In contemporary plant protection, mineral spray oil has been applied to most crops and effective methods for preventing insects, mite and diseases have been built for many crops. Along with the improvement of spray oil extraction technology, more potential will be exploited and more effects will be acknowledged. It can be expected that the reliance on traditional pesticide will be reduced and high-quality mineral spray oil will play an important role in future integrated pest management (IPM).
During its application to prevention of pests for one hundred years, mineral spray oil, once called “dormancy oil”, was only used in dormancy period in the past to prevent overwintering pests. However, Kaiwei Yongli pesticide mineral oil can be used in the whole season of growth.
In its application to agriculture, mineral oil is mainly required to have: 1) effect, 2) safety, which are determined by the following five chemical characteristics:
1. Chemical components
Mineral spray oil contains four basic chemical structural components, and each kind of spray oil contains two or more kinds of such components.
1)Paraffin: the most perfect structural formula, high insecticidal activity, and stable structure ensuring high safety.
2)Naphthene: no double bound contained but tended to break to cause reaction, risk of phytotoxicity and low insecticidal activity.
3)Aromatic compound: It has double bound structure, is unstable and easily causes phytotoxicity.
4)Olefin paraffin: double bound structure contained.
2.Number of carbon atoms
Along with the increase of the number of paraffin carbon atoms, the insecticidal activity also improves to about 23. When the number of carbon atoms is more than 25, the risk of phytotoxicity rapidly increases, so the carbon atom number of safe and effective mineral spray oil should be in narrow width. The carbon atom number of mineral oil with highest commercial value is 20~25.
As distillation temperature is an index for judging quality of spray oil, American administration adopts D1160 vacuum distillation method of American Society of Testing Materials to regulate spray oil. According to the method, the temperature of spray oil subjected to 10%, 50% and 90% distillation is measured under vacuum condition of 10 millimeter of mercury. If the temperature of 50% distillation is 224±4.5℃ (435±8°F) and the difference between 10% distillation and 90% distillation is 44.4℃ (80°F), the mineral oil is called 435 narrow-width spray oil. Narrow-width spray oil causes few reaction and is hardly phytotoxic, so that it can be used in the whole season of growth.
4.Precision of purification
The purification precision is indicated by the value of unsulfonated residues in spray oil. The amount of unsulfonated residues shows the amount of oil that does not react with sulfuric acid. When oil is exposed in sulfuric acid, the unsaturates or double-bound carbon chain in oil will react or be sulfonated, and aromatic compounds will be all reacted in sulfonation reaction. The value of unsulfonated residues represents the amount of remaining oil in the original oil. The minimal value for no phytotoxicity is 92. Higher value of unsulfonated residues (the value of Kaiwei Yongli pesticide mineral oil is 99) means higher safety and higher insecticidal activity.
Oil mobility and concentration of preparation settling in water influence safety and effect. It is easier for light oil to flow and expand on the surface of plants. The performance makes the spray oil more applicable in warm environment and plant flourishing season. Heavy oil that easily forms oil droplets is mostly used in dormancy period to reduce the harm of poor safety.
Action mechanism of mineral spray oil
1. Serve as insecticide
1) Suffocation effect
It is visual insecticide effect of spray oil. Kaiwei Yongli mineral oil forms oil film on insects, which enters pores of eggs and the spiracles and tracheae of larvae, pupae and adults through capillary action, and suffocates insects and mites until death. It takes effect in each stage of insect growth including the egg period and has very ideal effect in suffocating fixed and slowly moving bugs (such as mite, coccid, some aphids and aleyrodidae). But it has little effect on natural enemies as they are very active.
2)Penetrate egg shell
The spray oil can penetrate egg shells and interfere with the metabolism and respiratory system of eggs to kill them. It has huge value in controlling fulminating insects such as bemisia tabaci, trialeurodes vaporariorum and plutella xylostella.
3) Change behavior of insects
It is shown in significantly reduced spawning, feeding and mating. Phytophagous insects and mites only feed and spawn on certain plants. Using tentacles, mouthparts and the sense organs on feet and abdomen, they detect chemical substances of the plant to identify it. When the sensory organs and plant surfaces are covered by oil film, the insects cannot identify the host plant any more, which reduces their feeding and spawning on it. The spray oil can reduce the spawning rate of Panonychus citri McGregor by 90% and effectively reduce the spawning rate of phyllocnistis citrella, leaf miner and patella xylostella. Spray oil’s interference with the feeding of insects also has great significance, protecting plants while not killing the insects. Tentacles of insects such as flea beetle, aleyrodid and aphid are covered, so insect behaviors such as copulation are directly influenced, which is also founded in some experiments. Changing insect behavior directly reduces insect population and protects plants. The changing of insect behavior shows the great significance of mineral spray oil to farmers and to comprehensive insect treatment technology.
Mineral spray oil can interfere with alatae’s searching for host, preventing the spreading of viruses such as watermelon mosaic virus, squash mosaic virus and potato Y virus. It also can prevent viruses, such as tobacco mosaic virus, that are spread by operators and farm tools.
2.Serve as bactericide
Spray oil takes the effect by damaging the cell wall of germs and interfering with fungus’ breathing. It also disturbs the adherence of pathogene to host plant. Spray oil not only controls mycelium but also effectively prevents the germination and infection of spore. In prevention and control of powdery mildew, the spray oil has the effects of eradication and protection through fundamental physical contact and also has stable effect under low temperature. Killing powdery mildew spore soon after contacting it, mineral spray oil has been widely applied to prevention and control of powdery mildew. It also has good effect in preventing pepper phytophthora blight according to the test of Taizhou Agricultural Institute. In grape cultivation abroad, the mineral spray oil is singly used in germination stage, used together with iprodione in the flowering stage, together with antracol or dithane in the fruit-bearing stage, and together with copper agents after fruit picking to prevent annual disease of grape.
3.Serve as synergist
When used together with chemical pesticide, spray oil can improve the adhesiveness of pesticide and assist it in penetrating the wax coat in plant surface to enhance the effect of pesticide. According to modern research, it also can strengthen penetration into insect skin, retain the stability of pesticide on plant and reduce volatilization and fogdrop drifting. Its combination with organophosphorus and pyrethroid has been widely approved and its combination with fungicide is also successful in preventing diseases of banana and grape. Its combination with avermectin improves the penetration transfer effect and prolongs the retention time on plants so as to obviously improve effects including spawn killing effect, which has great significance in preventing and controlling leaf miner, phylloxera, aleyrodid and lepidoptera pests. Research also shows that mineral spray oil could strengthen the effect of most biological insecticides such as BT and NPV.