|
|
|
|
How to Manage PestsUC Pest Management Guidelines
Obtaining the proper distribution of a spray on or within the tree-a concept known as coverage-is essential for good management of citrus pests. Recommended coverage varies from pest to pest; for instance, an outside coverage spray is sufficient for active pests such as citrus thrips that are found mostly on the periphery of the tree, whereas relatively immobile pests such as armored scales will need a more thorough coverage. Obtaining the proper coverage can be difficult because of the dense canopy of a citrus tree and involves a balance of varying droplet size, amount of spray, and ground speed (generally, use 1.5 mph for scale insects, 2 mph for mites, and 3 mph for orangeworms, citrus thrips, and katydids). Spray coverage recommendations are listed as abbreviations in the Treatment Tables for each pest under the Amount Per Acre column. Brief descriptions for each type of coverage are available in the footnotes on each page; the following paragraphs give a more detailed description of the various types of coverage, starting with the lowest gallonage applications. See UC ANR Publication 3303, Integrated Pest Management for Citrus, 2nd edition, for more details on applying pesticides in citrus. Aircraft (A). Aircraft applications typically use 5 to 20 gallons of water per acre. Low-Volume (LV). Low-volume applications generally use 100 gallons of water per acre, but not less than 20 gallons per acre. To be effective and avoid phytotoxicity with oils and some chemicals, low-volume applications must be delivered in small drops having a median volume diameter of less than 50 to 150 microns. This droplet size can be obtained by providing air velocities in excess of 175 miles per hour (mph) at the discharge outlet if nonatomizing spray nozzles are used, or by utilizing spray pressure in excess of 250 pounds per square inch (psi) if atomizing nozzles are used. Low-volume applications use between 75 and 100% of the amount of pesticide active ingredient that would be applied per acre as a dilute spray. An exception is narrow range oil for mite control: it may be used at 10 to 15 gallons per acre plus water to make 50 to 100 gallons of spray per acre. In order to achieve proper coverage, apply low-volume treatments only when it is relatively calm. Coverage is especially critical when treating scale insects; do not treat if wind speeds exceed 2 mph. For other pests, if wind speeds exceed 2 mph, shut off nozzles on one side of the machine and spray only with the wind. Never apply low-volume applications if wind speeds exceed 5 mph. In addition, extra precautions must be taken to protect handlers and applicators because of the high concentrations of chemicals used in low-volume applications. Outside Coverage (OC). Outside coverage applications use 50 to 500 gallons of water per acre to achieve thorough distribution of the spray to the outside or peripheral parts of the tree only. Larger trees and/or high density plantings require the higher gallonage per acre. Outside coverage is used to control aphids, mites, citrus thrips, and several species of orangeworms. Because the spray distribution requirements are less stringent with this type of coverage, ground speeds may increase up to 3 mph (2 mph for mites, citrus thrips, and katydids) and the amount of spray/acre decreases, thus reducing the cost per acre. Thorough Distribution Coverage (TDC). Thorough distribution coverage uses 500 to 3,000 gallons of water per acre to achieve thorough distribution to all interior and exterior parts of the tree, but does not require a film wetting of the surfaces. While this type of coverage requires the same equipment and spraying techniques as thorough coverage, generally less water (5 to 10 gallons less per tree) is used. Certain non-oil miticides are applied with this type of coverage. Thorough Coverage (TC). Thorough coverage requires between 1,000 to 3,500 gallons of water per acre, depending on tree size, to achieve a film wetting on all interior and exterior parts of the tree. This is done primarily with mechanically oscillating boom sprayers; large trees may require spraying from a tower to obtain suitable coverage in the top part of trees. Ground speeds should be at 1.5 mph, pressures in the range of 450 to 550 psi, nozzle adjustments to provide a spray cone angle of less than 16 degrees, and the rate of boom oscillation between 62 to 70 oscillations per minute. No material requires more complete coverage than petroleum spray oils. Generally thorough coverage is used with all sprays targeted against scale insects. For fully mature trees, about 30 to 35 gallons per tree are used for oranges and 20 to 25 gallons per tree for lemons.
PUBLICATION![[UC Peer Reviewed]](/IMAGES/logo-ucpeerreviewed.jpg){kind=logo}
UC IPM Pest Management Guidelines: Citrus |
||||||||
![[Precautions]](/IMAGES/btn-precautions_bul.gif)