Berry Grower Says She’s Beating Spotted Wing Drosophila With Netting

Dale Ila Riggs shows how easy the 80-gram exclusion netting goes up over her existing frames at The Berry Patch in Stephentown, NY. (Photo: Christina Herrick)

Dale Ila Riggs says “I feel like I’m beating SWD,” while walking through her netted berry patch.

Riggs, co-owner of the Berry Patch in Stephentown, NY, with her husband Don Miles, used exclusion netting on her blueberries for four growing seasons to prevent spotted wing drosophila (SWD) from ravishing her crop, and she’s seen remarkable results.

Last season, through the end of August her covered berries had 3 larvae per 1,600 berries sampled.

But, that wasn’t always the case. Prior to 2014, Riggs was frustrated. SWD had arrived in the fall of 2011 and hit The Berry Patch hard the next year. Riggs estimates losing 40% of her half-acre blueberry crop and about 25% of her fall raspberries. She was spraying 6 out of 7 nights a week with a backpack sprayer just to get by.

“This isn’t going to work,” she thought.

And while 2013 wasn’t necessarily a tough year for SWD infestations, preliminary research on exclusion netting for SWD at Cornell University’s New York State Agricultural Experiment Station in Geneva, NY showed promise. She thought this would be a fit on her 240-acre berry, vegetable, and cut flower operation, and thanks to a Sustainable Agriculture Research and Education Program (SARE) grant, she was able to conduct her own trials.

Extensive Trials

She tested 80-gram and 60-gram exclusion netting and regular bird netting in 2014 in blueberries. She used existing bird netting frames she had on her farm. Riggs purchased her exclusion netting from Tek-Knit Industries in Montreal because she was able to have 13-foot pieces sewn together to cover her existing infrastructure.

Riggs set up the netting using existing greenhouse hoops that used to support her bird netting. She connected three 26-foot pieces together on greenhouse purlins to make 78 feet of netting, which covered six rows of blueberries. She had one entry to the planting, a double-entry doorway made from a wooden frame.

In that first year, she had a very small late-season infestation in the 80-gram netting, versus a large mid-to-late-season infestation in the 60-gram netting and the regular bird netting, which had four pesticide applications. Riggs says she had a 0.67% infestation rate during the 10-week harvest period on her farm. Her treated control had 60% infestation.

Laura McDermott of Cornell Cooperative Extension sampled 225 berries weekly from the trial, which were overnighted to Greg Loeb’s lab in Geneva, NY, where they were placed in rearing cups.

Replicating the Study

The next year, Riggs decided the-80 gram netting showed the most promise and continued her trial but compared seven rows to a control of traditional spraying. And they modified the entry ways with ripstop nylon and zippers to better secure the areas of the study.

She used greenhouse wire lock channels with wiggle wire on the purlins to connect the separate pieces on the hoop supports. She also placed baseboards at the bottom of the structure, to which the netting was wiggle wired in to protect the netting from damage.

“I’m always experimenting,” she says.

In the second year of her trials, she had a 0.34% infestation, and in 2016 she achieved 0.00% infestation to which Riggs says “I know this works.”

Expanding Her Study

She also netted her fall raspberries in 2017, because as Riggs says “Spotted wing loves raspberries.” She estimates it’s no more than $500 to net the raspberries using an existing tunnel.

SWD adults were trapped on the farm in mid-June, but they didn’t get the blueberry netting up until early July. McDermott found SWD adults inside her netted blueberries in mid-July and Riggs says “we went on a sanitization blitz.”

In her fall raspberries, a flotation test showed 22 larvae in one berry. She removed all ripening floricane fruit, applied a spinosad with sugar through a fixed sprayer, and installed netting on the tunnel side walls and doors.

Following that application, Riggs says a sample of 180 berries showed three larvae, and then only five more larvae were detected in the raspberries for the rest of the season, when she harvested until mid-November.

“Timing is everything,” she says. “We’ve shown you’ve got to get the net up before SWD because there’s very little chance of infestation.”

An Investment

Since the SARE trial, Riggs has become a supplier of Tek-Knit netting, adding that she didn’t begin this expecting to sell anything.  A grower can purchase the netting for around $4,200 for half an acre, with a lifespan of 7-12 years or more. And as far as installing, Riggs says “we estimate that it took my husband five hours to put it up by himself. It took two hours to take it down and get it wrapped up for winter protection.”

“[The netting] does more than protect from SWD,” Riggs says. “You have to look at it as an investment.”

The 80-gram netting also protected her berries from 3 hailstorms and thunderstorms with 40-60 mph winds and heavy rain.

“This diffused the wind and rain so we don’t get any fruit drop. My top three years for yields have been during the four years I have been using the netting,” she says.

The Whole Package

Riggs says she approaches the handling of her fruit differently post-SWD. Berries once picked get refrigerated in a 33°F cooler in standardized flats. She also works with her H-2A laborers to explain the problems with SWD and encourage sanitation in the patch.

“Sanitation is key,” she says. “We harvest every day, we don’t leave overripe berries.”

And marketing is different, as well, she says. Riggs says she communicates the need to handle berries differently with consumers, saying “berries are fragile.” Riggs says she suggests consumers refrigerate the berries if they will not be consumed within 24 hours. Although Riggs says 95% of her berries get consumed within 24 hours, she says the combination of exclusion netting, sanitation, and cold chain are all a part of a combined effort.

“It’s a package,” she says. “There is no silver bullet. Netting is taking us 98% of the way there.”