Insects lay their eggs in the young growth of citrus trees; when the larvae hatch, they can do extensive damage to both the fruit and the tree. Careful inspection of the tree and early action (depending on the type of insect causing the problem) are essential to keep damage to a minimum before the entire tree becomes compromised.
The citrus whitefly has been a problem for citrus growers in America since the late 19th century. The insect is found in all of the Gulf Coast states and in California. Citrus thrips will not develop if the temperature falls below 58 degrees, but if the conditions are right, eight generations can be born in a single year. A single, female citrus bud mite lays up to 50 eggs a year. Citrus red mites attack lemon and grapefruit first, then oranges and finally tangerines.
The citrus whitefly is less than 1/8 inch long, with two pairs of wings. Look for eggs on the new leaves, fruit and twigs that appear as dozens of tiny yellow specks with a smooth surface. Adult citrus thrips are orange-yellow with fringed wings. Citrus bud mites are tiny, elongated and pointed at the back, with four legs near the mouth.
The female citrus red mite is oval-shaped and bright red when young, changing to a dark purple-red as she ages. The male is smaller and tapered, with disproportionally large legs. Both have large pink to white hairs.
The citrus whitefly drains the sap from the trees, and covers the leaves and fruit with a black fungus that destroys the fruit and weakens the tree. Female citrus thrips lay their eggs in the fall on the new leaf tissue, new fruit and young twigs. The next spring, the larvae hatch and eat the young leaves and fruits.
Citrus bud mites eat the young buds from the inside out. The flowers and fruit become distorted and can die. The citrus red mite eats the leaves, fruit and green stems. The insect has pincers that it sticks in the plant, to suck out the cell structure--the internal living parts--of the plant, turning the leaves and fruit gray. The leaves and fruit drop off, twigs die back and large limbs can die.
Citrus whiteflies like young growth. Do not over-trim or top the tree, to limit the amount of new twigs. Citrus thrips thrive when an orchid is over-treated with pesticides. Minimal preventative treatments will help hold down the population.
There are no preventative measures for the citrus bud mites. Using only the recommended dose of pesticides that are allowed in your area can prevent citrus bud from becoming a serious problem.
Ladybird beetles and certain wasps will eat the citrus whitefly adults and eggs. Insecticides that are used for scale insects are also effective against the citrus white fly. Spiders, lacewings, dustywings and minute pirate bugs eat the citrus thrips. Over time, citrus thrips develop resistance to pesticides.
Insecticides are used to combat citrus bud mites Also, lady beetles, aphid lions, tan mites, shiny button mites and yellow mites will eat citrus red mites. Normal insecticide use may help reduce the citrus red mite population.