Cool temperatures slow leafy spurge flea beetles for redistribution

The cooler than normal spring temperatures will most likely delay normal emergence of leafy spurge flea beetles which is a bio-control agent because their life cycle is based on growing degree days much like plants, said Darrell Deneke, South Dakota State University Extension IPM program coordinator.

“However, as our daytime temperatures rise, the likelihood of adult flea beetle emergence also increases, so now is a good time to start watching for adult flea beetles,” Deneke said.

South Dakota has been using the leafy spurge flea beetle as a bio-control agent to manage the noxious weed, leafy spurge since the 1980s.

In the early years, Deneke said several species of the leafy spurge flea beetle were studied and released, but today two species are most commonly used. They include the black flea beetle, Aphthona lacertosa and the brown flea beetle, Aphthona nigriscutis.

“These two species of leafy spurge flea beetles have been very effective in the battle of managing leafy spurge infestation across the state,” Deneke said. “This group of flea beetles is very host-specific to the leafy spurge plant, which is why they make an ideal bio-control choice.”

The flea beetles typically take three to five years to establish and impact leafy spurge infestations. The adult will do some plant feeding, but it is the larval form of the insect that causes the lethal injury to the leafy spurge plant. The newly hatched larvae will feed on the leafy spurge roots and root hairs, ultimately affecting the plant’s ability to utilize water and nutrients. Deneke explained that this weakens the plant and makes it vulnerable to disease and winter temperatures.

The state of South Dakota has a program promoting the collection and distribution of leafy spurge flea beetles.

“Each year the South Dakota Department of Agriculture organizes leafy spurge collections around the state where land owners can help collect the flea beetles to be released on their leafy spurge infestations,” Deneke said.

To participate and add your name to the list to be notified of area collections contact Ron Moehring 605-773-3299, Brenda Sievers 605-353-6700, or Mike Stenson 605-773-5645 with the S.D. Department of Agriculture.

For additional information on noxious weed control using approved bio-control agents contact Darrell Deneke, SDSU Extension IPM Coordinator at 605-688-4595 or e-mail Darrell.deneke@sdstate.edu.

–SDSU Extension