When working the next cutting of alfalfa, hay croppers should be aware of a common garden pest causing damage to crops across the state, said Jeff Whitworth, Kansas State University Research and Extension entomologist.
"Second and subsequent cuttings of alfalfa may be susceptible to attack by potato leafhoppers," Whitworth said.
Leafhopper feeding may cause yellowing or reddening of the foliage or severe plant stunting, he said. Damage starts as a wedge-shaped yellowing at the tip of the leaves, commonly called hopper burn.
The insects are lime-green, torpedo or wedge-shaped insects with large white eyes. They are quite active as the adults will quickly hop--often sideways--or fly short distances when disturbed.
Nymphs are similar in color and shape with distinctive eyes but no wings, Whitworth said.
Potato leafhoppers have piercing-sucking mouthparts, and when they feed, they remove fluids and nutrients from the plants.
"As leaves turn yellow, crude protein is reduced making it less valuable for livestock," he said. "Continued feeding results in stunted plants, reduced yields, and allows for weed growth."
If potato leafhopper populations are present over several cuttings, alfalfa winter survival and future yield potential will be affected.
"We probably don't pay as much attention to scouting and managing this pest as it deserves," Whitworth said. "Often, slow regrowth is attributed to hot, dry weather when in fact, potato leafhoppers may be the culprit or a contributor."
Scouting should be conducted with the second cutting and continue to the fall. Treatments should be applied before enough feeding has caused yellowing, Whitworth said.
"One application is usually sufficient when applied to the stubble," he said. "Please refer to the 2003 Alfalfa Insect Management Recommendation (MF-809) publication for insecticides labeled for use against potato leafhoppers."
The publication can be obtained through county K-State Research and Extension offices or on the Web, at www.oznet.ksu.edu/library/ and type in MF809.
Alfalfa varieties Konza and Riley have potato leafhopper resistance and are recommended for new plantings, Whitworth said.