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Published September 03, 2010, 12:00 AM

Verticillium wilt may be killing apricot tree

Q: I live in east Texas. I planted an apricot tree this year, and it was thriving but now is losing leaves one branch at a time. The first leaves to fall off are those closest to the trunk. Within a week, the branch is bare. This has been going on for two months. I do not see any bugs, damaged leaves or sap.

By: Don Kinzler, INFORUM

Q: I live in east Texas. I planted an apricot tree this year, and it was thriving but now is losing leaves one branch at a time. The first leaves to fall off are those closest to the trunk. Within a week, the branch is bare. This has been going on for two months. I do not see any bugs, damaged leaves or sap.

Sometimes the leaves turn yellow before they fall. I found an article about a disease called black heart that kills apricot trees. It said the disease is caused by planting the tree too close to tomato plants. At one time, I did have tomatoes growing about 5 feet from where I planted the tree.

I called my local nursery and was told they had never heard of black heart and that my tree was suffering from heat stress. When this started, it wasn’t hot, and I don’t understand how heat stress would target one limb at a time. Advice would be helpful. (e-mail reference)

A: Unfortunately, you were given the brush-off by the nursery. This might be verticillium wilt that is killing your tree. However, you need to have it checked by a local horticulturist with the Texas Extension Service. To find a horticulturist, go to http://county-tx.tamu.edu.


Q: My wife and I purchased a ficus tree a couple of weeks ago. We keep it inside, and it looks healthy. However, we have been losing a lot of leaves recently. We are using regular tap water to water the tree every couple of days. Any advice to help make the tree healthy? (e-mail reference)

A: I have answered probably more than 100 questions of this sort on ficus trees.

Go to www.ext.nodak.edu/extnews/hortiscope/tree/ficus.htm for information. If you have more questions, get back to me and I’ll try my best to help you.


Q: Yesterday, I stopped at a feed store to pick up grass seed. In passing, I mentioned that it’s still too warm to plant grass seed, but I’ll spray for weeds. The gentlemen who sold me the seed said it’s also too hot for spraying.

He said you shouldn’t be spraying weeds when it’s over 80 degrees. The temperature was about 95 degrees at the time. What are your thoughts on this subject? (e-mail reference)

A: The man speaks the truth. In 90-plus heat, the weeds shut down, so any weed-killing applications won’t work very well and may cause extensive damage to surrounding plant material. Wait until the first week of September to do the weed killing and seed sowing.


Q: We have a large garden with about 50 tomato plants. Ten or more plants appear to have bacterial speck because there are many dark spots on the green tomatoes.

Are the tomatoes safe for canning if I blanch and remove the skins? (Spiritwood Lake, N.D.)

A: That’s a lot of tomatoes! Yes, you can consume and can the tomatoes because the damage is superficial. Go to www.ag.ndsu.edu/pubs/plantsci/

hortcrop/pp736w.htm for more information.


Q: Fist-sized brown spots began appearing around my garden last summer and started increasing in size this summer. Is this dollar spot and what are your recommendations for getting rid of the problem?

From the articles I have read, a lack of nitrogen and improper watering practices are the culprits. However, my brother has a new lawn with a sprinkler system and also is being hit hard with the same problem. He takes excellent care of his yard. What product should we be using? I read your column each week and enjoy it. (Carrington, N.D.)

A: Dollar spot, necrotic ring spot and many other patch diseases of summer can be controlled using good cultural practices. Use a balanced fertilizer program and proper watering techniques and scheduling. Select disease-resistant cultivars of turfgrass to match the maintenance regime intended. Core aerate for three consecutive growing seasons, then follow with a power raking and overseeding. This is best done in the spring after three mowings or at the end of August or beginning of September.

This practice will integrate soil microbes into the turfgrass canopy and crown, improve aeration and make the grass less vulnerable as a host for summer patch diseases. If you deem it necessary to employ chemicals for control, consider using fungicides that contain chlorothalonil or thiophanate-methyl, such as Cavalier or FugoFlo. Both are broad-spectrum chemicals that will control dollar spot and other summer patch diseases.

The most frequent practice in turfgrass care is mowing. Mow high (3 or more inches) and, when a disease is evident, collect the clippings to remove the spread of inoculum throughout the turfgrass environment. Mowing going into the evening hours also will be less stressful on the turfgrass. Short of giving you a complete course in turfgrass management, you now have the essence of good turf care. Thanks for being a loyal reader.


Q: When is the best time to prune black knot fungus? (e-mail reference)

A: When the fungus is not active, which would be in the early spring (best) or fall after defoliation. Never do it during the summer.


Q: I have been reading on your website the questions and answers on crepe myrtles. We planted ours in 2008. The past two years the myrtles have not bloomed. We prune them in the spring. Each year, they look like they’re growing to the heavens but do not bloom. What can we do and what is wrong? (e-mail reference)

A: You probably are overpruning the myrtles. Go to the nearest Extension Service office in your state to get some local help.


Q: I live in central Maine. I enjoyed reading your advice on growing tomatoes. A market gardener friend up the road told me that he prevents early blight by using a preventative spray of hydrogen peroxide and water. He uses one part hydrogen peroxide to nine parts water to prevent the blight. If blight does show, he uses one part of hydrogen peroxide to seven parts water.

I garden organically, so I don’t want to use fungicides. I mix the solution in a spray bottle and apply it regularly, particularly after a rain. So far, only some of my plants have shown a slight tinge of early blight. This is far better than years before.

Have you heard of this method? If so, how effective is it? Is it also effective as a preventative for late blight? Last year, the entire state suffered from a pandemic of late tomato blight. Previously, my tomatoes have been afflicted with early blight, but never late blight. I have dealt with early blight by rotating planting sites, cutting affected leaves and watering carefully. Despite the early blight, I always got a good crop of ripe tomatoes.

This year, I went on the defensive by being determined to beat out early blight.

There is not too much one can do organically for late blight. I am uncomfortable with the idea of using copper spray because it does have levels of toxicity and requires special handling. In late May, I planted 20 tomato plants in a sunny spot. I’ve never planted tomatoes there before. I spaced the plants farther apart than usual. Each planting hole was mixed with cow manure, bone meal and some organic fertilizer. I tried something new this year by mulching the entire bed with wide rolls of dark landscape paper. The tomato seedlings were planted through little slits I made in the paper. They’re doing great!

I’m not sure if the reduced levels of early blight have more to do with the landscape paper and brand new site than using the hydrogen peroxide spray. I hope they’ll ripen by late August and that we get a late frost. I also hope we don’t get trounced by late blight.

I read that you recommend water-stressing tomatoes to get them to ripen faster. Can you explain that in more detail? How often do you water them and when? By the way, organic gardening is huge in Maine. Small farms are springing up all around the state. A lot of this surge is due to the presence of the Maine Organic Farmers and Gardeners Association. (e-mail reference)

A: Thanks for the nice letter on your gardening techniques. Stop and think for a moment what you told me about hydrogen peroxide. The solution that is available over the counter is a 3 percent concentration. You will note that hydrogen peroxide is in a dark bottle and is recommended to be kept in a cool location.

This is because it is very unstable and reverts back to plain water after just a few hours of exposure. Your friend who is recommending the dilution rates is just using plain water. I’m too tired to do the math right now, but if it is diluted with seven to nine parts water, it seems to me that the actual amount of hydrogen peroxide in the mix would be minuscule.

Straight hydrogen peroxide at 3 percent will sanitize or sterilize surfaces and cuts on our skin. It also is used in some instances to sanitize the roots of transplants to temporarily assure that the root surfaces are free of diseases. Studies have been conducted to see what, if any, benefit the use of hydrogen peroxide would have on roses with black spot and powdery mildew. It failed in both instances.

Blights are limited on plants mostly through what you do, such as reducing dirt splash and plant spacing. You didn’t say if you trellised your tomatoes or allowed them to sprawl on the ground. Staking or trellising tomato plants will result in fewer disease problems and higher-quality tomatoes.

Any fruiting crop, such as grapes, raspberries, apples and sweet corn, will have a more intense flavor if slightly water-stressed. Tomatoes are no exception. Minor heat stresses and a little water deprivation result in more intense flavor and faster ripening. Watering should take place as the sun rises. How often is something I can’t answer. It depends on the soil and the meteorological factors that influence plant growth.

It is a judgment call that comes from experience. All the best to you.


To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail ronald.smith@ndsu.edu.

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