South Florida vegetable growers worried about the invasive tomato thrips should make certain they’re looking for the pest in the right places, say University of Florida researchers.

Also known as common blossom thrips, the species is native to South America and attacks a variety of crops.

A major pest of tomatoes and cucumbers in its home range, the thrips has been detected regularly in south Florida since 2008.

A team from UF’s Tropical Research and Education Center in Homestead recently published a study outlining their efforts to assess the abundance and distribution of tomato thrips in cucumber fields. Their findings appear in the June 2012 issue of the journal Bulletin of Entomological Research.

The study was conducted on commercial fields in the Homestead area. Once established, the vines were treated with Bacillus thuringiensis-based insecticides.

For three growing seasons, the researchers assessed thrips distribution in the fields and on individual plants. They found the insects first appeared on the blossoms of cucumbers planted at the edges of the fields, apparently arriving from nearby weed patches.

The insects remained on the margins initially, then began moving into the fields.

By the eighth week after planting, fields had developed “hot spots” of high thrips density. On individual plants, the pests congregated around blossoms — not surprising, because they’re members of the flower thrips family.

Garima Kakkar, a graduate research assistant at UF’s Fort Lauderdale Research and Education Center and one of the paper’s authors, said producers concerned about the pest should inspect blossoms rather than leaves, and continue inspections for several weeks after blossoms appear.

The study results also indicate that growers who seek to control tomato thrips might not need to apply pesticides uniformly throughout their fields.

If inspections show that tomato thrips are clumped together, it may be worth considering a spatially explicit treatment approach, with pesticides applied only where thrips are most likely to be present.

There’s also a lesson for home gardeners, Kakkar says: Keep weeds away from your garden, because they can harbor thrips.

For more information on tomato thrips, see http://goo.gl/hOCy1