Evaluation of exclusion and mass trapping as cultural controls of spotted-wing Drosophila in organic blueberry production

• 2013 annual report

Spotted Wing Drosophila (SWD) is an invasive fruit fly of Asian origin first detected in the Pacific Northwest in 2008. Since then it has rapidly expanded its range to include much of the continental US and many provinces in Canada. On my farm, SWD likely caused a 30% loss of my blueberry crop during this first season of infestation; extension reports indicate that many growers abandoned or even removed their fall raspberries as a result of this pest. Blackberries are also prime targets. SWD management is exceptionally challenging for organic berry growers, as existing recommendations involve extremely short spray rotations (3-7 days) with Entrust and Pyganic. Anecdotal information indicates that Pyganic is so ineffective that growers feel they lose ground when using it, yet a pesticide rotation is mandated to keep within the label requirements, and the rotation strategy is important as it helps prevent pest resistance. For many small berry growers, reliance on 100% chemical control is unsustainable. I have built my business on an organic production model and my customers place a high value on that. I truly believe that this pest, if left unchecked, will cause irreparable harm to my farm business. In an effort to be proactive, I would like to explore the combined approach of exclusion and trapping to reduce the number of SWD adults in my small organic blueberry planting. Through discussion with my cooperative extension agent and searching information on the web I have found that this approach has not been extensively explored in other areas of the country likely because large acreage farms would find it prohibitively expensive. There is one home gardener fact sheet written by the University of Oregon Cooperative Extension that suggests using exclusion as a way to control SWD in small plantings. Encouragingly first hand reports from Japan indicate that exclusion is a valuable control strategy for Japanese berry growers. I feel that on a small scale, exclusion and trapping would allow growers to reduce the amount of pesticides sprayed and still grow a high quality product. My approach will be to examine exclusion by itself, and combined with baited traps in comparison to a control. The importance of this work may only be temporary, as the long term solution to this pest seems likely to hinge on some type of mating disruption or introduction of a predator. The real value to the work will be to provide small, sustainable berry growers with a reasonable cultural control method that actually works. This approach may give growers enough encouragement that they will continue attempts to manage the pest and hopefully not interrupt the supply of locally grown berries for northeastern customers. Even temporary loss of the market would be difficult to regain. Spotted Wing Drosophila (SWD) is an invasive fruit fly that proved to be unusually damaging to 2012 berry crops. Unlike native species, SWD uses its formidable ovipositor to deposit eggs in ripening fruit resulting in larvae development inside the berry that corresponds to the ripening of blueberries, raspberries, day neutral strawberries and a variety of other cultivated and wild hosts. Levels of infestation ranged from 80-100% of fruit examined. Individual fruit had as many as 25 larvae; coastal farms were reported to have more than 3000 adults trapped in a 1-week interval. Traditional IPM approaches have been temporarily abandoned in hopes of controlling SWD populations. Insecticide applications at 3-7 day intervals are currently the recommended strategy. Many berry growers are not inclined nor prepared to use insecticides and their customers are particularly concerned about food safety. It is imperative that an effective cultural approach be developed to allow sustainable and organic berry production to continue. This project will evaluate the merits and costs of excluding SWD from a blueberry planting using insect netting. We will also examine the effect of exclusion used in conjunction with baited lures designed to trap out the adult insect. Hay Berry Farm LLC is uniquely suited to this work as we are attempting organic certification and have invested heavily in bird netting, trickle irrigation and deer fencing. Additionally the farm enjoys strong support from our Cornell Cooperative Extension agent, who will assist in evaluating fruit, assembling the nets and hosting a field meeting.