Corn earworm

Helicoverpa armigera

Looks like

Summary

The caterpillars of the corn earworm (Helicoverpa armigera), also known as the cotton bollworm, are a significant pest of cotton and can be problematic in other crops, including pulses, oilseeds, coarse grains and winter cereals, and some vegetables. It is more commonly found in the northern and coastal regions of eastern Australia, particularly in warmer areas.

This species has developed high levels of resistance to insecticides. To manage this pest effectively, it is important to use a combination of biological and cultural control methods, in addition to appropriate insecticides. This can help to minimize the use of insecticides and reduce the risk of further resistance developing.

Chemical Management

Controlling the corn earworm is complicated due to its resistance to many insecticides, including endosulfan, synthetic pyrethroids, and carbamates. This species also shows lower levels of resistance to organophosphates, spinosad, and indoxacarb.

There are resistance management frameworks to manage the pest in both Cotton and grains.

The timing of chemical applications and coverage are critical for effective control. It is important to target small larvae up to 7mm in length and apply insecticides before they move into flowering pods.

Selective insecticides for control are now widely registered in grain crops. Soft options, such as using Bt (Bacillus thuringiensis) and nucleopolyhedrosis virus (NPV) based biological insecticides, can also be used.

Resistance

Biological Management

The corn earworm has several natural enemies that can support control. These include shield bugs, damsel bugs, assassin bugs, native earwigs, tachinid flies, orange caterpillar parasite, two-toned caterpillar parasite, Trichogramma wasps, lacewings, and spiders.

Trichogramma pretiosum, an egg parasitoid that targets Helicoverpa among other caterpillars, is available to purchase for release.

Additionally, naturally occurring fungal diseases and viruses can also play an important role in reducing their numbers during some seasons. Utilising these natural enemies can be an effective and environmentally-friendly way to manage corn earworm infestations.

Natural Enemies

Locally occuring parasitoids can be highly effective at suppressing pest populations, and there is a wide diversity of parasitoids that target the caterpillars of lepidoptera (moths and butterflies)....

Lepidopteran larval parasitoids

Order: Hymenoptera

High efficacy

Rove beetles (family Staphylinidae) are a diverse group of beetles with elongated bodies, typically black or dark brown. They possess prominent forward projecting chewing mouthparts that are adapted f...

Rove beetles

Family: Staphylinidae

Moderate efficacy

There are at least six groups of spiders that are commonly found in grains crops. These include the wolf, huntsman, trapdoor, jewel, flower and jumping spiders. Most species live more than one year, w...

Spiders

Order: Araneae

Moderate efficacy

Hoverflies (Syrphidae sp) are a family of flies. They are characterized by their ability to hover in mid-air before quickly changing direction, hence their name....

Hoverflies

Syrphidae sp.

Moderate efficacy

Predatory bugs belong to the family Hemiptera or true bugs. This group includes many pest insects, but there are also many important beneficial insects. Some species are quite small, measuring a few m...

Predatory bugs

Order: Hemiptera

Low efficacy

Locally occuring parasitoids can be highly effective at suppressing pest populations, and there is a wide diversity of parasitoids that target the eggs of lepidoptera (moths and butterflies)....

Lepidopteran egg parasitoids

Order: Hymenoptera

High efficacy

Lacewings have elongated, slender bodies with prominent, bulging eyes. They measure 1 to 3 centimeters in length, varying by species. Their transparent wings have a delicate, net-like pattern resembli...

Lacewings

Family: Chrysopidae / Hemerobiidae

Moderate efficacy

Cultural Management

There are a range of options available to manage corn earworm in different areas and crops. In southern crops, windrowing canola or desiccating pulse crops like field peas can be a viable solution to hasten the drying of crops when small to medium-sized larvae are present. Cultivating and slashing can also help reduce pupal and larvae survival.

In northern areas, chickpeas can be planted as a trap crop to capture overwintering populations emerging from diapause. Avoid planting summer legumes successively. Proper weed management within and around crops can also help prevent the buildup of corn earworm and other insect pests. By implementing these methods, farmers can help control corn earworm and protect their crops.