Grapes

Nymphs

• Young nymphs are 1.5 mm in length, yellowish-green, and move very quickly on the underside of leaves.
• Older nymphs develop “wing pads” that distinguish them from the fully winged adults.
• Nymphs have the curious ability to walk sideways or backwards, and rapidly move to the other side of the leaf if disturbed.

Adults

• Light green,
• Long and narrow body,
• Wedge-shaped (forward pointing) head,
• About 3 mm long,
• They have sucking mouth parts,
• Can fly, walk and hop,
• Well-developed back legs and transparent wings that fold tent-like across their back.

Damage

• Leaf margins turn yellow and curl downward, eventually turning brittle and brown – a condition known as “hopper burn”

Potato leafhoppers do not overwinter in Ontario. Each spring adults are carried by wind currents from southern Gulf States and across the Great Lakes into Ontario. The first adults arrive as early as mid May and continue to arrive well into June. Adults are first noticed in vineyards in early or mid June, generally just after the first cut of alfalfa hay in the area. The removal of the food source (alfalfa) usually causes potato leafhoppers to migrate to nearby alternate host crops, including grapes. Adults mate and females deposit two to three eggs per day throughout their life span. Eggs are laid on leaves or stems in the upper part of the canopy and hatch in about 10 days. Potato leafhopper nymphs take about 25 days to pass through five life stages (instars), each larger than the previous stage. Only the last three instars possess visible wing pads, which become wings in the adult. As the insects molt from one instar to the next, they leave behind white cast skins. Three or four generations are produced each year and remain active until killed by a hard frost. In hot, dry summer weather, leafhopper populations can build to tremendous numbers and insecticide treatments may be necessary. Adults and nymphs feed by sucking plant juices from leaves. They inject a toxin into the plant while feeding, blocking vascular system flow. Feeding reduces plant vigour and plugs off the vascular system, preventing normal movement of water and nutrients to the affected area of the plant.

Adult potato leafhoppers lay eggs in the leaves, and the eggs hatch into nymphs in early-mid June, typically around the time of the first cut of hay.

Shaking the foliage of a vine can be used to see if any adult potato leafhoppers are present (they will fly off the vine), but this will not help in detecting the nymphs, which cannot fly. Sample on the shadiest part of the canopy.  Nymphs can be found on the undersides of leaves and on stems. Examine leaves by turning them over slowly. Bias sample to upper part of the canopy and select younger leaves on the shoot from midway to the newest fully expanded leaf near the growing tip.

Yellow sticky cards can be placed in the vineyard canopy close to the young shoots to monitor adults as they move into the vineyard and subsequent generations.  

There are no spray thresholds established for potato leafhopper in Ontario. A rule of thumb is that treatment with insecticides is necessary when active leafhoppers are found in the apical half of the shoots AND detectable injury is observed on 25% of shoots.  If vines are under stress, the threshold should be reduced to 10%.