1 as a spray improver
Van Valkenburg has divided pesticide adjuvants into two categories: spray improver and activator. Generally speaking, silicone surfactant is mainly a spray improver. Because of their strong activity, they can also be used as activators. The use of organosilicon surfactants can improve the ability of the spray to be absorbed by the leaves of the blowholes through the leaf surface. Therefore, it is necessary to study the characteristics of them in the spray.
Silicone surfactants are highly reactive and prone to excessive foaming. When applied, it is necessary to add some auxiliaries in the spray barrel and avoid excessive mixing to reduce the amount of foam. A proper amount of defoamer can be used to control the amount of foam, and a variety of antifoaming agents are available in the market, and the best defoamer, consisting of silicone - based turbid granular silica, is the best. Although they are effective in foam removal, they have limited capabilities. They must precede silicone spray improver and spray barrel. For example, the AF 9020 defoaming agent recommended by Monsanto New Zealand can reduce the foam produced by the mixture of herbicides and silicone spray Vitex, which has the same effect as the single use of herbicides, and the cost of the spray mixture does not increase significantly.
Spray atomization is controlled by surface tension. Silicone spray improver can reduce the surface tension of spray liquid and reduce the droplet size. When the concentration of the organosilicon surfactants is relatively high, and through the spray of high flow low pressure fog head by 8003l, it can reduce the size of the volume of the droplet (VMD) more than 50%, and avoid the increase of drift fog drop, but it has no effect on the VIVID of the 8001 low flow high pressure nozzle. It is reported that after adding L-77 to the spray liquid of glyphosate, the large fog droplets are crushed and the activity of herbicidal activity can achieve the effect of mist spray, and the proportion of the fine droplet is increased by the use of 8001 spray head. Obviously, silicone surfactant can reduce surface tension rapidly, so we must choose the spray equipment with fine sprinkler carefully. Organosilicon surfactants can greatly reduce the surface tension of the solution, reduce the contact angle between the droplets and the leaf surface, enhance the wetting, adhesion and spreading ability of the liquid in the body surface of the plant or the body of the insect, and thus improve the efficacy. Target pests are usually hidden in the gaps of fruit trees. They need to improve the micro coverage with auxiliaries, so that the sediment of liquid can enter human gaps and increase their contact with pests. In 1995, an insecticide efficacy test was carried out on Citrus in Spain (see Table 2). Although the concentration of L 77 is low and the spray volume is low to 0.04 L / m2, the insecticide has achieved a good effect only with half a dose.
3.2 as a leaf absorbent
The final action point of herbicides, plant growth regulators and nutrients is in plant tissue, and organosilicon surfactants can enhance the function of pesticide absorption on the leaf surface, which is of great significance to improve the efficiency of pesticides and reduce the dosage of pesticides.
In 1992, Buick et al. Studied the effect of organosilicon surfactant L-77 on the absorption of three chloramperidine leaf surface. The abscisic acid treated plants (closed stomata) were compared with plants without abscisic acid pretreatment. It is found that stomata are one of the main ways for agents to enter plants. The surface tension of the organosilicon surface can make the surface tension of the liquid lower than the critical value of the surface of the plant leaf (about 25 mN / M), so that the liquid can penetrate into the epidermis from the pores of the leaf. The permeability needs to be super extended, so it is limited to the osmotic phenomenon observed by three siloxane. In order to obtain appropriate pore permeability, the concentration of organosilicon surfactants in pesticide formulations requires more than 2 g/L of the threshold concentration, and the pesticide formulation tends to inhibit silicone. When using L 77, the permeability of glyphosate preparation is lower than that of pure effective ingredient. This is because a sufficient amount of organosilicon surfactants may be set up to overcome the inhibitory effects caused by pesticide formulations and provide the required permeability under the condition of less than a certain amount of liquid spray. Therefore, we should comprehensively optimize the formulation of the formulation rather than silicone surfactant itself.
Many crops have no stomata on their leaves, so they must penetrate the epidermis when they enter the leaf tissue. The interaction between active ingredients, plants and auxiliaries tends to be highly specific, and organosilicon surfactants can promote the permeability of some effective components to plants. The synergistic effect of L-77 on abamectin mainly reflects that it can make the liquid into the human microscopic insect hiding place; secondly, it depends on the absorption of the leaf surface and into the human epidermis, prolonging the residual effect period. The residual period of avermectin after L-77 is longer than that of mineral oil adjuvant. L-77 not only has superior performance and low consumption, but also can be directly added into the preparation as barrel mixing agent, which has commercial feasibility.
3.3 as an activator
So far, most of the research work of organosilicon surfactants used as pesticide adjuvants is aimed at herbicides. The application of insecticides, fungicides, growth regulators and foliar fertilizers has also been studied.
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