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Commercial Pecan Insect and Disease Control

Pecans are native to Oklahoma and can be seen growing in the wild in many areas of the state. Records reveal that Native Americans were the first to know of pecan trees and respect the value of this nut crop.

 

Even though pecans are native to Oklahoma, it doesn’t follow that they easily produce a consistently marketable product. A full management cultural program can make the difference between no marketable production and a consistent, high quality, profitable pecan crop. In the modern pecan tree management program, attention is given to

  1. reduction of weed and grass competition,
  2. annual fertilization,
  3. thinning over-crowded tree stands,
  4. managing destructive wildlife (e.g. crows, squirrels, feral hogs, etc.)
  5. controlling insects and diseases, and in the case of improved orchards,
  6. irrigation and
  7. crop load management.

 

Insect and disease control of pecan 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. While there are many cultural practices such as variety selection, orchard floor sanitation, use of cover crops (HLA-6250), use of trap crops, and thinning of orchards for adequate air circulation; in many seasons, insect and disease control through the application of pesticide sprays will be the difference between a good pecan crop and no crop.

 

No matter where one falls on the spectrum of chemical pest control, it is beneficial for all to scout for pests diligently and to make use of tools that have been developed to ensure peak results from any sprays applied. Proper product selection, rotation, and timing can provide safe and effective control while preserving beneficial organisms. For more information on pest monitoring and spray timing aids as well as resistant varieties, see Fact Sheets: EPP-7079, EPP-7163, EPP-7189, EPP-7190, EPP-7642, HLA-6200 and HLA-6201. The following website is also helpful in timing of fungicide applications: OSU Pecan Scab Advisor.

 

To apply an effective pesticide spray to pecan trees, follow these rules:

  • Use effective chemicals in rotation (failure to use a rotation of chemicals classes can cause that class of pesticide to be ineffective).
  • 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 de-liver 100 gallons of spray per acre. Each year, sprayer output should be calibrated and recorded with notes on pressure set-tings, 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. For more help with calibration - Sprayer Calibration for Pecans.

 

Variable tree size and spacing, particularly in native groves, 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.

 

Table 1. Number of trees per acre equivalent can be estimated from the following table.

Tree Diameter Tress per acre equivalent
13 inches 30
19 inches 15
23 inches 10

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.

 

Bee Precautions

Several insecticides listed are toxic to bees. Mow the orchard floor before application if weeds or cover crops are blooming. Read individual labels for specific bee protection measures for each product. Pecans are wind pollinated; however, bees and other pollinating insects by simply wander through orchards.

 

View Tables - PDF.

 

Phil Mulder

Professor and Department Head,

Entomology and Plant Pathology 

 

Becky Carroll

Associate Extension Specialist,

Fruit and Pecans

 

Sara Wallace

Extension Assistant

Entomology and Plant Pathology

 

Brenda Sanders

Extension Assistant,

Horticulture and Landscape Architecture

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