My grandfather would also take Red Devil Lye and use an old paint brush and brush it into the bark on the pecan trees every couple of years. It would turn the bark black. He said it killed bugs that lived in the bark.
Found this on line for the fertilizer:
Fertilizing Pecan Trees
There is debate among experts as to how much fertilizer a mature pecan tree actually needs. Some recommend up to 50 pounds or more of fertilizer per tree. While these amounts won't harm a mature pecan tree, it may not be necessary to apply such large amounts. Other experts suggest from their own experience that this amount can be reduced by 50 percent or more if ample water is supplied. So, if you have a free source of water, it may be more economical to supply your pecan trees with ample water, verses dumping large amounts of high-cost fertilizer around them. Which method is more economical might depend on where you live, and the cost of water compared to fertilizer.
Which Pecan Fertilizer To Use
The main thing pecan trees need to produce nuts is nitrogen (the first number in fertilizer). If you are growing a tree or two in your yard, 10-10-10 might be a suitable fertilizer for you, but you'll need to apply Zinc separately. This fertilizer can be tossed out by hand around small trees or spread with a small push-type rotary spreader around a large tree.
If you are growing an orchard of pecan trees, and looking to make a profit, you'll probably want to use a fertilizer containing ammonium sulphate, which is typically accepted as the suitable fertilizer by most pecan tree farmers. Ammonium sulfate can be bought in bulk form, or in bags. If you decide to purchase your fertilizer in bulk, you'll have to have a way to spread it. Usually, the places that sell bulk fertilizers have commercial spreaders available for lease. These commercial spreaders will work fine if your trees are 20 to 30' more in height. But if your trees are younger and smaller, commercial spreaders may sling out fertilizer in areas between the rows that won't be accessible by your trees. So, rather than waste fertilizer on the grass and weeds that grow between the rows of smaller trees, use a lawn fertilizer spreader. This puts the fertilizer exactly where it will benefit the tree. For newly planted pecan trees, spreading fertilizer by hand works well enough.
How much fertilizer?
As a general rule, use 3/4 to 1 pound of pecan tree fertilizer per 1 foot height of your pecan tree, per season, or use as directed on the bag of fertilizer. You'll want to break the application of fertilizer into two applications, as described in the next paragraph. You might also need to apply zinc sulfate, as described further below.
When to fertilize a pecan tree?
Apply half the amount of fertilizer you intend to use about a month or so prior to what is typically the last frost date in your area in late winter or early spring. Try to time this application just prior to rainfall, but not if the forecast is for torrential rainfall. Spread the other half of fertilizer about a 30-45 days after the first application, but no later than the end of May. Fertilization timing for pecan trees is very important and varies from one region to another. It's a good idea to consult with your local Extension Service agent to find out when is the best time to fertilize pecan trees in your area. Or better yet, talk to a local pecan tree farmer.
The importance of Zinc for pecan trees
If you do nothing else to your pecans trees, water them on a regular basis, and apply zinc during the early growing season. The easiest way for the home gardener is to apply granulated zinc sulfate beneath the branches of your pecan trees. Most specialty pecan tree fertilizers contain zinc.
Zinc can also be applied as a liquid foliar spray. If you have only a tree or two, or if you have a whole orchard of young, small trees, you can use a small pump-type sprayer. If your pecan trees are larger, and you have a lot of them, a mechanical sprayer will be necessary to do the job sufficiently.
If you can't reach the top of your trees using a pump-type sprayer, standing on the ground, you might have to stand on the tailgate of a pickup truck. Zinc sulfate dissolves well in water and a small amount goes a long way.
Signs and symptoms of Zinc deficiency in pecan trees
Pecan trees suffering from Zinc deficiency will display certain symptoms. Leaves that are discolored in the veins, wavy or curling leaves, or long bare branches with just a clump of leaves at the top are all symptoms of zinc deficiency. If the nut kernels are poorly filled or hollow, this too is a sign of zinc deficiency. Applications of zinc, especially in liquid form to the foliage, will insure these symptoms do not occur, and therefore insure a better crop of nuts.
When to apply Zinc to pecan trees?
As soon as leaves begin to emerge in spring, and are light yellow in color, make your first application of zinc. Zinc has a tendency to burn leaves, so spray your pecan trees in the early morning hours and not during the heat of the day. Follow directions on the package when mixing your zinc solution. Spray foliage of the trees until foliage is wet and starts to drip. Additional zinc applications should be made every two to three weeks for the next two months. If you determine your pecan trees require a pesticide treatment, most pesticides can be mixed into your zinc solution and applied concurrently.
