By Kelley Tilmon and Mark Sulc et.al
We are receiving reports of near or at-threshold levels of potato leafhopper in alfalfa. As second-cut alfalfa grows, farmers should scout for resurging numbers in their fields. Younger alfalfa is more susceptible to damage at lower leafhopper numbers. If alfalfa is more than 7 days from a cut and plants are under normal stress, a good rule of thumb for a treatment threshold is: when the number of leafhoppers in a 10-sweep set is equal to or greater than the height of the alfalfa. 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. Vigorous alfalfa can tolerate higher numbers, and stressed alfalfa can tolerate fewer. Special attention should also be paid to alfalfa fields that were damaged by fall armyworms last year.
Source : osu.edu