Potato leafhopper (PLH) is the most damaging alfalfa insect pest in Ontario in most years. While the damage created is not as dramatic as an alfalfa weevil or armyworm outbreak, leafhopper damage is more chronic and widespread. Many farmers are unaware of the significance of PLH damage, which is often blamed on the hot, dry weather that frequently accompanies it. PLH damage is common across southern Ontario. The Niagara area and counties north of Lake Erie are particularly affected and extensive damage often results.
Tiny, Green & Wedge Shaped
PLH do not overwinter in Ontario, but migrate annually from the Gulf States carried on weather-front air currents. They usually begin arriving in late May. Adult leafhoppers are 3 mm (1/8th inch) long, lime green and wedge-shaped. The adults lay a few eggs per day in the alfalfa stems and petioles, which hatch about 9 days later. Juvenile leafhoppers, also called nymphs, are about 1 mm (1/32nd inch) when they hatch. They resemble adults, except they are wingless and are often found on the underside of the leaves.
Explosive Growth
The generation interval is short, with about 25 days from egg laying to the adult stage. This gives the leafhopper the ability to have an explosive population growth. Farmers walking in their second and third cut alfalfa fields can often see leafhoppers flying or “hopping” sideways, as they are disturbed. PLH are killed by frost in the fall. Leafhoppers feed on a wide variety of host plants, including edible beans. Biological controls have not been very effective.
Hopperburn
Leafhoppers feed by inserting a stylet into a leaf midrib and sucking sap juices from the plant. They inject saliva containing a toxin into the plants as they feed. This causes abnormal cell growth and interferes with transportation of fluids and nutrients in the leaves. The result is the characteristic “hopperburn”, which starts as a wedge-shaped “V” yellowish pattern on the leaf tips.
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