Healthy pecan trees (Carya illinoinensis) require a spray program to combat nutritional deficiencies, insects and fungal pathogens. Which of these affect your tree depends on where you live, although some pests and diseases affect pecan trees in all areas. Pecans grow in U.S. Department of Agriculture plant hardiness zones 6 through 9. Take precautions when working with pesticides and fungicides, following the instructions and safety information on the labels.
The problem you'll likely face is that pecan trees can grow to 100 feet tall, making it a challenge to spray the top branches. Traditional spray equipment, such as a hose-end sprayer reaches a maximum of 30 feet so if your tree is taller you may need to hire a professional.
Zinc deficiencies are common in backyard-grown pecan trees. Symptoms of the deficiency include small leaves and shoot tips with branched twigs. Zinc sulfate sprays are an effective cure for this deficiency. Mix 2 teaspoons of zinc for each 1 gallon of water and spray the tree until the entire tree is covered but not dripping. Make the first application at bud break and apply twice more before the middle of June.
The type of pest that bothers your pecan tree depends largely on where you live, although some live all over the U.S. Three species of phylloxera are particularly attracted to pecans and can destroy your season's crop. These tiny, aphidlike pests -- as well as mites, aphids, pecan nut casebearer and most other pecan pests -- can be managed with carbaryl. The spray must be applied at bud break and can be repeated up to four times a season. Mix 4 teaspoons of liquid carbaryl in each 1 gallon of water and spray the tops and undersides of the pecan tree's leaves and branches until they are wet, but not dripping. Don't allow people or pets into the area until the spray has dried.
A fungicide with the active ingredient propiconazole treats scab, the most common disease of pecans. It will also take care of powdery mildew and common foliar fungal diseases of pecans. Use 2 tablespoons of fungicide in each 1 gallon of water and spray the pecan tree at bud break and twice more, 10 days apart.
The most efficient way to deliver the spray to the pecan tree is by starting at one side of the tree and working your way around it. Spray from the inside, at the trunk, to the outside as your work your way around the tree. When you complete this, go around the tree again, spraying the top of the foliage.