What's in store for summer pests?
As well as the usual mix of pests such as helicoverpa, mirids and podsucking bugs, this season northern growers also need to be on the lookout for soybean stem fly, bean podborer and etiella in vegetative soybeans says Queensland Department of Agriculture, Fisheries and Forestry (DAFF) researcher Hugh Brier.
“Knowing what pests are around each season is half the battle in controlling them,” Mr Brier says. Major pests in soybeans and mungbeans, plus advice on how to deal with them, are summarised below:
– normally a pod-boring pest but large numbers were reported in vegetative soybeans on the southern Darling Downs last summer. Such infestations are most likely isolated events but beware of the distinctive early damage symptoms, namely dead auxilliary buds (see the Beatsheet blog for details).
– flowering and podding mungbeans and soybeans are most attractive to helicoverpa but last summer, very high infestations (more than 20 per square metre) were reported in vegetative mungbeans on the Liverpool Plains, NSW, and in soybeans at Bundaberg, Queensland.
- The preferred control options in vegetative crops are biopesticides, for example nucleopolyhedrovirus (NPV) which is a disease of helicoverpa that occurs naturally in the Australian environment (see the Queensland DAFF Beatsheet blog).
- If crops suffer a very heavy pressure (>12/m2), and/or if larvae are more than 12 millimetres long, the preferred option is indoxacarb (Steward®). Using indoxacarb spray in vegetative crops is preferable to less selective alternatives.
Where possible, NPVs are the preferred option because they preserve beneficial insects and prevent build-up of insecticide resistance. It also allows growers to conserve the more potent pesticides (such as indoxacarb) for the flowering/podding stages.
– affect many crops, including mungbeans and soybeans, although they tend to cause less damage in soybeans. Bean podborer is more prevalent in wet years, and significant outbreaks were detected inland from the coast to the Darling Downs in 2011-12 and 2012-13. Sustained pressure as high as 100 borers/m2 were detected for up to four weeks in some crops.
– affect all major pulse crops. Avoid spraying until early podfill to minimise disruption of beneficial insects. Add a 0.5 per cent salt (NaCl) adjuvant to deltamethrin or clothianidin (Shield®, Permit 12699) to improve control of redbanded shield bug. Queensland DAFF has a series of factsheets available for all podsucking bugs that affect the northern region (see list below).
Soybean stem fly
– stem fly is a frequent pest of South-East Asian soybeans, and this pest is increasing in Australian soybeans. In summer 2012-13, stem flies damaged about 4000 hectares of crops in the Casino region of NSW. This led to significant crop losses and damage was increased by the widespread incidence of charcoal rot. This season, hot, humid weather could lead to further outbreaks, as were experienced last year. However, native stem fly parasites may stabilise populations of this pest.
Integrated pest management
When applying insecticide to control any of the pests described above, growers are advised to follow label restrictions carefully, for example by:
- not allowing grazing on recently sprayed pasture;
- ensuring thorough spray coverage for ingestion products such as NPV or indoxacarb; and
- only using registered (or under permit) chemicals at stated label rates.
Growers should avoid broad-spectrum pesticides wherever possible, and use integrated pest management to preserve beneficial insects, Mr Brier says.
“The widespread use of broad-spectrum pesticides leads to flaring of other pests and kills beneficial insects that may otherwise keep pest populations below threshold levels,” he says.
Details about integrated pest management (IPM) are available in GRDC’s IPM (northern) Fact Sheet, listed below.To win the battle with the bugs, Mr Brier says growers should remember these four key messages:
- sample crops regularly for pests;
- correctly identify the pests and beneficials;
- act only if pests cross over the threshold levels; and
- conserve beneficial insects.
Details about IPM can be found in the GRDC’s IPM (northern) Fact Sheet, www.grdc.com.au/GRDC-FS-IPM-N
Queensland DAFF has a series of fact sheets available for all podsucking bugs that affect the northern region, www.daff.qld.gov.au/plants/field-crops-and-pastures/broadacre-field-crops/integrated-pest-management/a-z-insect-pest-list/pod-sucking-bugs
DAFF’s Beatsheet blog contains information about all summer pests, including NPVs as a biopesticide, thebeatsheet.com.au/wp-content/uploads/2013/01/NPV.pdf
End of Ground Cover Issue 108 Northern region edition
Read the accompanying Ground Cover Supplement: Ground Cover Supplement Issue 108 - More Profit from Crop Nutrition
GRDC Project Code DAQ00153
Region North, South