Performing Department
(N/A)
Non Technical Summary
Swede midge is a highly-damaging invasive species of Brassica crops. In regions where it has become established, losses up to 100% have been reported. The central problem is the lack of effective reduced-risk tools and tactics for both organic and conventional vegetable growers. As a result, conventional growers have increased their use of neonicotinoid and systemic insecticides, while some organic growers have stopped growing Brassica crops. The midge has recently expanded to nine new states, so new pest management tools are urgently needed. We have evidence pheromone mating disruption can be effective in managing the midge and reducing marketable losses. But the main challenge is around the effective deployment of PMD in annual rotational vegetable systems. Here, our specific goals are to: 1) compare pheromone dispensers to determine efficacy and affordability, 2) compare how field weathering affects the attractiveness of the male midges, 3) determine how to deploy pheromone mating disruption within an annual cropping system, and 4) develop tools for educating growers nationally about this serious new pest. The novelty of this proposal rests on the use of midge mating behavior to identify where pheromones should be deployed within annual cropping systems. By developing an economical and effective PMD system, goals are to develop an effective PMD system (USDA CPPM #1 Plant Protection Tactics and Tools) while training a predoctoral and undergraduate students (USDA CPPM #5 Development of the Next Generation of IPM Scientists).
Animal Health Component
50%
Research Effort Categories
Basic
(N/A)
Applied
50%
Developmental
50%
Goals / Objectives
We have evidence pheromone mating disruption can be effective in managing the midge and reducing marketable losses. But the main challenge is around the effective deployment of PMD in annual rotational vegetable systems. Here, our specific goals are to: 1) compare pheromone dispensers to determine efficacy and affordability, 2) compare how field weathering affects the attractiveness of the male midges, 3) determine how to deploy pheromone mating disruption within an annual cropping system, and 4) develop tools for educating growers nationally about this serious new pest. The novelty of this proposal rests on the use of midge mating behavior to identify where pheromones should be deployed within annual cropping systems. By developing an economical and effective PMD system, goals are to develop an effective PMD system (USDA CPPM #1 Plant Protection Tactics and Tools) while training a predoctoral and undergraduate students (USDA CPPM #5 Development of the Next Generation of IPM Scientists).
Project Methods
We will use a multi-disciplinary approach to develop a new IPM tool, combining agricultural entomology, chemical ecology, and behavioral ecology to assess the efficacy of PMD in reducing midge damage (Obj. 1-3). Dr. Conner, an economist, will help with the partial budget analysis to determine the profitability of new pest management tools. Finally, extension specialists Hodgdon and Hoepting will oversee education, outreach, and evaluate the prospects for implementation (Obj. 4).Obj. 1. Test whether different pheromone dispenser systems disrupt male behaviorIn Year 1, we will test how different pheromone delivery systems disrupt male behavior by measuring trap shutdown. Trap shut down occurs when males are not caught in pheromone traps because the elevated ambient levels of pheromone exceed the attractiveness of the pheromone lures in the traps. PMD is considered effective when there is an 80-90% reduction of males caught in traps in pheromone-treated plots versus control plots64. We will compare trap catches using: 1) the current bag dispensers, 2) pheromone paste applied to stakes, and 3) a control of no pheromone dispensers tested, replicated over three field replicates. We will carefully select field sites to ensure that there is sufficient pest pressure but also treatment isolation, such as: swede midge damage (>30%) within 100 m of each field the previous year, three treated fields that are 400 m apart from each other ensure independence37, and a minimum Brassica cropped area of 8 m x 8 m for each experimental field.We will test how the treatments influence male midge pheromone trap catch using a generalized linear mixed model with a negative binomial error model in R.Obj. 2. Compare how field weathering affects the bioactivity of the pheromone dispensersPMD dispensers can differ in durability under ambient weather conditions, which may influence the release rates of pheromones and their attractiveness to males. While we previously found that the sachets with pheromone could disrupt male trap catch over an entire season14, it is unclear if the paste formulation is similarly attractive over the same duration.2.1. Midge colony. We have established a lab colony from field-collected midges. The midge colony will be reared using our previously described protocol43.2.2. Field weathering of pheromone dispensers. We will test how field weathering influences the efficacy of the Chemtica paste and the pheromone sachet dispensers in attracting male swede midge. We will compare a) pheromone contained in a small vial with a hold drilled in the top and held in a plastic sachet bag with b) Chemtica paste applied onto wooden stakes (N = 10). Chemtica will guide us to ensure that the pheromone concentrations are equivalent across the two dispenser types. We will put all of the dispensers in a vegetable field in the Horticultural Research Complex (HRC) at UVM in June of Year 1. Every two weeks for 12 weeks, we will pull the dispensers from the field for lab behavioral trials. We will use the NEWA weather station data at the HRC to monitor rainfall, temperature, wind, and humidity variables.2.3. Wind tunnel assay. In order to test if the PMD dispensers differ in ability to attract males as they age, we will expose males to the PMD dispenser in a Plexiglas wind tunnel (50 x 50 x 170 cm), with airflow pushed through an activated carbon filter and mesh screen. We will place each pheromone dispenser (sachet or paste on a stick) upwind in the wind tunnel. We will introduce ten males into the wind tunnel for each replicate dispenser, allowing the males 5 minutes to respond. We will test if the males are attracted to the pheromones by flying upwind or remaining stationary or the amount of pheromone might be overwhelming and cause arrestment.Obj. 3. Determine where the placement of pheromone dispensers are most effective This objective tests the proof-of-concept that PMD can be used in annual rotational cropping system to manage swede midge and increase crop yields. We hypothesize that the placement location of PMD dispensers influences adult density, male trap catch, and marketable yield. Our study design will test whether PMD placement at the emergence site will increase broccoli yield. Therefore, by managing the cohort of emerging adult midges will suppress damage in broccoli fields. Due to multiple logistical considerations, we will conduct field trials Vermont and New York.3.1 Experimental Design. We will test how pheromone treatment location influences swede midge activity and marketable yield for broccoli. We will place the PMD dispensers in: 1) the previous year's Brassica crop ("last field"), 2) current broccoli crop ("current field"), or 3) no PMD system ("control") (Fig. 5), repeated over a minimum of three replicates. As Fig. 5 shows, each treatment will consist of a pair of two fields (last and current fields) that are ~100 m apart from each other, which will allow the midges to migrate between the last and current fields26. The PMD treatments will need to be isolated to ensure independence, so we will be spatially separate plots by a minimum of 500 m. We expect that the vast majority of the midges infesting the crop will originate from the previous year's crop because weedy plants in the family Brassicaceae are poorer hosts for the midge68.We will set up three replicates at the research farm at University of Vermont (UVM). UVM owns over 300 acres of fields cropped in field corn or soybeans. In Year 1, we will plant canola in a minimum of three spatially isolated 16 m x 16 m plots in April, according to production guidelines69. As a field crop, canola would be an ideal host for swede midge, because it requires less irrigation than vegetables and has multiple infestation points throughout its life cycle. In June, we will introduce 100 midge-infested cauliflower plants (10 week old) to the canola plots. We will monitor the midge populations in Year 1 in the infested plots using pheromone traps, aiming to see a minimum of 100 male midges/week at the peak flight the first week of July.Obj. 4. Increase stakeholder knowledge of swede midge biology and management optionsBuilding baseline knowledge on the swede midge life cycle and behavior will be essential for convincing growers to adopt new management strategies. We will share our results through virtual outreach channels for stakeholders and extension personnel that will be available nationally. Using a semi-structured interview, they will interview participant growers on their experiences, perceptions, and biases with swede midge and pest management (focusing on economic impacts), and technical assistance (preferences for and efficacy of information sources, types, and delivery mechanisms). We hypothesize that increasing grower knowledge of swede midge life cycle and ecology will positively associated with their willingness to adopt PMD using a Spearman's rank-order correlation75.4.1.Webinar. Hoepting, Hodgdon, and Chen will present a webinar on the following topics: 1) How swede midge biology influences its management; 2) Management strategies; and 3) PMD as an experimental approach to managing swede midge. Given that peer influence on adoption76, we will encourage farmers to share experiencesduring the webinars. We hypothesize that our educational efforts will increase grower willingness to try PMD in post-webinar poll results.4.2.Swede midge website. The Swede Midge Information Center for the U.S. site was the most comprehensive online resource for swede midge biology and management in the U.S. Hodgdon will lead the effort to update and reformat the website with new research updates, webinar recordings, and other outreach materials.4.3. Swede midge outreach network. We will convene a group of researchers and extension professionals will meet annually to discuss swede midge research and project updates (see letters).