Citrus
Frequently Asked Questions

  1. Why are my fruit dry and pulpy?
  2. What causes my fruit to split?
  3. How and when should I fertilize my citrus tree?
  4. What is the black stuff that gets all over the leaves and fruit of my tree?
  5. Why do the leaves on my orange tree drop off during the late winter and early spring?
  6. My tree seems to be dying in sections. In just a matter of days the leaves wilt and die on one section of the tree at a time. What is wrong with my tree?
  7. I have a Hamlin orange tree in my backyard. The leaves, particularly the new flush, have clear areas in the tissue which almost look like a snail has been crawling over the leaf. The leaf eventually becomes twisted and distorted. What is wrong with my tree?
  8. I have a grapefruit tree in my backyard. The leaves are covered with funnel-like structures and the fruit have raised bumps. What is the problem?

1. Why are my fruit dry and pulpy?

Dry, Pulpy CitrusThere are several explanations for dry pulpy fruit. Drying appears to be associated with over-maturity, a lack of water, excessive tree vigor related to rootstock , extended and/or dry fall weather. Dry fruit may also be associated with young trees, a condition that is alleviated with tree maturity. In any case, there isn't much you can do other than keep the tree well fertilized and well watered particularly during times of drought. When you buy trees, ask about the root stock.

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2. What causes my fruit to split?

splitting fruitSplitting is more severe on Valencia, Hamlin, Navel oranges, and Murcotts. Fruit splitting is primarily a problem at high temperature during periods of high humidity and rainfall from August through the fall. The exact cause is unknown, but it is believed to be a problem of water relations and peel thickness. Low to deficient potassium levels resulting in thin peel promotes fruit splitting. The best treatment is to keep the tree well fertilized and well watered during dry periods.

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3. How and when should I fertilize my citrus tree?

Mature trees (over 5 years old) should be fertilized 3 times per year-January, May and October. Select a citrus fertilizer which has magnesium and apply 1 pound per year of age of the tree up until 8 years old. In other words, apply 5 pounds of fertilizer (6-6-6 or 8-8-8), on a five year old tree, evenly under the drip line and a few feet out from the drip line 3 times per year. Younger trees should be fertilized every 4-6 weeks starting in March and ending in October with 1/2 to 1 pound of fertilizer.

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4. What is the black stuff that gets all over the leaves and fruit of my tree?

Fruit with Sooty MoldThis is a fungus called sooty mold which grows on the fecal deposits (honey dew) of sucking insects (aphids, scales, mealybugs and whiteflies). The fungus does not infect the leaf, but merely grows on the leaf surface feeding on the honeydew. Control aphids and whiteflies with insecticidal soap. Use horticultural oil to control scales and mealybugs.

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5. Why do the leaves on my orange tree drop off during the late winter and early spring?

Greasy Spot FungusCitrus trees will normally drop their leaves about every 18 months, so it is normal for a few leaves to drop. Also, not enough nitrogen fertilizer will cause leaves to drop prematurely. A fungus called greasy spot infects citrus leaves in the summer and causes leaf drop during the winter-the leaf defoliation can be severe. This disease can be controlled with an application of copper at the end of May or the first of June.

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6. My tree seems to be dying in sections. In just a matter of days the leaves wilt and die on one section of the tree at a time. What is wrong with my tree?

Phytophthora Foot RotThis is caused by a fungus disease called foot rot. This disease often gains access to the tree from lawn mower, weed whacker or some other physical damage when the trees are young. The disease, caused by a fungus called Phytophthora, destroys the tree's vascular system at the point of entry and then slowly circles the entire trunk finally killing the whole tree. This disease can be treated with  fungicides which are quite expensive for the homeowner. The other less effective option is to remove all the dead and decaying bark from the infected area on the trunk and paint the area with a copper solution.

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7. I have a Hamlin orange tree in my backyard. The leaves, particularly the new flush, have clear areas in the tissue which almost look like a snail has been crawling over the leaf. The leaf eventually becomes twisted and distorted. What is wrong with my tree?

Citrus LeafminerThis sounds like citrus leafminer. This condition is caused by a little moth that lays it's eggs on the leaf surface of new growth. The egg hatches and the larva bores into the leaf and feeds between the upper and lower leaf surface making a clear snake-like mine. This insect does not pose a real threat to older trees other than making the new growth look bad. The leaves become distorted but seldom fall off so they are still photosynthesizing (producing food) for the tree. However, young trees that are heavily infested could be killed.

The only control option the homeowner has is to spray each new flush of growth every 7-10 days with a horticultural oil until the leaves have hardened off, which usually takes 3-4 weeks.

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8. I have a grapefruit tree in my backyard. The leaves are covered with funnel-like structures and the fruit have raised bumps. What is the problem?

Citrus scab symptoms on leavesThis could be citrus scab. The leaves often have funnel-like structures in the leaves in the early stages and eventually raised scabs or bumps on the fruit. As a homeowner, you don't need to be too concerned because this fungus disease does not damage the fruit quality.

Citrus scab symptoms on orangeSevere cases of this fungus disease can be treated with an application of copper two to three weeks after petal fall and again in two to three weeks.

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