sustainability through science & innovation

Helicoverpa: we’re watching!

We’ve seen the first signs of native budworm and corn earworm moth activity this season. So, who are these pests, and how can you stay up to date on their movements?


We’ll be watching Helicoverpa moth activity closely this season! (Source: cesar).

 

Native budworm (Helicoverpa punctigera) and corn earworm (Helicoverpa armigera) are two key pests to watch as canola and legumes crops are flowering. While the larvae of these species appear similar, it is important to know which pest you have in your paddock. This is because corn earworm is resistant to multiple insecticide chemistries and requires a different management approach to native budworm.  

Native budworm behaviour

Native budworm breeds over winter in the arid inland regions of Queensland, South Australia, Western Australia and New South Wales on desert plants before migrating into southern agricultural areas in late winter or spring. They can migrate as far south as Tasmania. 

The moths rest during the day and become active after sunset, feeding on nectar from flowers and laying eggs in crops. They fly rapidly from plant to plant throughout the night in a darting motion, feeding and laying eggs. They are also capable of flying from paddock to paddock, and from one region to another. Native budworm prefers broadleaf plants and are rarely found on grass or cereal crops. They attack pulse crops such as field peas, faba beans, lentils, chickpeas, lupins and soybeans, as well as canola, lucerne, sunflower, safflower, annual medic and clovers. 

Native budworm is at their most damaging when the caterpillars feed on the fruiting parts and seeds of plants. 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. Holes or chewing damage may be seen on pods and/or seed heads. Losses attributed to budworm come from direct weight loss through seeds being wholly or partly eaten. Grain quality may also be downgraded. Caterpillars eat increasing quantities of seed and plant material as they grow. The last two growth stages (5th & 6th instar) account for over 90% of their total grain consumption.

Corn earworm behaviour

The corn earworm has been recorded from all states and territories within Australia. They are more common in eastern Australia, particularly in warmer regions such as northern New South Wales and southern Queensland. In cooler regions such as Victoria, South Australia and Tasmania it is  often assumed that corn earworm is a minor pest, and generally only problematic in summer. Because corn earworm moths are less inclined than native budworm moths to undertake long-distance migratory flights, problems are thought to arise from local populations that survive over winter as pupae in crops. This season, we will be taking a closer look at corn earworm to better understand its activity and the potential risk posed to southern cropping regions. 

Corn earworm larvae attack all stages of plant growth. They have a wide host range and can attack all field crops, particularly cotton, sorghum, maize, sunflowers, chickpeas, lupins and lucerne. The species is also occasionally found grazing on wheat and barley heads. They can cause damage to foliage, flowers and pods on canola.

Distinguishing native budworm and corn earworm

Native budworm moths have a 30-35 mm wing-span, and are buff, light brown to red-brown in colour. Similarly, corn earworm moths have a 30-45 mm wing-span and are light brown to red-brown in colour. Both species have numerous dark spots and blotches, with pale hind wings with a dark band along the lower edge. But unlike native budworm, corn earworm has small pale patch within this dark band.  

Native budworm (left) and corn earworm (right) are almost indistinguishable to the naked eye. Look out for the small pale patch within the dark band on corn earworm (Source: cesar). 

 

Native budworm and corn earworm larvae can be difficult to distinguish with the naked eyed. Larvae of both species grow to 40 mm and vary substantially in colour that includes shades of brown, green, and orange. Regardless of colour, they usually have darkish stripes along the body and bumpy skin with sparse, stiff, stout hairs, and sharp downward angling at the rear of the body. There are two features to look out for. The first is the dark ‘saddle’ on the fourth body segment on corn earworm. This is absent on native budworm. The second feature is hair colouration. Around the head region, native budworm has black hairs, whereas corn earworm has white hairs.

 

Native budworm (top) and corn earworm larvae (bottom). Corn earworm has a ‘saddle’ on its fourth body segment, which is absent in native budworm (Source: cesar).

 

Monitoring moth activity

A broad network of pheromone moth traps (based on the female sex scent) has now been established throughout the cropping regions of eastern Australia. This has been made possible through a collaborative effort with agronomists and growers, and colleagues from SARDI and QDAF, in Victoria, New South Wales, Queensland, and South Australia. 

Pheromone traps specifically attract male moths of native budworm and corn earworm, providing an indication of current female egg-laying activity. From this network, we will provide an advanced warning system for southern New South Wales and Victorian regions. This year we are also collaborating with ADAMA Australia who have supplied cesar with three Trapview automated pest monitoring systems to trial and compare against the conventional green funnel traps for native budworm monitoring. 

Monitoring native budworm activity with green funnel moth traps (left) and Trapview automated monitoring system (right) (Source: Brad Bennett).

 

Throughout spring we will keep you updated on Helicoverpa moth activity and provide an indication of how big the egg-laying populations are in strategic cropping areas. From this information, we will also estimate when the most damaging native budworm caterpillars are likely to appear in canola and pulses. So far, we have seen relatively little moth activity, indicating that no large moth flights have arrived yet in southern NSW or the Victorian Wimmera and Mallee districts.

 

Acknowledgements

Thanks to ADAMA Australia for providing Trapview automated monitoring systems to trial in our moth trapping program and to Alex Mills for his technical assistance. 

Thanks to this season’s moth trap operators:

Brad Bennett – AGRIvision (Mallee, VIC)

Jim Cronin – Landmark (Central West Slopes & Plains, NSW)

Bill Gardner – WestVic AgServices (Wimmera, VIC)

Shayn Healy – Crop-Rite Pty. Ltd. (Mallee, VIC)

George Hepburn – Tylers Hardware & Rural Supplies (Wimmera, VIC)

Damian Jones – Irrigated Cropping Council (Kerang, VIC)

Michael Moodie – Moodie Agronomy (Mallee, VIC)

Andrew Rice – ASPIRE agri (Central West Slopes & Plains, NSW)

David White – Delta Agribusiness (Riverina, NSW)

PestFacts is supported by