Reduced risk pest management for root weevils in berry crops

Project code: PRR03-350

Project Lead

Kenna MacKenzie - Agriculture and Agri-Food Canada 

Objective

To investigate the use of alternative methods in the management of root weevil in strawberry crops

Summary of Results

Background

Root weevils are significant pests of many crops, including strawberry, a crop with an Ontario 2009 farm gate value of more than 22$ million. While adults feed on foliage, often leaving characteristic notches, economic injury is due to larvae feeding on roots. Severely damaged plants wilt and may even die, thinning strawberry stands and ultimately reducing yields. As part of a national, multi-year project to develop reduced risk pest management strategies for root weevils in Canadian berry crops, work was undertaken to identify root weevils active in fields in Ontario and Nova Scotia and to evaluate potential components of an integrated pest management (IPM) program.

Approaches

Monitoring: Root weevil populations were monitored from 2004 to 2006, from mid-May until mid-September each year, using either 1m barrier pitfall traps or 10m exclusion barriers.

Exclusion barriers: Relative protection of a first year planting by “Vernon Barriers” (linked 3m lengths of extruded black plastic designed to capture weevils) or “Sheet Barriers” (supported 30cm wide sheet plastic with 1 edge buried 5-10cm deep in soil) was evaluated in 2005. Cumulative numbers of adult root weevils captured in collection pails at barrier ends were recorded.

Foliar insecticides: Effectiveness of post-harvest application foliar insecticides was determined in 2008. Treatments were replicated 4X in a randomized complete block design on July 14. Relative effectiveness was measured by capturing adult weevils 2 and 10 days post-application, and by counting feeding notches 14 days post-application.

Results

Monitoring: Twelve different species of root weevils were collected, with black vine weevil (BVW) accounting for over 80% and strawberry root weevil ~5% of total captures. The authors concluded that the BVW is the most economically damaging root weevil attacking Ontario strawberries.

Exclusion barriers: Many more BVW were collected around Sheet Barriers than Vernon Barriers, which tended to warp and lift from the soil due to solar heating.

Foliar insecticides: Two days post-application, there were significantly less BVW in plots treated with thiamethoxam, cyazypyr, metaflumizone or bifenthrin than in untreated plots.

Overall, the following elements were identified as important for an effective IPM strategy to control root weevils in strawberry: use of tolerant cultivars; rotation and isolation of new plantings away from infested patches; use of Sheet Barriers for protection of new plantings; control by properly timed insecticides or entomopathogenic nematodes; and timely destruction of infested patches to minimize migration of adults.

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