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Agronomic Crops Network

Ohio State University Extension


Look Out for Potato Leafhoppers in Alfalfa

Now that most alfalfa has had its first cutting, it is time to begin sampling for potato leafhoppers as the crop reaches a sufficient height for sweep-net sampling.  A single sample is 10 sweeps of a sweep net. 

When the average number of adults and nymphs in a sample is equal to or greater than the average height of the alfalfa stand, insecticide treatment is warranted.  For example, if the alfalfa is 6 inches tall and the average number of leafhoppers is 6 or higher, you should consider an insecticide application. If the average is lower, then re-sample the field in a few days.

There are alfalfa varieties that are resistant to the leafhopper, these have glandular hairs which help limit feeding.  If you are growing resistant alfalfa, the above threshold should be increased 3-times (for example 18 leafhoppers for 6 inch tall alfalfa).  However, if the resistant alfalfa is a new planting this spring, growers might want to use thresholds meant for regular alfalfa during the very first growth from seeding.  After the first cutting, growers can then use 3X times the normal level threshold.

More information on potato leafhopper, including how alfalfa growing conditions might affect the threshold, is available 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.