Spotted Wing Drosophila Alert July 17

On June 29 I posted on the threat of a new pest, the spotted wing drosophila (SWD). This post is on the latest development of SWD in NC from Dr. Hannah Burrack.

Spotted Wing Drosophila Alert
For commercial fruit growers

Suspected spotted wing drosophila (SWD, Drosophila suzkii) larvae have been found in North Carolina grown caneberries. Growers in areas with a known history of SWD should undertake an aggressive management program for this potentially devastating pest. Growers in areas without a history of SWD should determine the status of SWD on their farm by sampling fruit and trapping adult flies.

SWD in North Carolina

SWD has been detected in the following 23 North Carolina counties:
Anson, Ashe, Burke, Bladen, Craven, Davidson, Edgecombe, Greene, Henderson, Johnston, Lee, Lenoir, Lincoln, Montgomery, New Hanover, Onslow, Pender, Person, Randolph, Rowan, Sampson, Wake and Wayne.

SWD larvae have been found in fruit in the counties indicated in bold. In all of the listed counteis, adult SWD have been captured in traps.

SWD can feed on blueberries, blackberries, raspberries, strawberries, grapes figs, peaches, cherries, and many other soft skinned fruits, both cultivated and wild.

Growers of these crops in and around the 22 counties where SWD has been detected should consider themselves to be in areas witha history of SWD and manage accordingly.

SWD Management

Because SWD is new to North Carolina, our current management strategy relies on insecticides. You can find lists of registered insecticides and their probable efficacy against SWD at www.ncsmallfruitsipm.blogspot.com.

Select insecticides that will be effective against SWD (those expected to provide "excellent" control), and apply insecticides at the high end of the labeled rate range. Apply insecticides every 7 days, ideally rotating between at least two insecticides with different modes of actions (MOAs).

Always observe proper preharvest intervals and be aware that many insecticides have maximum residue levels (MRLs) for the United States and other countries. These residue levels may potentially occur before the maximum number of allowable insectice applications per season is reached. USDA maintains a database of MRLs (http://www.mrldatabase.com/).

Check with your marketer or wholesaler before using a new insecticide on your crop to ensure that it is acceptable in all locations where your fruit may be sold.

SWD larvae take 7-10 days to mature, so larvae found in fruit now are the result of egg laying activity over 1 week prior. Larvae inside fruit cannot be controlled; only adult SWD can be killed with insecticides.

Sanitation is crucial for SWD management. All ripe fruit (marketable or not) must be removed from the field and disposed of. Culls should not be left on the ground or plant. Freezing or "baking" in clear plastic bags placed in the sun will kill larvae, Burying or composting may not.

New Pests: Spotted Wing Drosophila and Kudzu Bug

There are two new insect pests that growers need to be aware of, spotted wing drosophila and the kudzu bug.

Spotted wing drosophila (SWD) is an invasive fruit fly pest of soft-skinned fruit (strawberry, blueberry, blackberry, raspberry, etc.). SWD was first observed in California in 2008 and then identified in 2009. In 2010, Dr. Hannah Burrack of NC State began an intensive monitoring plan for SWD in the Southeast. SWD was captured in NC and SC late 2010. SWD gets its name because the males have two spots on the end of their wings (one on each). Female SWD do not have spotted wings, but do have a serrated oviposter. This serrated oviposter allows the female to lay eggs in sound fruit, unlike common fruit flies which prefer decaying fruit. Because of this, SWD has potential to be an economically limiting crop.

SWD trapping is well underway throughout NC, in fact SWD was captured in Henderson County in mid-June. Small fruits producers are encouraged to start a monitoring program. Dr. Burrack explains how to construct and monitor SWD traps and how to identify them.

For treatment considerations, visit Dr. Burrack's post What to watch for: When treating SWD.

To read more about SWD or to view images, please visit Dr. Burrack's SWD page on her NC Small Fruits, Specialty Crops and Tobacco IPM blog.

If you would like assistance with monitoring, please contact me at sue_colucci@ncsu.edu or your local extension office.

Kudzu bug (adult) on soybean leaf.

Multiple kudzu bugs (adults) on soybean stem.

The next pest is the kudzu bug. This pest prefers legume crops, especially soybeans, but has also been observed feeding on potatoes, cotton and wheat. The kudzu bug was confirmed in central Georgia in 2009 and then spread throughout the state and to neighboring states in 2010. This pest has been identified in many NC counties, including Buncombe and Henderson Counties on soybeans. This pest isn't thought to be a problem on most vegetables, but those who grow edamame soybeans or potatoes should be concerned. The kudzu bug is a stem and leaf feeder, so far there have been no reports of the kudzu bug feeding on blooms or pods.

Based on Georgia data the economic threshold is one bug per sweep with large nymphs present, or three bugs per plant with large nymphs present. This pest is very mobile and will re-invade after treatment, so capturing or observing nymphs is important. According to the latest edition of NC Pest News, killing this pest has been relatively easy with conventional insecticides except the neonicotinoids (kudzu bug seem to be attracted to areas that have been treated with neonicotinoids). For organic producers, PyGanic is recommended. Other options are options are azadirachtin (Azagard) or kaolin clay (Surround), but the efficacy of these products is unknown.

To read more about the pest, see more pictures and a map of kudzu bugs movement in the southeastern US, see the June 24th of NC Pest News.