POTATO LEAFHOPPER ON ALFALFA

A, Damaged plant showing discolored leaves, short internodes, and lack of bloom. B. The insect (greatly enlarged); a, nymph; b. adult.

POTATO LEAFHOPPER ON ALFALFA

The potato leafhopper is an important pest of alfalfa in the eastern half of the United States, as far west as Kansas. It also attacks many other plants. It is wedge-shaped, pale greenish-yellow, and about one-eighth inch long when full-grown. The females deposit their eggs in the petioles and in the larger veins of the leaves. In about a week the eggs hatch into wingless nymphs, which pass through five stages and become winged adults in 8 to 14 days. The period from egg to adult under most favorable conditions is about 3 weeks. The adults and nymphs are extremely active and feed on the petioles and lower surface of the leaves by sucking the plant juices. This leafhopper probably does not overwinter in the North but breeds throughout the year in Florida, and during most winters in other Gulf States. In the latitude of Washington, D. C., adults usually appear about May 3 to 10 and gradually become more abundant, causing yellowing and dwarfing of the second and third crop of alfalfa during July, August, and September. A severe attack causes the plants to wilt. Under favorable conditions, the leafhopper can build up its populations rapidly and cause important losses to both the quality and quantity of alfalfa. When young stands are injured, weeds and grass crowd out the alfalfa. Alfalfa is often so severely weakened by this leafhopper during the summer that it is unable to survive the following winter.

Control: The potato leafhopper can be controlled effectively on alfalfa with methoxychlor. Prepare a spray by mixing I quart of the 25-percent emulsifiable oil (one-half pound of methoxychlor) with 5 gallons of water and apply this amount per acre with sprayer at about 40 pounds pressure per square inch. Make the application midway in the development of the crop or earlier if the insect becomes abundant.

A delay of 10 days to 2 weeks in cutting the first crop, if this does not lower the quality of the hay, will destroy large numbers of eggs and young leafhoppers which otherwise would mature to adults and infest the next alfalfa crop.