How to Manage Pests

UC Pest Management Guidelines

Citrus

Precautions for Using Petroleum Oil Sprays

(Reviewed 9/08, updated 10/09, corrected 6/13)

In this Guideline

Oil sprays are an important component in citrus IPM programs for the control of armored and soft scales, aphids, leafminers, and certain species of mites. When used alone, they may be applied using outside coverage (OC) for aphids, leafminers or mites, intermediate coverage (IC) if used for soft scales, and thorough coverage (TC) if used for armored scales at rates of 1-6% depending on the crop, time of year and the target pest. Oils are frequently used at rates of 0.25-1% in combination with other insecticides. Because petroleum oils can cause phytotoxicity, the following precautions are important:

  • Soil moisture should be maximum before application; spray as soon after an irrigation as the ground will permit operation of the equipment. Be sure to maintain adequate soil moisture from spring throughout the entire irrigation season.
  • Do not spray oils when temperatures exceed 95°F or relative humidity falls to 20% or below (in coastal regions, do not spray if the temperature will exceed 85° to 90°F or the relative humidity goes below 30%); also do not use oil sprays immediately before, during, or following an unusually cold weather period.
  • Problems of leaf drop and fruit drop can be minimized, in general, by adding 2,4-D to the oil spray mixture. Be careful not to apply 2,4-D within 2 miles of sensitive crops such as tomatoes, cotton, olives, and grapes and do not use 2,4-D during spring to avoid phytotoxicity problems.
  • If navel orange orchards are treated with oil sprays when oranges are approaching maturity, generally from November until harvest, protection against water spot may be obtained by using gibberellic acid. (Caution: fall oil treatments may increase the risk of damage caused by frost).
  • Complete coverage of the tree with an oil spray provides more effective control than increased dosage. If spraying is done by ground, equip the rig with a tower capable of elevating a sprayer 4 feet above the tallest trees.
  • Generally, narrow range oils with a 50% distillation range of 415, 440, or 455 are recommended for use in citrus.
  • The heavier the oil is (e.g., NR 440 is heavier than NR 415), the better its insecticidal properties will be, but also the greater the potential for phytotoxicity to the tree. The following minimum oils standards were developed in the 1980s, to minimize phytotoxicity:
Minimum Oil Standards Developed by UC Researchers in the 1980s
Specification NR 415 NR 440
50% distillation point (F)1 415 ± 8 440 ± 8
10-90% distillation range (F)2 60 80
Unsulfonated residue, percent3 92 92
API gravity4 32 31
Viscosity, sec.5 70 100
Pour point (F) 6 20 20
1 The temperature at which half of the oil distills under a vacuum of 10mm of mercury (Hg), also know as the boiling point or midpoint. The ±8°F refers to the sensitivity of the analytical method used to calculate the midpoint, not the variability of the oil specimen.
2 The temperature range at which most of the oil distills (10mm Hg).
3 Minimum percent unsulfonated residue; the actual UR is often higher than 92%.
4 A measure of hydrocarbon composition usually ranging from 31 to 37.
5 Flowability of oil ranging from 60 to 200 seconds. (Unit of measure: SUS at 100°F where SUS = Saybolt Universal Seconds.)
6 Oils with a minimum pour point of 20°F should not be used when temperatures fall below 20°F.

Recent reductions in the sulfonated residue portion of petroleum oils (unsulfonated residues greater than 98%) have allowed higher distillation points to be used in citrus with less risk of phytotoxicity, as long as temperature and moisture conditions are optimal. The higher the distillation point, the greater the control of the insect pest achieved, especially for scale insects. The following table outlines the various properties for oils registered for citrus in California:

Product Company Distillation Point (°F) Unsulfonated Residue (%) API Gravity Viscosity (seconds) Pour Point (°F)
50% 10-90%
Biocover MLT Loveland 435 72 99 35 76 5
Biocover UL Loveland 415 55 99 35 64 5
Glacial Spray Fluid Loveland 435 72 99 35 74 5
Loveland 415 Oil Loveland 415 80 92 35 68 10
Spray Oil 415 Loveland 415 80 92 35 68 10
Britz 415 Supreme Spray Oil Britz Fertilizers

(Sales Specs)

404-420 80 92.0 32.1 70 +20
Britz 415 Supreme Spray Oil (typical inspections) 415 73.3 93.8 37.0 58.8 -9
IAP 415 Summer Spray Oil Independent Agribusiness Professionals 415 55 98 32.7 57 -15
IAP 440 All-Purpose Spray Oil Independent Agribusiness Professionals 440 78 98 34.8 70 - 20
Omni Oil 6E Helena Chemical Co., TN 407 55 99 32.8 60 -5
Omni Supreme Spray Helena Chemical Co., TN 438.5 78 98 31.86 83.3 -5
Purespray Green Petro Canada 434 80 99 34 76.2 0
Purespray Spray Oil 10E Petro Canada 408 76 99 34.2 60 0
Purespray Foliar 15E Petro Canada 454 74 99 34.7 83.4 -6
TriTek Brandt Consolidated 438.5 78 98 35.8 68.1 -5
Superior 415 Spray Oil Wilbur-Ellis 415 55 99 32.8 60

-5

For more information on oils, see Managing Insects and Mites with Spray Oils.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441

General Pesticide Information
    • E. E. Grafton-Cardwell, Entomology, UC Riverside and Kearney Agricultural Center, Parlier
    • J. G. Morse, Entomology, UC Riverside
    • N. V. O'Connell, UC Cooperative Extension, Tulare County
    • P. A. Phillips (emeritus), UC IPM Program, UC Cooperative Extension, Ventura County
    • C. E. Kallsen, UC Cooperative Extension, Kern County
    • D. R. Haviland, UC Cooperative Extension, Kern County

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