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Agronomic Crops Network

Ohio State University Extension


Time to Start Scouting for Potato Leafhoppers in Alfalfa

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.

For a video on scouting techniques

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For a video with detail on damage, ID, and control options 

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Our extension factsheet on potato leafhopper in alfalfa is at

A great resource for other forage-related questions is the Forage Page at

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.