Scientific pesticide use in rice: build a combination approach and master the key techniques
Rice is an important food crop in China, and it is also a crop severely attacked by pests and diseases, with the annual affected area exceeding 1.6 billion mu-times. Rice is also currently the crop with the largest pesticide use for pest and disease control in China, so promoting scientific reduced pesticide use in rice is especially important. Changing the extensive control methods of the past, scientifically using highly effective and low-toxicity pesticide varieties, and adopting combination pesticide use, reduced pesticide use, and improved application techniques can effectively raise the level of scientific pesticide use and control in rice.
1 Pest and disease damage to rice in China is worsening
In recent years, the scope of pest and disease occurrence in rice in China has continued to expand, and the frequency of severe outbreaks has risen. The rice leaf roller and rice planthopper have had major outbreaks for consecutive years in rice regions such as southwestern China, and formerly minor or new pests and diseases have become more damaging. Damage from rice pests and diseases such as the rice water weevil, rice white-tip nematode disease, southern rice black-streaked dwarf virus disease, and rice ragged stunt virus disease has worsened year by year. Affected by continuous cloudy, rainy, and sunless weather, late-season diseases such as rice blast, sheath blight, rice false smut, and sheath rot have become more severe, causing varying degrees of yield loss.
Climate change, rice variety layout, no-till and mechanical harvesting, planting structure and fertilizer-water management, and pesticide resistance are several major reasons for the severe occurrence of rice pests and diseases. The increase in high-temperature and high-humidity weather is conducive to the occurrence and spread of pests and diseases, especially to their movement toward higher latitudes.
At present, hybrid rice is planted on a large scale, and there is a lack of excellent disease-resistant and insect-resistant varieties, which also favors large-scale outbreaks and spread of many important pests and diseases. No-till methods increase the survival rate of overwintering insect sources; mechanical harvesting leaves relatively tall rice stubble in the field, increasing the base number of overwintering insect sources such as stem-boring pests and small brown planthoppers.
Dense planting, high fertilizer input, especially excessive nitrogen fertilizer and other high-yield cultivation measures, along with the household contract system and diversified planting, cause differences in sowing and transplanting times and varieties, forming large numbers of bridge fields and other conditions conducive to the spread and occurrence of pests and diseases. In addition, outbreaks of resistance in pests and diseases to the main control agents can also cause outbreaks and rampant damage from these pests and diseases.
2 Scientific pesticide use values "restraint"
Because rice pests and diseases occur severely and frequently, there are too many and too chaotic mixed formulations, especially mixtures of highly effective pesticides, and because of the household-based planting system and other reasons, farmers blindly and indiscriminately use pesticides to a serious degree. A number of new products such as Daoteng, Kangkuan, pymetrozine, and Nadiwen have successively been promoted and applied in production. These agents have novel mechanisms of action, high control efficacy, and long residual activity. We must change past pesticide use patterns and habits and guide farmers to use these new agents with restraint and in a scientific and reasonable way.
At the same time, rice fields are a relatively stable ecosystem, and the self-regulation role of the rice field ecosystem should be fully brought into play to protect the farmland ecosystem. To use pesticides cautiously, several basic principles must be mastered:
Emphasize ecological regulation. Rice has strong photosynthesis and good self-repair ability, so its own repair function should be fully brought into play. At the same time, effectively protect natural enemies in rice fields, give play to their natural control role, and apply pesticides strictly according to control thresholds.
Rational pesticide use. According to the mechanism of action of the pesticide, choose the appropriate control period for application. For example, buprofezin, which has slow insecticidal action, long residual activity, and good effect on rice planthopper nymphs but poor effect on adults, should be used during the young nymph stage of the generation before the main damaging generation of rice planthopper, so as to reduce the population of the main damaging generation and ease control pressure; while pymetrozine, which has high systemic activity, long residual activity, and is effective against both adults and nymphs, should be used during the local main damaging generation of rice planthopper.
Alternate pesticide use. Classify pesticides according to mechanism of action, and between successive generations or between the previous and following applications, alternately rotate pesticides with no cross-resistance or different mechanisms of action, avoiding continuous single use of a certain pesticide to delay the development of resistance. For example, to control rice brown planthopper, pymetrozine, nitenpyram, chlorpyrifos, and others can be selected; to control rice leaf roller, chlorantraniliprole, abamectin, emamectin benzoate, indoxacarb, furan tebufenozide, flufenoxuron, and others can be selected; to control rice blast, tricyclazole, isoprothiolane, kasugamycin, and other agents can be selected.
Restrict pesticide use. To delay the development of pest and disease resistance, implement the principle of restricted pesticide use for novel and highly effective pesticide varieties (that is, limiting the number of uses within one growing period). For example, chlorantraniliprole, an activator of ryanodine receptors, is mainly used to control the main damaging generations of rice leaf roller and striped stem borer, and it is recommended to limit use to 1 time per growing season; pymetrozine, a pyridine methylene imine heterocyclic insecticide, is mainly used to control the main damaging generations of rice brown planthopper, white-backed planthopper, and small brown planthopper, and it is recommended to limit use to 1-2 times per rice growing season (only 1 time for one type of planthopper).
Suspend pesticide use. Pesticides to which pests and diseases have developed high resistance and pesticides with cross-resistance must be suspended. For example, rice brown planthopper has developed extremely high-level resistance to imidacloprid, so imidacloprid is not suitable for controlling rice brown planthopper; in areas of Zhejiang, Jiangsu, and Hunan where striped stem borer has developed high to extremely high resistance to monosultap and triazophos, suspend the use of triazophos and monosultap to control striped stem borer.
Safe pesticide use. Rice fields are a special ecosystem with many kinds of natural enemies that have a good controlling effect on pests. Selective pesticides should be used, and pesticide varieties highly toxic to natural enemies in rice fields, such as deltamethrin, are prohibited to prevent killing natural enemies and triggering pest resurgence.
3 Master key techniques to achieve twice the result with half the effort
To raise the level of scientific prevention and control of rice pests and diseases, the following measures can be adopted.
Do a good job in green prevention and control. Do a good job in agronomic measures for variety and cultivation-based disease prevention, soil and seedling treatment, seed pesticide treatment, and control at the seedling stage, especially control in unified rice seedling-raising fields, and carry out "send-off pesticide" well, achieving twice the result with half the effort. It is necessary to integrate, support, promote, and apply a set of practical technologies. This includes the application of technologies and products such as ecological regulation, light trapping, mating disruption, odor repellence, and biological pesticides. In southern rice areas with suitable conditions, actively advocate raising ducks and crabs in rice fields, and promote environmentally friendly technologies such as biological pesticides. At the same time, actively promote and apply whole-process solutions for rice crops, which can reduce the number of pesticide applications by 2-3 times.
Implement combination pesticide use. Through carrying out experimental demonstrations, study the best pesticide combination models, including the optimal application time and minimum use dose of two or more agents, so as to lower pesticide use costs and reduce pesticide use amounts.
Actively promote reduced pesticide use. Adopt suitable application methods and timing, choose highly effective, safe, and environmentally friendly pesticide varieties, improve pest and disease control effects, delay the development of pesticide resistance in rice pests and diseases, and reduce control costs per unit area.
Vigorously carry out specialized unified prevention and control. Specialized unified prevention and control is an effective way to solve the difficulty of household-based disease and pest control, improve control effects, and reduce pesticide pollution. It is also an effective measure to control the use of highly toxic pesticides and reduce poisoning of pesticide applicators, and is especially suitable for the occurrence of migratory, epidemic, and explosive rice pests and diseases. It is necessary to vigorously advocate and promote various specialized control organizations to actively carry out specialized unified prevention and control of rice pests and diseases, ensure control effects, and lower production costs.
Promote highly efficient spray equipment and advanced spraying techniques. In the middle and late stages of rice growth, when plants and leaves are lush, knapsack motorized sprayers and high-efficiency wide-width long-range motorized sprayers can be selected for spraying. Such sprayers have good droplet penetration and can reach directly to the middle and lower parts of the plants, have a good control effect on rice planthoppers, and greatly improve work efficiency. In addition, during operation, use a lower operating speed and small-flow nozzles, and implement low-volume spraying to improve pesticide utilization.
Add adjuvants. The surface of rice leaves has a thick waxy layer, and the leaves are a natural superhydrophobic biological surface. Water droplets have a large contact angle on the rice leaf surface and are not easily wetted and retained. When spraying pesticides, organosilicone adjuvants can be added to the agent to improve the adhesion, diffusion, and spreading ability of the spray liquid on the crop surface, thereby improving pesticide utilization and control effects.
Actively promote pesticide use on the panicles in the later stage. In the late stage of rice growth, diseases such as rice blast, rice false smut, and sheath rot often occur, affecting yield and quality. Fungicides such as Shibaike, Aimiao, and Nadiwen can be vigorously promoted to control late-stage rice diseases well, increase thousand-grain weight, and raise yield.