Controlling the pepper weevil with sterile insecticide techniques

For the first time, researchers in Canada have investigated the use of a sterile insect technique to control populations of the pepper weevil Anthonamus eugenii, an economically important crop pest in North America.

Lead author, Jacob Basso, University of Guelph, Agriculture and Agri-Food Canada's Harrow Research and Development Centre, Harrow, Ontario (pictured)

Gamma radiation
The paper, published in SCI's Journal of Pest Management Science, revealed conclusive findings on the use of gamma radiation as a sterilization technique to improve the sustainability and effectiveness of pepper weevil management worldwide. The study is a collaboration between Bruce Power, Nordic Inc., the University of Guelph, Agriculture and Agri-Food Canada, and Canadian fruit and vegetable producers.

A. eugenii poses a significant challenge to pepper growers throughout much of North America, causing millions of dollars worth of crop damage annually. The beetle larvae damage the flowers and immature fruits of chilli plants, with the attack causing yield losses of up to 90%. As the development of beetle larvae takes place in the protective boundaries of pepper fruits, A. Managing eugenic populations is more challenging.

Bell pepper rows at Agriculture and Agri-Food Canada's Harrow Research and Development Center in Harrow, Ontario – Jacob Basso, University of Guelph

Useful strategies
Roseline Lab, Greenhouse Entomologist and Associate Editor of Agriculture and Agri-Food Canada Research, A. He explained the challenges of finding effective strategies to manage Eugenia's population. 'In previous research, we found that some conventional, reduced-risk or microbial insecticides can effectively kill pepper moth adults in greenhouse pepper crops. 'Even assessments of parasitoids attacking the larval stages of the pepper weevil (insects used to biologically control pest populations) had limitations because they sometimes had trouble accessing hosts inside the pit of the pepper fruit,' he said.

The team, led by researcher Jacob Basso of the University of Guelph, focused on the sterile insect technique (SIT), a genetic control method where large numbers of sterile insects reduce reproductive success in the wild. insect

Labbe noted, 'The sterile insecticide technique seemed promising as prior research had been done with this technique to control the cotton boll weevil (Anthonomus grandis), a congener of the pepper weevil.

The key to a successful SIT program is choosing the appropriate radiation dose for sterilization of the target species. The authors note, 'It is critical to determine the minimum radiation dose at which insects are effectively sterilized, yet maintain their ability to successfully locate and mate with wild individuals.'

Pepper moth (Anthonamus eugenii), captured by Jacob Basso of the University of Guelph

Gamma radiation doses
Analysis of the effects of different gamma radiation doses on A. eugenii pupae showed that irradiation of both males and females at 110 Gy produced completely sterile individuals.

The researchers noted that at these doses the lifespan of irradiated beetles was shortened to less than two weeks, so A. eugenii SIT programs should plan to release sterile insects repeatedly over two weeks to compensate for their mortality.

For the sterile insect technique to become a viable A. eugenii management strategy for farmers, several practical considerations must be addressed. Labe noted, 'We still need to investigate the dispersal potential of irradiated moths in the field, and more importantly, evaluate sterile males for mating competitiveness against non-irradiated male moths.'

The team now hopes to use SIT to control other pests of horticultural crops. There is still some information about this. 'We are interested in using this strategy to control lepidopteran pests that regularly invade greenhouse crops, for example,' said Labey.

Find the full study here eurekalert.org

Jacob V Basso, University of Guelph; Roselyne Labbe, Agriculture and Agri-Food Canada; Cynthia Scott-Dupree, University of Guelph