Currently, many growers in pest control process found that some conventional pesticides suddenly become less useful, and even increase the dosage is also less than ideal control effect, this is the pest weeds resistant to pesticides It is.
Drug resistance problems are currently outstanding
Herbicides have been used in China for decades, and the long-term use of single agents and unfamiliar drug habits have made the problem of resistance to herbicides more and more serious. The problem of weed resistance in rice fields is particularly prominent.
Liu Ducai, a researcher at the Institute of Plant Protection of Hunan Academy of Agricultural Sciences, who has long been concerned about this issue, said that with the use of amides and sulfonylurea herbicides for 20 to 30 years, some Chinese double-season rice areas are currently sown. Common herbicides such as quinclorac and penoxsulamide produce high levels of resistance.
Liang Diyun, a researcher at the National Agricultural Technology Center, pointed out that the direct seed fields in Hunan, Hubei, Anhui, Jiangxi, Jiangsu, Zhejiang and other provinces in the middle and lower reaches of the Yangtze River and Ningxia in the northwest have become the hardest hit areas for rice-field resistant weeds.
The problem of resistance to fungicides is also not to be ignored. Taking the resistance of cucumber downy mildew as an example, its resistance to metalaxyl (fine metal cream) and azoxystrobin is more serious and common, the resistance is rapid, the resistance level is high, and the drug effect is obviously reduced.
In terms of pesticides , the most prominent case of drug resistance was the promotion of the use of pyrethroid insecticides in cotton fields in the 1980s, which led to the emergence of severe resistance to cotton aphid in the late 1980s. Invalid.
Drug resistance "list"
According to preliminary statistics from the National Agricultural Technology Center, more than 80 important agricultural pests in China have developed resistance to pesticides. The most influential pests include rice planthopper (resistant to nicotine and buprofezin), stem borer (resistant to chlorantraniliprole, insecticide, triazophos); cotton bollworm (Resistant to pyrethroids); Plutella xylostella (resistant to almost all agents).
The disease includes wheat scab (resistant to carbendazim) and rice seedling disease (resistant to prochloraz).
In terms of grass damage, there are rice field valerian (resistant to butachlor, quinclorac, and penoxsulam), ginseng (resistant to cyhalofop), and wild sage (for butylamine, evil) Grass ketone, bensulfuron-methyl), comfrey (resistant to sulfonylureas). Wheat field, Mai Niang, Valerian (resistant to chloromeron, oxazolamide), swine fever (resistant to benzofuran); corn field, Matang (for atrazine, nicotinic acid) Sulfoxone is resistant), Orchard Goosegrass (resistant to glyphosate), etc.
Must be wary of "no medicine available"
In addition to causing increased drug use, phytotoxicity, and reduced yield, the severity of drug resistance is directly related to the life of a drug.
The current cost of developing a new pesticide requires $286 million, screening 160,000 compounds and spending more than 10 years. “The development of pest resistance has exceeded the speed of development of new drugs!†In the long run, it will even result in “no medicine availableâ€. Experts in the industry pointed out that it is necessary to vigorously promote the use of scientific drugs, and adopt comprehensive methods to comprehensively control to delay the development of resistance to pests and diseases .
Expert advice: how to use pesticides scientifically
01
Identify key symptomatic strategies
Li Yongping, senior agronomist of the National Agricultural Technology Center:
The resistance of harmful organisms includes the insensitivity of the target, the decrease of the penetration rate of the drug solution, and the enhancement of the activity of the metabolic enzymes. It is helpful to find a suitable solution after clarifying the mechanism, and several key points must be grasped.
The first is to change the variety of pesticides. The agent with the new mechanism of action re-sensitizes the drug-resistant individual to the agent. For example, the brown planthopper is highly resistant to imidacloprid and then switched to pymetrozine. Rotation, alternation or mixed use of drugs with negative cross-resistance, reduce pesticide selection pressure, reduce the speed of drug-resistant individuals and reduce the proportion of resistant individuals. For example, after Botrytis cinerea is resistant to carbendazim, it uses a drug with negative cross-resistance.
The second is to increase the penetration of the agent. For example, a solvent having a wax layer for dissolving an insect body surface is used to enhance the virulence of the agent to insects; vegetable oil or the like is used to increase the penetration ability of the herbicide to weeds and the like. It inhibits the metabolic enzyme activity of resistant individuals and reduces the degradation of pesticides. For example, multi-functional oxidase inhibitors such as piperonyl ether are used to inhibit the multi-functional oxidase activity of mosquitoes and increase the virulence of pyrethroids to mosquitoes.
Third, other measures such as cultivation mode and variety replacement can be comprehensively used.
02
More agricultural control measures
Li Jianhong, Professor of Huazhong Agricultural University:
The key to resistance management is early warning, and measures can only be taken to effectively delay the development of resistance before the level of resistance is significantly increased.
At present, rice planthopper has produced different degrees of resistance to commonly used insecticides with different mechanisms of action, and it is necessary to avoid the use of varieties that have produced high levels of resistance, such as imidacloprid, buprofezin, pymetrozine and the like. The brown planthopper can be selected from the alternate rotations of nitenpyram, flonicamid, nitrile, dinotefuran, clothianidin, chlorpyrifos, etherimide, dichlorvos, etc.; whitebacked planthopper can choose imidacloprid, acetamiprid Alternate rotation of amine, thiamethoxam, etofenproxil, isoprocarb, dichlorvos, etc.;
In addition, avoid using a variety of insecticides, such as triazophos. Avoid the use of cross-resistant insecticides such as ethiprole. Use insecticides that are low in toxicity to natural enemies, such as flonicamid, nitenpyram, trifluoropyrimidine, etc., pay attention to the appropriate medication.
In addition to scientific medicine, it is also possible to adopt agricultural control measures, such as rice non-woven fabric breeding or plastic film mulching, to prevent insects and disease, improve rice seedling quality, increase yield, etc.; adjust industrial layout, single and double season rice area planting, to achieve reasonable Crop layout; adjust the sowing period, the rice sowing period in the same area is as consistent as possible; reduce the bridge field and reduce the insect population base. In addition, different types of plants can be planted at the edge of the field to increase the complexity of the farmland ecosystem and enhance the natural control ability.
03
It is very important to cure early treatment and comprehensive prevention and control.
Liu Ducai, a researcher at the Hunan Academy of Agricultural Sciences:
Herbicide resistance management, early treatment, treatment, comprehensive prevention and control is very important. The best way to control weeds is to control, not to kill.
The main weeds in Chinese rice fields include alfalfa, Qianjin, weedy rice, crabgrass, squash, sedge, and broken sedge. Among them, more than 90% of weeds such as valerian and Qianjin are germinated within 10 days after sowing of rice. During this period of closure, more than 80% of the grass damage can be effectively prevented.
First, pay attention to the early control of weeds, and control in the most vulnerable growth period of weeds.
Second, rotation is an effective measure to delay resistance, crop diversity and date of planting, selection of competitive crops, adjustment of seeding, increased physical competition with weeds, and use of herbicide-tolerant crops to ensure the use of alternative mechanisms of action. herbicide.
Third, avoid using herbicides with a single mechanism of action for the same time in the same field, mixing herbicides, and using herbicides in order to achieve more effective weed control.
Fourth, physical control measures can be adopted to reduce the content of seed banks in the soil through reasonable agricultural measures, and at the same time, rational use of mechanical control and destruction of weed seeds.
More pesticide encyclopedia, please pay attention to China Pesticide Network
(Source: Agricultural Resources Guided Pesticide)
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