Management and economic thresholds for native budworm

Native budworm (Helicoverpa punctigera) is a major pest of pulse and canola crops in the south west of Western Australia. The native budworm is indigenous to Australia and can develop large populations over extensive areas on native plants.

These populations often migrate into agricultural regions in late winter and spring, causing damage to crops. Migratory flights are unpredictable, as moths may be carried hundreds of kilometres from breeding areas by high altitude air currents.

Effective control requires understanding when the crop is at risk and the economic threshold for when to spray.

Description and life history

Adult moth

The adult form of the native budworm is a moth that has rapid, low-level flight that takes a zig-zag path and ends with a dive into a crop or shrubs.

The moths have light brown, patterned forewings and mostly pale hind wings with a black patch at the tail end.

Native budworm moths are usually 20 mm long and 35 mm across on the outstretched wing
Native budworm moths are usually 20mm long and 35mm across on the outstretched wing

Eggs

White spherical eggs (0.5mm) are laid singly, mostly near the top of the plant. The eggs darken as they mature and tiny caterpillars hatch after about seven days.

Caterpillars

The young caterpillars feed on leaf or pod material for about two weeks before they become large enough (5mm long) to be noticed in the crop.

It takes a further four weeks until they are fully grown (40mm long) which is about seven weeks from the time of egg laying.

These development times are based on average spring temperatures when caterpillars are active in central cropping areas of Western Australia. Later in the season, or in more northerly areas, developmental rates for caterpillars will be faster.

The caterpillars vary greatly in colour from green through orange to dark brown and are often seen with their heads inside pods. They usually have dark stripes along the body and are sparsely covered with fine bristles.

Egg and six instar stages of native budworm
Egg and six instar stages of native budworm

New moth flights and egg laying will result in caterpillars of varying sizes in a crop. Caterpillars eat increasing quantities of seed and plant material as they grow with the last two growths stages (fifth and sixth instar) responsible for eating over 90% of their total grain consumption.

Native budworm and chewing damage in lupin pod
Native budworm and chewing damage in lupin pod

Pupa

When fully mature, the caterpillars crawl to the ground, burrow into the soil and pupate. The length of the pupal stage depends on several environmental factors and varies from two weeks to several months.

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Contact information

Alan Lord
+61 (0)8 9368 3758
Page last updated: Tuesday, 17 October 2017 - 4:23pm