Species

Leafhoppers belong to the order Homoptera and the family Cicadellidae. The species western grape leafhopper (Erythroneura elegantula) and the Virginia creeper leafhopper (Erythroneura ziczac) are the most common in the Northwest.

Host/Site

Leafhoppers are a common pest of produce crops in the Northwest, including grape, carrot, potato, sugar beet, tomato, lettuce, celery, cucumber, pumpkin, squash, and onion. They are an especially common problem in vineyards. Leafhoppers are also known to infest roses.

Identification

Life Cycle

Leafhoppers lay their eggs in the veins on the undersides of leaves in April and May. Within 10 days nymphs will hatch out of the eggs and go through 5 instars, development stages before becoming adults. Development lasts 4-6 weeks. Adults will go on to live around 40 days with some staying alive for up to 90. During their adult life, leafhoppers will lay hundreds of eggs, creating several generations in between April and October.

Natural Enemies

Lacewings, damsel bugs, lady beetles (ladybugs), minute pirate bugs, and spiders are all natural enemies of leafhoppers.

Monitoring

Action Threshold

In many cases plants may be able to tolerate leafhopper infestations, especially when natural enemies are active. When cash crops are involved there may be less of tolerance of small outbreaks due to fear that they could multiply and create a major infestation, destroying crop yields.

For the home garden and vegetable patch
Take action if an average of more than 20 of the outer canopy leaves have been chewed and fed on by leafhoppers, or if damage exceeds aesthetic standards.

Direct damage through feeding is minimal compared to the potential for plant disease transmission. If plant diseases occur concurrently with a leafhopper infestation, take action to eliminate leafhoppers as a possible disease vector.

Physical/Mechanical Controls

Remove leaves that show signs of leafhopper damage. Soak leaves in boiling water or Safer's Insecticidal Soap (see below).

Spraying the undersides of leaves with water when the leafhoppers are in the nymph and larvae stage will help to remove them from plants.

If erosion is not a risk, remove weeds around plants. This will eliminate a possible avenue of spreading leafhoppers.

Biological Controls

Parasitic Wasps of species Angrus spp. parasitize leafhoppers. Green Lacewings, Lady Beetles, and Minute Pirate Bugs can also all be purchased through online distributors for release in your garden to control leafhoppers and a variery of other pests.

Chemical Controls

Insecticidal soaps can be an effective control for soft-shelled insects, although their efficacy varies between different species of leafhoppers. Safer's Insecticidal Soap Concentrate is a popular choice among organic gardeners. Its active ingredient, potassium laurate, is of extremely low toxicity to mammals. As with all insecticidal soaps, it is only effective if applied directly to the insect. It works by desiccating (drying out) the cuticle of the insect, killing it within a matter of hours. It is nonselective for soft-shelled insects, but generally will not kill hard-shelled beneficials such as lady beetles and mantises.

References

Hudson, Randy and David Adms. "Leafhoppers." The Bugwood Network. 1999.
23 June 2008. < http://www.gaipm.org/top50/leafhoppers.html>.

James, David , Patty Skinkis, and Vaughn Walton. "PNW Insects- Grape." 2007.
24 June 2008. <http://pnwpest.org/pnw/insects?12SMFR06.dat>.