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Tips and Tricks

Tips and Tricks

Monitor Your Citrus Trees for Pests, Diseases, and Disorders

Citrus trees provide property owners with lovely foliage, blooms, and fruit. However, diseases and pests negatively impact lemon, orange, lime, and other citrus trees. Here's information to help you identify problems on your citrus trees.

Signs of Small Mammal Problems in Citrus Plants

A number of animal pests attack various parts of citrus trees. Squirrels, gophers, and rabbits are some of the vertebrates that chew on young citrus trees. Roof rats and Norway rats will also chew on citrus trees and citrus fruit.

Identify vertebrate damage to your citrus trees by looking at the trunks of trees where they meet the ground. Holes and burrows in the soil near citrus trees indicate likely ground squirrels, moles, or gophers.

While gophers feast underground on citrus-tree roots, moles disturb soil but rarely damage citrus trees. Ground squirrels chew bark and cambium of citrus trees, and their chew marks can be anywhere on a citrus tree.

Rabbits and voles (also called meadow mice) tend to girdle young fruit trees by chewing away bark in a circle around the lower trunks of the citrus trees. Look for missing rings of bark up to two feet from ground level when a rabbit is the culprit. Voles girdle citrus tree trunks up to two inches from the soil level.

Signs of Insect and Invertebrate Pests in Citrus

Citrus trees attract a wide variety of invertebrate pests throughout the year. Citrus pests damage young shoots, leaves, and mature fruit, but they also sometimes spread fatal diseases to citrus plants.

The most common invertebrate species that attack citrus trees and fruit in Florida include the following:

  • Aphids

  • Whiteflies

  • Fire ants

  • Mites

  • Scales

  • Grasshoppers

  • Caterpillars

Citrus-tree damage from aphids and whiteflies appears in the spring, when the insect pests feed on new flush growth. Young leaves affected by aphids distort and curl, which limits the growth of the new citrus shoots and leaves.

While whiteflies don't distort young shoots and leaves, their presence may cause friendly orange-red fungi to show up on bottoms of leaves. The orange-red fungi help control white fly invasions.

Tiny citrus, rust, and red mites attack trees mostly during the summer months in Florida, although Texas citrus mites are most damaging in winter. You need a magnifying glass to see these citrus pests, since mites are only around 1/200-inch in length. Mites lay their eggs on the leaves, stems, and fruit of citrus trees.

Mites cause the following symptoms in citrus trees:

  • Leaf and fruit drop

  • Blemishes on fruit

  • Scratches or etches on leaf tops and fruit

  • Fruit size reduction

  • Yellow spots on leaves

  • Cupping of leaves

When you notice larger spots on citrus tree foliage where insects have dined, suspect garden snails, grasshoppers, caterpillars, European earwigs, and Fuller rose beetles. A survey of affected citrus trees and the adjacent area is the best way to determine the precise insect chewing on citrus leaves.

Scales are persistent citrus pests that fix on citrus trees by inserting their sharp mouthparts into citrus plant tissue. Look for 1/8-inch-long purple spots on leaves and twigs toward the interior of citrus trees. Chaff scales are light brown and look like wheat chaff. Chaff scales infest citrus bark, leaves, and fruit, and the chaff scales can cause green spots on citrus fruits.

If you notice waxy white deposits on citrus foliage, and the leaves of the affected tree begin to distort, suspect the presence of Asian citrus psyllid. Asian citrus psyllids spread the fatal greening disease to citrus trees, and their presence should be reported to your local agricultural officials.

Symptoms of Citrus Tree Diseases

The most common Florida citrus tree diseases are fungal disorders including greasy spot, scab, melanose, and foot rot.

Greasy-spot symptoms include drops of oily looking substances just below the surfaces of citrus tree leaves and blotches on citrus fruit. The greasy spot fungus destroys citrus leaf tissue and can reduce a tree's health.

Signs of citrus scab include wounds on the leaves, twigs, and fruit of citrus trees. The wounds look like warts or scabs and are highly contagious. Fruit from scab-affected trees can become misshapen, but the scab fungus does not generally affect fruit quality.

Signs of fungal infection from melanose include raised brown lesions on citrus leaves. The lesions feel like sandpaper and will cover oil glands on fruit, while greasy spot does not cover oil glands of fruit. Melanose infections produce streaks of fungal spores on fruit and may cover fruit with muddy-looking lesions.

Foot rot is a common soil-borne disease of citrus trees. The foot rot fungus often starts where a bud union meets citrus root-tree stock. Irregular patches of soaked water on bark and oozing gum from citrus trees are the first signs of foot rot. Other signs of foot rot include reduced vigor, smaller leaves and fruit, and leaf drop.

Keep your Florida citrus trees healthy in Pinellas and Hillsborough counties by contacting Pete & Ron's Tree Service, Inc., today. We provide professional pruning, inspection, and treatment of citrus trees.