Stephanie Ann Veskoukis Helicoverpa punctigera, also known as native budworm moths have been reported from traps and sweep netting in parts of the Wimmera/Mallee regions of Victoria, as well as central south NSW. Now that these flights have arrived and their grubs are growing, what is there to do?
In this article we’ll cover where these moths have been found, and the importance of monitoring, as well as some management information.
Helicoverpa reported in north-western Victoria and southern NSW
Mid-September saw reports of Helicoverpa caterpillars found various host crops in Manangatang, VIC, including lentils, lupins, field pea and chickpea. Whilst not identified to species level, they are suspected to be H. punctigera given the region and time of year.
Two weeks after their arrival in the Mallee/Wimmera region, reports of native budworm caterpillars were received in Hopetoun, VIC. Lentils in full bloom here were host to larval stages of Helicoverpa and were detected at the rate of 2 caterpillars per 10 sweeps of the sweep net.
At the same time, Gredgwin, VIC saw native budworm arrive in lentils at the flat pod growth stage, again detected at 2 caterpillars per 10 sweeps of the net.
Early October saw native budworm flights and caterpillars reported in Marnoo, VIC in various crops, including lentils and vetch. The current vetch had been sown into ample hay residue from the last crop.
High caterpillar numbers were detected in a faba bean crop at Illabo, NSW just last week. In the lighter areas of the crop, 5-10 caterpillars per 10 sweeps were found. In healthier sections of the crop, there were nearly 50 caterpillars per 10 sweeps. In good news, at this stage, 15-20km to the west of this crop, no caterpillars were detected.
Additionally, a population thought to be a mix of H. punctigera and H. armigera (corn earworm) has been reported in Tamworth, NSW in a mature canola crop.
As Helicoverpa spp. can have 4 to 5 generations per season, with larval activity increasing in warmer conditions, the key monitoring period for these pests has well and truly begun.
Identification of native budworm
Since moths are being discovered in traps, and we have reports of caterpillars in northern Victoria, it’s time to keep a look out for native budworm.
Their small eggs (~0.5mm) can be found singly on the growing tips and buds of plants and are visible to the naked eye on inspection of the plant. Newly hatched caterpillars (larvae) are very small (approximately 1.5 mm), light in colour with dark brown heads. They can easily be missed when inspecting a crop. They will grow through six or seven stages or instars until reaching maturity (up to 40 mm long).
The defining characteristics of Helicoverpa caterpillars are the dark stripes along the body, sparse, stiff hairs and a sharp downward angling at the rear of the body.
It can be difficult to tell the difference between H.punctigera and H. armigera, but suspect caterpillars are found in cereal crops further north, they are more likely to be corn earworm. If they’re found in pulses, or in crops earlier in spring in Victoria, they are more likely to be native budworm.
For more comprehensive identification information, please read our article titled ‘Helicoverpa caterpillars: armigera or punctigera?’ or consult our PestNotes on corn earworm and native budworm.
Keeping an eye on future flights
The recent warm weather and dry finish has been conducive to moth activity. Native budworm larvae develop through six growth stages, becoming fully-grown in 2-3 weeks in summer and 4-6 weeks in spring, and moths will continue to migrate in, or emerge from local populations throughout spring.
Growers and agronomists are encouraged to monitor for Helicoverpa larvae, especially in the north-West of Victoria and south of NSW, where larvae may reach maturity in the coming weeks.
Monitoring and management
Native budworm infestations are most problematic in spring and early summer, and monitoring of susceptible crops should continue until harvest. During the formation and development of pods, field pea, chickpea, lentil and faba bean crops are very susceptible to all sizes of native budworm caterpillars. Small caterpillars can enter emerging pods and damage developing seed while larger caterpillars may devour the entire pod contents.
You can monitor for the white, spherical eggs typically laid at the top of a plant. For larvae use either a sweep net (eg. peas, lentils) or beat sheet (eg. chickpeas, lupins, beans). Monitor field pea, faba bean, lentil and chickpea crops from budding and flowering development through to maturity for larval activity. Monitor narrow leaf lupin and canola crops at pod development to maturity.
For more information on monitoring methods, please see these videos on using a beat sheet, or sweep netting.
Recording larvae according to size is also a useful tool to predict when they will do the most damage, and when control is most effective. Large larvae are typically above 24mm in length, and cause 90% of the crop damage.
Both corn earworm and native budworm are susceptible to natural enemies like the egg parasitoid Trichogramma wasps, lacewings, and naturally occurring fungal diseases and viruses. Windrowing canola, desiccating pulse crops, and cultivating and slashing can reduce pupal and larval survival.
Larvae are best chemically controlled when they are smaller than 7mm in length and have not yet moved into a crop’s flowering pods. But be aware that Corn earworm has evolved resistance in varying degrees to several insecticides, including pyrethroids, organophosphate and carbamates. Economic thresholds for both corn earworm and native budworm can be found in their respective PestNotes pages.
Acknowledgements
Thanks to Garry McDonald, Lilia Jenkins and Dr. Lizzy Lowe for contributions to this article, and to Andrew McMahen (Nutrien), Rob Fox (Fox and Miles), Jocelyn Martin (Nutrien) and Tim Condon (Delta Ag) for providing field reports.
Cover image: Photo by Andrew Weeks, Cesar Australia
