Potato Leafhoppers and Berries in 2012
Posted: August 8, 2012
Strawberry leaf curling is a sign of drought stress in addition to "hopperburn," the characteristic leaf yellowing and distortion that the leafhoppers cause.
In many cases where leafhopper feeding injury is severe, dry conditions cause plant growth to slow down, and damage from the leafhoppers then accrues and symptoms become more severe. This is evidenced in the photo shown to the right, where the strawberry leaf curling is a sign of drought stress in addition to "hopperburn," the characteristic leaf yellowing and distortion that the leafhoppers cause. In some cases, people have confused the symptoms of leafhopper damage with either herbicide injury or a nutrient deficiency, rather than the real cause. Damage from potato leafhoppers can severely stunt plant growth, especially in newly-established plantings.
Similar symptoms from potato leafhopper damage are also often seen on raspberries. With raspberries, damage often appears in the middle of the cane. Potato leafhoppers overwinter in southern states, and move northward as the growing season progresses; thus they are not typically present when the raspberry canes are first growing, so symptoms aren't present until the plants are one or two feet tall. Potato leafhoppers have three to four generations in Pennsylvania and are present for the remainder of the summer.
Leafhopper feeding results in a plugging of the portion of the leaves' vascular system that is used for moving photosynthates. Thus, symptoms are similar on different types of plants -- snapbeans and potatoes can be similarly affected. It should be noted, however, that there are large cultivar differences in amount of damage noted, and to some extent, in details of symptoms among different crops.
Potato leafhoppers are light-green, wedge-shaped insects that are about 1/8-inch long, and are found primarily on the leaf undersides. The adults fly quickly when disturbed. Nymphs cannot fly, and tend to move diagonally when disturbed.
Because potato leafhoppers move in from other areas, there are no effective cultural controls for avoiding their appearance. Alfalfa is a favored host, so leafhoppers frequently move into other host crops in large numbers when alfalfa is mowed. A number of insecticides, including Provado and Assail, will provide control. For organic growers, insecticidal soap may provide some control, but must be targeted against first generation nymphs. Additional information regarding control can be found in the Mid-Atlantic Berry Guide.
Penn State's Department of Entomology has a detailed fact sheet on potato leafhopper life cycle and biology at < http://goo.gl/3fa2x >.
Kathy Demchak, Penn State Plant Science, (firstname.lastname@example.org)