Leafhoppers

Potato Leafhopper, Empoasca fabae (Harris)

Description and Life Cycle

The potato leafhopper, a sucking insect, feeds sporadically on grape foliage.  The adult leafhopper is pale to bright green, wedge-shaped and about 1/8 inch long.  The adults are very active, jumping, flying or running when disturbed.  The immature forms, or nymphs, are pale green and wingless.  They run forward, backward or sideways rapidly when threatened.  The potato leafhopper feeds on more than 200 plant species.

The potato leafhopper does not overwinter in areas north of the Gulf States.  Each year large numbers of potato leafhoppers are carried to northern areas by warm spring air currents.  Injury to grapes occurs when the adults fly into vineyards and feed on the leaves.  Toxins injected while feeding cause leaves to cup and be misshapen.  These leaves are often in the top of the vine and are quite obvious, especially at the end of the growing season.

Eastern Grape Leafhopper, Erythroneura comes (Say) 

 

 

 

 

Three-banded Leafhopper, E. tricincta Fitch

 

 

 

 

Virginia Creeper Leafhopper, E. ziczac Walsh

These are three of the most common leafhoppers found on grapes in Ohio and they belong to the same genus Erythroneura.  These three species vary in their coloration and markings. 

The adults of these leafhoppers are about 1/8 inch long.  E. comes is pale yellow or white with yellow, red, and blue markings.  Overwintering adults are often nearly all red.  E. tricincta is brown and black with touches of orange on the wings.  E. ziczac is pale yellowish or white with a zigzaz stripe down each wing and cross veins distinctly red.

The biology of these three species is similar.  They overwinter as adults in sheltered places such as the remains of old plants.  During the first warm spring days the leafhoppers become active, and they feed on the foliage of many different plants until grape leaves appear.  Eggs are deposited under the leaf epidermis; they hatch in about two weeks.  The immature leafhoppers, or nymphs,  are wingless; they remain and feed on the leaves where they hatch.  Nymphs molt five times, then transform into adults.  There are two or three generations of leafhoppers each season.

Damage Symptoms

Adults and nymphs feed on leaves by puncturing the leaf cell and sucking out the contents.  Each puncture causes a white blotch to appear on the leaf.  In heavy infestations, the leaves turn yellow or brown, and many will fall off.  Feeding by these leafhoppers may reduce the photosynthetic capacity of the plant, and the quality and quantity of the fruit may be affected. 

Grapevines can tolerate populations of up to 15 insects per leaf with little or no economic damage.  However, heavy leafhopper feeding may result in premature leaf drop, lowered sugar content, increased acid and poor coloration of the fruit.  The sticky excrement (honeydew) of the leafhoppers, affects the appearance and support the growth of sooty molds.  Severely infested vines may be unable to produce sufficient wood the following year.  Damage to the vine can be serious if infestations are allowed to persist unchecked for two or more years.

Management

Weeds and trash in and around a vineyard is a source of leafhoppers.  If this material is cultivated before spring the adults loose their protection and feeding sites, although in areas with extensive agriculture this practice has less value as the adults will just move to an adjacent crop or weedy area.  

Certain cultivars are likely to suffer higher leafhopper populations than others.  Wine and table grape varieties fit this criteria.  Moreover, late producing cultivars are more likely to favor leafhoppers than early maturing cultivars.

Monitoring

Vigorous vines are preferred by leafhoppers.  The heaviest populations are normally found on end vines and on outside rows.  This is partly because these vines are usually the most vigorous and therefore the most attractive.  It also is partly because of the border or boundary effect.  Vigorous vines fortunately can tolerate the highest populations. 

Sampling for leafhoppers should be done at 10 days post-bloom, third week in July and again the third to fourth week of August.  This is approximately the same time one should be assessing grape berry moth risk and both surveys may be conducted at the same time. 

Ten Days Post-bloom - Only adult leafhoppers are present at this time of the year, so it is not necessary to count them.  If leafhoppers are present, you should see stippling damage on the lower "sucker" leaves and interior leaves of the grape canopy.  By shaking the vines adult leafhoppers if present will fly around the vine.  If stippling damage is present throughout the vineyard an application of insecticide is recommended to prevent later damage from occurring.  Early season damage may indicate that populations may potentially build up to damaging levels later in the season.  Vineyards that are at high risk for grape berry moth usually apply insecticide at this time so scouting for leafhoppers at this time is not necessary. 

Third Week in July - By mid-to-late-July first generation nymphs are present and feeding on the undersides of grape leaves.  At this time, the need to apply an insecticide for leafhopper control should be determined on a block by block basis.  Sampling for grape berry moth and leafhoppers can be done with a single pass through the vineyard. 

The first step in evaluating leafhopper damage is to look for stippling on leaves while you are doing counts of grape berry moth damage.  Most damage will be found on the first seven leaves from the base of the shoot.  If no stippling or minimal stippling is visible on the leaves, there is no point in counting how many leafhoppers are present.  If moderate to heavy stippling is visible, then it is necessary to do counts of leafhopper nymphs to determine if damage levels warrant treatment.  The sampling procedure for leafhoppers requires counting all leafhoppers on the undersides of the third through seventh leaves of one shoot on each of five vines.  Sampling for leafhoppers should take only a few minutes per vineyard. 

Late August - In years when leafhoppers do build up to damaging levels in vineyards, it is most common for them to do so in late August.  Vineyards with greater than 10 leafhoppers per leaf should be treated at this time.  If there is very little visible stippling, sampling will not be necessary.  Vineyards that had insecticides applied to them earlier in the season will probably not need treatment at this time.  In Ohio we experience more of a problem with leafhoppers on the islands in Lake Erie and in vineyards near Lake Erie.

Control