Symptoms and damage
Primarily phloem-feeding insects, leafhoppers use their piercing mouthparts to penetrate grapevine leaves and feed on the soft tissue and fluids within, resulting in three distinct types of damage.
Punctures refers to white stippling of the grapevine leaves and is caused by the removal of the chlorophyll from leaf cells and damage to chloroplasts, causing the leaves to lose their natural green pigmentation, turning yellow to brown. Depending on the generation, different areas on the vine and leaves are affected. First generation will typically feed on the basal leaves while the second generation, where most of the damage occurs, will feed on new shoots and lateral vines.
Hopper Burn happens at the top of the grapevine canopy. Feeding leafhoppers secrete a toxin that causes leaves to take on a blistered appearance, including severe wrinkling and cupping of leaves.
Disease Transmission occurs when leafhoppers carry viruses, bacteria (Pierce’s Disease) and phytoplasmas from one plant to another via their contaminated saliva. Two of the most prevalent and costly phytoplasmas detected in Canadian vineyards are Bois Noir and Aster Yellow.1
Additionally, leaves can become covered with a sticky, sugar-rich excretion from leafhoppers as they feed. This honeydew is known for staining the grapes, affecting the fruit and compromising wine quality.
Damage from leafhoppers can reduce photosynthesis, diminish respiration, stunt plant growth and cause considerable loss to both crop yield and quality potential. Leafhoppers can be difficult to control so it is imperative that growers are vigilant in scouting and implementing control measures.
Leafhopper Scouting and Control Tips:
Physical Checks: Different grape growing regions in Canada will differ for control timing and it's important to scout weekly. Typically, the first-generation timing in British Columbia would be in early June, however in Eastern Canada this could occur later. Second generation monitoring should begin in later July and continue into August. Leafhoppers are camouflage experts and are extremely active, eagerly flying or jumping when disturbed. Monitoring vineyards is important to catch early infestations.
Visual Checks: Inspect the underside of leaves (5-10 leaves per 10-20 plants) in multiple vineyard locations every week. In addition to looking for leafhoppers, scout for leaf discolouration that could be a symptom of feeding damage or translucent, whiteish spots that indicate fresh egg deposits.
Yellow Sticky Traps: These physical aids help monitor activity and record population surges by attracting and trapping leafhoppers. Sticky traps should be monitored beginning in mid-April, however this timing can differ across regions.
Sweep Net: Perform 20 sweeps in multiple vineyard locations (5 locations/field), sweeping 3-4 inches into the canopy line and following a zigzag pattern with at least two steps between each sweep. Count the number of leafhoppers (both nymphs and adults) and take action when required.
Thresholds: Economic thresholds can differ from province to province as well as from first to second generation. It is important to consult provincial guidelines to determine specific regional thresholds.
Natural Predators: Leafhoppers have several natural enemies including green lacewings, ladybird beetles, parasitoid wasps and many other predators.
Insecticides: As part of a fully integrated pest management program, insecticides continue to provide a reliable means of managing leafhoppers.
Protect your grapes with Closer™ Insecticide with Isoclast™ Active
Closer™ insecticide with Isoclast™ active provides exceptional, fast-acting suppression of leafhoppers through both contact and ingestion. Offering excellent translaminar and systemic activity, Closer starts working immediately to provide fast knockdown and long-lasting residual activity on leafhoppers in grapes and other sap-feeding insects in many horticulture crops. Additionally, Closer contains Isoclast™ active, a new class of insecticides (4C) known for effective resistance management and excellent efficacy at low use rates.
With multiple generations and extended hatching period within each generation, early control is important for managing leafhoppers. Apply Closer at 162 mL/acre in grapes for effective suppression of leafhoppers. To learn more please visit Closer.corteva.ca or contact your local Corteva Horticulture Expert.
1https://publications.gc.ca/collections/collection_2015/aac-aafc/A59-32-2015-eng.pdf
