Residential Lawn & Garden

Citrus FAQs

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What's causing the leaves of my citrus trees to be curled and crinkled?

Two Possibilities:

Citrus Leaf Miner Damage—This insect is the maggot of a tiny fly that lays eggs into the leaves. Maggots hatch from the eggs and "mine" their way through the leaves causing them to cup and crinkle. "Squiggly" lines can also be seen in the affected leaves. This insect is not harmful to the health or fruit production of established trees. Young citrus trees may benefit from sprays of horticulture oil which interfere with the fly's ability to lay eggs into the leaf. Spray each time a new flush of growth appears. Read the label of oil product carefully, as horticulture oil can burn the leaves when applied incorrectly. For more information, read this Citrus Leaf Miner publication.

Or Aphid Damage—Curled, distorted leaves can also be the result of aphid insects. These pests have needle-like mouthparts which pierce the leaves and feed on the plant sap. They always feed on the newest, most tender growth. As these leaves mature, they exhibit the damage, but by then the aphids are long-gone. Aphid damage is mostly aesthetic and can be ignored. If aphids are detected, they can be easily controlled by forceful sprays of water or by insecticidal soaps. For further information, read this Aphid publication.

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The leaves of my citrus tree are covered with black "stuff." Is it hurting my tree?

Sooty Mold—Appears as a black, sooty growth on the upper side of leaves. Is harmless, but indicates that an insect was or is present (usually aphids, whiteflies or scales).

Whiteflies—As these piercing-sucking insects feed on the undersides of the leaves, they secrete a sticky, clear fluid that drops onto the leaves below. Sooty mold grows upon this secretion. For more information, read this Sooty Mold publication.

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There are white and orange scale-like things growing on the undersides of my citrus leaves. Is this a problem?

Aschersonia (Friendly Fungus)This beneficial fungus grows on and kills whitefly insects. It looks scary, but it's a good thing.

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The fruits on my citrus tree are splitting and falling off. There are little bugs in the fruit. What can I do to prevent this?

Water or Varietal Problem. The problem of splitting fruits usually occurs in the early fall. At this time of year, the citrus fruits are mature in size and the peel is not expanding. If heavy rains occur, citrus trees absorb water and force it into the fruits. The peel cannot expand, and instead splits. The fruit will begin to decay and attract insects. Splitting fruit is also associated with young trees and certain varieties.

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How do I fertilize citrus?

Citrus which has been planted in the ground over four years should be fertilized three times per year (January/February, May/June, and October/November) at the rate of one pound per year of the tree's age (counting from the time it is planted) up to a maximum of 10 pounds per application. Young trees should receive between 4 and 6 applications per year at a rate of one pound per year of age. An 8-8-8 fertilizer that contains slow release nitrogen and secondary nutrients (particularly magnesium, manganese, copper and boron) is recommended. Apply the fertilizer to the entire rooting area which extends from the trunk out to several feet beyond the drip line of the tree.

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The peel on some of my oranges has turned brown. What's wrong with them?

Rust Mite Feeding—Tiny rust mites feed on the peel during the summer causing a russeting of the peel. The interior quality of the fruit is not affected. Homeowners can ignore this.

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There are yellowish spots on the leaves of my citrus and many leaves are dropping off.

Greasy Spot Fungus—The first appearance of the disease is as a yellow green spot, which becomes orange yellow. The area becomes raised on both sides of the leaf, and the color becomes tan, then dark brown to black. Leaves must be sprayed with copper fungicide before symptoms occur to prevent this problem. Once symptoms appear, no amount of spraying will cure the problem. Rake and remove fallen leaves to reduce future infections.

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The peel of my citrus fruits looks like it has scars. What causes this?

Abrasion/Wind scarring—Fruits blow about in heavy wind and rub against twigs, other fruits, leaves, etc. Does not affect interior quality of fruit.

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Something is chewing holes in the leaves of my citrus tree. Will it hurt my tree?

Chewing insect—Usually either a grasshopper or caterpillar. Damage is usually contained to a small proportion of leaves and should be ignored. The caterpillar is called an Orange Dog, and is the larval stage of the beautiful Giant Swallowtail butterfly.

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Why do my citrus blooms drop without setting?

Citrus must be planted 3 to 4 years before it becomes mature enough to set fruit. It may bloom prolifically, but it will drop its blooms. Even mature citrus sets only a very small amount of its bloom (less than 1%).

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Most of the leaves on my young citrus tree are yellowing and dropping. Why?

Foot Rot disease may be the problem. This fungal disease attacks the tree at or just below ground level, rotting through the bark and conducting tissue thereby stopping the flow of water and nutrients in the tree. It is aggravated by planting citrus too deep (the top of the root ball should be flush with the soil surface), mulching citrus (an excellent idea on every other plant, but not citrus) poor drainage (citrus likes very well drained soils) or over watering (citrus will thrive on an inch of water (or less) a week. Yellowing veins is a typical symptom of foot root or root rot disease.

Trunk damage. Check the lower trunk for areas where the bark may look "eaten away". If the damage has not completely circled the trunk, the disease can sometimes be halted by pulling back the soil or mulch from around the trunk, allowing the bark to dry and then applying copper fungicide to the area followed by pruning paint.

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