Clear81° WeatherClear81° Weather

Ask Dr. Hort: Why is my old orange tree is such bad shape?

Orange tree under viral disease attack

Q: I have an orange tree that I would guess is about 40-plus years old. For the last few growing seasons, the oranges have been horrible, very bitter and the skins look like they have been burned. The bark has spots on it and during the growing season it gets a cobweb effect on the branches. I do not see any bugs; could this be citrus canker?

Dori Law

A: In old age, citrus trees have several problems. The splotches on the trunk are just lichens, which are harmless. But therein ends the good news. The brown russeted skin of the oranges is from citrus rust mite and probably other mite species, which manifest during dry periods. That in itself is mostly an appearance problem.

However, the photo I examined of your peeling bark is due to a viral disease called psorosis, one of five viral diseases to attack citrus in their older age, based partly on the types of rootstock used 40 to 50 years ago. There is no cure for a virus in a plant. The tree will continue to decline, and when it no longer satisfies your needs it should be cut down.

Foot rot likely culprit in decline of trees

Q: I'm having problems with several citrus trees. I have one grapefruit, one tangerine and three orange trees, which I planted around my home 17 years ago. Up until about two years ago, they supplied more fruit than I could eat or drink. Then they developed a black mold and started losing fruit and branches. The main branches have a greenish, rough surface similar to the barnacles on the bottom of a boat. The few fruits that they bear are now small and almost all black. I have listened to many suggestions, none of which seems to have worked, the last being a combination of Malathion Plus and neem oil. Any suggestions would be greatly appreciated. Bill Zbikowski

A: The black or brown rind is from rust mites, which did their damage back in April and May last year. This might cause fruit to be a bit smaller. The greenish, barnacle-looking stuff are lichens, which is a fungus and an algae living together, also known as symbiosis. Lichens cause no harm to the tree, but are seen frequently on shrubs and trees in decline. Your trees are in severe decline, most likely caused by foot rot, a fungus that destroys the root system over time, set up by too much irrigation and/or poor drainage. Check at the base of the tree for peeling bark. This is the telltale sign, but it can also manifest just in the roots. Citrus trees that are 17 years old should be twice the size as those shown in the pictures you shared with me. There is no cure. Harvest while you can and replant with new trees.

Bermuda too much work for average homeowner

Q: I have had Bermuda grass growing on part of my lawn as a weed. I would eventually like all of my lawn to be Bermuda grass, as I am told it is easier to maintain and looks much greener than my St. Augustine. Looking ahead, how can I grow it? Anita R.

A: Bermuda grass, if highly maintained, is beautiful. Golf courses and athletic fields are hybrid Bermuda grasses. Having it as a lawn is a different story. For it to look its best, it needs to be mowed with a reel-type mower, not a rotary like the conventional lawn mower. It must be fertilized six times per year, has disease and insect problems and requires a lot of irrigation.

As a lawn weed it is extremely drought-tolerant and blends into your St. Augustine, filling in areas where chinch bugs have wiped out your grass. It is also seeded as a pasture grass and baled as a high-quality hay.

It is a very versatile grass, but requires too much maintenance for the average homeowner. You would be better off letting it blend into your St. Augustine. Were you to decide you wanted only St. Augustine, Bermuda grass is a bear to get rid of as a lawn weed.

Need help? Dr. Hort (Greg Charles) answers questions about garden problems. E-mail him at drhort@tampabay.rr.com or mail questions to HomeLink, Features Department, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731. Describe problem in full, and include your name, city of residence and contact information. If possible, include a good-quality photo. Fuzzy ones won't do. Photos cannot be returned.

Need help? Dr. Hort (Greg Charles) answers questions about garden problems. E-mail him at drhort@tampabay.rr.com or mail questions to HomeLink, Features Department, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731. Describe problem in full, and include your name, city of residence and contact information. If possible, include a good-quality photo. Fuzzy ones won't do. Photos cannot be returned.

Ask Dr. Hort: Why is my old orange tree is such bad shape? 01/07/11 [Last modified: Friday, January 7, 2011 7:27am]

© 2014 Tampa Bay Times

    

Join the discussion: Click to view comments, add yours

Loading...