Optimizing management of a new invasive species, swede midge, on small-scale organic farms

Optimizing management of a new invasive species, swede midge, on small-scale organic farms

Summary

Swede midge (SM) is an invasive insect pest that is threatening the viability of organic production of Brassica crops in the Northeastern US.  SM is quite small and its damage difficult to identify, so it is commonly misdiagnosed.  Currently, there are no organic methods that provide effective control of SM.  In this project, we partnered with 6 small-scale organic farms to develop effective pest management tools and to conduct outreach/education to familiarize at-risk small-scale organic growers with best management practices to protect them from devastating SM outbreaks.

Intensive monitoring of SM with 59 pheromone traps on 6 farms indicated that crop rotation/separation and selection of tolerant crop types can be effective management strategies for SM, but timing plantings to avoid SM emergence is critical. Insect exclusion netting in combination with various mulches including black plastic, landscape fabric, hay and straw was evaluated in seven small-plot on-farm trials and demonstrations. Results indicated that insect exclusion netting and mulches will protect brassica crops from SM, but its use regarding its effects on plant development and quality, and entire pest complex needs to be optimized.

Educational efforts included a “be on the lookout for SM” article printed in Cornell Vegetable Program newsletter, Veg Edge, and two grower-hosted twilight meetings where 13 growers learned how to identify and manage SM.  Additional educational activities are planned for winter 2016 including a workshop at NOFA-NY and adding an organic management section to the SM website. 

Tremendous progress has been made during this first year of study towards finding management strategies for SM that can be readily adopted by small-scale organic brassica growers. Data and economic analysis are in progress and plans are to continue this project in 2016.

Objectives/Performance Targets

Objective 1.

Advance understanding of swede midge (SM) pressure and invasion on small-scale organic farms growing Brassicas as it relates to management practices.

We partnered with 6 at-risk small-scale brassica organic farms with swede midge (SM) infestations in Allegany (Almond and Alfred Station, NY), Cattaraugus (Allegany, NY), Ontario (Phelps, NY), Schuyler (Hector, NY) and Seneca (Lodi, NY) counties in NY. Farms were selected based on their expressed interest in this project, geographic location and level of SM damage (minor to moderate/severe).  SM populations were monitored on each farm using female sex pheromone traps from early May until mid-November. In total, traps were deployed at 59 sites including in brassica transplant production, at spring emergence (where SM-infested crop occurred previous fall), and in spring, summer and fall brassica plantings.  Traps remained at a site as long as was relevant and male SM trap captures were enumerated weekly.  At harvest, Brassica crops were rated for SM damage using a 5-point scale (scale 0-4: 0 = no damage; 1 = minor damage, marketable yield not affected; 2 = moderate damage, yield/quality reduced; 3 = major damage, remnants of growing point, not marketable; 4 = severe damage, blind head, not marketable.  Trap catch data was related to brassica management practices that occurred on each farm.

Objective 2.

Optimize implementation of newly developed disruption tactics including insect exclusion netting and garlic oil repellant to manage SM in Brassicas on small-scale organic farms.

Insect exclusion (ProtekNet, 14’ width, 25 gram, Dubois Agrinovation) was evaluated over bare ground and in combination with various mulches including biodegradable black plastic, landscape fabric, hay and straw, for their ability to protect broccoli, Brussels sprouts and kohlrabi from SM. Seven on-farm small-plot trials were conducted with natural SM infestations including three in spring-planted broccoli, one in fall-planted broccoli, one in spring kohlrabi, two in fall kohlrabi and one in Brussels sprouts.  Plots were 4 feet wide with a minimum of 20 plants per replicate and treatments were replicated 1-2 times. Traps were placed in each treatment to monitor SM population and crop damage was evaluated at harvest.  Other differences among treatments including plant size, maturity and other pest pressure such as Lepidopteron insects, flea beetles and weeds were also recorded. 

Weekly applications of 1% solution of essential garlic oil (Bulk Apothecary) were evaluated in three spring-planted broccoli and one kohlrabi small-plot farm demonstrations. Garlic oil was applied to individual plants with a spray bottle until run-off.  Crop damage was evaluated at harvest.

SM damage ratings and incidence collected from replicated trials was/will be analyzed using General Analysis of Variance and means separated using Fisher’s Protected LSD test with a significance of 5%. Economic analysis is in progress.

Objective 3.

Increase awareness of SM and knowledge of its management practices among at-risk small-scale organic Brassica growers.

To inform at-risk small-scale brassica growers of swede midge (SM) and to demonstrate insect exclusion netting as a management strategy, twilight meetings were held at Quest Farms in Almond, NY on July 23 and at Muddy Fingers Farm in Hector, NY on September 1, which were attended by 7 and 6 growers, respectively. Attendance at these meetings was lighter than expected for a couple of reasons.  First, we decided to only put on a meeting if a demonstration trial was worth showing, which could not be determined until about 2 weeks prior to the meeting.  Unfortunately, such short notice was a hindrance to scheduling the meetings and adequately advertising for them.  The Almond meeting occurred during the same week as another Cornell Vegetable Program meeting in the same county, and the Hector meeting occurred on the same day as Bejo’s Open House.

Hoepting wrote an informational article alerting growers to look for SM with scouting and management tips, which was distributed in the July 22 issue of the Cornell Vegetable Program newsletter, Veg Edge. This article was not published in the Northeast Organic Farming Association (NOFA) newspaper, The Natural Farmer Summer 2015 issue as originally planned.  Instead, this information will be included with updated management recommendations for managing SM generated from this project in an article that will be distributed in The Natural Farmer in Spring 2016, as well as through the CCE Cornell Vegetable Program’s newsletter and website (http://cvp.cce.cornell.edu/) and other similar Extension newsletters/websites.  Hoepting and Hall are scheduled to present a SM workshop at the NOFA-NY conference in Saratoga Springs on January 23, 2016. 

SM was featured in the Finger Lakes Agriculture Report, which was broadcasted 5 times between September 21 and October 1 on the Finger Lakes Radio Group’s Geneva (WGVA), Auburn (WAUB) and Penn Yan (WFLR) stations.

In winter of 2016, we will develop a new section for the “Swede midge information site for the US” website (http://web.entomology.cornell.edu/shelton/swede-midge/), originally developed by Cornell University, to include organic management.  It will review all of the strategies that have been tested and failed in order to prevent blind implementation of failed methods as well as the new information and recommendations derived from this project.

Growers who hosted on-farm trials have also served as resources to other interested growers.

Accomplishments/Milestones

• Met with grower cooperators to devise their individual case studies and on-farm trials: where monitoring traps will be placed, how exclusion netting and garlic repellency trials will be set up (crop type, which planting, plot size, whether exclusion netting will be with or without mulch, type of mulch, etc. Hoepting and grower cooperators. April 2015. Executed successfully.

• Add organic management of SM section to website, “Swede midge information center for US”. Hoepting and Chen. April 2015. Re-scheduled for Winter 2016.

• Write and submit “Be on the lookout for SM” article to NOFA newspaper, The Natural Farmer. Hoepting and Chen. April 2015. Article only went out in July 22 issue of Veg Edge (Cornell Vegetable Program newsletter). Will be incorporated into another article for NOFA in spring 2016.

• Order field supplies (insect netting and associated supplies, pheromone traps and lures and associated supplies, etc.). Technician. April 2015. Executed successfully.

• Prepare exclusion netting for growers (cut 820’ into 100-150’ sections, bend hoops, cut stakes, etc.). Technician. April 2015. Executed successfully.

• Deploy first monitoring traps and drop off exclusion netting to growers. Technician. May 2015. Executed successfully.

• Set up exclusion netting trials. Hoepting, technician and grower cooperators. May to August, 2015. Executed successfully. Four broccoli trials had excellent swede midge pressure; spring kohlrabi trial lost due to severe slug infestation and fall kohlrabi and Brussels sprouts had very low SM pressure.

• Monitor traps and scout for SM damage. Technician, Hoepting. May to October 2015, biweekly visits. 13 hours per week. Executed successfully.

• Spray garlic repellency trials. Hoepting, technician. May to October, 2015, as needed. Executed successfully.

• Harvest evaluations of trials. Technician, Hoepting. June to October, 2015, as needed. Executed successfully.

• Conduct four Twilight Meetings. Hoepting, Technician, Grower cooperators. August and September, 2015. Conducted two twilight meetings, one at Quest Farm Produce on July 23 in Almond, NY and one at Muddy Fingers in Hector, NY on September 1. Fellenz Family Farm in Phelps, NY and Canticle Farms in Allegany, NY did not have enough SM pressure to make a twilight meeting worthwhile.

• Collect grower feedback and economic info from growers. Hoepting, technician, growers. November 2015. In-progress.

• Data entry, analysis and summary. Technician, Hoepting. May-December 2015. In-progress.

• Write and submit annual report. Hoepting. December 2015. Executed successfully.

• Present results at NOFA-NY winter conference. Hoepting. January 2016. Scheduled to do.

• Write and distribute project results in newsletter article, update SM website with latest information. Hoepting, Chen. February 2016. Scheduled to do.

• Present results at NOFA-VT winter conference. Chen. February 2016. Will not do.

• Write and submit final report to NESARE. Hoepting. May 2016. Scheduled to do.

Impacts and Contributions/Outcomes

Results from on-farm monitoring revealed that emergence of the overwintering SM population began during the first half of May. It was bimodal with the first peak occurring in mid-June and the second of similar magnitude occurring during the last week of June.  Dates of first emergence and peak flights, and magnitude of peak flights varied slightly and considerably, respectively, from farm to farm and from field to field on the same farm.  In secluded fields, more SM damage occurred in red cabbage that was planted during spring emergence in May (damage rating; 2.8/4.0 = severe) than when it was planted after spring emergence was complete in August (damage rating: 0.6/4.0 = minor).  These results indicated that crop rotation/separation can be a very effective management strategy for SM, but timing plantings to avoid SM emergence is critical.

Insect-exclusion netting was highly effective in protecting the crop from SM damage. No broccoli was damaged when using the netting, whereas 94-100% of the broccoli was damaged and 50-85% unmarketable in the untreated control (=no netting). Use of mulch under the netting reduced SM damage by 66% compared to bare ground when it was used on top of a SM emergence site.  Most importantly, weeds were managed more effectively using all mulch types compared with bare ground.  Differences in plant development and quality occurred between netting and open air and among mulch types under the netting that resulted in both increased and decreased yield.  Also, netting provided beneficial exclusion of flea beetles and detrimental inclusion of cabbage worms and slugs.  The use of insect-exclusion netting and mulches will protect brassica crops from SM.  Muddy Fingers Farm have adopted insect exclusion netting to manage SM in their broccoli plantings.  They plan to continue to work with us to optimize its use regarding its effects on plant development and quality, and entire pest complex. 

Differences in SM damage among different types of brassica crops exposed to the same SM population occurred. At one site, average SM damage rating at harvest of red cabbage, green cabbage and pointed cabbage in the same planting were 2.8, 1.8 and 1.5 out of 4.0, where zero indicated no damage and 4.0 indicated severe damage.  At another site, winterbor and purple kale had 20% and 30% plants with minor SM damage, respectively, while 75% of Red Russian kale plants were infested with minor/moderate damage.  Future studies are planned to better understand crop tolerance and SM preference in relation to crop rotation and separation management strategies.

At the twilight meeting held at Quest Farm Produce in Almond, NY, a new farming couple learned that it was in fact SM that decimated their summer broccoli crop. After discussing possible management options with Hoepting and Hall, they decided to not plant a fall broccoli crop, which undoubtedly saved them another crop failure.

SM monitoring at Fellenz Family Farm demonstrated that SM populations had dropped almost entirely in their front field, giving them confidence to grow kohlrabi in this location this fall. Without the SM monitoring data, they would not have taken that chance.

After reading the SM scouting article in Veg Edge, a project manager at the Cornell HTC Vegetable Research Farm, suspected that his intensive systems study which was planted to cabbage in 2015 was infested with SM.  We confirmed SM in his trial and plan to overlay an SM component to this study in 2016.  The project is studying six tillage systems overlaid with three mulch types.  We plan to compare the effect of permanent straw mulch to compost mulch (essentially bare ground) with spring shallow tillage on SM spring emergence.  Our 2015 studies demonstrated that SM will emerge through straw, but it is unknown whether it would serve as a barrier to SM dropping to the soil to pupate.  We will set up enclosed SM traps in early May in each of 4 replicates per treatment, and continue to monitor SM until their emergence is complete.  We will also monitor SM at the Vegetable Research Farm in 2016 and use the information to guide management decisions so that SM no longer confounds research results in trials conducted on brassica crops.  This project will be the beginning of a mutually beneficial partnership.

Collaborators: