Volatile-based trapping and management of flea beetles

Term: 3 years, beginning 2024
Status: Ongoing
Researcher(s): Maya Evenden, U of A
SaskCanola Investment: $104,506.25
Total Project Cost: $209,012.50
Funding Partners: ACPC

Objective

1. Compare the attractiveness of commercially available lures containing the plant host volatile, allyl isothiocyanate (AITC) to both sexes for both flea beetle species in spring and fall activity periods. 

2. Compare commercially available traps for capture and retention of flea beetles. 

3. Compare the attractiveness of lures formulated with different doses of AITC and pheromone to both sexes of both flea beetles. 

4. Compare the attractiveness of AITC lures to flea beetles with and without the presence of canola. 

5. Enumerate the non-target bycatch in traps baited with AITC. 

6. Illustrate attraction of flea beetles to an attract-and-kill formulation containing AITC. 

Project Description

Striped and crucifer flea beetles are the most significant insect pests of canola on the Canadian Prairies. Currently, >99% of canola acreage is grown from insecticide-treated seed, and even then, foliar insecticide applications are often required under high flea beetle population densities. Current monitoring for flea beetles involves in-field scouting from canola emergence through the third true-leaf stage, after which canola can tolerate feeding damage. Plants are examined for typical “shot-hole” and stem-feeding damage and ranked on a 0-100% damage scale. The current recommended action threshold is set at 25% damage. 

In addition to in-field scouting, semiochemical-based monitoring with plant volatiles and flea beetle pheromones has been tested on different North American flea beetle populations with varying degrees of success. The plant volatile, allyl isothiocyanate (AITC), is attractive to both flea beetle species in the field in both the spring and fall activity periods. Spring and fall populations of P. cruciferae, however, respond differentially to AITC in lab bioassays. Although attraction to AITC lures is enhanced by flea beetle pheromones, the magnitude of the increase is not large enough to warrant the development of pheromone-baited lures. Flea beetle pheromones are complicated chiral sesquiterpenes for which lures are not available commercially and synthesis is difficult and expensive. A system that focusses on AITC lures for flea beetle attraction will be the easiest, fastest and cheapest approach to development of semiochemical-based monitoring for flea beetles. 

Different lure types (e.g. rubber septa, glass vials, coaster lure packs) have been used to release semiochemicals to attract flea beetles with varying success, and other lure properties (e.g. dose and release rates) can also affect flea beetle capture, with release of more AITC generally attracting more beetles. Doses of AITC between 10-200 μl released from glass vials and capillary tubes attracted flea beetles. Trap type, design and colour can also influence flea beetle capture with yellow sticky cards or modified boll weevil (rocket) traps used most often. The number and variety of insects captured on yellow sticky cards make them difficult to use and inconsistency of modified commercial traps makes them unavailable for use by crop scouts. Traps baited with blends of different isothiocyanates also capture several other Brassica specialists such as pollen beetles, and cabbage seedpod weevils. Allyl isothiocyanate alone does not attract cabbage seedpod weevils but does elicit a strong electroantennal response by female diamondback moths, and is attractive to cabbage flies, in wind tunnel and field assays. Researchers report some parasitoid bycatch in traps baited with AITC lures. It is important to assess the non-target bycatch captured in AITC-baited traps to determine if traps can also monitor other pests and natural enemies at the same time. 

In addition to monitoring insects, attractive semiochemicals can also be used to directly manage insect pests. Attract-and-kill formulations use semiochemicals to attract insects to a killing agent, such as an insecticide or pathogen. Mass trapping is the use of many semiochemical-baited traps positioned in the agroecosystem to attract insects and reduce insect population numbers. Before either attract-and-kill or mass trapping can be implemented, behavioural studies are needed to determine insect response to the technologies. For instance, depending on the substance used to release the semiochemical, insects may not make contact with the killing agent. 

The proposed research will test commercially available semiochemicals and traps as well as develop and test new semiochemical tools to improve monitoring and management of flea beetles in canola.