Fertilize fruit trees early in year, before growth begins

Q: Is there a recommended schedule for fertilizing fruit trees in the valley? Also for citrus and grapevines? The schedules I've read for each of these differ depending upon who wrote the article and are not specific for the valley.

A: It does not make that much difference as long as the plant has nutrients available during times of fruit production and fruit bud development. But, generally speaking, we avoid applications that might encourage a flush of succulent growth just before winter sets in. This just means try not to apply fertilizers after about mid-July.

You can get by with a one-time fertilization in early January for most fruit trees if you want to. The other thing you can do is a half application in January and the other half after harvesting the fruit. The third way is very light monthly applications of fertilizer sprayed on the foliage, or leaves of the trees, except from August through November as the tree sets up for winter dormancy.

I usually use one of the granular fertilizers that dissolve totally in water, such as Miracle-Gro, or you can use your favorite organic liquid fertilizer. We fertilize just about all our fruit trees and vines once in January with a soil application and that's it.

Q: My gorgeous, dark green, full and old jasmine has stopped blooming. I have tried several remedies and none have worked. Can you give me some pointers to get back the heavenly white fragrant blossoms?

A: By jasmine I take it to mean star jasmine. This vine also can be used as a ground cover and must be supported on a trellis if used as a vine. It blooms only in the spring, so it may not be the time of year for it yet.

Just be patient. There is no secret formula. Fertilize with any good fertilizer for flowering shrubs in January through February, or even now.

Be careful when pruning; you do not prune out flowering wood. Do your pruning immediately after flowering is finished, not during the winter unless you know where the flowering wood is located.

An old horticultural adage is that if a plant is not performing well and you are considering getting rid of it, then cut it back hard. Of course this will damage flowering for awhile but you may get the plant's "attention" and they will sometimes respond very positively.

Q: Through the years I have planted many fruit trees and lost many to borers, especially stone-fruit trees. My grapevines have been devastated by whiteflies to the point where I could not harvest one healthy grape leaf last season. I have tried soap water but to no avail. Also, I have tried lindane against borers but their work keeps appearing on my plum trees.

A: Whiteflies can be a difficult problem. We have not experienced whiteflies on grapes. The closest insect that might be confused with whiteflies, and is a common problem on grapes, are leafhoppers.

Please make sure you are not confusing whiteflies with leafhoppers because the treatment is very, very different. Whiteflies are like dandruff and usually fly in a cloud of small white insects when the leaves are disturbed. They usually leave a sticky substance on the leaf's surface from feeding.

Leafhoppers, on the other hand, jump and are brown in color; they can accumulate in thousands on grapes and jump in your face, nostrils and eyes as you pass the grapes and disturb the foliage. Both are nearly the same size .

If soap and water sprays are used religiously on the grapes when these insects are small, it should give fairly good control. If soap and water is delayed until they are mature adults, then control is probably iffy at best.

Whiteflies are not listed on the University of California and pests lists for grapes . If they are whiteflies, then sprays such as pyrethrins might be a good choice, but the label must include grapes if you are to use it within the law. If these are leafhoppers, then sprays applied in May, such as spinosad, might be useful when this insect is still juvenile. In both cases, when these insects are adults they are much more difficult to control.

Regarding the borers in your plum tree, plum can be attacked by boring insects but it not as commonly as other fruit trees like peach, nectarine or even apple. Please check and make sure that this is in fact borers causing damage and not just sap oozing from a stressed out tree. When plum trees are stressed from water, intense sunlight or heat stress they will ooze sap.

In my opinion there is no insecticide you can use on fruit trees once they are attacked by boring insects and still safely eat the fruit. Most insecticides recommended after fruit trees have been infested are usually systemic in nature. This means that the insecticide also could be in the fruit, not just on the surface.

Q: I have a problem on some fruit trees on a property I have in Tonopah. These cherry trees have large swellings like tumors on the trunk. I spoke with some nursery people in California and described the problem and they knew what the problem was immediately.

She concurred with me to get rid of the tree and the nearby rose bush because the rose bush carried the disease and transferred it to both of the fruit trees. I chopped down the cherry tree as it was dead all the way through. She told me the whole area around it would be bacteria infested for a while and even if I put the product she gave me to kill algae and bacteria in the soil, it might still come back.

A: The only thing I can think of that comes close to your description is a relatively benign disease called crown gall. And this is probably what your cherry tree has. This bacterium does infest the soil. It is not typically transferred from plant to plant so getting rid of the roses is not necessary. A healthy tree can become infested if contaminated soil comes in contact with a fresh wound on the plant.

Actually, this is a very interesting plant disease and was used in the early pioneering days of genetic engineering. When plant tissue is infected with this bacterium, the plant cells multiply uncontrollably producing a large woody or corky "tumor" or swelling on the trunk or roots. The reason it is called "crown" gall is the typical site where the gall or tumor is seen.

The crown of a plant is the general location where the trunk meets the soil. However, these tumors can appear less commonly on roots and stems as well. I will try to post more about this disease and how it is used in genetic engineering on my blog.

Plants can live for many years with crown gall and appear to be quite healthy. It is possible, I guess, to transmit it from plant to plant by cutting into the crown gall and then cutting another plant with the same unsanitized tool, but otherwise you will not transmit it. The usual method whereby it infests a plant is from contact of infested soil with a fresh wound, usually at the time of planting.

Bob Morris is a horticulture expert living in Las Vegas. Visit his blog at xtremehorticulture.blogspot.com.