When you’re scouting your fields this summer, keep an eye out for ladybugs. If you spot some, pull out your cell phone and snap a quick photo. You’ll help entomologists understand what is happening to native ladybugs, and why several formerly abundant species have suddenly become rare.
The Lost Ladybug Project is charting ladybug populations across the U.S., with the help of 4-H clubs, students, gardeners and more than 3,000 others. Since the informal survey began three years ago, 10,000 ladybug digital images have been sent in from all over the country, says Cornell University Extension Entomologist John Losey, program founder. Farmers and crop scouts are in an ideal position to report on which ladybug species are thriving in cropland habitat, Losey says.
Why should you give a hoot about ladybugs?
For starters, they have voracious appetites for insect pests. One ladybug may eat 5,000 aphids. They also feed on spider mites and the eggs of corn borers, corn earworms, fall armyworms and many other damaging pests. That reduces the need for insecticides to protect crops.
“Lady beetles are so important for controlling pests,” Losey says. “We want to get a handle on what population shifts are taking place, and what that will mean for agriculture.”
Before about 1985, 98% of ladybugs in this country were natives, Losey says. Today, it’s fewer than 70%.
Three native species have all but vanished in the last 25 years, says Louis Hesler, an entomologist at the USDA Agricultural Research Laboratory in Brookings, SD. The nine-spotted ladybug, the two-spotted ladybug and the transverse ladybug were once common in farm fields across the U.S., but are rarely seen these days. Meanwhile, populations of foreign species, such as Asian ladybugs and seven-spotted ladybugs, have exploded. “We are concerned.” Hesler says. “What has changed? We don’t have answers.”
Still, don’t foreign ladybugs devour crop pests the same as natives?
Certainly, Hesler says. Seven-spotted ladybugs, for instance, were introduced intentionally to feed on pea aphids. Likewise, multicolored Asian ladybugs were brought to this country to help control pecan aphids in the Southeastern U.S. Both types have become major predators of soybean aphids.
In fact, “The total number of ladybugs may not have declined,” Losey says. However, “We’ve gone to a less diverse mix of species dominated by foreign ladybugs.” That weakens biological pest control. “In general, you get the best pest suppression with a diverse group of species that includes natives.”