A bird’s eye view of Helicoverpa moth activity

A national network of traps for native budworm and corn earworm moths will guide monitoring time for these pests.

cesar and members of the GRDC-funded National Pest Information Service as well as a team of regional agronomists and growers, are again running a national monitoring (trapping) program for native budworm (Helicoverpa punctigera) and the corn earworm (Helicoverpa armigera) over late winter and spring this year.  

From early August, pheromone traps have been set up alongside crops, particularly pulses, across the cropping zones. The timing (and size) of moth catches provide an indication of when egg-laying commences, and when crop monitoring should start.

The following is an update on our understanding of the status of conditions this year for Helicoverpa moth flights.

Native budworm

Native budworm moths are thought to directly arise from breeding in and migration from the eastern inland (stretching from south western Qld to northern SA and far western NSW) during autumn and winter. Moderate to heavy rainfall events, and subsequent growth of native plants, often result in large flights of moths in the cropping zone.

Following a review of Bureau of Meteorology data on inland rainfall patterns for 2018, it is not surprising that the monthly rainfall decile ratings for the eastern inland mostly indicate “exceptionally dry” or sometimes “average” since summer (see figure provided). The small exception were confined areas of ‘above average’ rainfall in northern South Australia and the Queensland channel country in March.

There are 2 possible conclusions from this analysis:

1) any moth flights arising from this March rainfall event would be expected from early August to early September.

2) moth catches this spring are unlikely to be large. Nonetheless, even low catches will indicate the start of egg-laying.

Rainfall deciles for autumn 2018 in Australia (Source: Bureau of Meteorology, ‘Climate Maps’)

This analysis does not account for smaller populations that may have bred locally and would emerge and disperse over the August-October period. However, in much of our south-eastern Australian trapping zone, opportunities for autumn breeding would have been limited.

Corn earworm

Inland Australian rainfall conditions have little to no influence on H. armigera moth catches, according to extensive studies by researchers at the University of New England. This species does not commonly breed inland and is more associated with breeding conditions in the agricultural belt. This would include the higher rainfall southern regions of Victoria, and in the irrigation regions of northern Victoria and NSW. For this reason, we may expect relatively larger catches of corn earworm than native budworm this year, although the absolute numbers will probably still be low. 

Monitoring results arising from the southern trapping network will be reported in subsequent editions of PestFacts-south eastern and will be viewable on our interactive online map.