Home > Cooler weather, but keep an eye on Silver Leaf Whitefly in Cotton

Silverleaf whitefly, a small white-coloured insect, has been found in numbers that may require control in some cotton fields in the Namoi and Gwydir Valleys, and low populations are now also being found in the Macquarie Valley.

Rain and cooler weather over the last two weeks has slowed populations but this should not lead to complacency.

Dr Lewis Wilson, Entomologist with CSIRO Plant Industry and the Cotton CRC said it is important that consultants and growers keep monitoring silver leaf whitefly populations until the crop is no longer at risk.

‘Cotton consultants have been reporting high numbers of silver leaf whitefly in some crops, and some have had to spray them to prevent problems. They have also reported populations in some grain crops, especially soybeans’

‘There are very comprehensive recommendations for sampling, deciding if control is required and what option will work best, developed by Dr Richard Sequiera from QDPI&F. These can be found on the Cotton CRC website and the Cotton Pest Management Guide’ Dr Wilson said.

Silver leaf whitefly can cause damage to growing cotton plants through their feeding but the main problem is that they secrete a sticky substance known as honey dew. If this occurs once the cotton bolls have opened, exposing the lint which can be become contaminated and results in significant downgrading.

‘This pest is usually more of a problem in northern cotton regions, but this year populations have built up in these more central and southern regions.’

‘Once the problem was identified the Cotton CRC organised workshops in the Namoi and Gwydir Valleys for growers and consultants to explain sampling techniques, control decisions and options. These were led by Dr David Murray and Zara Ludgate of the QDPI&F who have had previous experience in managing this pest’

‘Extension staff and cotton consultants in both valleys were able to quickly respond to the need for information, especially the NSW DPI District Agronomist at Moree, Tim Burley, who had only been in the job for 5 days, yet managed to organise a workshop at very short notice and Amber Dimond of the CCA who quickly got the word out to consultants’ Dr Wilson said.

‘We were also lucky to be able to call on other scientists for advice, especially Dr Sequiera and Dr Paul Grundy, QDPI&F, who have extensive experience with management of this pest from the severe outbreaks that occurred in Emerald in 2002.’

‘This really shows the Cotton CRC team in action as we were able to identify a problem quickly, through good linkages with the cotton consultants, and mobilise expertise to help crop manages to make the best decisions. We operate across borders, with information being quickly compiled and sent to all growers and consultants by extension officers from different states, Susan Maas (QDPI&F) and Sally Ceeny and David Larsen (NSW DPI).’

As crops begin to finish off and the bolls open there is the risk of honeydew contamination of lint. By monitoring silver leaf whitefly population growers and consultants can ensure they make appropriate control decisions. Detailed information can be found on the Cotton CRC Website (www.cottoncrc.org.au) and in the Cotton Pest Management Guide.

For more information please contact Dr Lewis Wilson Office: 02 6799 1550
Mobile: 0427 991 550