Empoasca fabae (soybean)
Authors: Buyung Hadi, Jan Knodel and Ken Ostlie
Potato leafhopper, Empoasca fabae, is a native species to Northern America.
Adult potato leafhoppers are small (about 0.125 inch or 0.3 cm in length), wedge-shaped and green in color. Adults are very active, jumping rapidly when disturbed. The nymph has the adult's appearance, but is much smaller in size and lighter in color. The nymphs do not have wings. Later stage nymphs typically have wing buds growing on their backs.
Life Cycle and Seasonal History
The potato leafhopper cannot endure prolonged exposure to temperatures below 25°F (-4°C) and thus overwinters in the southern states. Adult potato leafhoppers migrate northward and can usually be found in the northern states as early as May. Typically, the adults colonize alfalfa before soybean emerges and move to soybean later. Mated females of potato leafhopper insert eggs into the soybean plants, especially within leaf veins and petioles. The eggs are very small and relatively pale in color, making them difficult to find within the plant. The eggs hatch and the nymphs feed and complete their development on the leaf nearest to their hatching site. It takes about three to four weeks to complete the development from eggs to nymph maturation. An adult female can survive for a month on soybean plant, laying two to three eggs per day. Adult potato leafhoppers migrate southward around September. In the northern states there are two or three generations of potato leafhopper produced per growing season.
Plant Injury and Damage
The potato leafhopper has piercing and sucking mouthparts. They feed by inserting the mouthpart into the leaf tissue and sucking plant sap. Most feeding occur on the leaf veins although feeding on the mesophyll has been documented on alfalfa and broadbean. When feeding, potato leafhoppers inject toxic saliva into the leaf tissue. This toxin cause localized stippling, yellowish to reddish yellow discoloration of the leaf (especially at the tip), leaf vein distortion and leaf curling. These symptoms of potato leafhopper feeding are commonly referred to as hopperburn. Heavy feeding may cause plant stunting and may significantly reduce yield.
Movement of potato leafhoppers from freshly cut alfalfa fields to adjacent soybean fields have been reported. Thus soybean fields planted in vicinity to alfalfa fields may stand a greater risk of early potato leafhopper colonization.
The short leaf hairs found on older soybean leaves deter feeding and oviposition by potato leafhopper. Young soybean leaves usually have less leaf hairs and may be subject to heavier feeding by potato leafhopper. Soybean cultivars with less leaf hairs maybe exposed to similar risk. Stressed plants, for example plants exposed to drought, may suffer heavier damage due to leafhopper feeding compared to healthy plants.
Scouting and Threshold
Scouting can be conducted by direct count of potato leafhoppers when soybean are still young. After the stage V4 of soybean growth, the plant and insect population sizes render direct counting ineffective in estimating potato leafhopper population. In conducting direct count of potato leafhoppers, the observer walks along 1 ft row-length, gently tapping the plants and counting the number of leafhoppers jumping or flying from the leaves. The observer must advance against the wind to minimize the chance that the leafhoppers jump to the plants ahead of the observers, thus avoiding double counting of the same individual. Repeat the observation on 5-10 random 1 ft row length throughout the field. The number of leafhoppers per row-ft can then be estimated. By knowing the number of plant per row-ft, the estimate of leafhoppers per plant can be calculated.
After the stage V4 of soybean growth, sweep net is recommended to estimate leafhopper population. To do the sampling, walk a predetermined distant (e.g. 1 ft) between soybean rows and sweep the net across one row. Count the number of potato leafhoppers caught in the net after each walk. Repeat the sweep on 10 random predetermined row-length throughout the field. The number of leafhoppers per row-ft can be estimated, and by factoring the number of plant per row-ft the number of leafhoppers per plant can then be calculated.
The economic threshold for potato leafhoppers are the average of 5 leafhoppers (adults and nymphs) when the plants are in vegetative stages and the average of 9 leafhoppers (adults and nymphs) when the plants are in reproductive stages.
Other Online Resources
For information regarding labels of chemical control options, please visit Agrian.com