Pecans are native to Oklahoma. Records reveal that Native Americans were the first to know of pecan trees and respect the value of this nut crop.
Today, more and more pecan growers are realizing that a full management cultural program must be employed if consistent, high quality, profitable pecan crops are to be expected. In the modern pecan tree management program, attention is given to (1) annual fertilization, (2) reduction of weed and grass competition plus irrigation where practical, (3) relieving over-crowding of trees, and (4) controlling insects and diseases.
The influx of insects and incidences of diseases in recent years has made the application of sprays to control these pests a very important factor in pecan production. In many seasons, insect and disease control will be the difference between a good pecan crop and no crop.
Even with the best chemicals and the most modern equipment, insect and disease control is not an easy job. Approximately seven months are required for growth and development of a pecan crop. At some time during this period, weather conditions are likely to be favorable for numerous pests.
To apply an effective pesticide spray to pecan trees, follow these rules:
• Use an effective chemical(s)
• At the proper rate (concentration)
• Apply thoroughly
• At the proper time.
When one or more of these four rules is not carried out properly, the spray effectiveness is reduced or could totally fail.
The amount of spray applied to an individual tree or acre of trees may vary greatly depending on the type of equipment used and the manner in which it is operated. Most pecan growers in Oklahoma use ground machines calibrated to deliver 100 gallons of spray per acre. Each year, sprayer output should be calibrated and recorded with notes on pressure settings, tractor speed, and rpm’s.
Regardless of the gallonage of spray applied, the amount of chemical (pesticide) applied to an acre should remain the same.
Suggested chemical rates in this publication are given as rate/acre.
Variable tree size and spacing complicate estimates of quantity of spray solution needed. These decisions must be made on an individual basis. An acre equivalent of pecan trees is approximately 30 square feet of cross sectional trunk area. This figure is derived by measuring tree trunks at 4.5 feet above ground, calculating and totaling the area. When this total reaches 30 the number of trees is one acre equivalent.
Number of trees per acre equivalent can be estimated from the following table:
|Tree Diameter||Trees per acre equivalent|
For additional information on calculating cross sectional trunk area consult OSU Fact Sheet EPP-6208.
If the label requires 1 pound of chemical per acre and if the average tree size is 23 inches in diameter then 10 trees should receive 1 pound of chemical. The chemical should be dissolved in adequate water to wet the entire tree canopy. The amount of water required can vary depending on the amount of tree canopy and other conditions. Native trees that have been crowded for example, may not have canopy normally associated with the trunk size. In those cases grower judgment must be utilized to determine if the volume of water utilized is adequate to cover the leaves. It is better to apply too much water than an inadequate amount.
Adequate spray solution must be applied to insure coverage of the entire tree canopy. Larger trees require more solution. Manufacturers’ recommendations for gallons vary from 100 to 600 gallons per acre. Refer to the chemical label for any manufacturers’ recommendations on gallons per acre to apply. This table is a guideline and not a legal document. Changes in registration status may occur. Consult the pesticide label before application. The label is the law.
Former Extension Entomologist
Extension Educator, Horticulture/ 4-H Youth Dev.