Selection and application of insecticide
Insecticide can kill the pests only when it enters the pest body and reaches the site of action. However, different insecticides will have different ways of entering the pest body. Therefore, Tri-DWARF Industrial Co.Ltd has summarized a set of related knowledge about pesticide selection and application.
Choose insecticide according to the pest mounthparts characteristics
As long as we can fully understand the characteristics and life habits of pests as well as grasp some related knowledge about insecticide, we can correctly use insecticide formulations on pests in the chemical prevention process. As we all know that there are mainly 9 kinds of pests in the agricultural production, which are coleoptera (beetle), Lepidoptera (moth and butterfly), orthoptera (locust, cricket and mole cricket), hymenoptera (sawfly and stem sawfly), isopteran (termite), thysanoptera (thrips), diptera (fly and mosquito), hemiptera (stinkbug) and homoptera (cicada, louse, scale insect and aphid). However, most of the insecticides can only reach the nervous system target and kill pests after they enter the pest body through pest mouthparts. Therefore, in order to correctly choose the insecticide formulations and ensure the insecticidal efficacy, it is very important to understand the pest mouthparts. Pests can be divided according to the feeding and mouthparts characteristics.
These kinds of mouthparts pests will certainly eat the plant leaves or other tissues when they do harm to the crops, which will cause blade incision and other damages. The pests mainly include lepidopterous larvae (such as leaf roller, noctuid larvae, papilio xuthus and so on), coleopteran pests (beetle), orthoptera nymphae and imago (locust, cricket and mole cricket) as well as hymenoptera larvae and imago. Insecticide that has strong stomach toxicity will have obvious control efficiency on these kinds of pests, while the insecticide that has good systemic action but is lack of contact action and stomach action will have no effect on these kinds of pests. Therefore, we can choose insecticide that has good stomach toxicity in controlling them. For example, lambda-cyhalothrin and ivermectin both have good stomach action, which can be used in controlling flea beetle, moth and butterfly larvae as well as locust and other pests.
Sucking mouthparts pests
These kinds of pests mainly pierce and absorb plant young tissues through pest mouthparts, thus they can suck the juice in the tissues. The pests mainly include aphid, leafhopper, stinkbug, scale insect nymph and imago, mosquito imago, thrips and so on. Insecticide that has good systemic action or good endosmose as well as good stomach action can be used on controlling these kinds of pests. As imidacloprid has good systemic action, it can be used in controlling aphid, thrips and plant hopper.
Endosmose of insecticide and the application of contact insecticide on controlling pests
As insecticide that has contact action mainly enters pest body through the pest body surface, the pest body wall structure characteristics will influence the effect of contact insecticide. As the waxes and lipid compound in the epicuticle of pest body wall have no affinity with water, the pest cuticula usually will not be wet by water. Therefore, when the insecticide is diluted and sprayed on the pest body, the liquid will aggregate into spherical shape as well as tumble and run away from the insect body surface. However, as scale insect and other pests have thick waxes on the body surface, the liquid will be more difficult to wet the insect body, thus the contact insecticide will lose the insecticidal power. In order to solve this problem, except for the insecticide composition, insecticide auxiliaries and dosage form are also important. This could be the reason that different manufacturers will produce insecticide that has same compositions but different insecticidal efficacy. Therefore, the quality of emulgator of emulsifiable concentrate, microemulsion and EW is the key factor in improving the effect of insecticide. Besides, the effect of adhesive, wetting agent and synergist also cannot be ignored.
Except for considering the effect of contact insecticide, we should also consider the permeability function. By understanding this kind of effect, it will have important significance for us to use the insecticide. For example, organophosphates insecticide, except for part of them have systemic action, the others all have good contact action and stomach action, but most of them have good permeability function, thus the insecticide particles can rapidly permeate into the insect body. For example, parathion methyl is a kind of preparations that is mixed by phoxim and chlorpyrifos, which has good contact action and stomach action and can be widely used in controlling moth and butterfly larvae as well as other chewing mouthparts pests. While most of the pyrethroid insecticides have no systemic action, but as they have contact action and stomach action as well as good endosmose, they will have broad insecticidal spectrum. For example, lambda-cyhalothrin can be used in controlling leaf beetle, moth and butterfly larvae and other pests. In addition, we can control some borer pests in the gramineae by using the endosmose of insecticide. Therefore, in order to control some borer pests, insecticide that has good permeability but poor systemic action can be used.
In fact, many pesticides and insecticides have various insecticidal mechanisms, but we have to understand some of the outstanding mechanisms of them.
Use of inhibitor and ecdysone that are synthesized by chitin
This kind of insecticide mainly influences the formation of chitin on the pest body surface or lead to abnormal ecdysis. As it has strong stomach action, it can only be used in the larvae or nymph stage and especially has good effect on chewing mouthparts pests, but it will not have good effect if it used in other stages of pests (such as pupa and imago stage). As this kind of insecticide has slow killing effect, it is often mixed with pyrethroid and organophosphates insecticide. This kind of insecticide has been used very little, but it will have obvious effect on controlling many high resistance pests and should be used in larvae or the nymph early stage. For example, chlorfluazuron, methamidophos (diafenthiuron) and other insecticides that used in controlling moth and butterfly larvae, can be added with abamectin or deoxygenation emamectin benzoate so as to improve the fast-acting property.
Insecticides that used in controlling soil insects
Soil insects mainly include grub (scarab larvae), cutworm (a kind of moth pest), cricket and mole cricket. There are other insect pests such as blossom midge and leaf beetle pests that may live in the soil in a certain stage due to their life characteristics, which can also be considered as the soil insects and should be controlled by soil insect control agent.
As soil insects have special damage characteristics and mainly live in soil or on the soil surface, after spraying the insecticide, the combination between insecticide and soil particles should be considered in case that some insecticides will lose the insecticidal efficacy after combining with soil. Therefore, it is very important to correctly choose the insecticide composition. Currently, it mainly controls the soil insect by broadcasting phoxim or mixing it with fertilizer, but also can water and spray with ivermectin or the compound of abamectin and chlorpyrifos.
Insecticide formulations that used in controlling some special pests
Fruit-piercing moth is a kind of pest that is difficult to control in the fruit trees, which will do serious harm to plum, peach, longan, litchi and orange. Many growers feel it is really difficult to control. Although the imago mainly do harm to the fruit trees by piecing and sucking the fruits with their mouth, some people still control the pests by spraying the insecticide that has strong systemic action and only achieve little effect. In fact, repellent can be used in controlling these kinds of pests. According to the feedback, the compound of cyhalothrin and triazole will have good repelling action, which can be sprayed one time every 15 days with 1500 times liquid in the fruit maturation period.
As fruit flies have caused serious damage on melon crops and oranges in some area as well as the control effect is not very ideal, attractant can be used in controlling them considering their taxis to sweet and sour food. Omethoate is often mixed with sweet and sour liquid to trap and kill the fruit flies.
Formulations that used in controlling borer pests
Longicorn that will do harm to the branches is often controlled by injecting with high concentrations of liquid. Insecticide that has good fumigation action and systemic action will have good control effect. For example, 20-30 times liquid omethoate can be injected in the wormhole. Other insecticides, such as carbosulfan can also be used.
Carpenter moth and clearwing moth that will do harm to current-year branches should be controlled by spraying the insecticide according to the egg incubation period. Insecticide that has good stomach action and contact action (also has good endosmose) can be used.
Regarding some borer pests in the graminaceous crops, as is mentioned above, insecticide that has good endosmose can permeate well into the plant stem and will have good control effect. For example, the mixture of abamectin insecticide and triazophos can kill the rice stem borer due to its strong endosmose, which is very popular in the market.
In conclusion, there is a wide range of knowledge in the use of insecticide. Therefore, in the chemical prevention of pests, we should continue to master various kinds of knowledge. We should not only understand the characteristics of various insecticides, but also should understand the life habit of pests as well as combine the growth and phonological phase of crops. As long as we can fully master these three aspects of knowledge, we can become a real plant doctor.