Damage from potato leafhoppers is showing up in strawberry and raspberry fields, and by some accounts, seemingly came out of nowhere. This pest moves up from the South in the spring, and by early summer is established in a wide range of crops in the Mid-Atlantic region.
Potato leafhopper damage. Note the yellow discolored areas along the leaf edges.
When fields are mowed or even just weeded, leafhoppers that had been present in them may quickly find a home in a different location. Often this is a strawberry or raspberry planting. Usually the first noticed symptom of potato leafhopper presence is a downward curling of the strawberry or raspberry leaves with yellow discolored areas along the leaf edges. This symptom is caused by feeding injury, as the leafhoppers inject a toxin into the plants’ leaves. With raspberries, primocane elongation may slow enough that plants appear to stop growing. Injured leaves may appear to be more closely spaced along the cane than usual.
Potato leafhopper on raspberry
Even though a high proportion of the leaves might be affected, it is often surprisingly difficult to find the leafhoppers themselves, which are tiny light green or yellowish-green wedge-shaped insects. The adults fly quickly when disturbed, so sometimes you can brush the foliage to see whether small light-green insects fly out that you can then try to track and identify. The nymphs however, cannot fly, and so are often more easily found. Adults or nymphs are found on the leaf undersides rather than the top, and will usually move sideways when disturbed.
Potato leafhopper early-instar nymph.