Winning The War on Pests in Edible Beans

Beginning in 2006, edible bean growers will have access to a new tool for fighting an old nemesis, the potato leafhopper (PLH). The potato leafhopper is the most serious pest of edible beans, with damage each year exceeding $3 million. PLH feeding can be very damaging reducing growth and vigour of plants.

Thiamethoxam (Cruiser)

A new seed-applied insecticide, thiamethoxam (Cruiser) from Syngenta Crop Protection, provides early-season control of PLH. In trials conducted by Ridgetown College, control of PLH lasted for up to 4-6 weeks after planting. In some years, this could provide season-long control, but not in others. It will eliminate the need for at least one foliar application.

Thiamethoxam is a neonicotinoid insecticide, similar to imidacloprid, as found in Gaucho. Thiamethoxam has systemic activity, translocating throughout the plant. When an insect is exposed to thiamethoxam it is incapacitated and stops feeding within several hours, preventing further plant damage. Thiamethoxam has an excellent safety profile and is regarded as an alternative to organophosphate seed treatments, such as lindane. Growers will need to continue to scout their dry bean fields up to first flower in order to determine if foliar control will be required.

Early PLH Control

In 2005, PLH populations were very low in many dry bean growing regions of Ontario. Fewer storm fronts from the USA during the growing season reduced the number of PLH being carried into Ontario. Threshold populations of PLH were not reached in many areas, reducing or eliminating the need for foliar control.

In previous years, leafhoppers often arrived early in the season shortly after emergence of the beans. Scouting for this early population of leafhoppers is difficult, because the first PLH, are all adults which are very mobile and hop or fly away when disturbed. Severe yield loss occurs before hopperburn is seen, particularly in seedling beans. The difficulty in finding leafhoppers at this stage, results in fields not being sprayed that required it. Thiamethoxam will help to control this early population.

Wireworm & Seedcorn Maggot

Thiamethoxam also provides good control of wireworm and seedcorn maggot. However, it should be noted that using a seed insecticide does not guarantee 100% control of soil insect pests. Under heavy pressure, some injury should be expected. Fields at higher risk are those with heavy annual weed pressure, sandy soils, following sod or pasture, or fields recently out of pasture, or sod. In the spring, the risk is higher in fields where manure or green residue was recently incorporated.