Potential for a Pheromone Mating Disruption Program for the Invasive Swede Midge within Complex Annual Rotational Systems

View the project final report

Commodities

• Vegetables: broccoli, brussel sprouts, cabbages, cauliflower, rutabagas, turnips

Practices

• Crop Production: cropping systems, crop rotation
• Pest Management: cultural control, integrated pest management, mating disruption
• Production Systems: agroecosystems, organic agriculture

Problem, novel approach and justification

Swede midge, Contarinia nasturtii (Diptera: Cecidomyiidae), is an invasive pest that has recently caused up to 100% losses for organic broccoli and brassica crops in New York, Vermont, and Eastern Canada. Due to the lack of effective management options for organic growers, the midge is undermining the competitiveness of brassica production in the Northeastern US, and some growers have recently decided to abandon brassica production. One promising strategy is pheromone mating disruption (PMD), which is the use of high doses of synthetic female sex pheromones to prevent males from finding females to mate. PMD has rarely been attempted in annual cropping systems because adults typically emerge from previously cropped fields, where they can mate outside of pheromone-treated plots. Another limitation is that fly sex pheromones are more difficult and expensive to synthesize, so they need to be used judiciously in order for PMD to be commercially feasible. Our novel approach is to study when and where swede midge adults mate in order to better strategize the delivery of pheromones within complex annual cropping systems.

Hypothesis and Research plan

We plan to develop an improved understanding of swede midge adult emergence, mating, and dispersal in order to develop recommendations on where and how pheromone emitters should be deployed within annual vegetable cropping systems.

Obj. 1.

Determine when and where swede midge adults mate

1.1 Does the distribution of adult midge emergence differ among replicated field plots?

1.2 How does adult dispersal influence their propensity to mate?

1.3 Do we see evidence of sex-biased dispersal based upon distance from emergence sites?

Obj. 2.

Determine if swede midge mating disruption acts competitively or non-competitively

2.1 What is the relationship between emitter density and male trap capture?

2.2 How does male exposure to high pheromone doses influence their responsiveness to mating with females?

We plan to test these questions through a combination of field and laboratory studies, using the swede midge sex pheromone. Both the PI and co-PI maintain midge colonies in the lab, which will guarantee a supply of insects for these studies.

Outreach plan

We plan to present at regional grower meetings such as the New England Vegetable and Fruit Conference and at grower talks. Information will be posted on the Swede Midge Information Center for the US (http://web.entomology.cornell.edu/shelton/swede-midge/). We will publish peer-reviewed papers and present at one regional and one national Entomological Society of America meeting.

We will develop recommendations on where and how pheromone dispensers should be deployed for a swede midge PMD program within annual cropping systems. If half of the population mates in the previous year’s field and half in the current year’s field, then double the area would need to be treated. The required area for treatment would be substantially reduced if all adult emerge within the year following pupation. Similarly, a greater understanding is needed to understand how PMD works mechanistically to identify options for manipulating pheromone deployment and dosages.