Scientific name: Empoasca fabae
Order: Hemiptera
Family: Cicadellidae

Info

Biological Description

• Adults: 1/8" long, wedge shaped, fluorescent green colored, winged
• Nymphs: less than 1/8" long, wedge shaped, range in color from yellow-green to fluorescent green, do not have wings, walk sideways when disturbed

Economic Importance

• Potato leafhopper is the most significant insect pest on alfalfa in the Midwest.
• Outbreaks:
  • Damage is sporadic and dependent upon migrations from the south
  • Localized outbreaks can occur in the absence of a larger regional outbreak
• Susceptible crops:
  • alfalfa

Life Cycle

• Migrating leafhoppers typically appear in Wisconsin in mid to late May.
• Females can deposit 2 or 3 tiny eggs a day on alfalfa.
• Nymphs emerge from eggs after 7 to 10 days. They go through 5 instars in about 25 days before their final molt into adults.
• Generations:
  • There are 3 to 4 generations per year in the Midwest
  • Each generation lasts 4-5 weeks

Damage/Symptoms

• Damage is a result of nymph and adult feeding. Potato leafhoppers suck plant sap and inject toxins back into the plant. The toxins inhibit water and nutrient transport.
• Damage appears as plant stunting and leaf yellowing. Leaves yellow in a v-shaped pattern starting at the leaf tip. As damage increases, leaves may become completely yellow or reddish.
• Economic damage can be caused in three ways from this feeding:
  • Yield loss
  • Quality loss (attacked plants produce sugars instead of protein)
  • Reduction in overall plant vigor (this causes slower regrowth after harvest, increased stand loss from winter kill, and potential yield loss the following season when leafhopper populations are high)
• Potato leafhoppers can cause economic damage from late May through late summer or early fall.

Scouting Procedure and Economic Threshold

• The only way to accurately determine damage potential is by monitoring fields on a weekly schedule. To do this, you will need a standard 15" diameter insect sweep net. Walk an M-shaped pattern in the field taking 20 consecutive sweeps in 5 random locations (100 sweeps total). Sweeps should be forceful enough to knock insects off plants, but not so forceful as to break off alfalfa stems. Count the total number of nymphs and adults in the field, and divide that number by 100 (the total number of sweeps).
• While adults are often found at the bottom of the sweep net, nymphs are commonly found along the rim.
• The threshold for potato leafhopper is based on plant height.
  • Alfalfa is 3" tall: threshold = 0.2 leafhoppers/sweep
  • Alfalfa is 6" tall: threshold = 0.5 leafhoppers/sweep
  • Alfalfa is 8-11" tall: threshold = 1.0 leafhoppers/sweep
  • Alfalfa is >12" tall: threshold = 2.0 leafhoppers/sweep
• Do not spray if you are within 7 days of your normal cutting schedule. Instead, cut the alfalfa and reassess the leafhopper population in the regrowth.

Integrated Control

• Cultural control: Commercial alfalfa varieties are available that claim resistance to leafhoppers. Additionally, cutting alfalfa kills a high percentage of nymphs and forces adults out of the field.
• Biological Control: There are few natural predators and parasites of the potato leafhopper, and those present do not provide adequate and consistent control.
• Chemical Control: For current Wisconsin recommendations, consult University of Wisconsin-Extension Bulletin #A3646, Pest Management in Wisconsin Field Crops.

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Site Links

Insect Images

• Alfalfa pest images

Publications

• Alfalfa Management Guide. North Central Region Extension Publications.

Websites

• Research
  • Alfalfa host plant resistance and intercropping for potato leafhopper management
  • Organic crop plant nutrition and insect response

Wisconsin Crop Manager Articles

• Potato leafhopper populations in alfalfa. Wisconsin Crop Manager, Vol.14 No.15, June 15, 2007. Cullen, E.

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