Louisiana blueberry growers have a new pest to watch for that has the potential of reducing their yield by up to 30 percent.
LSU AgCenter entomologists have confirmed that the spotted wing drosophilla, a member of the fruit fly family that has been moving across the nation since the early 1990s, has finally reached the state.
“This insect was originally observed in Japan and later moved in China,” said LSU AgCenter entomologist Michael Ferro. “In the 1980s it was found in Hawaii, then in the 1990s in California.”
The pest moved across the northern part of the country, then down the East Coast in recent years.
“This fruit fly is different in that normally fruit flies will only attack ripened fruit, with a wound or a bit of blemish or a problem,” Ferro said. “The spotted wing drosophilla likes soft fruit like blueberries, blackberries, raspberries, but it will also attack plums and cherries.”
There are about 1,500 species of fruit flies, and they all look alike. But the one good thing about this species is the male is very distinct.“This guy has these black dots on its wings, red eyes and black bands on its front legs.”
Unlike other fruit flies, the spotted wing drosophilla female has a long, spike-like ovipositor, which is an egg-laying device with serrated teeth on it.“The female will land on a fresh, not quite ripe blueberry, puncture the skin and lay her eggs inside.”
Females have the ability to lay up to 350 eggs during their lifetime. And with heavy infestation, multiple females may lay eggs in the same berry.
Ferro said if you pick a berry with a fresh egg inside you won’t know there’s a problem, but after a while, the berry will become soft.
Louisiana has three varieties of blueberries that provide three picking seasons that run from late May through mid-August.
The insect is not good news for Louisiana growers because the southern climate allows for up to 13 generations, which can live up to 300 days as adults.
Ferro said because this is the first year the pest has been seen here, nobody really knows how bad the losses will be.“We do know the first year of infestation is normally the worst because you don’t yet know how to deal with it. In California, there was about $500 million in losses the first year it was seen.”
This year growers are told to watch for the pest, which can be done by making homemade monitoring/traps.
“They are really easy to make. What you’ll need is a plastic cup with some holes in it, and you’ll put apple cider vinegar in the bottom as the bait. Hang a sticky trap inside and watch how the numbers change over time.”
Spikes and falls in numbers can be correlated to generation times, which will let one know when spraying is needed.
“The good news about this insect is that there have been no cases where it is shown to transmit disease. So, at the end of the season, you may have fruit loss, but there should be no problem with the trees.”
Several approved pesticides are available to growers, but Ferro also suggests that growers remove fallen or damaged fruit.
For additional information on the spotted wing drosophilla, contact your local LSU AgCenter office.