With the aid of advisors around Victoria and southern NSW, we have been tracking native budworm (Helicoverpa puntigera) flights into cropping areas.
As moths have been caught in pheromone traps since early August, we recommend that you keep a close eye on pulse and oilseed crops for the larval offspring of these flights.
Look for small larvae
Larvae are likely to still be smallish at the moment.
For example, if larvae hatched from moths caught between early August in Ouyen in Victorian Mallee, based on historical average temperature data, a predictive model tells us they would now be, or approaching, approximately 10 mm long (third instar).
This is supported by observations in the NSW Riverina, where larvae found in a field pea crop were no more than 15 mm long.
But don’t be tricked by their size – field pea, chickpea, lentil and faba bean crops are very susceptible to all sizes of native budworm larvae. While larger larvae may devour the entire pod contents, small larvae can enter emerging pods and damage developing seed.
Monitor crops for activity by taking a minimum of 5 sets of 10 sweeps and calculating the average number of larvae per 10 sweeps. Each sweep should involve moving the net through the crop in an arc of approximately 180°.
Sweep netting in taller or rigid crops (e.g. faba beans) can be less efficient than in lentils, peas or vetch, so you may want to try monitoring with a beat sheet instead.
Native budworm larvae vary in colour between shades of brown, green and orange and grow to around 40 mm. While they usually have darkish stripes along the body and bumpy skin with sparse, stiff, stout hairs, these features can be less obvious in smaller larvae.
Don’t forget that not all crops are equally susceptible to damage, and native budworm is one of the very few pests that have economic thresholds that consider crop type, grain price and control costs. Detailed instructions for following thresholds can be found on our native budworm PestNote.
Moth trap update
Native budworm moths have continued to be detected in some cropping regions of south-east Australia, although at much lower levels than in August (see moth trap data here).
We now have traps set up in:
Deniliquin (Riverina NSW)
Ouyen, Swan Hill and Kerang (Mallee)
Rupanyup, Marnoo, Laharum (Wimmera VIC)
Hamilton (South West VIC)
Rokewood (Central VIC)
Even if moth activity has been light in September, any eggs laid this month could still have a fighting chance of surviving in drier than average conditions in much of Victoria and southern NSW (rainfall helps dislodge eggs from plants).
Continued monitoring for larvae in spring until crop maturity is a must!
Brad Bennett – AGRIvision (Mallee VIC)
David Bufton (South West VIC)
Neilson Carr (Central VIC)
Adam Dellwo – Elders (Riverina NSW)
Rob Fox – AGRIvision (Wimmera VIC)
Bill Gardner (Wimmera VIC)
Shayn Healey – Crop Rite (Mallee VIC)
George Hepburn – Tylers Hardware & Rural Supplies (Wimmera VIC)
Aaron Hutchison (Riverina NSW)
Damian Jones – Irrigated Cropping Council (Mallee VIC)