- Published: Friday, June 26, 2020
By Andy Luke, Field Specialist in Agronomy
Potato leafhoppers have been found in area alfalfa fields lately. Farmers should scout their fields to see if this damaging insect is present.
Potato leafhoppers are tiny insects that feed on more than 100 plant species including soybeans, clovers, alfalfa and apples. They do not overwinter in Missouri, but arrive on jet streams from southern states and Mexico. Once they make it to Missouri, we often get two to three generations of potato leafhoppers per year.
Damage from potato leafhoppers occurs when both adults and nymphs are feeding. The tiny, pale green insect has piercing-sucking mouthparts that penetrate alfalfa leaflets and remove plant juices, causing yellowing of the established plants. The yellowing generally begins as wedge-shaped yellow areas on the leaf tips, but can expand to turn the entire leaf yellow. In heavy infestations, the entire field can exhibit a yellow appearance.
The best way to scout for potato leafhopper is using a sweep net. The adults are approximately 1/8 of an inch, so spotting them in the field can be difficult. Take 10 pendulum sweeps at five random locations in the field, then average the number of potato leafhopper adults and nymphs per sweep to use in the treatment threshold table.
The economic threshold in alfalfa for treatment of potato leafhoppers is based on hay value, control costs and the size of the alfalfa. Several insecticides are labeled for leafhopper control, but fields can be re-infested by insects from neighboring fields. If the alfalfa is nearing harvest, cutting it will disrupt the life cycle of the feeding nymphs who will starve or be destroyed before regrowth occurs. It is important to start scouting 7-10 days after each cutting to monitor for re-infestations, though.
Writer: Andrew Luke
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