Potato Leaf Hopper in Alfalfa

Alfalfa growers should be keeping an eye on the populations of Potato Leaf Hoppers in their fields. On the most recent C.O.R.N. (Crop Observation and Recommendation Network) call, it was shared that around the state there are very active populations of PLH. In several cases it was shared that PLH levels were reaching more than double the action threshold. The threshold for 20+ inch alfalfa is 20 PLH and levels were seen as high as 50-60 PLH per 10 sweeps. Even for alfalfa with a high tolerance to stress from PLH feeding, these elevated PLH population levels will almost certainly result in a yield reduction. This yield reduction can not only impact the current stand, but the stress of heavy PLH feeding may result in a yield loss in subsequent cuttings. Management of the PLH can be broken down into three strategies: growing PLH resistant or tolerant varieties, harvesting at an appropriate time to limit population growth, and if warranted, a rescue insecticide treatment.

In the PLH Fact Sheet written by Ron Hammond, Andy Michel, James Eisley and Mark Sulc, attention is brought to considering the economics of deciding whether a treatment would be justified. “The economic value of an alfalfa stand is also a key factor in a treatment decision. Treatment of a 1st or 2nd year stand of alfalfa may be justified, whereas treatment of an older, thinner alfalfa stand may not be warranted unless the PLH infestation is very heavy. In the case of a new alfalfa seeding, treatment may be warranted for marginal infestations of PLH to insure stand establishment.”

Action threshold table from the PLH Factsheet

 

-Frank Becker, IPM Program Coordinator, OSU Extension Wayne County