Berry Crops Destroyed By Pests

Jun 16, 2014

Credit University of California

A little pest is causing big trouble in the local berry community.

With a name longer than its 2 mm size, the spotted wing drosophila attacks ripe fruits and berries, laying eggs in the fruit and decimating the crop.

“They are a very big problem,” said Bracken County Extension Agent David Appelman. “I did verify the presence of the insect in both Mason and Bracken County last year.”

Appelman's crop was not immune.

“They devastated my blackberries last year and we will have to wait and see if the harsh winter will reduce their population,” he said.

According to Rusty Monahon, who operated Bracken Berry Farm until this year, the pests have destroyed a family business.

“We are no longer in operation,” Monahon said, recently posting photos on his Facebook page of his former berry patch field plowed under.

The pest, a fly the size of a common vinegar or “fruit-fly” is to blame, said Appelman, who helped Monahon identify the problem in his crop last year.

The larvae are not toxic, but infested fruit are not desirable for commercial, or home gardening consumers.

“There is no chemical yet to fight them,” Monahon said. “The problem is if there was a chemical for this, the application of it would be too close to harvesting and you would have residue left on the fruit. (You) just can't win.”

Unlike other fruit flies that lay eggs in over ripe or rotting fruit, this insect can lay eggs in fruit before it ripens, Appelman said.

“This results in poor shelf life or even unusable fruit. Small, backyard gardeners can try to use traps as a means of control. Instructions on how to make traps are available from our office,” he said.

With a SWD larvae infestation damaging his crop, Monahon's berries were unsellable, therefore SWD destroyed a business that signified a decade-long family operation and the work of his daughter and late son, Monahon said.

Monahon is not sure when or if he will go into the berry business again.

“We might start again sometime but won't until this problem is solved,” he said. “Then there will come another problem.”

It takes a few years for a new berry patch to mature to a commercial level.

“This is very discouraging for many growers as blueberries, blackberries and raspberries are fruits that we could grow with limited or no pesticide applications,” Appelman said. “Grapes and possibly peaches will need insecticide to protect the fruit from this insect.”

Identifying SWD is tricky. It resembles a vinegar fly, which is often seen near rotted fruit.

According to research officials, SWD are distinguished from other vinegar flies by markings and prominence on ripe fruit on the vine or tree versus downed or decayed fruit.

SWD prefer softer and thinner skin\fruits as host for their offspring, but may infest figs, apples, tomatoes and grapes, where skins may have split.

Each egg has two fine, white, hair-like structures that stick out of the fruit that function as breathing tubes for the larvae.

Infested fruit will begin to collapse, bruise, or wrinkle within a few days after the female has laid eggs. The cycle from larvae to breeding SWP is about two weeks, so multiplication of the pest in a crop can be rapid, official said.

On the bright side, locally, strawberries seem to be free of the pest.

“I did not see any indications that the strawberries were affected in this area,” Appelman said.

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