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SWD recommendations for sweet cherry

These recommendations are derived from translated Japanese research articles on spotted wing drosophila (SWD), preliminary trapping data from Janet Caprile (UCCE farm advisor – Contra Costa County) and Bill Coates (UCCE farm advisor – San Benito County), insecticide efficacy data from Mark Bolda (UCCE farm advisor – Santa Cruz) and fruit maturity susceptibility data from Jana Lee (USDA – Corvallis, Ore.).

Control procedures are conservative due to the lack of insecticide efficacy data on California cherries and damage experience by cherry growers this past season. These are our best guesses with limited data and we expect the recommendations to change over time.

• Monitoring

Place a commercial bucket style trap or a 1 quart plastic container with screen (three-sixteenth inch holes hardware cloth) on the top and bait the trap with 1 inch of apple cider vinegar. The three-sixteenth inch holes will limit the number of large moths, flies and bees captured in the traps.

The plastic containers are about 50 cents each and apple cider vinegar is about $3 per gallon from Smart & Final. Replace the vinegar weekly (remove spent bait from the orchard – do not dump the spent bait on the ground in the orchard). Place trap about 3 feet to 5 feet off the orchard floor and monitor twice weekly from first color change (light green to straw) until completion of harvest. Count only flies with spots on the tip of the wings (male SWD). OptiVISOR (optical glass binocular magnifier) will aid in the identification of flies. If any SWD are found in the traps, take control action immediately.

• Generation time

One generation requires 338 DD with a lower threshold limit of 48 degrees. The table below shows the approximate generation times throughout the spring and summer in the northern San Joaquin Valley (Linden) and the central coast (Hollister). These generation times are based on 30-year average temperatures from the UC IPM weather network and will vary depending on current temperatures.

• Cultural control

If conventional insecticide treatments are not an option (organic growers), and if fruit from pollinizer varieties matures earlier than the main variety and the pollinizer fruit will not to be picked and sold, then pick and remove pollinizer fruit at least one week before harvest of the main variety.

This will prevent the SWD from emerging from the pollinizer fruit during the main variety harvest. Fruit removal is a critical control step for organic growers because of the lack of known effective organic insecticides. Conventional growers can suppress SWD on pollinizer fruit by insecticide applications.

• Chemical control

Begin applications when the pollinizer or the earliest variety in the orchard, changes color from pink to red. Repeat applications at seven to 10 day intervals until harvest.

From Jana Lee and from Japanese literature it appears that the SWD will infest ripe cherries of red to mahogany color. Also, from the Japanese literature it appears that three or four applications are required to control the pest and that the organophosphate and pyrethroid insecticides are effective for one to possibly two weeks.

Observe all pre-harvest intervals (PHI) and re-entry interval (REI) periods and rotate between materials of different chemical classes between applications to slow the development of resistance. At this point in time, we are recommending adding Nu-Lure bait at 3 pints per gallon per 100 gallons, with a final spray volume of 50 gallons per acre. Do not include surfactant with Nu-Lure. Nu-Lure should be removed during post-harvest washing.

Discussion of research findings necessitates using trade names. This does not constitute product endorsement, nor does it suggest products not listed would not be suitable for use. Some research results included involve use of chemicals which are not currently registered for use, or may involve use which would be considered out of label.

These results are reported but are not a recommendation from the University of California for use. Consult the label and use it as the basis of all recommendations.

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