Semiochemically assisted trap cropping to reduce broad bean beetle (Bruchus rufimanus) infestation in faba bean

Abstract

Damaged beans and adults of broad bean beetles (Bruchus rufimanus) in harvested beans are currently a bottleneck for faba bean production, especially for human consumption. The availability and efficiency of insecticides to control broad bean beetles are limited. We tested trap cropping combined with semiochemical trapping as an alternative pest management strategy. A field experiment was performed in south central Sweden over two years, in 2021 and 2023, in a total of 24 faba bean fields. Fields were paired, such that each pair (n = 12) contained one treated field with a perimeter strip of an early flowering faba bean cultivar used as a trap crop in combination with semiochemical traps, and one control field with just the faba bean main crop without a trap crop or semiochemical traps. Eggs per pod and proportion of beans with emergence holes were 147 % and 73 % higher in the trap crop strip in treated fields compared to the corresponding area grown with the main crop cultivar in control fields. Eggs per pod and proportion beans with emergence holes were conversely 28 % and 18 % lower respectively, in the main crop in fields with trap crops compared to control fields, but only in the field centers and not the field edges. Yield of the main crop was not affected by semiochemically assisted trap cropping. Overall the trap crop treatment successfully reduced damage by broad bean beetles but only modestly so. Further development of the trap cropping strategy might, however, be able to contribute to satisfactory broad bean beetle control.