Lockyer Valley vegetable growers should consider starting a silverleaf whitefly management plan now to reduce likely problems with the destructive pest in autumn next year.

Queensland Department of Primary Industries and Fisheries (DPI&F) entomologist Brendan Nolan said silverleaf whitefly (SLW) had become a serious pest of vegetable crops in the Lockyer.

Mr Nolan said the region's climate and continuous production of suitable hosts contributed to its year-round activity, with SLW numbers always peaking in autumn.

"The large numbers of SLW seen in autumn are due to the way populations grow exponentially, with two SLW becoming four, four becoming eight, and so on until autumn when numbers always peak.

'If growers reduce SLW numbers in spring and early summer, the flow-on effect will be lower numbers in autumn," he said.

Mr Nolan said the success of this management strategy relied on all growers participating, so SLW needed to be managed at the community level.

Mr Nolan said some of the issues to consider in developing a management plan included knowing the extent of the pest.

"Awareness of SLW on properties is very important and requires regular monitoring of susceptible crops to be able to make the right decision about the need for control," he said.

Removing volunteer crop plants and all host weeds such as slender celery, milk thistle, fat hen, bellvine, common morning glory, spurge, deadnettle, bladder ketmia, anoda weed, apple of Peru, wild gooseberry, glossy nightshade, purple top and lantana could reduce SLW populations.


Where possible, pest management should also allow a silverleaf whitefly host-free period by planting non-host crops such as maize or sorghum during summer and younger susceptible crops some distance away or up-wind of mature crops, he said.

Another way of managing the pest was to destroy host crop residues immediately after harvest and optimise water management to avoid moisture stress, which increased silverleaf whitefly severity and the level of honeydew residue.

He said beneficial insects such as wasps and ladybirds could enhance silverleaf whitefly control if pyrethroids, organophosphates and other broad-spectrum insecticides were not used.

More information on silverleaf whitefly management is available from Brendan Nolan, DPI&F Gatton Research Station (5466 2222 or 0417634815).