Some pesticides are becoming ineffective due to growing pest and disease resistance, the Agricultural Technology Center warns
In early 2017, the National Agricultural Technology Center organized 60 pesticide resistance monitoring sites across 20 provinces (regions, municipalities) to monitor the resistance of 11 major pests and diseases in vegetables, rice, wheat, cotton and other crops. The results showed that some pests and diseases have developed significantly increased resistance to commonly used field control agents. Which pesticides no longer work against pests and diseases? How should pesticides be used to delay resistance? Let us look at the scientific pesticide use strategies given by experts.
I. Vegetables
1. Beet armyworm: Suspend or reduce the use of chlorantraniliprole in East China and South China
Beet armyworm populations in Fengxian and Chongming of Shanghai and Baiyun of Guangdong are at a high level of resistance to the diamide insecticide chlorantraniliprole (resistance ratios of 112-805 times); at a moderate level of resistance to indoxacarb and the insect growth regulator methoxyfenozide; and at a sensitive to moderate level of resistance to the macrolide insecticide spinosad. The Hubei Huangpi population is at a moderate level of resistance to chlorantraniliprole only, and is sensitive to the other 3 insecticides. Beet armyworm populations have developed moderate or higher resistance to chlorantraniliprole and methoxyfenozide, with resistance ratios all above 15 times.
Recommended strategies:
In vegetable production areas of East China and South China, it is recommended to adjust pesticide use strategies in a timely manner, suspend or reduce the use of chlorantraniliprole to control beet armyworm, strictly control the number of applications of methoxyfenozide, indoxacarb, spinosad and other insecticides, and pay attention to alternating and rotating insecticides with different modes of action. It is recommended to add silicone and Jiamei Gold Point to enhance efficacy.
2. Whitefly resistance is lighter in the north and heavier in the south; pay attention to alternating and rotating insecticides
Whitefly populations in northern vegetable production areas such as Beijing, Tianjin, Shanxi and Shandong are sensitive to the neonicotinoid thiamethoxam and the macrolide abamectin; they are at a moderate level of resistance to the diamide cyantraniliprole, the insect growth regulator pyriproxyfen and the tetronic acid derivative spirotetramat. Whitefly populations in vegetable production areas such as Hubei, Hunan and Hainan have higher resistance levels than those in northern vegetable production areas: sensitive to low-level resistance to abamectin, low-level resistance to thiamethoxam, moderate to high-level resistance to pyriproxyfen and spirotetramat, and high-level resistance to cyantraniliprole.
Recommended strategies:
In view of the characteristic that whitefly resistance is lighter in the north and heavier in the south, vegetable production areas such as Hubei, Hunan and Hainan should reduce the number of applications of a single insecticide to control whitefly and pay attention to alternating and rotating insecticides with different modes of action.
3. Diamondback moth resistance to chlorantraniliprole, chlorfenapyr, indoxacarb, abamectin and beta-cypermethrin.
The results showed that in southern vegetable production areas such as Hunan, Guangdong, Hainan and Yunnan, pest resistance to commonly used field insecticides rose rapidly compared with northern vegetable production areas, showing a pattern of heavier in the south and lighter in the north. Diamondback moth populations have developed high-level resistance to abamectin and beta-cypermethrin, and moderate to high-level resistance to chlorantraniliprole, chlorfenapyr and indoxacarb.
Recommended strategies:
Experts recommend alternating and rotating insecticides with different modes of action. The rapid rise in vegetable pest resistance is largely caused by excessive pesticide use and arbitrary increases in the number of applications and concentrations used. Therefore, it is recommended to adjust pesticide use strategies in a timely manner and implement alternating and rotating use of insecticides with different modes of action. Especially in Hunan, Guangdong, Yunnan, Hainan and other areas, each type of pesticide should be used no more than 1 time per vegetable season to delay the development of resistance. Given that diamondback moth populations in most parts of China currently have high-level resistance to abamectin and beta-cypermethrin, it is recommended to suspend their use and instead rotate insecticides with other different modes of action such as spinetoram, diafenthiuron and azadirachtin. It is recommended to add silicone and Jiamei Gold Point to reduce resistance and enhance efficacy.
4. Black-headed maggots basically have no particularly ideal pesticide control
This maggot has caused near total crop failure of garlic and Chinese chives in many places. From large manufacturers to small ones, a large number of various special-effect pesticides have been used, and the feedback has all been that there is no ideal control effect. Moreover, although some organophosphorus pesticides have been banned in many areas, farmers still use them secretly. Even so, the control effect is still not ideal. For chlorpyrifos and phoxim, whether used as single agents or mixtures, the application rate per mu is calculated in kilograms, and the results are still not ideal. Only phorate still has some effect, but complete kill is also very difficult.
At present, various formulations have been tried, the most common being dinotefuran, clothianidin, abamectin, chlorpyrifos, phoxim, cyromazine, diflubenzuron, as well as compounded uses of beta-cypermethrin, lambda-cyhalothrin, alpha-cypermethrin and so on. Some have also tried imidacloprid, acetamiprid, thiamethoxam and others in compounds with other products.
5. Root-knot nematodes cause very serious damage in many vegetable crops, field crops and fruit trees. Some literature, because they are invisible to the naked eye, calls them nematode diseases and classifies them as diseases, but here they are still called pests. At present, the most widely used product for nematode control is still abamectin, in emulsifiable concentrate, aqueous emulsion and granule forms, applied by broadcasting, furrow application, hole application and drenching. Because it is relatively economical and affordable, it is used in very large amounts. For this reason, after years of continuous use, resistance has become very obvious. Another reason is that abamectin is difficult to move through the soil, causing its control effect on nematodes to become increasingly poor.
Fosthiazate is currently a product with high expectations that is gradually replacing abamectin. In addition to the original granules, major manufacturers are gradually developing liquid drenching formulations such as aqueous emulsions, emulsifiable concentrates and soluble concentrates, both as single agents and mixtures. At present, resistance has been reported in a small number of areas, but because costs have only just come down and it has not yet been widely used, resistance has not shown an overly serious trend.
Fluopyram is a product that has not yet shown resistance. Personally, I believe this is because the cost is too high and not many farmers are willing to use it repeatedly, since it is too expensive.
6. The whitefly is one of the main vectors for spreading viral diseases. It can damage many vegetables and even broadleaf field crops. In many cases, if whitefly control is not adequate, the spread of viral diseases is almost unavoidable.
At present, as far as single agents are concerned, there seem to be no products with particularly good effects. Acetamiprid, imidacloprid, pymetrozine, thiamethoxam, deltamethrin, bifenthrin and others, and for a time a mixture of nitenpyram and pymetrozine was very popular with very good reported effects, but resistance is now already considerable.
There are many special-effect products on the market for whitefly control, most of which contain hidden ingredients. Most of their effects last well for two years and then decline, and there is nothing that can truly remain effective for a long time.
There is however a small method: use thiamethoxam water-dispersible granules and place a little at the base of each vegetable plant. This is basically enough to control whiteflies, thrips, aphids and similar piercing-sucking pests throughout the entire growth period.
7. When it comes to flea beetle resistance, basically everyone who makes insecticides knows that resistance is very high. Products such as dichlorvos, trichlorfon, phoxim, chlorpyrifos, thiamethoxam, deltamethrin and others all have some control effect, but none are truly very effective. At present, among single agents, it seems that malathion and fipronil are relatively better, while the rest are various mixtures whose formulations cannot be listed one by one. It is only known that adding pyridaben gives a fairly good effect.
II. Rice
1. Brown planthopper has developed high-level resistance to imidacloprid, thiamethoxam and buprofezin
At present, all brown planthopper populations in the monitored areas have developed high-level resistance to the first-generation neonicotinoid insecticide imidacloprid (resistance ratios above 1200 times), and have also developed high-level resistance to the second-generation neonicotinoid insecticide thiamethoxam (resistance ratios of 200-500 times), but are at a sensitive to moderate level of resistance to nitenpyram; they are at a low to moderate level of resistance to the third-generation neonicotinoid insecticide dinotefuran. They have developed high-level resistance to the insect growth regulator buprofezin (resistance ratios above 500 times). Compared with 2015, the resistance ratios of brown planthopper to buprofezin have increased substantially, especially in Jiangsu, Jiangxi and Hubei, where resistance ratios are all above 1000 times.
They have developed moderate-level resistance to the organophosphorus insecticide chlorpyrifos. According to feedback from plant protection stations in Zhejiang, Jiangxi, Hunan and other provinces, due to many years of use, pymetrozine has shown continuously declining field control effects against brown planthopper. During monitoring, it was found that the difference in brown planthopper mortality between high and low concentrations of pymetrozine was very small, and resistance ratios could not be calculated in either case, indicating that the current resistance level to pymetrozine is continuously rising, which should attract great attention from agricultural departments in all regions.
Recommended strategies:
Brown planthopper has developed varying degrees of resistance to various insecticides. Therefore, during brown planthopper control, between source and destination areas and between successive generations in the same area, insecticides with different modes of action and no cross-resistance should be used alternately and in rotation, avoiding continuous and single-agent use. Given that brown planthopper has currently reached high-level resistance to imidacloprid, thiamethoxam and buprofezin, it is recommended that all rice areas suspend the use of imidacloprid, thiamethoxam and buprofezin to control brown planthopper; strictly limit the number of applications of pymetrozine and chlorpyrifos for brown planthopper control, preferably to 1 time per rice season; and alternately rotate new insecticides such as nitenpyram, dinotefuran and triflumezopyrim to delay the development of brown planthopper resistance.
2. White-backed planthopper resistance levels show an obvious upward trend
At present, white-backed planthopper populations in the monitored areas are at a moderate to high level of resistance to insecticides such as buprofezin and chlorpyrifos; they are at a sensitive to low level of resistance to the neonicotinoid insecticides imidacloprid and thiamethoxam. Compared with 2015, the overall resistance level of white-backed planthopper to various insecticides shows an obvious upward trend.
Recommended strategies:
Given that white-backed planthopper and brown planthopper usually occur together, and that brown planthopper has already developed high-level resistance to buprofezin, it is recommended that all rice areas suspend the use of buprofezin to control white-backed planthopper and delay the further development of resistance. At the same time, because neonicotinoid insecticides still have very high toxicity to white-backed planthopper, consideration can be given to using imidacloprid, thiamethoxam or sulfoxaflor when the field planthopper population is mainly white-backed planthopper, alternating with pymetrozine for control.
3. For small brown planthopper, the number of chlorpyrifos applications should continue to be limited in the future
Small brown planthopper populations in the middle and lower reaches of the Yangtze River (Jiangsu, Anhui, Zhejiang and other provinces) are sensitive to insecticides such as thiamethoxam, nitenpyram and pymetrozine; they are at a moderate level of resistance to chlorpyrifos. Compared with the 2015 monitoring results, the resistance ratios of most small brown planthopper populations to chlorpyrifos have decreased somewhat.
Recommended strategies:
In the future, the number of chlorpyrifos applications should continue to be limited, and it should be used in alternating rotation with insecticides such as thiamethoxam, nitenpyram or pymetrozine to delay the further development of resistance.
4. Striped stem borer resistance to diamide insecticides shows an obvious upward trend
Striped stem borer populations in the eastern coastal area of Zhejiang, the Poyang Lake area of Jiangxi, and southern Hunan have relatively high resistance to the diamide insecticide chlorantraniliprole, at a moderate level of resistance, with overall resistance ratios increased compared with 2015. Field efficacy trial results from multiple locations in Jiangxi showed that 14 days after treatment, the insecticidal effect of chlorantraniliprole against striped stem borer was only 30%-70%.
At present, all striped stem borer populations in the monitored areas are at a moderate level of resistance to the macrolide insecticide abamectin. Compared with 2015, the resistance ratios of most striped stem borer populations have increased significantly, especially in Zhejiang and Hunan, where resistance ratios are all above 50 times. Striped stem borer populations in Zhejiang, Jiangxi, Hunan and other areas are at a low to moderate level of resistance to chlorpyrifos and triazophos, while populations in Jiangsu, Anhui, Hubei and other areas are at a sensitive to low level of resistance to chlorpyrifos and triazophos.
Recommended strategies:
The resistance status of striped stem borer populations to insecticides has obvious regional characteristics. Among them, populations in most areas of Zhejiang, Jiangxi and Hunan have generally developed low to moderate level resistance to organophosphorus insecticides, and resistance to diamide and macrolide insecticides shows an obvious upward trend. In the future, the number of applications of diamide and macrolide insecticides should continue to be limited to avoid continuous exposure of striped stem borer to insecticides with the same mode of action across multiple generations. At the same time, excessive use of abamectin should be controlled to reduce its harmful effects on natural enemies.
III. Wheat
1. Fusarium head blight: carbendazim control is relatively poor in Jiangsu and other places
Resistance monitoring results show that resistance of the Fusarium head blight pathogen to carbendazim mainly occurs in Jiangsu Province and its surrounding provinces, and the degree of resistance has reached a dangerous level detectable by conventional methods. In some areas of Jiangsu Province, the effect of using carbendazim to control Fusarium head blight is already very poor.
Recommended strategies:
It is recommended to rotate insecticides with different modes of action such as phenamacril and tebuconazole in areas where carbendazim resistance has developed, to delay the development of resistance.
2. Wheat aphids require rotation of insecticides to delay the development of resistance
At present, English grain aphid populations in the monitored areas are sensitive to commonly used field insecticides such as imidacloprid, acetamiprid, sulfoxaflor, the organophosphorus insecticide omethoate, the carbamate insecticide pirimicarb, and the pyrethroid insecticide beta-cypermethrin. The sensitivity of the bird cherry-oat aphid to insecticides varies more among populations at different locations than that of the English grain aphid. Low to moderate level resistance to imidacloprid was detected in populations from Dongtai of Jiangsu and Zhumadian of Henan; moderate level resistance to beta-cypermethrin was detected in the Zhumadian of Henan population; and they are sensitive to insecticides such as sulfoxaflor, acetamiprid, pirimicarb and omethoate.
Recommended strategies:
It is recommended to rotate neonicotinoid insecticides, pirimicarb and other insecticides with different modes of action in areas where wheat aphid resistance has developed, to delay the development of wheat aphid resistance.
IV. Cotton
1. Cotton bollworm: pyrethroid insecticides should be banned in the North China cotton region
Populations from Wangjiang of Anhui, Jingzhou and Zaoyang of Hubei were detected at a low level of resistance to the pyrethroid insecticide cyhalothrin, while other populations are already at a moderate to high level of resistance. In particular, populations from Qiu County of Hebei, Anyang of Henan, Binzhou and Xiajin of Shandong in the North China cotton region have developed high-level resistance to cyhalothrin (resistance ratios of 129-166 times). Cotton bollworm populations in the North China cotton region and the Yangtze River basin cotton region are at a moderate level of resistance to the organophosphorus insecticide phoxim and the macrolide insecticide emamectin benzoate, while populations in the Xinjiang cotton region are at a low level of resistance. Compared with the 2015 monitoring results, resistance ratios to phoxim have all increased somewhat. The resistance ratios of cotton bollworm populations in the North China cotton region to emamectin benzoate have increased compared with 2015.
Recommended strategies:
In areas where cotton bollworm has developed high-level resistance to pyrethroid insecticides, especially in the North China cotton region, the use of pyrethroid insecticides to control cotton bollworm should be prohibited to delay the continued rise in resistance. In the North China cotton region and the Yangtze River basin cotton region, the number of applications of organophosphorus and macrolide insecticides should be limited (no more than 2 times during the cotton growing period), and insecticides with other different modes of action such as spinosad and chlorantraniliprole can be used in alternating rotation.
2. All cotton aphid populations are at a high level of resistance to deltamethrin and imidacloprid
At present, all cotton aphid populations in the monitored areas are at a high level of resistance to the pyrethroid deltamethrin and the neonicotinoid imidacloprid, with resistance ratios in some areas reaching tens of thousands of times or more (resistance ratio to deltamethrin >4545 times, resistance ratio to imidacloprid 188-316402 times); they are at a moderate to high level of resistance to the carbamate insecticide carbosulfan; and at a moderate level of resistance to the organophosphorus insecticide omethoate. Cotton aphid resistance develops rapidly, and it has developed resistance to almost all currently used insecticides. In particular, resistance levels to pyrethroid, carbamate and neonicotinoid insecticides are relatively high and still show an increasing trend.
Recommended strategies:
Cotton aphid has become one of the pests with severe resistance that is difficult to manage. It is recommended to suspend the use of deltamethrin, carbosulfan, imidacloprid and other insecticides in agricultural production, choose other insecticides with different modes of action for control, and at the same time adopt integrated resistance management measures to achieve better control effects.