Thrips Gone Wild

01/01/2010 02:00:00 AM
Vicky Boyd, Editor

Western flower thrips and the virus have a unique relationship, Funderburk says. Only the nymphs can pick up the viral disease when feeding on infected plants.

The virus remains in the insect until it reaches adulthood, at which time the adults can spread it to healthy plants.

Western flower thrips head south

Western flower thrips were first confirmed in the state in 1985 in the northern production areas.

Growers have always seen the native Eastern flower thrips and Florida flower thrips, but they typically don’t cause economic damage, Funderburk says. In addition, they tend to outcompete the Western flower thrips under natural circumstances.

When the competition and beneficial insects were removed by broad-spectrum pesticides, Western flower thrips took over.

“The worst thing that can happen to pepper growers is when a [pepper] weevil problem comes in,” says Madeline Mellinger, president and founder of Glades Crop Care. “Once you nuke the weevil, you kill the Florida thrips and you open yourself up to the damaging thrips.”

Meanwhile, in the southern part of the state, Western flower thrips didn’t appear until 2005.

Funderburk and UF colleagues have developed an IPM program for peppers and eggplant that relies heavily on preserving the minute pirate bug, a voracious enemy of Western flower thrips. A thrips management plan for tomatoes is in the works.

Photo by Frank Peairs, Colorado State University;
When battling Western flower thrips, take an integrated approach and choose pesticides that preserve beneficial insects, such as the minute pirate bug (above). And make sure they don’t flare Western flower thrips (above right).
Photo courtesy of the Agricultural Research Service

ID, thresholds and beneficials

Key to the programs is identifying thrips species when scouting, Funderburk says.

If you’re growing peppers in the north, the treatment thresholds are six Western flower thrips per flower or two larvae per fruit.

One minute pirate bug can consume up to 100 thrips. That means that one Orius spp.—as the group is known scientifically—per 50 Western flower thrips can keep the pest under control without spraying.

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