consideration to time of planting, destruction of residues and volunteer crop plants and weeds, the use of appropriate insecticides, the establishment of thresholds for insecticide action, and cross-commodity co-operation and co-ordination.

“The broadacre grain and horticulture industries, and the urban community, also need to understand the SLW life cycle, and its potential for build-up.

“This knowledge will help ensure that small populations do not escalate to damaging proportions under favourable conditions, affecting all industries.

“The challenge now is to use and apply the knowledge the study tour delegation has obtained, and to develop strategies to effectively manage Silver Leaf Whitefly,” John Marshall said.

Further Information: Robert Eveleigh, John Marshall, Greg Kauter or Craig McDonald