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NMSU entomologist warns of new invasive fruit fly arrival to New Mexico

LOS LUNAS – A new pest has arrived in New Mexico, and a New Mexico State University entomologist says the insect could spell trouble for soft fruit growers.


One bugs
Drosophila suzukii, commonly known as the spotted wing drosophila, is a new pest not found in New Mexico before last summer. New Mexico State University entomologist Tessa Grasswitz is tracking the spread of this invasive pest.

Tessa Grasswitz, NMSU Extension integrated pest management specialist, reports that the Asian fruit fly Drosophila suzukii, commonly known as the spotted wing drosophila, was found in three locations in the Los Lunas area last summer.

“The arrival of this invasive insect is going to be tough on New Mexico growers,” Grasswitz said. “Cane fruits, like blackberries and raspberries, used to be good money spinners for our producers because they are high-value crops with no serious native pest problems. But this new insect is going to impact growers’ revenue.”

The spotted wing drosophila was first detected in California in 2009. Since then, it has spread across the country and has been present in some of the major fruit-producing states, including Oregon, Washington and Michigan, for some years.

The small fly lays its eggs in ripe or ripening fruits of cherry, raspberry, strawberry, blackberry, grape and similar crops.

“We first found the insect in mid-August last year, Grasswitz said. “And if the experiences of other states are anything to go by, we can expect it to become much more widely distributed in New Mexico this year.”

Because of its short life cycle, the spotted wing drosophila can complete multiple generations during a growing season, so it can build up very quickly. Growers in other states are spraying every week throughout the fruiting season to control the fly. They have to target the adults, because the eggs and larvae are protected inside the fruit.

“Many of the more effective pesticides that are being used in other states are not currently registered for this purpose in New Mexico,” Grasswitz said. “I am working with manufacturers to get some of the key pesticides registered with the New Mexico Department of Agriculture so that our growers have more control options.”

Until the pesticides are registered, Grasswitz said growers have very few tools to prevent the destruction of their fruit crops. Organic growers have even fewer choices.

“The spotted wing drosophila has destroyed existing integrated pest management programs for native pests of soft fruit crops in other states,” she said.

As the USDA integrated pest management coordinator for New Mexico, Grasswitz will be joining researchers from across the nation to help determine region-appropriate management strategies based on the biology and ecology of the spotted wing drosophila.

She has established insect traps to monitor the fly’s populations at NMSU’s agricultural science centers at Los Lunas and Alcalde, where soft fruit and berry crops are raised for research.

One aspect of the insect’s biology, which Grasswitz hopes will help New Mexico growers, is that the adult fly seems less able to survive the winter in areas where humidity is low.

“This observation is based on research conducted elsewhere in the United States,” Grasswitz said. “It’s probably the only thing we have in our favor, although at the moment, we really don’t know if our low humidity will slow down the spread of this pest within New Mexico.”