- Fruits: berries (blueberries), berries (other)
- Crop Production: food product quality/safety
- Education and Training: extension, on-farm/ranch research, workshop
- Energy: energy conservation/efficiency
- Farm Business Management: budgets/cost and returns, risk management
- Pest Management: chemical control, field monitoring/scouting, integrated pest management
Since the arrival of Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), field applications of broad-spectrum insecticides have significantly increased to protect susceptible fruit from infestation in berry crop production. These cover sprays have increased production costs, disrupted existing IPM programs, and potentially caused inadvertent environmental and non-target impacts. Field studies were conducted from 2012–2013 to determine whether border treated reduced spray programs could manage D. suzukii, as well as cover sprays, and have less of an impact on non-target arthropods. Three blueberry plots of a mid-late season variety were border sprayed and captures of D. suzukii adults and larvae were compared to conventional cover spray programs. Non-target arthropods were evaluated seven days post-harvest.
No differences in mean adult numbers and larvae of D. suzukii were detected between treatments. Border sprays had significantly more Stethorus spp. No difference in fruit knockdown by border or cover spray was observed.
This reduced pesticide strategy is an additional tool to consider in D. suzukii IPM programs that reduce the amount of spray area, application time, and input costs while conserving natural enemies.
Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is an invasive pest of small and stone fruits in the Americas and Europe (Walsh et al., 2011; Cini et al., 2012; Deprá et al., 2014). Female flies cause direct damage by ovipositing into susceptible ripe fruit (Lee et al., 2011a). Eggs develop into larvae that feed on fruit flesh, rendering fruit unmarketable. To prevent fruit loss and to meet zero to low tolerance infestation levels set by packing plants, growers currently apply broad-spectrum insecticides multiple times during the harvest season (Bruck et al., 2011). They are faced with several challenges, such as knocking mature fruits off of plants, managing insecticide pre-harvest and restricted entry intervals (PHI and REI), impacting natural enemies (Roubos et al., 2014a), and risking possible secondary pest outbreaks, all of which increase production costs. A reduced insecticide spray strategy, such as border sprays, is a possible tool to curtail these challenges (VanEe et al., 2000; Roubos et al., 2014b).
In border sprays (DeBach & Bartlett, 1951), pesticide is applied to crop plants in the field border at the same rate and volume as cover sprays, while leaving the center of the field untreated. Border sprays are typically effective against pests migrating into the field from field margins (Lafleur & Hill, 1987; Ferguson et al., 2000) and against ‘edge oriented’ colonizers (Reardon & Spurgeon, 2003). Border sprays have been used to manage apple maggot, codling moth (Trimble & Solymar, 1997; Trimble & Vickers, 2000), and plum curculio (Chouinard et al., 1992; Vincent et al., 1997) in apple orchards; alfalfa weevil in alfalfa (Roberts et al., 1987); and strawberry bud weevil in strawberries (Kovach et al., 1999). Systemic insecticides have been applied to potato borders for Colorado potato beetle (Blom et al., 2002) and an attract and kill applied to cucumber borders for melon fly management (Prokopy et al., 2003). Possible advantages of border sprays include reduced fruit knockdown within the field, reduction of insecticide inputs, fewer environmental impacts, and conservation of natural enemies (Trimble & Solymar, 1997). A disadvantage includes a greater risk of leaving the center of a treatment plot vulnerable to pest attack.
We hypothesized that reduced spray strategies of border sprays would be as effective as cover applications at managing the highly mobile D. suzukii (Mitsui et al., 2010) and would conserve natural enemies. Mobility of D. suzukii was tested by a preliminary mark-release-recapture study using fluorescent dusts that showed D. suzukii moved approximately 67–87 m in 36 h (J.C. Lee, unpublished). Field margins with non-crop hosts such as ‘Himalaya’ blackberry (Rubus armeniacus F.) may also provide refuge for overwintering adults and a source for invasion of the cultivated raspberry fields when ripe (Klick et al., 2014).
The objectives were to determine if border sprays for spotted wing Drosophila, Drosophila suzukii, (SWD) are
(I) as efficacious as conventional covers sprays,
(II) result in less fruit knockdown, and
(III) conserve natural enemies and result in fewer secondary pests.