Potato Leafhoppers (PLH) are one of the most common and destructive insects affecting alfalfa. While there is no reliable method to forecast damage, DuPont Pioneer forage specialists offer up scouting tips for this pest.
Adult PLH are yellow, wedge-shaped insects that can grow to be 1/8 inch long and can jump or fly from plant to plant. Nymphs are paler in color, smaller in size and lack wings.
PLH feeding causes leaf chlorosis and plant stunting. An initial symptom is V-shaped yellowing at the leaf tips. With severe or prolonged feeding, stressed leaves will turn reddish or bronze.
Economic damages include yield reduction, but severe damage can cause a reduction in crude protein content, carbohydrate reserves in the taproot and plant growth.
Another item to keep in mind is that very young plants in early stages of regrowth, and second- and third-cutting alfalfa are most susceptible to PLH and resulting plant damage.
Thresholds for treatment
Growers should scout alfalfa fields using a sweep net beginning in June. When scouting, be sure to log findings in the Pioneer® Field360 Notes app. This will allow growers to see if a problem is arising nearby.
For non-LH resistant varieties, spray when leafhopper count per ten sweeps exceeds average plant height in inches. For LH resistant varieties, spray when leafhopper count per ten sweeps exceeds three times the alfalfa height in inches.
Harvesting infected stands is another option and may be required as this potentially reduces egg, nymph and adult populations.
For more information on potato leafhoppers or management tips, visit www.pioneer.com or contact your local DuPont Pioneer livestock specialist.