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How to Manage Pests
UC Pest Management Guidelines
Citrus
Precautions for Using Petroleum Oil Sprays
(Reviewed 7/03,
updated 7/03)
In this Guideline:
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Oil sprays are an important component in citrus IPM programs for the control of
scales, aphids, and certain species of mites. Generally they are applied as
emulsives in thorough coverage (TC) sprays using 1,000 to 3,500 gallons of
water per acre, depending on tree size, or in low-volume applications for mite
control. Because petroleum oils can cause phytotoxicity, the following
precautions are important:
| 1. |
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. |
| 2. |
Do not spray oils if temperatures will exceed 95°F during
the day 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. |
| 3. |
When mixing with an oil spray, use liquid or water-soluble
formulations of insecticides instead of insoluble powders whenever possible;
insoluble powder affects interfacial surface relations and stability of dilute
spray mixtures as well as the spreading and availability of oil in the spray
deposit. If unavoidable, do not add more than 1.5 pounds of insoluble powders
per 100 gallons of dilute oil spray mixture. Also, do not put the powders into
the tank until the dilute mixture is above the three-fourth level. |
| 4. |
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. |
| 5. |
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. |
| 6. |
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. |
| 7. |
Generally, narrow range oils with a distillation range of 415
or 440 are recommended for use in citrus. |
| 8. |
The heavier the oil is (e.g., NR440 is heavier than NR415), the
better its insecticidal properties will be, but also the greater the potential
for damaging the tree. |
| 9. |
The unclassified oils, sometimes called medium oils or
medium-light oils, are no longer available for use on citrus in California.
Oils recommended in this guideline are the narrow range 415 or 440 oils with
the following properties: |
TABLE 3. Optimal Properties of Narrow Range (NR) Oils for the Western
United States.
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Specification
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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, F6 |
20 |
20 |
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| 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. |
| 6 |
Oils with a minimum pour point of 20°F
should not be used when temperatures fall below 20°F. |
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UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441
General Pesticide Information
E. E. Grafton-Cardwell, Kearney Agricultural Center, Parlier
J. G. Morse, Entomology, UC Riverside
N. V. O’Connell, UC Cooperative Extension, Tulare Co.
P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura Co.
C. E. Kallsen, UC Cooperative Extension, Kern Co.
D. R. Haviland, UC Cooperative Extension, Kern Co.
Acknowledgments for contributions to the insect, mite, and snail section:
J. Barcinas, E. S. I., Corona, CA
R. Dunn, Badger Farming Co., Exeter, CA
J. Gorden, Pest Management Associates, Exeter, CA
H. Griffiths, E. S. I., Corona, CA
D. Machlitt, Consulting Entomology Services, Moorpark, CA
C. Musgrove, retired entomologist, Riverside, CA
K. Olsen, S & J Ranch, Pinedale, CA
T. Roberts, E. S. I., Corona, CA
J. Stewart, Pest Management Associates, Exeter, CA
P. Washburn, Washburn & Sons Citrus Pest Control, Riverside, CA
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