Colorado potato beetles are deceptively beautiful insects, with five shiny black stripes on a yellow background decorating each wing.
But this beetle is notoriously destructive. Each year, it and its larvae ravage potato, eggplant and tomato plants.
But this pest is also notorious for its ability to develop resistance to insecticides, making biocontrol a viable option. The use of one natural organism to control another without chemicals has a place in farming systems, including organic farming.
United States Department of Agriculture entomologist Kevin Thorpe and collaborators at the University of Maryland have found that an organic mulch made from a cover crop called hairy vetch can reduce Colorado potato beetle damage.
Read Also
Going beyond “Resistant” on crop seed labels
Variety resistance is getting more specific on crop disease pathogens, but that information must be conveyed in a way that actually helps producers make rotation decisions.
The hairy vetch is planted in the fall and mowed in the spring before transplanting. The vetch impedes the movement of beetles, lessening their damage.
Because it is a legume, the vetch also adds nitrogen to the soil.
In the study, fewer beetles infested tomatoes transplanted into hairy vetch mulch compared to tomatoes transplanted into black plastic mulch. Yields of staked, fresh-market tomatoes grown in the vetch mulch were comparable to tomatoes treated with insecticides.
The Colorado potato beetle costs U.S. potato, tomato and eggplant growers about $150 million (U.S.) a year in losses and insecticide-related costs.
Many growers are using imadacloprid, a new systemic insecticide that provides excellent control. However, resistance will develop unless appropriate measures are taken.
Non-insecticidal methods of control can be useful components of a sustainable, integrated pest management strategy if they reduce pesticide inputs and slow the rate of resistance.
Thorpe’s next step is to investigate the use of organic mulches in larger fields of staked fresh-market tomatoes grown on a commercial scale.
