Citrus FAQs - Citrus

1.  Crinkled and curled leaves
2.  Leaves coated with black "stuff"
3.  Splitting fruits
4.  Fertilizing
5.  Holes in leaves
6.  Citrus blooms dropping
7.  What citrus trees grow well in the Florida Keys?
8. Premature fruit drying (granulation)

1. 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.   Leaf Miner Damage

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.

2. 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).  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.

3. 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.

4. 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.

5. 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.

6. 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%).

7. What citrus trees grow well in the Florida Keys?
The more tropical citrus fruits like Key Lime, Tahiti Lime and Pummelo, all the other citrus varieties do well but are more cold hardy.  On oranges, you may not get good orange color because of the lack of cool weather, but the fruit is fine.  The most important factor when selecting a citrus for your yard is the root stock - use lemon types (rough lemon and macrophylla are the best) for our alkaline soils.

8. We have a 5 year old naval orange tree in our yard, and it has begun to bear the past two or three years.  The only problem is, the oranges are dry when we cut them open.  They are beautiful on the outside, but are pithy and have no juice. What is wrong?
Premature fruit drying (granulation) navel, mandarins, mandarin hybrids, grapefruit and Valencia fruit sometimes exhibit drying of juice vesicles when harvest is delayed or when the trees are grown on lemon or other vigorous rootstocks. The problem varies seasonally and is more of a problem on larger size or late bloom fruit. Drying appears to be associated with over-maturity, a lack of water, excessive tree vigor, extended warm, and/or dry fall weather. Premature fruit drying is also a problem associated with young trees, a condition that is alleviated with tree maturity. Refer to EDIS document Citrus Problems in the Home Landscape. Review each of the factors listed: rootstock type, was the fruit picked as over mature fruit, did the tree receive regular watering.

See the links listed below for more citrus information: