A leading entomologist is warning grain growers and agronomists in NSW and Queensland they will need to be actively ‘searching and detecting’ for pests this winter, rather than just monitoring crops.
The call for increased vigilance is due to the potential spread of the high priority pest Russian Wheat Aphid (RWA), as well as growing awareness of the benefits of early detection when it comes to insect pests, like winter cereal aphids and green mirids in faba beans. Speaking at Grains Research and Development Corporation updates recently, entomologist Melina Miles said growers and advisors needed to be alert and ready to take action to reduce the profit risk of insect pests. Dr Miles, from the Queensland Department of Agriculture and Fisheries, said while RWA had not yet been detected north of Rankin Springs, vigilance was required to ensure early detection.
“RWA is a high priority pest because of its potential to cause significant yield losses in wheat and barley if not well managed. Triticale and rye are also susceptible but oats are considered relatively resistant,” she said. “It is inevitable that RWA will establish in the northern grains region, but we don’t know when we will start to see it in crops, so it is critical that crops are monitored more frequently during the 2017 season.
“Growers should sample for the RWA in the same way they do for other cereal aphids. Concentrate on the field margins and in areas of the paddock which are stressed, looking for both the symptoms and presence of aphids.”
Key symptoms include striking symptoms in wheat and barley, rolled leaves or rolling of the flag leaf. Plant damage is in response to direct aphid feeding, so only the leaves and/or tillers infested show symptoms. An Emergency Use Permit (APVMA PER82792) is in place for chlorpyrifos and pirimicarb and is valid until June 2018. Pirimicarb will kill aphids but not the beneficial insects in the crop so should be used in the first case.
“Other things to watch for are winter cereal aphids, which can be managed with nominal thresholds and an understanding of their damage potential,” she said. “Field trials attempting to determine the impact aphids have on winter cereals over the past ten years and proven extremely difficult, but a combination of some Northern Grower Alliance work and some glasshouse trials… has been useful in developing a greater understanding.
“Weather, crop conditions and natural enemies all play a role in influencing aphid numbers. The damage potential of aphids in cereals seems to be based on the relationship between crop stage at infestation, density and duration of infestation.”
Seed treatment is an option for districts where aphid pressure is high in most seasons, although the use of neonicotinoid seed dressing poses some risks to the build-up of natural enemies and potential insecticide resistance. It’s also worth noting the potential impact of late infestations on yield, particularly from grain-fill on, is low. The exception is RWA where infestations from stem elongation can prevent heads from emerging normally and impact on grain set and filling.
