Tolerance to organic controls observed in California SWD population

Mark Bolda, Santa Cruz, Monterey & San Benito UC County Farm Adviser, has reported on recent laboratory assays conducted in California demonstrating tolerance to Pyganic (pyrethrins), an organic insecticide used against spotted wing drosophila (SWD). The assays were conducted on a population that had been treated in the field with Pyganic many times.

Organic management tools for SWD are very limited. Entrust (spinosad) and Pyganic (pyrethrins) are the two most effective organic control methods, but both have short residual control times and must be applied frequently. This means that SWD are exposed to pesticides over multiple generations, which is a recipe for resistance development. The same situation exists with conventional insecticides, but there are more modes of action available to rotate, which lessens the likelihood of short term resistance development.

The two-year period from SWD detection to potential pesticide tolerance development is definitely short term and only highlights the fact that we need to manage SWD on a system-wide scale: optimizing non chemical/cultural management to reduce populations, wisely selecting pesticides, and rotating modes of action.

More information
Suspected Tolerance to Pyganic (pyrethrin) Found in Spotted Wing Drosophila - Strawberries and Caneberries Blog

Southeastern Strawberry Expo - A busy 3 days

The 2009 Southeastern Strawberry Expo wrapped up Tuesday. The meeting fostered lots of great conversation and research ideas. I always enjoy seeing growers who I have not encountered over the summer, including John Vollmer, who's farm we visited Sunday afternoon.

John and his family have been growing strawberries and other crops organically for 7 years, and come March 2010, his entire farm will be certified organic. John chose organic production to address a market need and has actively sought information on how optimize this system for his farm. This has lead John to cooperate with several extension specialists, including me. On Sunday, I shared some of the results for work we conducted on organic mite management in 2009 as well as some of the system-wide approaches to minimizing spider mites in organic strawberries.

John also detailed some of his other production practices and showed off a thriving winter cover crop of oats and red clover. Finding organically certified strawberry plugs has been a major challenge in recent years. This year, weather added another layer of difficultly. The California nurseries that John works with were flooded in late summer, resulting in a total loss of his intended plants. After much scrambling, John made the switch to cut off plants for his entire farm. Their first field leaves are just coming in, and they are smaller than John would like for this time of year, but they appear otherwise healthy.

On Monday, the NC Strawberry Association recognized its outstanding grower of 2009, Lee Berry (could you pick a better name?) of the Berry Patch. Lee shared his marketing strategy, which relies in no small part on his store, which he has dubbed the "world's largest strawberry". According to Lee, his only competition has been from "some folks in Iowa". Well, being that much of my extended family is from Strawberry Point, I am pretty sure I know where he's talking about! Lee's strawberry wins, hands down, despite the mid Western fondness for all things fiberglass.

Honored for their service to the industry were the NC Plant Disease & Insect Clinic at NCSU and a truly unsung hero of the NCSU strawberry horticulture program, technician Rocco Schiavone. I know I would have been lost without his advice many, many times.

My session on when not to treat strawberries is available in pdf form by request as are additional handouts. The 2010 Southern Region Stawberry IPM Guide will be online in January.