Description
Many different insects transmit plant diseases, but the most common and widespread carriers are aphids and leafhoppers. Aphids transmit most plant diseases, especially those caused by viruses. A single species of aphid may transmit up to 50 different plant viruses. Aphids and leafhoppers are small insects with sucking mouthparts. Their needlelike mouths pierce plant tissue and suck out the sap. Aphids and leafhoppers may acquire disease organisms as they feed on an infected plant. Disease organisms may also be transmitted to offspring through the eggs laid by the infectious mother. When the infectious insects feed on healthy, susceptible plants, they inject the disease organisms into the tissue, infecting the plant. Less common plant disease vectors are treehoppers, whiteflies, mealybugs, grasshoppers, beetles, earwigs, and mites.
Control
Controlling insect vectors is especially difficult because it takes only 1 insect to infect a plant. If you are troubled by a vector-borne disease, you can reduce future damage by taking these precautions:
1. Begin a spray program before the insect is expected in the spring. To determine when the insect is expected, contact your local County Extension Agent (see County Extension Agents). Spray the plants you wish to protect and any nearby plants that the insect may feed on.
2. Destroy any diseased plants and any weeds that may harbor the disease. Do not use diseased materials for mulch or bury them in planting beds.
3. If possible, construct a cage of cheesecloth around the plants you wish to protect to keep the insect vector from reaching them.
