Issue No. 11, Article 6/June 3, 2005
Arrival of Potato Leafhoppers
Potato leafhoppers have made the trip north and were found in Illinois alfalfa fields last week. Since potato leafhoppers do not survive Illinois winters, infestations require spring migration from the southern Gulf Coast states. Leafhoppers are small (1/8-inch-long), wedge-shaped insects with piercing and sucking mouthparts. Potato leafhoppers are pale green, with a row of six white spots located behind the head. Females live for approximately 1 month, and during this time lay two to three eggs in the stems and veins of plants each day. Nymphs hatch after 7 to 10 days and mature to become adults in about 2 weeks. The entire cycle takes about 1 month, and three to four generations may be observed each year in Illinois.
Potato leafhopper adult.
Injury caused by the potato leafhopper is a result of their removing nutrients from plants. This is most commonly referred to as "hopperburn." As these insects remove nutrients from the vascular tissue of a plant, they simultaneously inject toxic substances into it. This results in a yellowing of the foliage, characterized by a V-shaped yellow area on the leaf tip. However, don't confuse hopperburn with disease and nutritional disorders with similar leaf symptoms. Boron deficiency, which is quite similar to potato leafhopper injury, is usually limited to the younger leaves, whereas leafhopper injury is found on older leaves. Watch field margins for the first signs of potato leafhopper feeding as the insects move into the field.
Potato leafhopper and "hopperburn."
Alfalfa fields should be monitored weekly following the first cutting of hay. Feeding on new regrowth may stunt or delay plant growth. Using a 15-inch sweep net, make 20 sweeps in five locations of the field. Be sure to avoid sweeping wet fields; results are not necessarily representative of the damage potential of the field. Calculate a field average of potato leafhoppers per sweep. Randomly collect 20 alfalfa stems across the field to determine the average stem length. Table 1 provides the economic thresholds for potato leafhoppers. Infestations will persist in fields until hard frosts occur in the fall.
Insecticides suggested for control of potato leafhoppers in alfalfa are listed in Table 2. Please follow all label directions and precautions.
For more information on the potato leafhopper, please visit the Potato Leafhopper Factsheet (Adobe PDF).-- Kelly Cook