What to do this week –By Mark Govan, Host “Florida Gardening”
My last two articles have covered problems associated with citrus. My first article covered citrus diseases and my second article covered citrus insect problems and the proper care you must do to prevent these diseases and insects from limiting your citrus crop. In this article I would like to go over some of the disorders citrus trees are affected by. Citrus disorders are divided into two categories, Abiotic and Nutrient disorders.
Abiotic disorders refer to those stresses put on citrus by fluctuations in the environment such as sunlight, wind patterns, temperature, and precipitation. Nutrient disorders are problems associated with the limited availability of the essential elements necessary for plant growth. By learning about these disorders, you will be able to have a better understanding of how these imbalances affect your citrus trees. Some of these problems may require corrections in the environment, additions of nutrients, or both.
One of the most common problems I hear of is about dry fruit. Even though the fruit looks good on the outside, the fruit is dry or has a limited amount of juice. This condition is also called granulation and is caused when the juice sacs which hold the liquid in the fruit begin to break down. Normally this occurs on young trees which are being over fertilized with a high nitrogen fertilizer or on young trees which produce large fruit.
Excessive nitrogen, the first number you find on a bag of fertilizer, can cause the tree to grow too quickly and the juice sacs in the fruit lose their sugar and acid. This condition is normally accompanied by reduced rainfall or too little irrigation. As the tree responds to the nitrogen by growing quickly, the reduced rainfall limits the uptake of liquids causing the fruit to be dry and inedible. To limit this problem on your tree you will need to reduce the nitrogen content of the fertilizer you are using. I use an 8-10-10 slow release fertilizer and instead of doing one or two heavy applications per year, try to fertilize lightly every other month. You will also need to increase your watering schedule.
New trees need to be watered frequently and you should build a soil berm around the roots of your tree to help direct water to the plants root system. New trees should be watered every other day to ensure the entire root ball is saturated. Dry soil tends to repel water or direct water away from the root balls of trees. A berm will hold the water around the tender roots and allow the water to slowly percolate through the soil. Established trees do not require a berm.
Puffing is another problem caused when fruit are left on the tree past their maturity. Puffing describes what happens when the peel or skin of the fruit separates from the pulp, causing the fruit to feel puffy. This happens quite often on large trees where the fruit is not picked soon enough because of the height of the tree. Navel oranges and Duncangrapefruit are also susceptible. Naval oranges normally ripen in November even though the skin of the fruit is still yellow. Many people will not pick the fruit because they think the fruit has not ripened yet and they want to wait until the fruit takes on the orange color they see in the stores. Unfortunately, most navels purchased in Floridastores are gown in Californiaand have that beautiful orange color. Our navels grown in Florida (especially the red navels) do not ripen like the California Navels do. If you have not started harvesting your Navel’s by Thanksgiving, then you are missing the best time to start enjoying your fruit.
The Duncangrapefruit is another tree that puffing of the fruit has been a problem. Because of the Duncan’s ability to overproduce, many people can not eat all the fruit the tree can produce. Sometimes, by the time the fruit is picked, the seeds in the fruit have already sprouted and started to grow. Even though the fruit was still juicy, the fruit should have been picked much earlier.
The control for this problem is to occasionally sample the fruit on your tree and harvest them when they are juicy and taste good. I would like to tell you to mark your calendar and pick them on the same date each year but because of rainfall and varying weather conditions, you will be the best judge as to when your fruit taste the best. Remember, each variety of citrus ripens at different times of the year so if you are growing different varieties, you will have to make adjustments to your particular harvest times. I also believe the best place to store your unused fruit is on the tree so you should only harvest the amount of fruit you are going to use over the next week. If you mark your calendar when you harvest this year you should be able to use these approximate times to harvest your fruit next year. Just do not wait too long to harvest all the fruit.
Another problem I see on developing fruit and mature fruit is often misidentified as an insect problem. This problem is called Wind Damage. Wind damage may not sound threatening but any problem affecting your tree or fruit can give a homeowner a scare. This problem starts during the spring and summer months as wind blows through a tree. Damage to the fruit occurs as the developing fruit rubs against thorns, branches, or other fruit. Newly planted trees or trees with an open canopy seem to have more fruit affected then well established trees. Fruit damaged by this problem develop ridges and irregularly shaped raised areas on the skin of the fruit which grow as the fruit matures. These areas eventually take on a grayish color with rough edges and they do not turn orange as the fruit ripens making them very noticeable.
Control of this problem can be as simple as placing windbreaks for protection in the area of your young developing trees. Windbreaks may also include other trees or shrubs strategically placed to protect your new trees as they grow. You should also remove any dead or diseased branches which may injure developing fruit. Remove water sprouts which grow from the base of the tree with thorny spines that can injure your fruit. Also you should try to limit your pruning of individual branches which may lead to a lopsided tree.
The last problem I need to touch on is nutrient deficiencies. Nutrient deficiencies can be caused by not applying the proper fertilizers to your trees, using well water with high pH content, or not applying foliar applications of citrus minor essential elements. Symptoms of nutrient deficiencies include but are not limited to yellowing leaves, rotting or sunken areas on the bottom of the fruit, reduction of fruit production, and pockets of brown or decaying matter inside the fruit. Most of us grow our citrus in native Florida sand which has few if any micro nutrients. In order for our trees to produce consistently, we must replenish these nutrients used by our trees on a regular basis.
Make sure the fertilizer you are using is made for citrus and is a slow release type of fertilizer. Some micro nutrients may be included in the fertilizer bag you purchase but I have found that you will still need to purchase a citrus micro nutritional package at a local garden center in either a liquid or granular form. I prefer the liquid type you spray onto the tree leaves. Leaves absorb the nutrients directly by bypassing the root system which helps when pH is the problem. High pH soils bind these elements making them unable to be absorbed by the tree roots even if you have applied them to the soil.
I hope this series of articles on citrus will give you some diagnostic tools to help you identify problems you may find on your trees. Being able to tell the difference between insect, disease, or citrus disorders may save you money and allow you to treat your trees accordingly. Citrus can be a wonderful plant for any garden and will give you years of enjoyment and fruit for your table. Keep these articles with you when you look at your trees and hopefully you will find them useful! Since my next article will not be until next year, I wish you all a Merry Christmas and Happy Holiday Season! Thank you for your support and remember, without plants we would not be here!