LUCERNE seed wasp has been a major issue for South East growers in the past few years, wiping out thousands of dollars of their seed crops and causing headaches for seed cleaners in blocked equipment.
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But Lucerne Australia has received nearly $90,000 from Rural Industries Research & Development Corporation’s pasture seed funding for a three-year project to tackle the pest.
The seed wasp is attracted to flowering lucerne and lays its eggs in the developing seed pods, preventing the seed from maturing.
Shutting paddocks up earlier has been shown to reduce damage, but growers are concerned about the potential yield penalty.
The research being conducted by NSW Department of Primary Industries will include a comprehensive literature review summarising the existing knowledge on the biology of the wasp and biologically similar insects, developing a Polymerase Chain Reaction test for the absence or presence of the wasp, glass house and field studies of the wasp, including whether it is possible to develop a soil test.
At last week’s Lucerne Australia annual general meeting in Keith, NSW DPI Orange entomologist Ainsley Seago highlighted some of the literature review findings.
Lucerne seed wasp is a member of the chalcidoid family which has more than 22,000 species providing good amounts of research to drawn on.
Dr Seago said previous research had found that foliar pesticide sprays never work for seed-galling wasps, control of volunteer plants was critical to reduce populations in subsequent seasons, and using yellow sticky traps was an effective way to monitor them.
Post-harvest irrigation may also contribute to sanitation.
Dr Seago will be collecting live wasp adults and larvae from lucerne paddocks in SA and NSW later in the year to study regional variation and as a source of DNA to develop a PCR test. She is keen to hear from growers willing to allow her to sample their soils post-harvest.
“We are unlikely to come up with a way to eliminate seed wasp entirely from lucerne paddocks, but hopefully we can give more information to help growers work around them,” she said.
Lucerne Australia chairman Guy Cunningham said the pest had struck seed yields hard in two recent SE harvests – 2012 and 2014.
“In some late crops we went from 700 to 800 kilograms a hectare down to 200kg/ha so 60-70 per cent yield losses occurred in the worst cases,” he said.
“The biggest thing is the second time we didn’t see it coming and it was only when they put the header in we found the damage, with nothing in many of the pods.”
Mr Cunningham was pleased they had been successful lobbying for the RIRDC funding and hoped it would deliver more effective ways to manage the pest and reduce financial losses.
The pest is difficult to control in-crop with foliar pesticide sprays and Mr Cunningham said growers were looking for other recommendations to improve control.
“Because their life cycle is so short and generations overlap, they can turn up again in sprayed paddocks, so it is going to be cultural practices, time of paddock closure and taking a longer term view,” he said.
Mr Cunningham hoped the project would deliver more reliable predictors of wasp numbers through soil sampling and a greater understanding of climatic triggers. He said it was pleasing to have Dr Seago on board with her literature review of previous research already highlighting ideas they had not considered.
“We want to remain open to where the research goes but for example there may be varietal differences – some varieties with woolly pods may be more resistant,” he said.
“Lucerne prices are great and the industry is in good shape so it would be nice to get some (seed) to sell.”
