Spotted Wing Drosophila (SWD) is a serious pest of berries and cherries; as the primary driver of insecticide applications in those crops, growers of susceptible fruits are all too familiar with this insect. For a review of SWD biology and identification you can visit the NYSIPM Factsheet and the Cornell Fruit Resources websites on SWD, as well as other extension resources such as the University of Minnesota SWD webpage and the Oregon State SCRI webpage.
Monitoring
Monitoring and correct identification are critical steps for effective management. Especially for early ripening fruits such as strawberries and early raspberry varieties, the beginning of spotted wing flight may or may not coincide with ripe fruit; on-farm monitoring traps will let you know when spotted wing drosophila moves into your crop field so that you can initiate management in time to protect your crop, while also minimizing pesticide use. Potential benefits of using monitoring data to initiate management include reduced spray cost, lowering negative effects on the environment and human health, slowing development of pesticide resistance, and improved fruit quality.
Given the warm season, now is a good time to be preparing and setting out traps. Average emergence ranges from late May to early July across the state, depending on the site, crop and year. Average degree days (seasonal heat accumulation) and phenology are well ahead of averages, up to two weeks in Western NY, so we may see SWD flight sooner rather than later this year. Precipitation has also been average to greater than average across the northeast, which may lend to earlier fly emergence.
Both red jar (drowning) traps and red sticky cards baited with a scented lure can be used to monitor. Our research comparing SWD trap types on commercial farms over the past three years has demonstrated that both of these trap types are comparable for detecting first and sustained trap capture of SWD. Complete protocols for using these traps are on the Cornell Fruit Resources website.
Survey responses from berry growers in winter 2023-24 indicated that 78.6% of growers are monitoring or using the SWD blog for guidance on their farm. About 57% of respondents were actively doing their own management or extension was monitoring on their farm. About 43% reported they were not monitoring on their farm, but more than half of these people were still using the extension blog to make management decisions. Of those monitoring themselves, jar traps were more popular (77.8%) than sticky cards (22.2%), but this may be because the sticky cards are newer and there is less familiarity with them.
The salt floatation technique can also be used to detect fruit infestation. A sample of berries is submerged in a salt water solution for a brief period of time. The process is simple and requires few materials, but detecting the tiny maggots can be challenging. A video on the protocol for the salt flotation technique is available on the SWD Management Website.
| Research Protocols – Sustainable Spotted Wing Drosophila Management
Semi-field Bioassays (PDF) : This document provides details of a laboratory bioassay method as described in Van Timmeren, S. and Isaacs, R. (2013). Control of swdmanagement.org |
Management
Below are a few reminders of management tactics that should be used to successfully manage SWD this season:
- Sanitation – Harvest fruit frequently to prevent populations from building up. If possible, do not leave berries on the ground. Remove infested fruit and freeze, seal in bag and place in the sun or dispose off-site.
- Canopy management – Excellent pruning and weed management reduce humidity, creating an environment less conducive to SWD.
- Monitoring – Begin to spray as soon as fruits begin to ripen, once SWD has been trapped in your orchard/region.
- Rotate active ingredients (IRAC groups) through to harvest for resistance management. Resistance has been documented in other states, rotating is essential for preventing this in our region!
- Avoid the temptation to stretch spray intervals! 7-day interval should be the maximum.
- Plan out the order of insecticides you will use wisely, so that you save products with a lower PHI for use close to harvest.
- Focus on complete coverage, especially in the middle of the canopy where high humidity creates an ideal SWD habitat, and be sure to reach to the top of the tree.
- If it rains, reapply (according to label instructions).
- When choosing insecticides for European Cherry Fruit Fly and native Tephritid fruit fly control, prioritize those that have activity against SWD (more information about ECFF to come in an upcoming Fruit Notes issue).
- Exclusion – Polyethylene netting (80 gram or 1.0 x 0.6mm) requires a high upfront installation cost and must be very thoroughly maintained to provide no possible entry to the flies, but if done well can bean extremely effective method of preventing infestation. Exclusion netting must be installed before SWD arrival and must be well maintained.
Quick Guides for choosing insecticides.
- SWD Insecticide Quick Guide for Berries (Updated for 2024)
- SWD Insecticide Quick Guide for Tree Fruit and Grapes
New Berry Pest Monitoring Blog!
If you’re reading this post, chances are you already know about this change: This year we are creating a new blog for monitoring SWD along with other berry insect pests across the state. This blog includes a dynamic map of pest occurrence in geographic regions, rather than counties.
To subscribe, visit the Berry Pest Monitoring Blog and click ‘Subscribe’ on the right hand column. You will need to verify your email afterward. We will do our best to cross post during the transition. The most accurate, up-to-date information will be hosted on the new blog!