Work is underway this summer field-testing traps designed to lure black field crickets, a pest which causes significant economic damage to kūmara crops.
The Vegetables New Zealand-A Lighter Touch project, being undertaken by the Bioeconomy Science Institute, is focused on finding new control options for the pest, which also economically impacts other vegetable crops and pasture in northern New Zealand, particularly Northland. Existing control options are limited, and consequently, the risk of resistance development due to the limited modes of action is high and of concern to growers.
All life stages of the cricket feeds on kūmara tubers underground, resulting in damage which can lead to crop losses of $10,000 to $30,000 per hectare depending on market pricing. Damage caused by the cricket feeding also results in significantly reduced crop yields in other vegetable crops and poor pasture growth. While complete crop loss is rare, in some cases entire fields can be rendered practically worthless due to feeding damage.
Sophie Hunt, of BSI, sets up a night vision camera to film a black field cricket trap as part of an earlier AGMARDT-funded study. Credit: BSI
Male crickets call using a series of chirps and trills to attract females, and high-quality males are more likely to be selected by females for mating. A previous Plant & Food Research AGMARDT-funded study investigated the feasibility of using an acoustic caller to attract and trap female crickets and successfully demonstrated that the concept of an electronic caller to attract crickets can work. The work now underway as part of the VNZ-ALT project will help refine the caller and trap combination to maximise trap effectiveness and efficiency.
The trials being undertaken near Dargaville involve two types of traps, which use recorded male cricket mating calls to lure the black field crickets into the traps. One larger type of trap is designed to capture flying crickets, while the smaller trap is targeting both flying and crawling crickets. Both traps have a false bottom which the crickets fall through into a net below, enabling the numbers of crickets being captured to be recorded. This capture data will identify which type of trap is most effective.
Following the trap field-testing over summer, the next phase of the project will be to evaluate a biopesticide to determine if it will infect and kill black field cricket. The biopesticide would be sprayed on crickets caught in the trap, which would then be released to infect other crickets.
Black field cricket on a kūmara tuber, showing the damage the pest causes to this crop. Credit BSI.
If the laboratory screening shows the biopesticide is not effective, the alternative is to use an insecticide-treated grain bait to kill trapped crickets lured into the trap. Using the trap to lure and kill crickets would improve the longevity of the bait and growers would not need to broadcast spread bait, reducing the potential for non-target impacts, such as birds feeding on it, as well as allaying environmental concerns.
For growers, existing control options include seasonal applications of synthetic pyrethroid insecticide sprays, and the use of insecticide-treated grain baits. Kūmara growers have found the baits are not as effective in-crop for complete cricket control and prefer to use the insecticide spray option as the main in-crop management tool.
The preference for use of a single mode of action insecticide brings the threat of resistance, and the long-term sustainability of continuing to rely on it for control are a growing concern for kūmara growers. The use of targeted insecticide applications, which this project is investigating, will become increasingly important to reduce the risk of resistance developing.
Black field cricket, Teleogryllus commodus. Credit: BSI.
An earlier stage of the project involved a knowledge review of both the literature and current kūmara grower pest management practice. It aimed to identify possible control options, or gaps in knowledge required to be filled in order to develop control options for black field crickets as well as other vegetables and pasture.
Keep up to date with new developments via the project page on the ALT website.
