Native budworm (Helicoverpa punctigera) 1st instar larvae have been identified in the Mid North, in lentils at Locheil and peas at Telowie. High levels of moth activity have been observed in many legume crops across the Mid North. On upper Eyre Peninsula, 1st instar larvae have been collected during sweep netting of a number of crops of peas, vetch and lupins. University of New England Researcher, Peter Gregg, has recently observed high populations of native budworm and lesser budworm (Heliothis punctifera) during sweep net surveys of native hosts in northern South Australia and southwest Queensland. Peter believes these population levels create potential for above average populations in cropping areas this spring.
Native budworm populations breed on a range of native host plants in inland Australia during winter. In spring, moths undertake flights into cropping areas of southern Australia typically on suitable northerly-easterly weather systems. Detecting moth flight activity provides an early warning of potential egg lay and larval activity in crops.
The latest counts of native budworm moths captured in the trapping network indicate the occurrence of moderate to high moth flights around the Cleve-Kimba-Pinkawillinie, and Port Broughton - Mannanarie areas, with light activity elsewhere (see table below). These figures indicate that numbers are increasing on upper Eyre Peninsula and in the Mid North; there was a flight on upper Yorke Peninsula during the week ending 31st August, and significant flights on upper Eyre Peninsula on 1st September, and in the Mid North on 6th September.
Modelling of native budworm development (thanks to Dr. Garry McDonald, cesar, University of Melbourne) currentlypredicts that 3rd instar larvae could be found in crops around the 10th October, and the most damaging 5th instars on 13th - 20th October. To avoid 5th instar damage, it is advisable to time appropriate insecticide treatments when 3rd instars first appear.
Native budworm moth counts from seven trap locations are:
Monitor crops by taking multiples of ten sweeps in representative locations across the paddock and calculate the average number of larvae per 10 sweeps. An economic threshold calculator for direct yield loss (not grain quality), developed by DAFWA, is demonstrated in the PestNotes Southern fact sheet (link below). Growers should substitute in their own control costs and grain prices. Research by QDAF has shown that, under current cost structures, spray decisions in smaller seeded pulse crops (e.g. desi chickpea) can be made based on these calculated yield loss thresholds without risking penalties for reduced grain quality; however, this may not apply to larger seeded grains (e.g. Faba bean, field pea) where there is a higher likelihood of unacceptable levels of partially chewed grain in the sample. If treatment is warranted, one well-timed synthetic pyrethroid application often provides effective control and may prevent reinfestation for up to six weeks.
Further updates of trapping results will appear in future issues of PestFacts newsletters.
Sources of reports: Michael Brougham (Elders), Iain Tod (Kerin Agencies, Landmark), Ryan Bateman (FPAG), Chris Davey (YPAG, Kadina), Sarah Traeger (Cleve Rural Traders), Adam Hancock (Elders), Steve Richmond (Landmark), Amy Wright (AgSave Merchandise), George Pedler (Cummins Ag), Troy Maitland (EPAgnFert).