Consumer Foundation random inspection: Half of bean vegetables exceed pesticide limits, snow peas completely non-compliant, single sample has up to 14 pesticide residues, experts offer solutions for improvement
Between September and October last year, the Consumers' Foundation purchased a total of 39 samples of 5 types of bean vegetables from hypermarkets, supermarkets, grocery stores and traditional markets in Taipei and New Taipei, Taichung, Tainan and Kaohsiung, testing for 381 pesticide residues, and found that every sample had pesticide residues; apart from the pesticide residue values in hyacinth beans being within the allowable limit, all four other bean vegetables had pesticide residues exceeding the limits.
Among them, the most serious pesticide residues were in snow peas, with a non-compliance rate of 100%, and one sample contained as many as 14 pesticide residues; next was garden peas, with a non-compliance rate of 87.5%; then came snap beans, with a non-compliance rate of 35.7%; and finally cowpeas, with a non-compliance rate of 12.5%.
In response to beans frequently being found to exceed pesticide limits, Hong Qiaozhen, associate researcher in the Biopesticide Division of the Taiwan Agricultural Chemicals and Toxic Substances Research Institute, said that bean vegetables are continuous-harvest crops, with the same plant simultaneously bearing leaves, flowers and fruits, and "farmers buy a pesticide every time they see a disease or pest," and this cocktail-style application of pesticides causes residues of multiple items at varying concentrations. Hong Qiaozhen explained that most pesticides are broad-spectrum and can control more than one disease or pest, and only by understanding the characteristics of the pesticides can pesticide use be reduced.
More than half of bean vegetables exceed pesticide limits, snow peas contain 14 pesticides, pesticide cocktails harm human health
Consumers' Foundation secretary-general Wu Rongda said that this sampling scope covered northern, central and southern Taiwan, and the residue situation in bean vegetables from southern distribution channels was especially serious. Among the 39 samples, most of the non-compliant pesticide items were fungicides, including propiconazole (detected in 11 samples), prochloraz (detected in 8 samples), difenoconazole (detected in 5 samples), fenbuconazole (detected in 5 samples) and flusilazole (detected in 3 samples), among others.
Among the 20 non-compliant samples, snow pea samples had residues of 7 to 14 pesticides, with 2 to 6 pesticides exceeding the limit; garden peas had residues of 6 to 13 pesticides, with 1 to 4 pesticides exceeding the limit; snap beans had residues of 3 to 7 pesticides, with 1 to 2 pesticides exceeding the limit; 1 cowpea sample was non-compliant, with 11 pesticides detected and 1 pesticide exceeding the limit.
Regarding these inspection results, Ling Yongjian, professor in the Department of Chemistry at National Tsing Hua University, expressed surprise and said that in past inspections of bean vegetables, a single type of sample had at most 8 pesticide residues detected, and this time 14 were detected, breaking past records; he speculated that the reason was that bean vegetables are continuous-harvest crops, and the overlapping period of the planting and harvest seasons is two to three months, so farmers, seeking effective pest and disease control, spray multiple pesticides, causing residues.
"Whether or not they exceed the limit, all of them have pesticides, and not just one kind." Ling Yongjian said that in this sampling result, for example hyacinth beans, although none exceeded the limit, they still contained pesticides, and among the other four non-compliant bean vegetables, not all types of detected residual pesticides exceeded the limit, but if consumers eat agricultural products with "pesticide cocktail" residues, it may burden the organs, and long-term intake will affect health.
Consumers' Foundation: There is a gap between official and private inspections, the central government should sample distribution channels closest to consumers
Consumers' Foundation secretary-general Wu Rongda said that comparing the Council of Agriculture's sampling results for bean vegetables in fields and collection markets between January 2018 and October 2019, the Council of Agriculture's average non-compliance rate was 14.2%, which differs from the Consumers' Foundation's over 50% non-compliance rate in traditional market inspections.
Wu Rongda believes that official sampling is all done in fields, and problematic or rushed-to-harvest items do not enter the official inspection system, but the Consumers' Foundation samples in markets and distribution channels closest to consumers, which is closer to the results of consumer purchases, and the central government should pay attention to the problem of pesticide residues exceeding limits in agricultural products in end-point distribution channels.
Reasons bean vegetables exceed pesticide limits: continuous harvesting, continuous use of diverse control pesticides
Bean vegetables are randomly inspected every year, and pesticide residues exceeding limits are common; what causes this phenomenon? Hong Qiaozhen, who has long studied plant protection, said that this is related to the cultivation methods of bean vegetables and farmers' pesticide use habits.
"Bean vegetables can serve as green manure and also earn some pocket money." Hong Qiaozhen explained that bean vegetables such as garden peas are mostly planted after the second rice crop is harvested, both to replenish soil fertility and to supplement farmers' income between the second rice crop and the first rice crop, and bean vegetables generally bloom continuously and bear fruit continuously, making them continuous-harvest crops.
"Every time they see a disease or pest, they buy a pesticide." Hong said that farmers growing bean vegetables are not specialized growers, so for pest and disease control methods they mostly consult pesticide shops, and usually mix a pesticide every time they see a disease; because bean vegetables are continuous-harvest crops, the same plant has leaves, flowers and fruits at different growth stages, and cocktail-style pesticide application causes residues of multiple items at varying concentrations.
"We must solve it from the root of the problem." Hong Qiaozhen believes that the key to pesticide residues lies in field production, and both cultivation methods and pesticide use habits must change. She gave an example: farmers buy a pesticide every time they see a disease or pest, but in fact most pesticides are broad-spectrum and can control more than one disease or pest, and understanding pesticide characteristics can reduce pesticide use.
Prevention is better than treatment, control must be done before sowing, flowering and pod formation
"Control must be done well before flowering." Hong Qiaozhen explained that waiting until flowering and pod formation, when pests and diseases are present, to carry out control is actually too late; for continuous-harvest crops, the most critical things are actually clearing the field before sowing and control before the first flowering. She gave an example: before sowing, pheromones can first be used to trap noctuid pests, reducing the pest population before sowing, and if pesticides are to be used, it must be before the flowering period, with organic-friendly materials used after the first flowering.
"Once the bean pod borer bores into the pod, no amount of control is useful." Hong Qiaozhen took snap beans as an example: Bacillus thuringiensis among organic-friendly materials can deal with the bean pod borer, but once the bean pod borer bores into the pod, any surface pesticide application is ineffective, so field cleanup before planting and the timing of control after sowing are very important.
Garden peas: upright cultivation, first use pheromones to catch noctuids
"Garden peas had pesticide residues in the past, and the key is that the farmers growing garden peas are not specialized garden pea growers." Hong Qiaozhen, who has long studied garden pea cultivation, explained that because it is non-specialized cultivation, farmers, for convenience of management, use pesticides and materials meant for rice on garden peas, which causes serious pesticide residues; for garden pea cultivation, she gave the following suggestions.
If one wants to reduce pesticide-based control in garden peas, the first thing is to improve cultivation methods; in the past, management was more extensive, letting garden peas in the field grow prostrate on the ground, but now more farmers have switched to upright cultivation, reducing contact with the soil, and standing upright is also healthier for the plants; with ventilation between plants and less contact surface with the soil, the probability of pests and diseases can naturally be reduced.
Next is the use of materials; because garden peas bloom continuously, once pesticides are used they easily contaminate the pods that are setting fruit, and pests and diseases are harder to control once they occur, so prevention must come first; garden peas are mostly planted after the second rice crop is harvested, and this period is when tobacco cutworms and beet armyworms are prone to occur, so farmers are advised not to rush to plant, and can first hang sex pheromones to trap larvae, and plant after they have been cleared out.
After planting, use friendly materials to control lower leaves without contaminating the fruit harvested above
After garden peas are planted, the main problems encountered are thrips and powdery mildew; against thrips, warning pheromones can be used. In past field trials there were two comparison groups, one spraying pesticide once every four days, and the other spraying pesticide once every eight days combined with warning pheromones; comparing the two groups, it was found that the control effect when combined with pheromones was better, showing that the use of warning pheromones can reduce pesticide use.
For powdery mildew control, Bacillus subtilis preparations or mineral oil can be used; powdery mildew mostly occurs on the lower leaves of garden pea plants, and combined with upright cultivation, it is only necessary to apply diluted Bacillus subtilis preparations or mineral oil to the lower leaves, so that the harvested parts above will not be contaminated. If other pests or diseases are encountered, friendly materials can also be used, for example liquefied starch against brown spot, or Bacillus thuringiensis against pests.
Agricultural Chemicals and Toxic Substances Research Institute: Striving to lower the cost of friendly materials so that farmers' acceptance gradually increases
"I have seen farmers buy all the materials in the plant protection manual." Hong Qiaozhen smiled; she believes that changing farmers' concepts must rely on continuous guidance and patience, and in recent years during advisory work she has found that farmers' acceptance of organic-friendly materials has increased.
"We will strive to make these materials lower in cost, and then more farmers will use them." Hong Qiaozhen said that in the past, for promotion, agricultural improvement stations and the Agricultural Chemicals and Toxic Substances Research Institute would give farmers biological agents for free, but now farmers are all willing to pay for biological materials that are friendlier to the environment, and afterward they will continue to keep material costs within a range all farmers can afford.
In addition to advice for farmers, Hong Qiaozhen believes: "The danger of pesticide poisoning from spraying is more frightening than eating pesticides from bought vegetables." She said that the risks farmers bear are higher than those of end consumers; even if pesticides in agricultural products exceed limits, they are still at the ppm level, but farmers spraying in fields use extremely high concentrations, so the probability of poisoning is higher.
As for how to avoid ingesting pesticides when buying, cooking or eating vegetables? Hong Qiaozhen suggested not being a picky eater, and diversely consuming all kinds of foods to spread the risk; in addition, most pesticides are fat-soluble, so the effect of washing vegetables to remove pesticides is limited, and after stir-frying, the liquid at the bottom of the pan can be drained off, eating only the cooked agricultural product, which can reduce the probability of ingesting pesticides.