David Cappaert, Bugwood.org.
My friend Kristen asked me about some small, fast-moving bugs plaguing her vegetables and flowers. When she described them, I pulled up a photo of leafhoppers on my phone and showed her. “Yes, that’s them!” she said. They look like miniature cicadas with their wedge-shaped bodies.
University of California Integrated Pest Management Program reports over 380 species of leafhoppers in California, although some entomologists suspect there may be 100,000 species in the world.
Some only feed on specific plant types, but others suck the sap out of just about anything. The most common sign is the speckling or stippling spots left behind on leaves from their piercing-sucking mouthparts.
Turn a leaf over and you may find these pests, but as the name suggests, they hop or fly away quickly. They are often green, but may be brown, gray, or mottled.
The adult female inserts her eggs into plant tissue “causing tiny pimplelike wounds” (https://ipm.ucanr.edu/PMG/GARDEN/VEGES/PESTS/leafhopper.html). After hatching, nymphs go through five skin molts (instars) before becoming adults.
There can be a few generations per year, with the last one overwintering as eggs, emerging in spring. After the pale specks appear, the leaves and plant tips may turn yellow, brown and then die, if the feeding is excessive.
As with other plant-sucking insects such as aphids, leafhoppers exude excess juice intake as a sticky honeydew. This gooey substance can encourage and feed black sooty mold fungus and ants. Their feeding can also transmit viral diseases into the plant, which can cause more damage than the feeding itself.
However, for the most part, leafhoppers are just annoying and don’t usually threaten the long-term health of plants. In home gardens chemical-based insecticides are generally unwarranted. Their natural enemies are lacewings, lady beetles (ladybugs), minute pirate bugs and spiders.
Sometimes eliminating perennial weeds around a garden can reduce populations. Using row covers before the insects emerge can protect plants. Regular monitoring of the undersides of leaves as the nymphs emerge in the spring can inform when to spray with horticulture oil, insecticidal soap or neem oil.
Dusting plants with diatomaceous earth can help. Sometimes the overuse of nitrogen fertilizers can increase populations because it encourages young luscious growth for feeding.
Some years there is a transitory surge in leafhoppers that feels like an invasion. This may happen when insects are on the move at the end of the season. Another of nature’s challenges!
JoAnne Skelly is Associate Professor & Extension Educator Emerita at University of Nevada Cooperative Extension. Email skellyj@unr.edu.