Spray peaches to keep shothole fungus at bay

Now is the time to spray peaches and nectarines to help prevent a disease that causes yellowing and early leaf drop. The disease is called shothole fungus or Coryneum blight.

A good way to determine if your tree has it is to look at its leaves. The leaves will be peppered with holes the size of BBs. Frequently, these small holes with be bordered with a purple or possibly brown margin .

If your tree has this problem, then read on.

Q: I'm hoping you can help me with a couple of problems in my backyard. I have a peach tree and an almond tree that both show wilted leaves. I've include pictures of the trees and leaves and also a picture of a fungicide and insect killer I've been using. They don't seem to help. The new growth at the top of the peach tree looks good but all the other leaves look yellow and wilted.

A: The peach tree picture shows some evidence of a disease called Coryneum blight or shothole fungus. The close-up of the peach leaf shows red spots on the leaf. These red spots and yellowing leaves are indicators of shothole fungus.

Over a period of a few days, these red spots will turn brown and die resulting in a leaf with holes in it. The holes will be approximately the size of BBs, thus the name shothole fungus.

The best thing to do is reduce the water stress to the tree or any other stresses by growing them in wood mulch. To help prevent this disease from occurring, spray with Bordeaux fungicide immediately after leaf drop in the fall. The spray must cover the exposed openings on the branches left when the leaves drop. This helps prevent the new growth on the tree from becoming further infected by covering open wounds left behind when the leaves separate from the stems.

This disease seems to develop frequently when the tree is stressed, often from water stress. I noticed that your peach tree is growing in a lawn and does not up appear to have any other source of irrigation besides water from the lawn sprinklers. This is a big no-no.

Watering a lawn does not provide adequate water for woody plants. Lawn irrigations are too frequent and are not deep enough. If you want any good measure of success for your peach tree, you will have to separate the lawn from the fruit trees and put them on separate sources of irrigation.

Q: I had some large squash plants growing with very large blooms. However they never produced any squash. What do I do to get them to produce. Another lady asked you this question awhile ago. I recall some of your answer, which was to use a Q-tip and pollinate them yourself since Nevada does not have bees to do it. Would you please explain this process? As I recall, one bloom is male and one is female. I cannot tell which is which. Please explain how to recognize the difference.

A: Generally, there are enough bees, both Italian honeybees and native bees, to get the pollination done.

Another problem can be if you plant at a time of year when it is too hot for good pollination; but even at times like this you should still get at least some pollination.

If a lack of bees is a problem, you should see a lack of fruit set or very diminished production on many of your other garden plants as well. Water will attract bees during the heat of the summer. They haul water to help cool down their hives, if they are the type to form colonies.

However if you are having trouble, then I would follow this great resource I found on the Web for you, http://forums.gardenweb.com/forums/load/gourds/msg0611545713356.html.

Q: We've had a problem with our Modesto ash and Santa Rosa plum trees. After researching online, we think both trees are infected with sooty fungus. I've attached photos of the ash tree.

On several websites it was suggested to use a mixture of copper sulfate and hydrated lime to effectively treat sooty canker fungus.

A: After looking at the picture you sent to me, I do not believe this is sooty canker fungus. Modesto ash develops a black appearance along its bark as it ages. Sooty canker develops under tree bark, not along its surface.

Sooty canker, when the bark is removed from a dead or dying limb, can be rubbed off on your finger and it will appear on your finger just as if you had robbed it against inside of an extremely dirty, sooty chimney. The finger will be absolutely dark with sooty fungus. I have attached a picture of sooty canker rubbed off an infected tree with a finger. Newsletter subscribers will see it as well.

Modesto ash has a problem with branch dieback. This has been a continual problem on Modesto ash four decades in our valley. Numerous people have tried to identify a disease along with this branch dieback but no one has been successful.

I have seen very old Modesto ash stricken with this problem. Fungicide injections, fertilizer injections and numerous other attempts to correct it have been unsuccessful. Eventually, the trees have so many limbs that die back and the tree becomes so unhealthy it is removed. I'm sorry to say but Modesto ash no longer has a very good reputation in this valley.

Q: I've attached a couple of pictures of our poor pineapple guava plant. It did well until this year, but for some reason it is dying. The leaves are turning brown and dropping even though it gets plenty of water. It sits on the north side of a wall and next to the house, so it does get reflective heat. It has been fertilized and I have found no bugs or fungus. Can you shed any light on what is killing it?

A: It appears to be not getting enough water in combination with poor soils. Pineapple guava does like to have a soil higher in organic matter than a soil covered in rock can provide.

I know you think it has plenty of water but I would be giving this plant 5-10 gallons of water about three times a week in midsummer and about the same amount per application now but twice per week.

Rock mulches tend to allow the soil to mineralize (deplete the soil of organic matter and nutrients) in three to five years after planting . I think you will see a dramatic improvement in the plant if you pull back the rock mulch about 3 feet from the tree trunk, put about 2 inches of compost around the base and cover that open spot with 4 inches of wood mulch and water with larger volumes.

Q: I have a neighbor that has 10-year-old date trees he started from seeds. They have been producing for a couple years so we know now which one of the trees are males and which ones are females. Do you think I can cut the shoot off a female tree, plant it and, if successful, get an adult female tree? Do you think the same rule applies to removing a shoot from a male tree, thus guaranteeing I would get an adult male tree?

A: Removing suckers from date palms and replanting them is not that easy to do physically. You are correct that taking a sucker from a male tree will produce another male plant identical to its parent. In the same fashion, removing a sucker from a female plant will result in a female plant identical to its parent.

Suckers from date palms are not that easy to remove successfully. The usual field method is to wait for the sucker to reach about 4 feet tall (three to four years old) and then remove it at the proper angle so that roots as well as parts of the mother plant are removed as well.

Removal of the suckers is usually done in May here. This involves severing a 4-foot sucker from the mother plant through soft woody tissue. The sucker can be dried in the shade for a few days to allow for the wound to heal and partial dry around the base. These are then planted directly into the field at the same depth that they were taken from the mother plant.

It would be a good idea to stake them until they get established and plant them in native soil modified with compost and phosphorus fertilizers.

You can also start date palms from seed, but about half of those seedlings will be male and not produce fruit. It will take about eight years for them to flower and produce fruit; consequently you will not know which are male and which are female until that time.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at morrisr@unce.unr.edu.