Pecan, Page 2
15. Q: How do webworms get there? Is there anything I can do now to keep them from coming back next year? I notice that a live oak across the street doesn't get them. Someone mentioned a product with a 2 letter name, TC or similar, that you could put on the trunk but a local nursery doesn't know of this product. The trees are 30 to 40 feet tall. The pecans are never much good, sort of dried up.
A: Webworms overwinter as pupa in the soil. Hence, there is no way to prevent them from coming out or back. The adults emerge in the spring although the damage from these pests is usually worse in late summer or fall. They begin by laying their eggs on the bottom of the leaves. This is the ideal time to control them because they are super small and only occupy a small amount of space. However, they are hard to see at this time unless you are really looking for them. These worms only attack certain species of trees which is why you don't see them on oak trees.
They can be controlled with a foliar spray of a B.T. product which is totally safe to humans. However, the spray needs to cover all leaves of the trees.
These worms appear to be worse some years than others due to attack by a variety of parasites. Unfortunately there is no fool proof way to prevent them except to spray them.
The drought the past few years has been exceptionally hard on the quality of pecans. A few good rains in late summer tends to improve pecan quality.
16. Q: Each year I have a problem with my pecan tree that is now about 11 years old. The green covering around the nut gets black spots on them. I do not use chemicals, only organic methods. Please tell me how I can fix this problem so that we may have a crop to enjoy this year.
A: You have several options for protecting your pecans from pecan scab. The simplest would be to use a fungicide such as benomyl about twice a year. This product is perfectly safe when used according to label directions. Since scab pressure is dictated by the environmental conditions, ie. worse in warm, wet weather than during dry cool weather, the problem is worse some years than others. Hence, only one fungicide spray may be required and in certain years, none would be used. It is the IPM approach or only spray as needed.
Your next option is use a product called Basicop which is a copper sulfate product. It is labeled for use in an organic production system. However, if the weather is extremely wet, it will do a poor job of controlling scab. Basically it will make you feel good because you have tried to control the problem.
Another option is to raise the tree skirt off ot the ground so that there is good air movement under the tree and up through the middle of the tree. This speeds up the drying time of the leaves and hence reduces the chance of infection. Sanitation goes along way to making this work as well. All the old shucks, leaves and pecans should be raked up and buried as they contain the innoculum for infecting this year's crop.
Finally, you can topwork your tree to a resistant variety such as Desirable, Elliott, Melrose,or Oconee. These varieties have genetic resistance to the scab fungus and only get the disease under intense pressure, ie. very wet, warm conditions. Topworking is a lot of work, but it is not impossible. If your tree is 11 years old, you need to do it now before the tree gets extremely large. The procedures are outlined at the following site: http://aggie-horticulture.tamu.edu/propagation/propagation.html
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