Identification (and life cycle/seasonal history)
The potato leafhopper, Empoasca fabae (Harris), occasionally damages alfalfa in our area. They feed on weeds during the early spring, and then adults fly into alfalfa fields where several generations may be completed during the rest of the growing season. Adult leafhoppers are green, wedge shaped insects about 1/8 inch long. Immature leafhoppers are shaped similarly, but are smaller and do not have fully developed wings. Adult leafhoppers are quite active, usually jumping or flying away when disturbed.
Plant Response and Damage
Leafhoppers feed on plant sap at leaf tips. A toxin is introduced into the plant during feeding, causing small yellowish or purple triangular areas. Heavy infestations may cause leaves to become curled or stunted, and can cause "hopper burn," in which the whole stand is yellowish and stunted. Seedling plants may die under heavy attack by leafhoppers. Leafhoppers are usually more abundant during second and third cuttings, but do not economically damage alfalfa every year.
Harvest will kill the egg and small nymphal stages of potato leafhopper, so can be used in place of chemical control if the alfalfa is taller than 12 inches or is approaching bloom. Surviving leafhoppers will often be few enough that populations do not build to economic levels after cutting.
Host plant resistance
Some varieties are moderately resistant to leafhopper feeding, and if acceptable otherwise (in terms of agronomic superiority and disease resistance), can be planted in place of susceptible varieties.
Natural enemies of potato leafhoppers do not suppress leafhopper populations satisfactorily during outbreak years.
Plants should be inspected for signs of leafhopper feeding, looking for chlorosis at the tips of individual leaflets. Newly established stands should be scouted vigorously if leafhoppers are present in older fields. Using a standard (15 inch diameter) sweep net randomly through the field, the following treatment thresholds are recommended.
Table X-6. Treatment threshold for potato leafhoppers.
|Alfalfa height (inches)||Average number of potato leafhoppers per sweep|
|1Early harvest should be considered in place of insecticides at these heights, or if bloom is approaching (See Cultural methods, above.)|
Product List for Potato Leafhopper:
|Insecticide||Product per Acre (Fl oz. or oz. product)||Preharvest Interval, remarks|
|Baythroid XLR,1||0.8-1.6||7 days. Extremely Hazardous to Bees!|
|carbaryl1,2||See labels||7 days. Most formulations are Extremely Hazardous to Bees! Do not apply to alfalfa in bloom. Sevin XLR+ is safe for bees if applied at <1.5 lbs ai/acre when no bees are in the field.|
|chlorpyrifos 4ER,1,2||See labels||14 days (1 pt), 21 days (over 1 pt rate). 24 hr REI. Do not make more than 4 applications/year or more than one application per cutting. Extremely Hazardous to Bees! Do not apply when bees are present. Minor phytotoxicity may occur on rapidly growing foliage.|
|chlorpyrifos + gamma cyhalothrinR,1,2||See labels||See labels for preharvest intervals and specific use restrictions. 24 hr REI. Extremely Hazardous to Bees! Do not apply when bees are present. See labels for additional restrictions for individual active ingredients.|
|Cobalt AdvancedR,1||6-13||21 days. 14 days to graze. 24 hour REI. See labels for additional restrictions for individual active ingredients. Extremely Hazardous to Bees!|
|cyfluthrinR,1,2||See labels||7 days. 12 hr REI. Extremely Hazardous to Bees! Maximum of 0.05 lb a.i./acre applied per cutting and total 0.2 lb ai/acre applied per season. Do not apply to seed alfalfa.|
|dimethoate1,2||See labels||10 days (harvest, grazing). Extremely Hazardous to Bees! Do not apply to alfalfa in bloom. 1 application/cutting.|
|gamma cyhalothrinR,1,2||See labels||7 days. 24 hr REI. Extremely Hazardous to Bees! Do not apply to alfalfa in bloom. Do not apply more than 0.03 lb ai/A per cutting. Do not apply more than 0.12 lb ai/A per season. Advisable to move bees during application and allow 3 (low rate) or 5 (high rate) days before re-introduction of bees.|
|lambda cyhalothrinR,1,2||See labels||7 days. 24 hr REI. Extremely Hazardous to Bees! Do not apply to alfalfa in bloom. Do not apply more than 0.03 lb ai/A per cutting. Do not apply more than 0.12 lb ai/A per season. Advisable to move bees during application and allow 3 (low rate) or 5 (high rate) days before re-introduction of bees.|
|BesiegeR||5 - 8||1 day for forage, 7 days for hay. 24 hr REI. Make applications when bees are not actively foraging by applying during early morning or evening hours. See labels for additional restrictions for individual active ingredients. Do not apply more than 9 fl oz product per cutting or 31 fl oz per season.|
|malathion2||See labels||0 days. Hazardous to bees. Apply only during late evening.|
|permethrinR,1,2||See labels||0 days for rate of 0.1 lb a.i. or less. 14 days for higher rates. No more than 0.2 lb a.i. per cutting. Extremely hazardous to bees! Do not apply to alfalfa in bloom.|
|zeta cypermethrinR,1,2||See labels||3 days. Extremely Hazardous to Bees! Do not apply to alfalfa in bloom. No more than 11.75 oz per cutting, 35.25 oz per season.|
|StallionR,1||5.0 - 11.75||7 days. 24 hr REI. Extremely Hazardous to Bees! Do not apply to alfalfa in bloom. See labels for additional restrictions for individual active ingredients. No more than 11.75 oz per cutting, 35.25 oz per season.|
|RRestricted use pesticide 1Labeled for chemigation 2Generic active ingredient, several formulations.|
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.