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Integrated Pest & Crop Management Newsletter
University of Missouri-Columbia Vol. 16, No. 13 Article 2 of 7 July 14, 2006
MU Entomologists Find Potato Leafhoppers in Alfalfa COLUMBIA, Mo. – Summer cold fronts and associated thunderstorms bring more than rain, they can drop clouds of potato leafhoppers onto Missouri alfalfa fields. "After the last two storm fronts, we started finding lots of adult leafhoppers," said Wayne Bailey, University of Missouri Extension entomologist. Leafhoppers are carried on upper-level winds from Gulf Coast states where they overwinter in large numbers. The leafhoppers, both adults and nymphs, suck juice from the leaves and stems of alfalfa plants. Close examination of individual leaves shows a wedge-shaped injury on the leaf tip that dies and turns yellow. Eventually the whole leaf turns yellow, Bailey said. Fields heavily infested with the pests take on a yellow color. The damage not only reduces hay yields for the current year but also reduces stand vigor for the next year. Newly seeded alfalfa fields and fields recently cut for hay are most vulnerable, Bailey said. A stubble field starting to grow again after hay harvest can be heavily damaged by a small infestation of leafhoppers. The recommended economic threshold for treatment is only 10 hoppers per 50 sweeps when a stand is less than three inches tall. For alfalfa 12 inches or taller, the threshold is 100 hoppers per 50 sweeps. Scouting sweeps are made with a 15-inch insect net. "Alfalfa producers should be scouting their fields at least twice a week, especially after thunderstorms," Bailey said. "If high numbers of insects are found, an insecticide treatment should be considered," he said. "If the alfalfa field is ready for a third cutting of hay, an insecticide treatment can be avoided." University of Missouri research shows that harvesting with a disk- mower conditioner can reduce hopper nymph counts by 90 percent. Fewer adult leafhoppers are killed by mechanical harvesters, as the hoppers jump out of the way. Newer alfalfa varieties, with glandular hairs on their stems and leaves, are resistant to leafhoppers. "The hairs form a physical barrier which holds the hoppers away from the plant surface." Information on leafhopper controls can be obtained from MU Extension regional agronomists. Insect information can be found on the MU plant protection program’s integrated pest management Web site at http://ipm.missouri.edu. Source: Wayne Bailey 573-864-9905
Duane Dailey |