Released: May 31, 2001

Spring’s Mobs of Lepidoptera No Reason to Worry - Yet

MANHATTAN, Kan. – The whirring of wings that’s been worrying Kansas gardeners this spring is an unusually large flurry of moths – many of which are actually foraging during daylight hours. Delicate butterflies seem to be everywhere, too.

Kansans know these flittering fliers always produce eggs that hatch into plant-chewing caterpillars.

"The adults are no cause for concern. Their mouthpart is like a coiled straw that can only suck up liquids, such as water and flower nectar," said Bob Bauernfeind, entomologist at Kansas State University.

Whether their offspring will be a problem depends on the moth or butterfly species, he added.

Ironically, the moths now teeming in towns and cities can be a bigger threat for farms than for yard plantings. Even so, their news-making caterpillars can cast suspicion on all members of the lepidoptera family – many of which are harmless, if not beneficial to home landscapes.

"Large numbers of lepidopterans doesn’t mean gardens and landscape plants will soon be eaten bare," Bauernfeind said. "For example, red admiral, hackberry and painted lady butterflies have been filling the air in recent weeks. But the larvae of these butterflies, respectively, prefer to feed on nettles, hackberry trees and thistles."

The moths swarming at night in brightly lit parking lots and convenience stores are often looper species.

"Forage looper larvae feed on clovers and alfalfa, primarily in rural settings. They pupate there," he said. "When they hatch, the adults can be drawn to the lights of the city. But those moths will return to the country to deposit their eggs because that’s where their larvae’s preferred host plants are."

To a point, army cutworm moths follow the same script. Their city-light-seeking adults are the millers that stream out when people walk by low bushes, garages, sheds and cars.

"But they don’t produce nearby rural offspring, as loopers do," the entomologist said. "Army cutworm moths simply disappear, as if on cue. They migrate to the upper elevations of the Rockies, where they spend the summer eating and maturing. In the fall, they migrate back to the central Plains to deposit their eggs in alfalfa and wheat fields – where the larvae can become a major yield-damaging pest."

A more universal threat among spring’s fliers is the variegated cutworm moth. Its larvae like to feed on alfalfa and clover. But they’ll also feed on anything from tender flower and vegetable plants to tough yucca leaves and tree bark.

Beyond that, variegated cutworms are a climbing species that produce several generations per year.

"Still, the moths don’t necessarily spell trouble for homeowners," Bauernfeind said. "For one thing, the moths tend to disperse from areas of high concentration before laying eggs. Not all the eggs they deposit are viable, plus many dry up during hot, dry conditions. Predators and parasites of both eggs and larvae also tend to reduce the variegated cutworm threat."

The entomologist does not recommend trying to control moths or butterflies, although their populations seem unusually large this year.

"Even if there were an advantage to controlling adult lepidopterans, the attempt would be futile, due to the wide area where they occur and all the nooks and crannies they occupy," he said.

Nonetheless, the adults can serve as a reminder.

"Homeowners should periodically inspect all landscape plants throughout the growing season, looking for damaging larvae and other insect problems," Bauernfeind said. "Generally, the younger and smaller they are, the easier pests are to control."

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward, Communications Specialist
kward@oznet.ksu.edu
K-State Research& Extension News