In the last couple weeks, there have been numerous reports of spotted wing drosophila (SWD) damage on blueberries, brambles, and grapes. Tennessee counties reporting spotted wing drosophila trap catches or damage to fruit crops include Unicoi, Anderson, Greene, Warren, Grundy, Franklin, Coffee, DeKalb, Cannon, Moore, Franklin, Davidson, Cheatham, Sumner, Lawrence, Benton, and Gibson.
This pest apparently overwinters in many areas of the U.S. and seems to be active practically year-round here in the South. It can reproduce on all sorts of weeds and other wild plants that produce soft fruit. SWD is spreading rapidly and they should be about everywhere in Tennessee within the next couple years. Besides small fruit crops, it is also a pest of cherries.
We are currently transitioning from a detection phase 'have we got them?' to "hey we got them, how do we stop them?' phase. A chemical control program is warranted if the adults are being detected by using the sugar, water and yeast baited traps or the larvae are being found in fruit. Fruit can be visually inspected for the presence of larvae and damaged fruit. Fruit can also be placed in a plastic bag with either salt or sugar in a water solution.
If possible, start your spray program early, when fruit first start to show color (varaison for grapes) and continue up to harvest (obey pre-harvest intervals). Spray on a 5-7 day spray schedule. Reapply insecticide after heavy rains, which have been common this summer.
Organic growers should definitely spray on a 5 day or shorter schedule. The OMRI approved insecticides that are the most effective are Entrust and Pyganic. An on-line MSU Extension raspberry and blackberry publication states that Entrust has a 5 day residual and Pyganic has only a 2 day residual. A similar MSU Extension blueberry publication states that Pyganic has ~ 3 days of control. Whether 2 or 3 days, the residual is short and thorough spray coverage is essential with any insecticide. Use a sprayer that can apply a high spray volume with enough pressure to turn over leaves and get adequate insecticide into the densest part of the plant where many adult flies are found. Try to rotate between organophosphate/carbamate insecticides, pyrethroids, and spinosyns with each application. Insecticide recommendations for SWD are available at: http://www.smallfruits.org/ SmallFruitsRegGuide/index.htm.
SWD can develop in leftover fruit on the plant or in dropped fruit. Some have suggested that collecting fruit that can't be sold and disposing of it in a manner that will kill SWD larvae and other life stages is a worthwhile practice. Fruit needs to be buried beneath 30 cm (1 foot) of sand to prevent emergence of the adult SWD flies. Other options include placing fruit to be disposed of in a plastic bag and placing it in the sunlight or the freezer. Place larger amounts of fruit in a sunny area of the ground, cover with a sheet of clear plastic and seal the edges with soil to heat and kill all life stages present. Detecting spotted wing drosophila damaged fruit and being able to sort it out is challenging to say the least. Dr. Hannah Barrack, NCSU Entomologist, addresses some strategies that growers can use post-harvest to decrease the chance of sending infested fruit off for processing such as holding fruit at less than 41F and sorting out soft fruit.
For additional information, please refer to the following links:
Hello fellow gardeners... Welcome to our blog site!