SWD Update 13 July 2011
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Spotted Wing Drosophila Update for 7-13-11
This Update is a collective effort. It is composed by Peerbolt Crop Management with contributions from OSU, USDA-ARS, WSU, B.C. Ministry of Agriculture and various northwest berry industry people.
Note: A Regional Monitoring report has not been included this week in order to have the space to pass on the following information. In general, most apple cider vinegar traps in commercial berry fields continue to have low overall SWD adult numbers. Commercial growers however are advised to not rely too heavily on these monitoring traps to time their insecticide applications. In this period of time, when we’re still in the process of developing an effective IPM decision making model for SWD, and with fruit ripening, growers should rely primarily on past experience, fruit ripening stage, and the fruit sampling protocols listed below to make their management decisions.
• Last year mid to late July was the window of time in which we saw a dramatic increase in SWD pressure on all west side berry crops from Northern California into The Fraser Valley in B.C.
• With the 2011 crops being 10 to 14 days later than 2010, it is possible that SWD will also be a little later in its development. But we shouldn’t take that for granted.
• Be prepared. Be conservative & pro-active. If you or your neighbors had SWD pressure last year, take all reasonable precautions to minimize the risk this insect poses to your crop.
• SWD populations are starting to increase with breeding activity and the spring generations emerging in cherries, strawberries, caneberries and other ripening fruit in California, Oregon, and Southwest Washington.
• The presence of ripening fruit draws SWD into the fields from border areas.
• From this point on, each successively emerging generation will quickly increase SWD numbers and the pressure on susceptible crops.
• In late season strawberries, the primary confusion appears to be between our regular fruit flies and SWD with some growers showing concern with what is most likely our usual over-ripe fruit insect.
• Once ripe fruit is present in the field the traps’ ability to attract adult flies is much diminished.
• In view of this, growers & fieldmen are advised to rely more on regular sampling of the fruit using the salt solution method to monitor SWD once there is ripe fruit.
• The salt solution sampling method is a valuable additional tool for growers and processors. Allowing them to determine infestation levels well before the fruit enters the processing plant.
From Michigan State: Comparison of fruit sampling methods for spotted wing Drosophila in blueberries (7/12)
This recent study shows some very interesting results. The salt test we’re outlining below did not compare well with some other more intensive types of sampling methods. However, our researchers in the Northwest (both public & private) have had good results with these protocols and, for now, we’d advise to stay with the salt immersion test. This all is a work in progress!
Guidelines for checking the fruit for SWD larvae in the field
These suggestions are based on techniques that various public researchers and industry personnel have been developing over the past year and a half. If any of you have ideas for improvements to these protocols, please pass them along. We’re all in this together.
•Depending on size of fruit (strawberries take longer than caneberries or blueberries), the larvae will emerge from the fruit into the salt solution in a short period of time.
•The smaller the larvae and the lighter the infestation, the more difficult it is to see the larvae.
•Excellent lighting when looking for the larvae is critical to being able to see the smaller ones.
Present suggested methods:
For scouts/field checking (We have created a video of this larvae-checking method.):
1. Collect a sample of fruit to be tested (Strawberries: 25-30 per sample, Caneberries/blueberries: 75 per sample)
2. Put fruit in a gallon size sealable plastic bag.
3. Pour in enough of the salt water solution to allow the fruit to float (solution is: 1 cup of salt per gallon of water).
4. Mark bag with field code/date.
5. For a quick check in the field after a designated period of time (at least 15 minutes) holding the baggie up to light. This helps to see the larvae in the solution
6. For a more thorough examination, after a designated period of time (at least 15 minutes), pour the fruit and salt solution out into a shallow tray and use a piece of wire mesh screen to hold the fruit down making it easier to separate the larvae from the fruit.
For processors or fruit handling stations:
1. Collect a two pound sample of fruit to be tested.
2. Put the sample into a shallow tray and cover with the salt water solution (1 cup of salt per gallon of water).
3. After a designated period of time (at least 15 minutes) use a piece of wire mesh screen to hold the fruit down to make it easier to separate the larvae from the fruit.
Management Material Resources
Oregon & Washington
•Blueberries: SWD pesticide options & information
•Raspberries & blackberries: SWD pesticide options & information
•Strawberries: SWD pesticide options & information
British Columbia (6/28/11): SWD Management in BC Berry Crops (with insecticide options listed)
Use of Entrust insecticide in organic berry production (Click here for label)
There are limitations on the use of Entrust that need to be strictly followed. Spinosad, the active ingredient, is very susceptible to insects developing resistance to it. Entrust is the only major material that can be used in an SWD organic insecticide program. You can’t afford to ‘burn up’ Entrust as a control option by overuse.
Blueberries (3 day PHI, 4 hour REI)
• Do not apply Entrust more than 3 times in any 30 day period.
• Whenever Entrust is applied three times in succession this should be followed by no use of Entrust for a 30 day period or rotation to another insecticide class.
• Do not apply more than a total of 9 oz of Entrust (0.45 lb a.i. of spinosad) per acre per crop or make more than 6 applications per calendar year.
• Minimum Treatment Interval: Do not make applications less than 6 days apart.
Caneberries (1 day PHI, 4 hour REI)
• Do not apply Entrust more than 3 times in any 30 day period.
• Whenever Entrust is applied three times in succession, this should be followed by no use of Entrust for a 30 day period or rotation to another insecticide class.
• Do not apply more than a total of 9 oz of Entrust (0.45 lb a.i. of spinosad) per acre per crop
• Or make more than 6 applications per calendar year.
• Minimum Treatment Interval: Do not make applications less than 5 days apart.
Pesticide tank mixes caution
In an effort to manage the risk involved with this new pest, some growers are using combinations of pesticides that they have not used in the past. Before applying an unfamiliar tank mix, be sure to check with your supplier, crop consultant, or other advisor to be sure it won’t cause damage. Some mixes have the potential for unexpected, economically damaging effects—just the thing we’re trying to avoid by using them.