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MANAGING INSECTS and MITES with 



Spray Oils 



Dr. Stanley R. Swier 



There is probably no other pest 

 control product on the market that 

 is so underutilized and has so much 

 misinformation printed about it. 

 Oils have been around a long time, 

 but they have changed tremen- 

 dously over the years. 



The first oils were very heavy 

 and could only be used during 

 plant dormancy, hence the term 

 "dormant oils". If used during the 

 growing season, they often caused 

 phytotoxicity, hence, many horror 

 stories developed about using oils. 

 Today there are lighter oils on the 

 market that can be used throughout 

 the growing season. These oils 

 have been termed "summer oils", 

 "horticultural oils," or "superior 

 oils." The best oil to use for spray- 

 ing ornamental crops is Safer's 

 "Sunspray Ultra Fine Spray Oil." 

 This oil is 92% unsulfonated and 

 has a 414° distillation (boiling) tem- 

 perature. The lower the sulfur con- 

 tent and distillation temperature, 

 the less phytotoxic an oil is. Some 

 horticultural spray oils boil at 

 higher temperatures, as much as 

 470° F. So not all horticultural 

 spray oils are created equal. The 

 Sunspray oil is the best of the cur- 

 rently available horticultural oils. 



Oils kill insects, mites, and eggs 

 by contact only. The pest will only 

 die if it is thoroughly covered by 

 the oil mixtures. Pests migrating to 

 a treated plant are not affected. 

 The oil kills by primarily suffocating 

 the insect. However, there is some 

 evidence that oil also acts as a re- 

 pellent and the oil film may pre- 

 vent scale crawlers from attaching 

 to the plant. Due to its mode of 

 action, oil is most effective against 

 scales, mites, mealybugs, aphids, 

 and white flies. Oils are generally 

 not effective against mobile insects 

 such as caterpillars and beetles. 

 However, oils are generally safe to 



beneficial insects. Thus, oils are a 

 very important tool in IPM programs 

 that will use biological control. 



Oils damage plants by blocking 

 the air openings, preventing gas ex- 

 change. They also penetrate plant 

 membranes, and kill cells, leading 

 to the yellowing of the leaf. Phyto- 

 toxicity is less common with the 

 lighter, more refined oils but it still 

 occurs. To minimize damage obey 

 the guidelines othis page.. 



Oils are relatively non-toxic com- 

 pared to synthetic pesticides. Hor- 

 ticultural oils are similar to the min- 

 eral oils used in skin lotions and 

 baby oils. However, certain safety 

 precautions should be observed. 

 Petroleum-based products are cor- 

 rosive to membranes lining the 

 mouth, throat and lungs, and vomit- 

 ing should not be induced if oil is 

 swallowed. Skin exposure to large 

 amounts of oil can cause irritation 

 and dermatitis. Therefore protec- 

 tive clothing such as long sleeved 

 shirts and pants should be worn. If 

 oil enters the eyes, flush with water 

 until the irritation stops. 



Horticultural spray oils, when 

 used properly, are an effective al- 

 ternative to traditional synthetic 

 pesticides. They are safe to use, 

 environmentally friendly, inexpen- 

 sive, and kind to beneficial insects. 

 More use of horticultural oils will 

 occur as growers learn to apply oils 

 and integrate them into their man- 

 agement program. No insect has 

 ever become resistant to oils. 

 Therefore, oils are becoming in- 

 creasingly important in resistance 

 management. However, much more 

 research needs to be done to use 

 oils more effectively while minimiz- 

 ing plant damage 



Dr. Swier is UNH Cooperative Extension 

 Entomology Spt'cialist. His address is 

 Uesmith Hall, UNH. Durham, NH 

 03824; His phone- 603-862-1 159, ^• 



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GUIDELINES 

 for SPRAY OILS 



1. Plants should not be stressed In any 

 way. Do not apply oils when the tem- 

 perature is too hot or too cold. A good 

 guideline Is not to spray above 90'F or 

 below 45°F. At high temperatures the oil 

 reduces the plants respiration. At low 

 temperatures, excessive deposition 

 occurs. 



2. Do not apply oil on plants suffering 

 from moisture stress. Oils increase mois' 

 ture stress. 



3. Do not mix oil with fungicides such 

 as Captan, Folpet Dyrene, Karathane, 

 Morestan, or any product containing sul- 

 fur. Do not use any of these products 

 any sooner than 3 weeks before or after 

 the application of oil. 



4. In general, oils will Increase the likeli- 

 hood of phytotoxicity with most pesti- 

 cides. Keep good records and soon 

 you'll notice certain combinations which 

 may lead to plant injury. 



3. Weekly applications of oil are more 

 likely to cause injury than if used every 

 2 weeks or more. 



6. Avoid using oils during poor drying 

 conditions such as high humidity and 

 long periods of cloudiness. The longer 

 the oil remains wet on the foliage, the 

 more likelihood of damage. 



7. Use a separate sprayer for oil appli- 

 cations, or thoroughly clean out the 

 sprayer between applications. 



8. Calibrate your sprayer using water to 

 insure proper dosage and thorough cov- 

 erage. Thorough coverage of the upper 

 and lower leaf surfaces is necessary for 

 good control. 



9. On oil-sensitive plants use wettable 

 powder formulations. 



10. Test old oil for emulsifying before 

 using. Horticultural oils are formulated 

 with an emulsifying agent so that the oil 

 can be diluted with water. Use a jar 

 test to make sure that the oil will emul- 

 sify and oil globules are not floating In 

 the water. 



1 1 . Continued agitation of the spray mix 

 Is very important. Otherwise, oil will 

 quickly separate from the water and 

 pure globules of oil may be sprayed on 

 the plant, increasing the likelihood of 

 phytotoxicity. In hot weather, the spray 

 left in hose lines separates quickly If left 

 Idle. If you haven't sprayed for 15 min- 

 utes, run the spray mix from the hose 

 back Into the tank to be agitated. 



12. Various plant varieties respond dif- 

 ferently to oils. Test new varieties. No 

 label can list all the sensitive varieties 



■ nder all possible environmental condi- 

 tions. It Is up to you, the grower, to do 

 small scale trials and keep accurate 

 records of varietal responses. 



The Plants man 

 12 



