This past week has been excellent for alfalfa growth with the recent rainfall and the warm temperatures. While I have not heard of any problems with insects, it is always important to watch out for potential problems. In the past we have had infestations of potato leafhoppers (PLH) in alfalfa fields throughout the summer. It is important to monitor your fields for potato leafhopper and treat fields if population levels warrant it. If you have feeding damage on alfalfa from potato leaf hoppers, it is characterized by a wedge-shaped yellow or sometimes purple area formed on the leaf tips known as hopper burn. The leafhoppers inject a toxin into the plant as they feed and can cause severe damage to alfalfa, especially in seedling alfalfa.
Potato leafhoppers are 1/8 inch long or less, bright green, wedge-shaped insects. First year spring planted alfalfa fields and fields planted last year are particularly attractive to and vulnerable to potato leafhoppers. Older fields can also be affected and usually a problem on second and third cuttings.
Resistant varieties provide fairly good protection from potato leafhoppers, but alfalfa in the seedling stage may still be damaged. All fields should still be scouted, as large numbers of leafhoppers may still cause a problem, even in resistant variety fields.
Treatment decisions are based on numbers captured by a sweep net. (A sweep net is the only reliable way to scout for potato leafhoppers.) We have sweep net in our office if you are interested in borrowing it. For information about treatment thresholds, the link to this article is: https://cropwatch.unl.edu/start-scouting-potato-leafhoppers-alfalfa-unl-cropwatch-july-3-2013 .
Many insecticides are registered for control, and all will provide good results when applied properly. Commonly used insecticides include Mustang, Warrior, Baythroid, and Lorsban, or products with the same active ingredients.
Feel free to contact Gary Lesoing at (402) 274-4755 or firstname.lastname@example.org if you have questions about this pest or want to borrow our sweep net.