Silverleaf whitefly outbreak in northern NSW (North, 16 March 2009)

Date: 16 Mar 2009

Entomologists met with grain growers and consultants in the Narrabri and Moree, NSW districts this week to plan management strategies for a damaging outbreak of silverleaf whitefly (SLW).

The Grains Research and Development Corporation (GRDC) urges growers to closely monitor crops for the pest, especially near cotton and horticultural areas.

Ian McMaster, GRDC project manager practices says SLW can impact on soybeans, peanuts and cowpeas.

Mr McMaster says growers should practice good broadleaf weed control in and around crop areas as SLW has a very wide host range and can rapidly develop resistance to insecticides.

“There are reports of large infestations of SLW in the Narrabri/Moree region,” Mr McMaster said.

Queensland Department of Primary Industries and Fisheries (QDPI&F) entomologists have visited the area and also report cotton fields around St George are at or reaching high densities of SLW.

QDPI&F graduate entomologist Zara Ludgate says the whitefly present in the Narrabri/Moree areas are predominantly SLW.

The Moree/Narrabri region has traditionally not had a problem with SLW because the cooler winters made it a more marginal area for whitefly. Greenhouse whitefly (GHW) and East Australian native whitefly have been common in the past but are easy to control compared with SLW.

“It is thought that increased host plant availability from a wet winter/spring, warm conditions and a decline in natural enemies due to the use of broad spectrum insecticides has contributed to the high SLW numbers,” Ms Ludgate said.

“Reports indicate Admiral® has been applied on many fields to suppress SLW populations in the St George area.”

Parasitism levels of 50 per cent and 70pc were recorded from two fields in the St George area.

Ms Ludgate says this should help to keep SLW in check later in the season even if they start to re-infest crops post Admiral® spray.SLW numbers in central Queensland around Biloela and Theodore are reportedly dropping off, partly due to parasitism levels.

Recent testing for insecticide resistance in populations of SLW from Biloela and Theodore show no alarming results for Admiral®. These results were expected due to the minimal use of Admiral® in central Queensland this season.

GHW are in moderate densities in the Norwin region on the Darling Downs, Queensland. While GHW will produce honeydew it does not normally cause the same problems as SLW which has a wider host range, higher reproductive rate, develops resistance to insecticides rapidly, and is adapted to high temperatures. Where populations are a mix of SLW and GHW, consider treating as if all are SLW.

For more information on managing silverleaf whitefly see www.thebeatsheet-ipmnews.blogspot.com or contact
Kylie Paulsen, GRDC Communication Manager Ph: (02) 6166 4565 m: 0428 864 934

GRDC Code: DAQ00086, DAQ00074, CSG00046

Region North