Potato leafhoppers have been found in alfalfa in eastern parts of the state along I-29, and now is definitely the time to scout for them in alfalfa fields in South Dakota. Scouting is critical: once you see symptoms of their damage, known as hopper burn, it is too late. Hopper burn, the characteristic V-shaped yellowing of the leaf tips, is caused by the toxic properties of saliva of these leafhoppers, which have piercing-sucking mouthparts. Potato leafhoppers have multiple generations per year, and while the first cutting of alfalfa is usually not affected, all later cuttings are at risk. They are especially damaging to new seedlings. Heavy populations of potato leafhoppers can stunt the plants and significantly reduce the yield.
Fields should be scouted every week following the first cutting of alfalfa. Use a 15” sweep net, and sample when the plants are dry. Take 10 sweeps at 10 random locations within the field by walking in a ‘U’ pattern, avoiding field margins. After taking 10 sweeps, swing the net a few more times to force the insects to the bottom of the net, grasp the net about 10 inches from the bottom and slowly open the net. Count the potato leafhoppers while slowly opening the net: they are going to be jumping out fast but if you unfold the net slowly, you will be able to count them. Count only the pale green or yellow leafhoppers; there may be other leafhoppers and jumping insect that are captured in the net. Average the number of leafhoppers you captured per 10 sweeps and use tables below to make a management decision based on height of alfalfa and cost of insecticide applications. To reduce potential losses to alfalfa yield implement timely harvest, consider using alfalfa varieties resistant to potato leafhoppers, and apply pesticides when it is warranted.
Click here to see more...