Arizona's warm climate lends itself to growing citrus trees, and it is one of only four states with significant citrus production in the United States. In particular, lemons and tangerines are grown in Arizona. Several pests of citrus trees are indigenous to the state and range from mild nuisances to significant threats.
Orange Dog Caterpillar
Orange dog caterpillars are the larvae of the giant swallowtail butterfly. They have a mottled appearance, ranging in color from light brown to dark gray. When disturbed, the caterpillar produces a characteristic odor that smells of lemons. While not considered a significant threat to mature trees, they can cause damage to younger, less resilient trees. These caterpillars are usually controlled by crushing the eggs or picking the caterpillars by hand.
Both the cotton and melon aphid attack citrus trees. These insects have been known to transmit the tristeza virus, any serious and often fatal disease of citrus plants. They are best controlled biologically by using beneficial insects such as ladybugs or lacewings to control populations. Parasitic wasps may also be used.
Female cottony-cushion scale are approximately 1/2 inch long, yellow to orange in color, and are often covered with yellowish wax ridges. Both the eggs and newly hatched insects are bright red in color. California Red Scale are usually found within the Phoenix area. They appear as small reddish brown spots that are most visible when on fruit. These are a significant test of citrus trees. If scale is found, trees should be treated immediately. Branches infected with this insect should be removed and destroyed. Organic control with beneficial insects, such as ladybugs, is effective.
Found primarily in Central Arizona, citrus peelminers often attack grapefruit and navel oranges. The larva of a small gray moth, the citrus peelminer will burrow beneath the skin of citrus fruit and feed, mining tiny tunnels, and damaging the fruit cosmetically.
Wooly whiteflies are relatively new to Arizona and are presently confined to the area around Yuma. They are small flying insects with a white waxy covering on their wings and body. They damage citrus trees by feeding on plant sap. This causes the leaves to wilt and drop from the tree when the insect is present in sufficient numbers. Natural parasites and predators have proven to be an effective control of this insect.
Thrips are one of the most significant pests of citrus trees in Arizona. They are insects with thin, tubular bodies. They are very small, usually not reaching more than 1/16 inch in length and have narrow wings trimmed with tiny hairs.There are two types of thrips that affect citrus trees. Flowers thrips feed on citrus blossoms. Citrus thrips generally feed on new leaves and small fruit early in the season. Citrus thrips are the half the size of flower thrips and lighter in color. These insects generally produce only cosmetic damage to fruit, although this can reduce the value of crops intended for sale to fresh markets.
Citrus mites are tiny arachnids, similar to spiders, but much smaller. In fact, they are difficult to see without the help of a magnifying glass. Threat species in Arizona include the Texas citrus mite, the two-spotted mite and the Yuma spider mite. They have eight legs and round bodies. Mites often occur during times of water stress when dusty conditions prevail. They attack the leaves of citrus trees, producing tiny yellow spots on the leaves. Some species produce a fine webbing between fruits or on the undersides of leaves. Proper irrigation can help control these tiny pests.