Jeff Burbrink

By JEFF BURBRINK
Extension Educator, Purdue Extension Elkhart County

GOSHEN — A local crop consultant told me they were seeing a growing number of potato leafhoppers this week. In most cases, the second cutting of hay has happened or is happening in many locations.

Potato leafhopper are tiny little insects. They do not overwinter here, but instead ride the spring winds up from warmer climates. If you leave your lights on at night and crack open a few windows, you’ll soon find potato leafhoppers flitting about near the light. Leafhoppers are often scouted with a sweepnet because they are so small.

When leafhoppers feed, they first force some of their digestive juices into the leaf with their mosquito-like mouthparts. The leaf tissue is partially digested when it is sucked back into the leafhopper. The injury occurs because the some digestive juices are left behind and continue to destroy the tissues in the leaf.

A good rule of thumb for treating alfalfa is, if there are more than 7 days until the next cutting, when the average number of leafhoppers in a single sample (10 sweeps) equals or is greater than the height of the alfalfa, treatment should be considered if harvest is more than 7 days away.

For example, if the alfalfa is 8 inches tall and the average number of leafhoppers per sample is 8 or higher, treatment is warranted. If the average is 7 or lower, the grower should come back within a few days to see if the population is higher or lower.

There are quite a few products labeled for leafhopper control. Purdue’s recommendations for alfalfa pests are posted here.