Lychee Tree Insects

Mites

• Red spider mites (Paratetranychus hawaiiensis) occasionally infest lychee foliage. These tiny arachnids form colonies beneath the leaves, with each colony hosting several hundred pests. Although spider mites are too tiny to see with the naked eye, you can usually spot the fine silk webbing they spin on the leaves. Red spider mites damage foliage by piercing the tissue and sucking out the cell contents. While small populations don't typically cause visible damage, large groups can cause a stippling of small spots to appear on the leaves. Continued feeding can make the leaves turn bronze, yellow or red before falling from the tree. Defoliation typically won't affect that season's fruit harvest, but can reduce yields the following year.

  The leaf-curl mite (Aceria litchii), also called the hairy mite, can seriously damage newly developing foliage on lychees grown in Hawaii, Asia and Australia, and some have been found in the U.S. The feeding activity causes small, hairy blisters to form on the tops of leaves, while the undersides develop a brown, felt-like growth. Affected leaves eventually thicken, wrinkle and curl up.

Scales

• Lychees attract various soft scale species, including the green-shield scale (Pulvinaria psidii) and the Florida red scale (Chrysomphalus aonidum). These small pests typically reach less than 1/4 inch in length and look more like small, immobile bumps on the plant tissue rather than insects.

  Scales feed on lychee foliage by piercing the tissue and withdrawing the fluids. Large scale populations cause the affected foliage to yellow, wilt and fall from the tree prematurely. Severe infestations can cause stem or branch dieback, stunted plant growth and loss of vigor. Soft scales also excrete abundant amounts of honeydew, a sweet substance that promotes the growth of sooty mold.

Weevils

• Lychee trees occasionally suffer from root weevil infestations, but the large Diaprepes root weevil (Diaprepes abbreviatus) often causes the worst damage. These colorful pests have yellow, orange, black or gray bodies that reach about 1/2 to 3/4 inch long.

  Adult weevils damage the foliage by chewing notches on leaf margins. The females lay egg clusters in the leaves and the eggs hatch about a week later. The grub-like larvae fall to the ground, enter the soil and start feeding on the tree's roots. The feeding activity damages the roots, which can weaken or kill the lychee tree.

Nonchemical Controls

• Red spider mites thrive in dusty, hot conditions, so spray the leaves clean and wet down pathways or dirt roads to reduce the amount of dust floating in the air. Remove small scale populations by scraping the pests off your tree with a dull knife or your fingernails. Thoroughly spraying the tops and undersides of leaves with a strong stream of water from your garden hose can also help reduce insect populations. Prune off and destroy all plant parts severely infested with mites, weevils or scale insects.

Chemical Controls

• Avoid using broad-spectrum pesticides except as a last resort, since the chemicals kill beneficial bugs as well as the pests. Predatory mites, thrips, ladybugs, minute pirate bugs, lacewing larvae and predatory flies all feed on the common lychee tree insects. If chemical control proves necessary for spider mite, weevil and scale infestations, the University of Florida IFAS Extension recommends spraying your tree with a 1-1/2 to 3 percent horticultural oil solution. Following the specific instructions on the product's label, mix 5 to 7-1/2 tablespoons of product for each gallon of water. Thoroughly spray your tree until the foliage glistens with moisture.

  Wettable sulfur products often control leaf-curl mite populations if you spray your lychee tree every two or three weeks as the new leaves emerge. Following the manufacturer's directions, mix about 4 tablespoons of sulfur product for each gallon of water. Spray the foliage thoroughly and don't re-enter the treated area for a minimum of 24 hours.