Leafhopper Control Measures: 

• Water Sprays: Dislodge nymphs with blasts of water at the underside of the leaves. Adults just jump around, avoiding the blast, but the ones that are hit, are sufficiently damaged so they can't feed anymore. this is good for all soft-bodied plant-eating pests like aphids, thrips and spider mites. You want a forceful spray that will cover a large area. Keep the stream moving back and forth, to not damage foliage or flowers. Make sure to attack the undersides of the leaves, too. The negative aspect of this method is with dangers of overwatering or hurting plants physically. Stay away from seedlings, since they are tender. Avoid during humid or wet weather so you don't encourage fungal diseases. In order to not burn the foliage in hot sunlight, spray in the early morning or at dusk.
• insecticides that work on aphids work on leafhoppers, although a direct hit is often required, which adults are good at avoiding.
  • Neem Oil
  • Insecticidal Soap (spray in the evening)
  • Insecticidal Soap & Alcohol Mix:
    • 1 Tablespoon 70% isopropyl alcohol
    • 1 pint insecticidal soap
    • spray once every 3 days for 3 times.
  • spray or dust with pyrethrin if insecticidal soap doesn't work
  • make sure to get the underside of the leaves where the nymphs are
  • Garlic Oil
  • Diatomite, or diatomaceous earth: sprinkle on foliage and in a band on soil around the plant (avoid sprinkling on flowers) when wet. kills all soft-bodied crawling insects, like aphids, caterpillars, and thrips. Since it can irritate mucosal membranes, wear a mask when sprinkling. Pool grade diatomaceous earth is treated with chemicals, so don't use in the garden. One big negative with the use of DE is that it is non-selective. it will kill beneficial insects as well as the pests, so it should only be applied where there is a problem. Can also be painted on tree trunks as a slurry (mix DE with dish soap and water to make a thick slurry).
  • pyrethrins
  • rotenone or sabadilla as last resort
• Plant MLO Resistant varieties: carrots, tomatoes, and potatoes have resistant varieties.
• Traps:
  • Blacklight traps
  • Yellow sticky paper
• Floating rowcover (cheese cloth: 22 threads per inch; wire: 18strands per inch)
• Natural enemies:
  • Bigeyed Bugs
  • Parasitic Wasps
  • Predatory Flies
• Mulches
  • Organic mulch, replaced several times per year
  • Aluminum foil mulch will control aphids, leafhoppers & thrips on cabbages and peppers. Needs to be removed later in the summer to prevent heat damage from the reflected sunlight. You can just lay strips of foil in between the plants.
• Systemic
• Companion Planting:
  • keep beets away from tomatoes (beet leafhoppers can transmit Curly Top to tomatoes)

Sources: