Citrus trees, with their sweet blossoms and the fruit that follows, grace many yards and personal orchards. A host of pests increase in numbers in spring when citrus trees develop new leaves, shoots and fruit. According to the University of Florida IFAS Extension, various pests can damage leaves and fruit of citrus trees, and cause "moderate to severe defoliation and fruit drop." In Texas, citrus has been a crop since the mid-1800s and pests have been a problem just as long.
All citrus trees require similar care and protection, and grow best in areas that offer warm, humid summers and relatively mild winters. These conditions are a breeding ground for pests, as well. The best region for growing citrus of all kinds is the Sunbelt, which reaches from southern Texas to Southern California. Florida is also an ideal climate for citrus tree growth. Gardeners who can't offer the right outdoor conditions grow many citrus trees as houseplants, with good success.
Types of Pests
Citrus trees are vulnerable to a myriad of pests. These include aphids, whiteflies, fire ants, mites, scales, grasshoppers, katydids and caterpillars, according to the University of Florida IFAS Extension. Gall wasps and leaf miners also feed on citrus trees. The Asian citrus leafminer arrived in Texas in the mid-1990s, according to Texas A&M Aggie Horticulture, and can be particularly devastating to citrus trees.
Gall wasps lay eggs in the wood of citrus trees and cause lumpy growths on the trunks and roots. Although these galls are unattractive, they don't cause any outright harm to the trees. According to Aggie Horticulture, both armored and soft-scale insects attack citrus trees and suck juice from citrus leaves to cause discoloration, wilting, leaf drop and fruit failure. Aphids attack citrus trees in large numbers and build colonies on new growth to suck the juice from stems and leaves. Black and brown citrus aphids, melon aphids and spirea aphids damage citrus leaves and restrict a tree's ability to produce energy for fruit growth.
The only way to get rid of galls and the insect larva they harbor is to physically cut them out of the wood and destroy them. Commercial citrus growers spray their trees in the spring to kill any gall wasps in the area. Aggie Horticulture states that biological sprays like Bt and neem oil effectively control scale insects, while the University of Florida also recommends biological insecticides and predator insects like lady bugs for aphid control. Caterpillars can be plucked off leaves with tweezers.
Citrus growers must balance pesticide use with the presence of natural control, according to the Texas Agricultural Extension Service. Some pesticides are harmful to insects that are beneficial to citrus tree growth. "Recognition of both harmful and beneficial organisms impacting on citrus production is essential to development of a sound integrated pest management program," the Extension Service says. Growers are encouraged to identify damaging pests as well as beneficial pests in their orchards.