US department of agriculture (USDA) scientists are using what they have termed “DNA barcodes” to monitor insects that damage potato crops and to make pest management decisions.
In DNA barcoding, scientists sequence a designated part of an organism’s genome and produce a barcode from it for a systematic comparison with the sequenced DNA of other closely related species. Matthew Greenstone, an entomologist with the USDA’s Agricultural Research Service (ARS) at its invasive insect bio-control laboratory in Maryland is using DNA barcodes to identify insect predators best equipped to control the Colorado potato beetle, which is the single most damaging insect pest of potatoes in the eastern US.
Numerous studies have analysed the gut contents of predatory insects to evaluate their ability to control pests in a field. But predators digest prey at different rates, so simple gut analysis is insufficient for accurately comparing the effectiveness of different predators. Greenstone has fine-tuned the approach, using barcodes to come up with a way to factor in how quickly different insects digest prey.
He and his colleagues collected four potato beetle predators, fed them lab-raised potato beetles and determined how long the pest’s bar-coded DNA could be detected in the predators’ guts. The results, published in the journal Entomologia Experimentalis et Applicata, show the importance of taking digestive rates into account when evaluating insect predators as bio-control agents. They may also provide a breakthrough in guidance to growers on the most effective control strategies for combating a voracious pest.
Greenstone said: “Different pesticides have different effects on different predators, and not all predators are equally susceptible to all insecticides. Based on what you learn, you might delay spraying insecticides, rule out the use of insecticides that harm your most important bio-control agents, or limit spraying to certain times, depending on the predator’s habits.”
