A lot of Marco Island homes have citrus trees in the yard. Unfortunately, the hurricanes this summer have damaged many of them. Citrus is not salt tolerant. Most trees suffer no damage from salt water even though they are in back yards next to canals. But the constant tropical storm winds carried enough salt in the air to coat the trees with salt and burn the branches and foliage. If your citrus trees appear to have a lot of dead wood facing the water this is why. You can have the dead wood trimmed back to healthy, green wood to encourage new growth on the damaged side. Also, January is one of the months to fertilize citrus so be sure you don’t miss this chance to fertilize. And to encourage regrowth you may want to lightly fertilize every month through the summer avoiding the time when the tree is flowering.
The planting and care of citrus trees is very important. Many do not survive due to a lack of understanding of proper care.
Citrus need full sun and anything less will affect the growth and production of the trees. Appropriate spacing is necessary as most citrus trees are rapid growers and large round trees. Plant citrus trees at least 20 to 25 feet apart to allow for mature growth. Citrus trees should be planted at least 15 feet from buildings or other large ornamentals.
Before planting clear the area of all grass and weeds. Add 4 to 5 shovelfuls of organic matter like peat moss or manure to amend sandy soils. Citrus trees will not tolerate sitting in wet soil so avoid planting in boggy areas unless you raise the soil level by building a planting bed.
Citrus can be planted any time of the year but late winter to early spring is the best time. Make sure the tree you select is healthy with a nice straight trunk. If it is diseased or insect infested, or if the roots are coming out of the drain holes indicating a potbound tree, leave these at the nursery. When ready to plant remove the tree from the growers pot and check for roots which are spiraling around the root ball. Gently pull these roots free so they protrude from the ball. If the tap root is coiled at the bottom soak the root ball for several hours in water to allow for some straightening of the tap root and any other badly coiled roots before planting.
Dig the planting hole large enough that you can spread the roots out if necessary. Set the plant slightly higher than it grew in the container making sure the bud union (or grafting site) is at least 6 inches above the soil line. This area of the tree is very vulnerable to infection of foot rot, a soil fungi which are splashed onto the susceptible area.
Backfill half the hole and compress the soil to remove air pockets. Water to help settle the soil around the roots and finish filling the hole. Form a water basin around the tree by making a ring of soil 4 to 6 inches high to allow for adequate watering while the tree is young. Do not mound the soil around the base of the tree! Leave the water basin for six months to a year.
Water your new tree two to three times a week for the first month and then twice a week for the next month. Taper off to a thorough watering once a week if there has not been adequate rainfall.
The only pruning necessary on a citrus tree is to remove sprouts or suckers from the trunk or to remove dead wood or crossing branches which could cause damage to the other branches. Also low hanging branches to allow air flow under the tree.
Do not fertilize your new tree until it shows signs of new growth. Spread the fertilizer evenly in your water basin the first year and then enlarge the area after that to cover an area twice the diameter of the tree canopy and water in thoroughly. Use a balanced citrus special fertilizer with the necessary minor elements four to five times a year the first year. The first application should be in February and the last in September. The second year fertilize four times and three times thereafter in January, June and October.
Citrus can suffer many insect and disease problems. Listed below are some of these problems.
Keep the area beneath the canopy free of weeds to the drip line. The herbicide Round-up is safe for use under citrus. If you chose to cultivate your weeds keep it shallow as the citrus tree has shallow and widespread feeder roots. Mulching citrus is not recommended as it can increase the chance of infection by the soil borne fungi which cause foot rot.
Foot rot is a leading cause of death for dooryard citrus. This destructive soil borne disease of citrus is encouraged by high soil moisture, planting too deeply, mulching or too many weeds under the canopy of the tree. Foot rot lesions develop at or just above the bud union and on the bark of the crown roots. The first sign of infection is drops of gum on the bark. The bark near the lesion will be brown and slippery. As the dead bark dries it shrinks and splits, eventually sloughing off and girdling the tree. The part of the tree fed by the damaged bark dies and so the disease progresses.
Another common disease of citrus roots is root rot which causes the destruction of the shallow feeder roots mentioned earlier. Roots infected with this disease will have decaying outer tissue which easily slides off the root. If new roots don’t regenerate quickly enough the tree starves to death. Root rot may have no above ground symptoms. Often the tree will look good one week and be dead the next.
Cultural practices to follow to avoid these diseases in your citrus trees are as follows:
Prune low hanging branches to allow good air circulation and light under the canopy.
Plant new trees at or above the level they were in the container – never lower.
Keep soil, weeds and brush away from the base of the tree.
Avoid mulching which causes high soil moisture.
Use chemical rather than mechanical weed control to avoid damaging the trunk and feeder roots.
You can try to control or slow the progression of the disease on older trees with chemicals if you catch it in the early stages of the disease. First remove the soil from the base of the trunk and crown (top) roots in an area one to three feet in all directions. Washing with a low pressure hose is a good way to accomplish this. Second, remove all diseased tissue including about an inch of healthy tissue beyond. Third, drench with a systemic fungicide specific for phytophtora.
Some insects which affect citrus are mites, scale, whitefly, mealybugs, aphids and caterpillars. There are many beneficial enemies of all of the above pests and they do a good job of keeping these pests under control so you can avoid using chemicals on your trees. Parasitic wasps, ladybeetle and lacewing larvae, and adult ladybeetle are some of the more common beneficial insects to watch for. If you should need to spray, Malathion is a good choice for citrus. Two parasitic fungi infect immature whitefly. Red Aschersonia form pink and reddish pustules 1/8 inch or less on the underside of the leaves. It is very colorful and noticeable. Acgerita or brown whitefly fungus appears as cinnamon pustules also about 1/8 inch diameter on the underside of leaves. This fungus is often thought to be Florida red scale. There are other fungi which attack citrus mites, especially in the summer.
Sooty mold is caused by insect honeydew left on the leaves while feeding. Controlling these insects will prevent this and an oil spray will help the fungus flake off cleaning the fruit and leaves. Scab, melanose and greasy spot are all diseases of fruit and leaves of citrus trees. Copper fungicide sprays will bring these diseases under control if they get out of hand.
It is best to depend entirely on natural control of insects and disease on your citrus trees. Many are never sprayed and yet the trees survive and produce good crops of satisfactory fruit.
There are several other problems homeowners may experience with their citrus trees. Blossom and fruit drop may just be the tree ridding itself of excess fruit or it could be the result of improper fertilizing. Be sure to fertilize three times a year with a quality citrus fertilizer. Do not fertilize while the tree is flowering as the nitrogen can cause the blossoms to fall off. If you are late with your January fertilization wait until the fruit has formed and set before you fertilize. Improper watering during the dry spring months when the tree is flowering and setting fruit is another cause of blossom drop. Be sure to provide irrigation at regular intervals during the dry months. And strong winds will cause blossoms and small fruit to drop.
Granulation of citrus fruit causes enlarged, hardened and colorless juice vessels. Several factors can contribute to this problem. Young trees are more likely to have this problem than older trees and large fruit more than small. Leaving the fruit on the tree too late in the season. High soil moisture. This condition may be inherent to particular trees as it tends to recur in the same trees year after year.
Fruit splitting can be a problem in September and October. Nutritional deficiencies, especially copper, can contribute to this problem. Or after a series of heavy rains, especially following drought, the tree takes up a lot of moisture and forces it into the fruit. The fruit is nearing maturity and the rind has become less pliable and splits. To prevent splitting on future crops use a balanced fertilizer program and make sure you irrigate uniformly during the growing season.
Citrus canker and citrus greening are two very serious diseases of citrus and I will go into more detail in a later column on these diseases.
Citrus canker is a serious disease of citrus especially for commercial growers. It causes unsightly lesions, premature fruit drop and can weaken and kill a tree. The only sure way to get rid of canker is by destroying infected or exposed trees. This disease has been discovered in many groves in our area and also in backyards in Golden Gate. State or federal inspectors may request access to your property to examine your citrus trees if canker is discovered in our area. They will be from the U.S. Department of Agriculture or Florida Department of Agriculture and Consumer Services. They will inspect the trees and take samples if canker is suspected. If the tree is infected it must be destroyed. Your trees will also be destroyed if they were purchased from a nursery exposed to canker. This is a necessary evil to protect our commercial citrus groves.
This disease is highly contagious and can be spread by wind driven rain, lawn mowers, pruning tools, animals and people and the movement of infected plant materials. As a lawn care company we recently received a notice of quarantine area from the Fl. Dept. of Ag. & Consumer Services. Within this area they regulate businesses whose activity may result in the spread of canker. There are special regulations regarding disinfection of personnel, vehicles and equipment and special handling and procedures for moving and disposing of plant clippings and yard debris. In order to work inside the quarantine area (they provide you with a map detailing the area) all lawn maintenance operators must enter into a May 1999 Compliance Agreement agreeing to follow decontamination procedures. Failure to do so will result in your business being suspended from working in the quarantine area and a violation.
The cooperation of all homeowners and horticultural workers is necessary to eradicate citrus canker from Florida so that we can continue to step out the back door for some fresh citrus off the tree.