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.
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.
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.
Small plot studies in rice paddies have shown a spider, Pardosa ramulosa, to significantly reduce populations of the aster leafhopper.
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.
|Common name||Amount per acre||REI‡||PHI‡|
|(Example trade name)||(hours)||(days)|
|Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.|
|(Sevin 4F)||1–1.5 qt||12||14|
|(Sevin XLR Plus)||1–1.5 qt||12||14|
|MODE-OF-ACTION GROUP NUMBER1: 1A|
|COMMENTS: Do not apply within 15 days before or after application of propanil or crop injury may result.|
|‡||Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.|
|1||Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode-of-action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee).|
|*||Permit required for county agricultural commissioner for purchase or use.|