Trevor Hylton| UF/Leon County Extension
Pecans have particular requirements for pollination, nutrients, and pest management if they are to produce abundant crops. Remember that many pecan cultivars do not start producing nuts until they are 12 to 15 years of age.
One of the most overlooked reasons why pecan trees sometimes fail to produce is poor variety.
Pecan varieties vary in production capacity and susceptibility to diseases. This is why some varieties will not produce without good pest control measures, while the unsusceptible varieties will produce with little or no maintenance pest control. The UF/IFAS Leon County Extension office can help you in selecting the varieties best suited for our area.
Pecan trees grow best in well-drained sandy loam soil. Sandy soils will need to be fertilized often to maintain productivity, as nutrients will quickly leach through the large soil pore space of sand.
Low fertility and aninadequate amount of zinc can limit nut production. Fertilize according to soil test and tissue analysis. Without a soil test, the rule of thumb for fertilizing pecan trees is one pound of 13-13-13 fertilizer per tree for every year of the tree’s age, up to 25 pounds. So for example, if the tree were 10 years old, you would add 10 pounds of 13-13-13 fertilizer that year. Also, add one pound of ammonium nitrate per tree for every year of the tree’s age, up to 20 pounds and 0.1-pound zinc sulfate per tree for every year of the tree’s age, up to two pounds.
Apply the fertilizers when the soil begins to warm up in March. For young trees, apply half the ammonium nitrate in April and the other half in June. Broadcast the fertilizers on the surface in a circle twice the width of the canopy.
Most pecan varieties shed pollen either too early or too late to pollinate the female flower of the same tree. Multiple varieties in the same area can improve pollination. Photo by Trevor Hylton.
Too much or too little water can have an adverse effect on a tree’s ability to produce. Lack of water, especially in the dry hot summer, can reduce yields and nut quality and lessen the prospects for production in the ensuing year. On poorly drained soil, waterlogging can cause similar outcomes.
A single isolated tree will not produce very well because it will not be effectively pollinated. Most varieties shed pollen either too early or too late to pollinate the female flower of the same tree. Having different varieties within a couple hundred yards increase the probability for good pollination. Rainy weather in early spring can wash off pollen and restrict the movement of pollen by wind.
Overcrowding due to over grown trees or too close spacing will eventually lessen production. Pecan trees need maximum exposure to light to have good production. If limbs overlap, remove the least desirable tree.
Pest and disease play a role in reducing production in pecan orchards. Pecan scab can be a detriment to production; even affecting varieties once thought to be resistant are showing signs of infection without prophylactic spraying. Aphids, pecan weevils, and hickory shuckworms are among some of the insects that can limit production. Spraying may not be a viable option for growers with just a few trees, but proper sanitary control can help in pest control.
Mistletoe is a parasite of pecan trees and diverts nutrients from the tree. The only method to remove mistletoe is to cut it out below the point of attachment.
Spanish moss is not technically a parasite, though it is a symptom of low tree vigor. The biggest problem of Spanish moss is tree shading. If you wish to control Spanish moss, apply 10 pounds of copper sulfate per 100 gallons of water during the dormant season.
Squirrels are the main mammal pests of pecans. Estimates in Georgia indicate that one squirrel can consume 50 pounds of nuts per year. It is especially difficult for homeowners in residential areas to control squirrels because control measures are difficult to implement. No poisons or chemicals are currently registered for control of squirrels in Florida.
Alternate pecan production (on and off years) is mainly the result of inadequate fertilization. When trees set a large nut crop, there are not enough nutrients for both that year’s nuts to mature and for the tree to store enough plant food for adequate production in the following year. Early defoliation in the fall usually means no nut crop the next year. Diseases and insects affecting the leaves also contribute to alternate bearing by causing early leaf drop in the fall. It is believed that alternative production is an adaptive response to reduce pest pressure by not allowing a consistent supply of nuts, for which pests can thrive.
Trevor Hylton is an Extension Agent with FAMU and UF/IFAS Leon County Extension. For gardening questions, email the extension office at AskAMasterGardener@ifas.ufl.edu.
