How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Several species of leafhoppers feed on rice plants in California, but the only one known to be of economic importance is the aster leafhopper. The adults are about 0.125 inch long, with transparent wings that are strongly veined, and body background colors of gray and black. The nymphs have small wing pads in their last instar and range in color from yellow to dark green.

Leafhoppers usually pass the winter in the egg stage, although nymphs and adults may be found all year round. The leafhopper inserts its eggs into tender plant tissues. Wingless nymphs hatch from the eggs and go through four to five molts before reaching maturity. Up to six generations may be completed between spring and fall.

DAMAGE

Although leafhoppers can be present in fields during most of the growing season, the heaviest populations usually occur from early July through mid-August. Leafhoppers feed on rice plants by sucking up plant fluids through their long, piercing mouthparts. Although they are not known to vector of any rice pathogens in California, leafhoppers may occasionally occur in sufficient numbers to cause damage by their feeding. Injury associated with leafhoppers include stippling, yellowing, and drying leaves. Leafhoppers prefer senescing leaves, and symptoms usually occur on older leaves first. Leafhoppers are very mobile; adults fly and nymphs jump. Thus, infestations are rarely localized but appear generally throughout the field.

MANAGEMENT

High populations of this pest are associated with weedy rice fields. Control weeds and monitor during the summer to determine the need to treat. Predation can provide significant reduction of leafhopper populations.

Biological Control
Small plot studies in rice paddies have shown a spider, Pardosa ramulosa, to significantly reduce populations of the aster leafhopper.

Cultural Control
High populations of aster leafhoppers are frequently associated with paddies heavily infested with broadleaf weeds and sedges. An early and effective weed control program is an important way to discourage the development of economically damaging populations of leafhoppers on weeds and future movement of leafhoppers to rice.

Organically Acceptable Methods
Cultural controls, such as described above, and reliance on biological control are organically acceptable methods.

Monitoring and Treatment Decisions
Observe fields weekly from July through August for leafhoppers and their damage. Leaf yellowing and stippling can be associated with other stresses, so always check for the presence of leafhoppers. Leafhopper adults, nymphs, and molted skins are easy to see as you walk slowly through a field. Always inspect fields carefully after broadleaf herbicide treatment; the killing of broadleaf weeds may cause the leafhoppers to move from the dying weeds to the rice plants. Although there are no available treatment thresholds, a good rule of thumb is to treat when young upper leaves become infested and begin to dry.

PUBLICATION

UC IPM Pest Management Guidelines: Rice
UC ANR Publication 3465
Invertebrates
L. D. Godfrey, Entomology, UC Davis
L. A. Espino, UC Cooperative Extension, Colusa County

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