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 seven 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 eight or higher, treatment is warranted. If the average is seven 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.
For a video on scouting techniques visit https://forages.osu.edu/video/scouting-potato-leafhopper-alfalfa?width=657px&height=460px&inline=true#colorbox-inline-51399545
For a video with detail on damage, ID, and control options visit https://forages.osu.edu/video/potato-leafhopper-identification-and-damage-alfalfa?width=657px&height=460px&inline=true#colorbox-inline-397628030
Our extension factsheet on potato leafhopper in alfalfa is at https://ohioline.osu.edu/factsheet/ENT-33
An excellent resource for other forage-related questions is the Forage Page at https://forages.osu.edu/home