Leafhoppers

Adults:

• about 3mm long
• wedge-shaped with broad, rounded head
• short antennae
• quick to jump, hop sideways or fly away if disturbed
• patterned brown to yellow, yellow-green or bright green.

Nymphs usually resemble adults but are smaller and wingless.

• A planthopper (Oteana lubra) found in pulses looks similar to the brown leafhopper, but is much larger (10mm long).
• Leafhoppers can be distinguished from other small insects, such as mirids, damsel bug nymphs and Rutherglen bugs by their wedge shape and tendency to jump.

Leafhoppers are widespread and common in Australia. They are usually only minor or occasional pests, but sometimes occur in large numbers (100 or more per square metre).

• Cotton leafhopper: cotton.
• Vegetable leafhopper: lucerne, summer pulses, peanut, cotton, various vegetable crops.
• Lucerne leafhopper: lucerne, peanut, navy bean, mungbean, pigeon pea, soy bean.
• Spotted leafhopper: clover, lucerne, mungbean, pigeon pea, soybean, weed.
• Maize leafhopper: maize, sorghum, millet, mungbean.
• Brown leafhopper: pasture, weed, cotton, oilseed and pulses including mungbean, soybean, peanut, pigeon pea and chickpea.

Visual damage:

• Some leafhopper species cause stippling (tiny pale dots) on leaves that may appear as wiggly lines from a distance. This stippling reduces the photosynthetic capacity of affected leaves, but limited data is available on the impact on crop yield.
• Toxins from the lucerne leafhopper cause necrosis (yellowing and browning) on the leaf tip, known as ‘hopper burn’.
  • Heavy infestations can cause plant stunting or death.
  • Peanuts are particularly sensitive to hopper burn.

Vectors (carriers) of pathogens (disease-causing microorganisms):

• Maize leafhopper transmits wallaby ear in maize. Affected plants turn dark green, leaf veins thicken and leaves distort.
• Some leafhopper species (including brown and spotted leafhoppers) feed on vascular phloem tissue, and have been implicated in the transmission of viral and phytoplasma diseases.

Eggs are laid into plant tissue, and there are usually 5 nymphal stages.

• Visually check leaves for the distinctive stippling or hopper burn.
• Use a sweep net to sample for leafhoppers. Transferring samples to a container that contains methylated spirits or is suitable for the freezer will help prevent leafhoppers escaping before they can be counted.

Examples of thresholds:

• Peanuts—30% of leaves have hopper burn symptoms.
• Cotton—50 leafhoppers/50m row or 50% damage to the upper leaf surface.
• Maize—more than 10 leafhoppers per plant (and wallaby ear is present).
• Pastures—20 lucerne leafhoppers or 100 vegetable leafhoppers per sweep.

Generalist predators will attack leafhoppers but are unlikely to provide sufficient control of leafhopper outbreaks, or impact on vector management.

Well-watered, vigorously growing crops can tolerate damage, and control is usually not warranted, unless the diseases they vector are likely to be an issue.

Cultural options

• Host-plant resistance (some maize hybrid varieties offer resistance to wallaby ear).
• Maintain good farm hygiene and remove other host plants (e.g. weeds) that may harbour viruses or phytoplasma.
• For pastures, early cutting or grazing may be an option.

Chemical options

• Perimeter sprays may be an option to minimise vector transmission.
• Broad-spectrum insecticide use reduces beneficial insect populations, which may create outbreaks of other pests, such as mites and helicoverpa.
• During outbreaks, crops can rapidly become re-infested after spraying.