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Extension of Good Agricultural Practices Towards Safety of Fresh Fruit and Vegetables

 

 Tze-Chung Huang and Hau-Ping Chou

Kaohsiung District Agricultural Research and Extension Station, Council of Agriculture, Executive Yuan. ROC; Present Address: Changzhi , Pingtung, Taiwan

e-mail: tch1@mail.kdais.gov.tw

 

ABSTRACT

In order to achieve sustainable agriculture, developed countries currently emphasize the implementation and validation of Good Agriculture Practice (GAP). GAP is a collection of practice principles to apply for agricultural production, resulting in safe agricultural products. At present, “quality agriculture” is an important agricultural policy in Taiwan and is the main theme of “quality agriculture”. The content of healthy agriculture includes the validation systems of GAP, Ji-Yuan-Pu in Chinese, Traceable Agricultural Products (TAP), Organic Agriculture, Certified Agricultural Standards (CAS). Among these, the GAP label is the most commonly accepted safe validation certificate for agricultural products since its application procedure is simple, easy, and free for farmers. Located in the subtropical region, the temperature and humidity in Taiwan are favorable for the occurrence and spread of pests, therefore pest control is the most serious problem for the cultivation of crops in Taiwan. Although the use of chemical pesticides is convenient, fast, and effective, the overuse of chemicals resulted in resistance to pesticides, pesticide residue on agricultural products as well as environmental pollution. Thus, healthy agriculture emphasizes the establishment and extension of crop health management systems for efficient and effective pest control. Integrated Pest Management (IPM) is the most important executive strategy to ensure safe agricultural products. The Taiwan government has established the pest diagnosis services as well as the pest monitoring and alert system for pest and disease prevention and control. Besides, academies, agricultural institutes, and District Agricultural Research and Extension Stations (DARESs) in Taiwan especially focus on the development of IPM technologies, including field sanitation management, breeding of pest resistance, cultivation management such as crop rotation, green manure crops, sod cultivation, management of soils and seedbeds, rational fertilization, non-pesticide control of pests such as physical, biochemical, and biological measures, and economical and safe application of pesticides. We transferred these technologies to farmers for application through professional education courses and multiple public media. The agricultural agencies also execute the practices of random inspection of pesticide residue, the follow-up education, the infraction judgment and penalties, etc. to ensure the marketing of safe agricultural products. Till the end of 2013, the GAP-certificated production areas for fruit and vegetables have reached a total of 25,649 hectares and the certified TAP and organic crop production areas are 6,542 and 5,821 hectares, respectively. According to the most recent data, the rate of fruit and vegetables that passed the pesticide residue inspection at both production and distributing sites has increased to >96%. This has well safeguarded the consumers’ health in Taiwan.

 

Keywords: safe agricultural products, good agricultural practice, integrated pest management, non-pesticide control, farmers’ education, pest monitoring and alert system

 

INTRODUCTION

“Agricultural products safety and traceability” has been a main concern for the general public in many countries around the world since consumers are becoming increasingly aware of food safety. Reflecting this global trend and consumers’ demand, the government continues to focus on promoting healthy agriculture in Taiwan. At present, “quality agriculture” is Taiwan’s core agricultural policy. It consists of three main themes: healthy agriculture, excellent agriculture, and LOHAS (lifestyles of health and sustainability) agriculture. In terms of healthy agriculture, it includes the certification systems for “the label of Ji-Yuan-Pu safe fruit and vegetables” (GAP), the Traceable Agricultural Products (TAP), the CAS Taiwan Premium Agricultural Products, and the organic agriculture (20). Located in the subtropical region, the temperature and humidity of Taiwan are both favorable for the occurrence and spread of pests, therefore pest control is the most serious problem for the cultivation of crops in Taiwan.

Thus, implementation of healthy agriculture is highly related to plant protection work. Taiwan has been promoting crop health management measures for a long time, which are based on the concepts of the integrated pest management (IPM) to develop and extend various non- pesticide technologies for improving crop health and reducing the use of chemical pesticides.

The overall goals are to protect environments, reduce pesticide residue, and ensure consumers’ health. IPM is the most important executive strategy in conducting crop health management. It means integration of available production techniques especially appropriate biological control measures to keep pests at levels that are economically justified and minimize risks to humans and the environment. The main principles are (1) Accurate and economical use of chemical materials, (2) Choosing right materials carefully and optimizing effectiveness by combining different materials, (3) Emphasis of mass production and application of natural enemies and beneficial microorganisms as well as the establishment of environmental conditions that is suitable for crop growth but pest propagation, (4) By using appropriate crop rotation and cultivation model to optimize and maintain soil fertility, (5) Keep economic benefits, and high crop yield is not the ultimate goal for production, (6) Reducing interventions against sustainable ecological environments, and (7) Preventing or postponing resistance of pests to pesticides or biological control methods (27,38).

SAFETY CERTIFICATION SYSTEMS AND RESIDUAL PESTICIDES INSPECTION FOR AGRICULTURAL PRODUCTS IN TAIWAN

Good Agriculture Practice (GAP) label

In Taiwan,“the label of Ji-Yuan-Pu safe fruit and vegetables” is abbreviated to the GAP label. Internationally, GAP is the abbreviation for Good Agricultural Practice, which applies sustainable agriculture methods to crop cultivation. The purpose of GAP is to protect crops from pests and increase crop quality through rational and environmentally-friendly application of agricultural materials (i.e. fertilizers and pesticides) at appropriate timing and sites for specific crop varieties. Thus, the GAP label is a certificate for high-quality agricultural products produced in accordance with Taiwan Good Agricultural Practices (TGAP)(7,40). The GAP label certification which took effect in 1993 not only represents safe agricultural products, but is also regarded as recognition of farmers’ contribution. To produce safe agricultural products, the primary principle is to reduce dependency on pesticides. If farmers have to use chemicals, registered pesticides should be applied in a manner that leaves residues below the Maximum Residue Limits (MRL). Furthermore, farmers have to keep records of the pesticide usage with details of the kinds, quantities, and effectiveness of the pesticides.

The regulation for the management of the GAP label was formulated in 2009 by the Council of Agriculture (COA), Executive Yuan, ROC (Taiwan). The applicants are limited to registered agricultural production and marketing groups or farms that are supervised by the COA on the pest control and safe use of pesticides. The residual pesticides on their agricultural products also should pass the pesticide tests in order to obtain the GAP label(7). The applicable products are positively listed by the COA. They include mainly fresh vegetables and fruit as well as some specialties, cereal crops and self-produced processed agricultural products. The GAP label issued by authorized agencies facilitates the sale of high-quality agricultural products and therefore ensures consumers’ health.

 

Fig. 1. (A)The GAP label

 

Fig. 1A shows the GAP label. The two green leaves represent agriculture. The three red circles have double meanings. One is to emphasize the practices of the “rational pest control”, “use of recommended pesticides”, and “compliance with safe duration between pesticide application and harvest”. The other is to indicate this product is “supervised”, “inspected”, and “regulated” by the COA. The nine identification numbers at the bottom represent counties/cities, crop categories, and regulated running numbers, respectively. Each label is owned by a specific farmer so that consumers can access the website (http://gap.afa.gov.tw/faq/) to trace the names of the producers, the crops, and the agricultural production and marketing groups by the identification numbers.

Our government currently keeps promoting the GAP label validation system. To ensure the credibility of this system, we investigate the applications carefully as well as strengthen the inspection of the label usage and pesticide residue. The GAP label is very popular because it’s simple, easy, and use free application procedure. It has become the foundation of a healthy agriculture policy in Taiwan. At the end of 2013, there are 2,126 certified GAP production and marketing groups with a total production area up to 25,649 hectares and annual yield of approximately 550,000 tons. These numbers have increased year by year as shown in Table 1. To facilitate the visibility of the label, we promoted the mother-baby package for vegetables and fruit with the GAP label for wholesale markets. In 2013, 22,774 tons of vegetables and fruit have been sold to our consumers through 137 chain supermarkets and 2,300 convenience stores (32).

 

Table 1.  The number of production and marketing groups certificated with GAP and production area from 2007 to 2014 in Taiwan.

 

Traceable Agricultural Products (TAP) label

Good Agricultural Practice (GAP) and Traceability are currently two main management systems for safe agricultural products in the world (16). The former is to reduce the risk of production and the latter, to clarify the responsibility of all participants involved in production and sales. The purpose of traceability systems is to clarify responsibilities, remove unsafe products, reduce consumers’ risks, and reduce economic losses of qualified producers caused by lack of consumers’ confidence. In Taiwan, the COA combined GAP and Traceability systems to manage risks and to ensure safety of agricultural products. In 2007, Taiwan also announced the “Traceable Agricultural Products Certification Management Regulations” and started to implement the voluntary Traceable Agricultural Products (TAP) system for farmers.

The system emphasizes the comprehensive records of agricultural products in the process of production, post-harvest treatments, processing, transportation, and sales. TAP combined the principles from the two international regulation systems (GAP and Traceability) for agricultural products to manage the entire process from production to sales of agricultural products.(28,40) According to “Traceable Agricultural Products Certification Management Regulations”, the production process of agricultural products should follow the standard operation procedures and models required by the central competent authority, and the production process flowcharts, risk management tables, production and delivery recording sheets,  and the records of cultivation management, fertilization methods, pests control, etc. have to be kept for reducing the risk.(4) The applicants can be individuals, production and marketing groups, unions, and farms. The government subsidizes part of the certification fee. After submitting the applications, the authorized TAP certificate agencies verify that the applicants implement all TGAP operation recommendations. The authorized agencies for certification have to meet the requirements of ISO GUIDE 65 and the specific requests by the COA. They also have to be approved by the International Accreditation Forum Multilateral Recognition Arrangement (IAF) and the COA for their independence and ability to certify TGAP applicants.

Traceability systems can keep track the entire processes of agricultural products from production to sales. The information is open, transparent, and traceable in order to enhance consumers trust in the certified products (18). Consumers can access the “TAP website” (http://taft.coa.gov.tw/) to trace the farmers’ production records for the agricultural products with the TGAP label (shown in Figure 1B). Till the end of Dec in 2013, the TAP-certificated production area is 993 hectares of vegetables, 945 hectares of fruit trees, 1,518 hectares of cereal crops and specialties, 2,841 hectares of rice, 231 hectares of organic rice, 23 hectares of organic vegetables and fruit, 6.8 hectares of organic cereal crops and specialties. The gross value of production has reached a total at NT$ 2.522 billions (32) (Table 2) and the numbers keep increasing.

 

 Fig. 1. (B)The TAP label

 

 

Table 2. The production area certificated with TAP in Taiwan from 2007 to 2013.

 

Organic agriculture label

Organic agriculture is a production management system that emphasizes water and soil resources conservation and ecological harmony. It is based on the principles of sustainable utilization of nature resources. Synthetic chemicals are prohibited. Since 2007, the “Agricultural Production and Certification Act” has started to implement in Taiwan and has also started to apply to organic agricultural products and their processed products. The certified products are labeled with the CAS Label adding the word of ORGANIC for consumers to recognize (6,9,26,37) (Figure 1C). The certification represents that the production, processing, packaging, transportation, and sales all comply with the regulations of organic farming and the certified products are free of chemical fertilizers, chemical pesticides, and food additives.

 

 Fig. 1. (C) CAS organic label

 

According to the statistics of Agriculture and Food Agency, COA, the current certified area for organic production is 5,821 hectares and covers 0.7% of the agricultural land area in Taiwan. The certified area increased 1.47 times compared with that (2,356 hectares) in the end of December, 2008. However, it is relatively low compared to Italy (9.1%), Spain (6.4%), and Germany (6.2%). The main organic crops are vegetables (36%), rice (30%), fruit trees (15%), tea (8%), and others (11%). The goal set for our organic agricultural area is 15,000 hectares in 2020.

CAS Taiwan premium agricultural products

Since 1989, Taiwan has started to promote the certification system of CAS (Certified Agricultural Standards) Taiwan Premium Agricultural Products. CAS is the symbol for the highest quality of the domestic agricultural products and their processed products in Taiwan. The applicants need to meet the following qualification requirements: (1) A factory (farm), farmer group or business entity established or registered in accordance with related regulations, (2) factory (farm) sanitation management and the sanitation and packaging of products in accordance with related regulations, (3) a factory (farm) and its products meet the certification criteria required by the central competent authority. Taiwan Premium Agricultural Products Development Institute is the current certification agency authorized by COA and is entitled to issue the CAS labels to the applicants. Currently, there are a total of 16 main CAS certified categories including meat, frozen foods, fruit and vegetable juices, quality rice, preserved fruit and vegetables, ready-to-serve meals, refrigerated foods, fresh edible mushrooms, fermented foods, snack foods, egg products, fresh-cut fruit and vegetables, aquaculture, forestry products, dairy, and feathers. 

The CAS label emphasizes the qualification of software and hardware facilities, and the quality and sanitation of agricultural products. Its features using mainly locally produced raw materials, meeting hygiene and safety requirements, national quality standards, and label regulations. To ensure consumers’ rights, the CAS label has been regulated under the “Agricultural Production and Certification Act”. The “regulations for good agricultural products certification” and the “regulations for agricultural product labeling” have further reinforced the certification management and the product label audit (20).

Inspection and management for safe agricultural products

To improve the quality of domestic agricultural products and to provide safe foods for consumers, our governments regularly inspect the residual pesticides on fruit and vegetables, tea, rice, etc. at both production and distributing sites. In 2013, there are a total of 7,901 vegetables and fruit (3,483 of vegetables and 4,417 of fruit) which were examined for pesticide residue using chemical analyses. The rate of samples that passed the examination are 92.4% for vegetables and 93.6% for fruit (Table 3-4), respectively, and all the unqualified products were banned from marketing. At the end of August in 2014, there were 5,410 samples of vegetables and fruit inspected and 5,199 samples (96.1%) passed the examination. According to regulations, the products that fail to pass the test should be destroyed or postpone their harvest. Relevant government agencies conduct follow-up education and investigate violating cases according to the law. Furthermore, the COA helps local farmers’ associations, unions, and fruit and vegetable markets analyze the residue of some toxic pesticides by a quick biochemical method to preliminarily ensure the safety of agricultural products. In 2013, there are a total of 566,006 tests, and the passing rate was 99.1%. Through safety inspection and management, we ensure safe agricultural products and therefore effectively protect consumers’ health.

 

Table 3. Random inspection of pesticide residues in pre-marketing vegetables at production and distributing sites from January to December, 2013.

 

 

Table 4. Random inspection of pesticide residues on pre-marketing fruit at production and distributing sites from January to December, 2013.a,b

a According to the most recent data, the rate of fruit and vegetables that passed the pesticide residue inspection at both production and distributing sites has increased to >96%.

b Unqualified produces were banned from marketing and subjected to investigation.

 

 

DEVELOPMENT AND APPLICATION OF INTEGRATED PEST MANAGEMENT TECHNIQUES

Services of pest diagnosis and pest monitoring and alert system

The hot and humid weather in Taiwan and the rapid climate change in recent years have caused the fluctuation of primary and secondary pests in agricultural systems. Growth in international trade has also brought higher risk of the invasion, colonization, and dispersal of new pests, which pose serious threats to crop production. By integration and application of monitoring and diagnosis techniques developed by agricultural and academic research institutes, the Bureau of Animal and Plant Health Inspection and Quarantine (hereafter referred to as the “BAPHIQ”) has established a national system for the diagnosis, identification, notification, and early warning of crop pests. The BAPHIQ collaborates with different institutes to conduct periodic monitoring of important pests in various crops. The monitoring data and pest status information are promptly delivered to farmers and relevant plant protection authorities to assist the development of pest management strategies, which help prevent the outbreak of plant epidemics.

To strengthen technical services of pest diagnosis and control, since 1985, “Crop Pest Diagnostic Service Stations” have been established in some universities and almost all agricultural research institutes and District Agricultural and Extension Stations (DARESs) around Taiwan. These stations provide free diagnosis and identification service and advices on pest control. Farmers can send the samples to the service stations for diagnosis. If needed, the researchers also conduct on-site investigation and diagnosis in the field. There are currently 26 “Crop Pest Diagnostic Service Stations” operating in different areas in Taiwan. The service station in Kaohsiung DARES had 8,209 diagnostic cases from January 2007 to December 2013. Statistics shows that 54.4% of the diagnostic cases (4,469 cases) were about fruit trees, and 22.5% of the cases (1,855 cases) were about vegetables, gourds, and fruit vegetables. Fewer cases were related to flowers, ornamental crops, and forest trees. In most cases, pathogens and insect pests were identified as the causative agents. Fewer cases were determined to be caused by physiological disorders (35)

The “Plant Pests Monitoring System” established in 1997 integrated the monitoring, surveillance, investigation, and reporting of plant pests in Taiwan. With internet connection, the plant pests monitoring work was modernized and computerized. After its establishment in 1998, the BAPHIQ started to collaborate with agricultural research institutes and DARESs, plant protection-related departments in universities, county/city governments, and bodies corporate, to conduct detection survey, active monitoring, pest notification, and early warning. In 2001, the BAPHIQ further established the “Plant Pests Notification System” which served as a nationwide information network for the diagnostic services, active monitoring, and reporting of plant pests. The system has made the communication of pest information more systemic and efficient (35) (Figure 2) and all the DARESs play critical roles in the operation of the system.

 

Fig. 2. The network was established in Taiwan to conduct active monitoring and alert of pests on major crops to prevent the outbreak of plant epidemics. 

 

Field sanitation and soil management

The development and educational outreach of pest management techniques are fundamental solutions to the dependence on agricultural chemicals. Besides the rational use of pesticides, farmers can implement good cultural practices and field sanitation measures to alleviate pest problems. These include the maintenance of field environment with enough sunlight and ventilation and clean-up of plant residues (wilted branches, fallen leaves and fruit) so that the inoculum in the field can be greatly reduced. For example, the implementation of field sanitation in papaya and guava orchards greatly reduced the infestation of fruit by the pathogens of anthracnose, Phytophthora blight, black spot (Phyllosticta rot), guava scab, and oriental fruit fly. Sod cultivation is another important technique for soil management and pest control in orchards. Our results showed that sod cultivation helped maintain soil moisture, avoid the dispersal of soil-borne pathogens by rain splash, improve soil permeability, increase organic materials in the soil, lower soil temperature, prevent the nymphosis of some insect pests in the soil, and protect natural enemies. Farmers who adopted these techniques have benefited from efficient and effective pest control and also significantly reduced the use of chemical pesticides (38,39).

Breeding for pest resistance

The use of resistance cultivars to control crop pests is the most direct and effective non-pesticide pest management strategy (27). Breeding for pest resistance usually takes a lot of time and effort. In Taiwan, breeding for disease and insect resistance has been a long-term goal of agricultural institutes, DARESs, and some private seed companies. For example, in the production of asparagus bean, Fusarium wilt caused by Fusarium oxysporum f. sp. tracheiphilum is a key limiting factor. Since there is currently no fungicide available for disease control, resistance breeding becomes a good and feasible strategy. To identify genetic resource for disease resistance, Kaohsiung DARES evaluated the resistance performance of previously collected Asparagus bean germplasm in disease nursery fields. Thirteen lines showing high resistance to Fusarium wilt were selected as rootstocks, and the scions of a mainstream susceptible variety “San chr ching pi” were grafted onto the rootstocks. By investigating the quality, yield, and disease incidence of the grafted lines, the effect of grafting on disease control can be determined. Our results based on several compatible scion/stock combinations showed that grafting has no adverse effect on taste and appearance. Compared to the susceptible variety (no grafting) which had an average disease incidence of 86.7%, the use of the highest resistant rootstock showed an average disease incidence of as low as 4.4% and a 2.3-fold increase in yield, suggesting the feasibility of applying grafting technique for controlling Fusarium wilt of asparagus bean. Kaohsiung DARES also works on the breeding of resistance against powdery mildew on muskmelon. Six highly resistant lines with good horticultural characteristics have been selected. The denomination, release, and popularization of these new resistant varieties will greatly reduce the application of fungicides in the field.

Development and application of non-pesticide agents

Due to increasing public awareness of environmental issues, the development and application of non-pesticide agents have become an important trend. After many years of efforts, the plant protection researchers in Taiwan have developed various types of non-pesticide techniques, targeting different pests with distinct characteristics. These techniques have been tested and validated to work well in pest control. The techniques have been transferred to farmers for application and therefore significantly reduce the use of chemical pesticides.

Phytophthora blight is a destructive fungal disease of a wide range of fruit trees, vegetables, and flowers. In Taiwan, the rainy and humid conditions are favorable for the formation and dissemination of the sporangia and zoospores of the pathogen, leading to a high risk of the outbreak and rapid spread of the epidemics (29). Mixture of phosphorous acid and potassium hydroxide (H3PO3+ KOH) can be used to effectively control the Oomycetes pathogens. Farmers can dissolve an equal amount of commercialized phosphorous acid (industrial grade H3PO3, 95-99%) and potassium hydroxide (KOH, 95%) in water then 1:1000 diluted solution of the mixture is used for foliar spraying and 1:200 diluted solution for soil drenching. The mode of action is to activate defense mechanisms in host plants. Several important diseases caused by Oomycetes pathogens, such as downy mildew, Peronophythora downy blight, and Albugo white blister, can be prevented by using the technique. Phosphorous acid is also a disease control material approved for use in organic farming (1,8,27). With efforts on extension and outreach, phosphorous acid has been commonly known and widely used by farmers.

In regard to the control of powdery mildew, although some fungicides have been approved to be used for this disease, our long-term trials showed that several non-pesticide agents were even more effective than the chemical fungicides. For example, cucumber is one of the crops of continuous-harvest type, and therefore the overdoses of pesticide residues have been a major concern of consumers.

Problems have arisen from time to time. Kaohsiung DARES selected several plant protection agents with no MRL (maximum residue limit) requirement and tested their efficacy on the control of powdery mildew of cucumber in multiple field trials across many years. These safe agents include carbonate, phosphate, mineral oil, copper agents, sulfur agents, agriculturally used antibiotics, potassium bicarbonate (KHCO3), narrow range oil, Polyoxins,  and netralized phosphorous acid , etc. All of these safe and less toxic agents have been waived for MRL requirement by the Ministry of Health and Welfare. According to the data of field trials, their effectiveness on the control of powdery mildew was not lower than the chemical pesticides in field trials (Table 5-7). For organic farming, the use of narrow range oil (200X) mixed with neutralized phosphoric acid (800X) in autumn and winter can effectively control downy mildew, powdery mildew, aphids, and some other small insects until the end of harvest. The research and application of these safe agents profoundly improved safety of fruit and vegetables especially for continuously-harvested crops.

 

Table 5. Control of powdery mildew on cucumber by using safe materials (1)

a The disease severity is 0% before treatment. Each experiment was conducted with 3 replicates.

 

 

 

Table 6. Control of powdery mildew on cucumber by using safe materials (2)

a Each experiment was conducted with 3 replicates.

 

Table 7. Application of Bacillus amyloliquefaciens PMB01 to control bacterial wilt caused by Ralstonia solanacearum.a

a Experiment was conducted with randomized complete block design (RCBD), each treatment was 120 plants with 3 replicates. BaPMB01 broth with 200 ~ 300ml of 107cfu / ml was drenched around the base of each tested plant. The disease severity is 2% ~3% before treatment. The same letters in the same column followed by the same letters were not significantly different according to LSD (p = 0.05) analysis.

* The treatment “ Blank” was culture medium only.

 

Biological control

Beneficial microorganisms have been widely applied for disease management on crop production. Using Streptomyces saraceticus KH400, Kaohsiung DARES has developed disease-suppressive growing substrate which is effective in controlling damping-off disease in vegetable seedlings (caused by Rhizoctonia solani). Streptomyces, belonging to Gram-positive bacteria, are the most frequently used beneficial microorganisms for disease control (27). The antibiotics and lytic enzymes (such as chitinases and celluloses) secreted by Streptomyces spp. are harmful to soil-borne pathogens and parasitic nematodes. The beneficial bacteria are prevalent in native soil and can be activated by shrimp and crab shell powder. Upon induction by chitin-containing materials, Streptomyces spp. propagate, produce enzymes, and therefore inhibit diseases and parasitic nematodes.

Kaohsiung DARES has also developed effective biocontrol techniques against the ‘incurable crop diseases’ such as bacterial wilt and Fusarium wilt, using an indigenous strain (PMB01) of Bacillus amyloliquefaciens as the biocontrol agent. Bacillus amyloliquefaciens is a Gram-positive bacterium which shares similar morphological and functional characteristics with B. subtilis. It is known that B. amyloliquefaciens can produce many extracellular lytic enzymes (such as celluloses, proteases, lipases, and amylases) and antibiotics (such as iturin A, fengycin, and surfactin), and has great potential in crop disease control (11,25). The causal agent of bacterial wilt, Ralstonia solanacearum, has a very wide host range, including over 200 host species and Solanaceae plants such as tomatoes, potatoes, eggplants, and peppers are the most seriously affected crops. R. solanacearum can survive in soil for more than 10 years and causes devastating crop diseases in the tropics, subtropics, and some temperate areas with humid and hot summers.

On the other hand, Fusarium wilt is a soil-borne disease caused by different forma specialis (f.sp.) of the fungal pathogen Fusarium oxysporum. It is considered a key limiting factor in the cultivation of beans and cucrbits. It infects plants by direct penetration of the root tips or cortex and the hyphae grow upwards in the vascular system, resulting in the death of infected plants. There used to be no effective control measures for both bacterial wilt and Fusarium wilt. After many trials in greenhouses and fields, Kaohsiung DARES found that B. amyloliquefaciens PMB01 reduced the severity of bacterial wilt and Fusarium wilt by over 70%(12). Severity scores of bacterial wilt disease in tomato plants treated with and without PMB01 were 43.2% and 8.2%, respectively. Significant effect was also found for controlling Fusarium wilt of cucurbits. In cucumber, while the average severity of Fusarium wilt in non-treated plots was 47.7%, the average severity in PMB01-drenched plots was reduced to 11.6% (Table 9).

 

Table 8. Application of Bacillus amyloliquefaciens PMB01 to control Fusarium wilt caused by Fusarium oxysporum f.sp. cucumerinum.a

a Experiment was conducted with randomized complete block design (RCBD) with 3 replicates as described in Table 7. The numbers in the same column followed by the same letters were not significantly different according to LSD (p = 0.05) analysis.

*The treatment “ Blank” was culture medium only.

 

Table 9. Application of Bacillus amyloliquefaciens PMB01 to control Fusarium wilt caused by Fusarium oxysporum f.sp. tracheiphilum.a

a Experiments was performed with randomized complete block design (RCBD), 3 replicates as described in Table 7. The numbers in the same column followed by the same letters were not significantly different according to LSD (p = 0.05) analyzing.

*The treatment “ Blank” was culture medium only.

 

In asparagus bean, the severity scores of Fusarium wilt in non-treated and PMB01-drenched plots were 29.4% and 3.2%, respectively. Based on acute oral toxicity and pathogenicity study and acute pulmonary toxicity and pathogenicity study, B. amyloliquefaciens PMB01 is non-toxic to mammals. The abovementioned biological control technology has transferred to the industry and Kaohsiung DARES keeps working on preparing the data required for biopesticide registration. After completing the registration process, the commercialized product can be used by farmers in the near future.

In insect pest management, Kaohsiung DARES also developed the technique of using Aschersonia sp in biological control of whiteflies. Silverleaf whitefly (Bemisia argentifolii; Homoptera: Aleyrodidae) was identified for the first time in Taiwan in 1990. Since its invasion, the pest was found to infest and damage more and more crop species, including many vegetables, fruit, and flowers. Although many insecticides were approved and applied for its control, cases of whitefly resistance to insecticides have been reported worldwide. The evolution of insecticide resistance has resulted in increased use of chemicals. Aschersonia sp. is an entomopathogenic fungus which can infect silverleaf whitefly. Aiming to use Aschersonia sp. for biological control, Kaohsiung DARES started the collection of entomopathogenic fungal strains from several years ago. With continuous efforts to optimize the culturing and large-scale fermentation conditions, we hope that Aschersonia sp. can be widely used for field application in the near future.

Broad-sense biological control includes the use of antagonistic plants. In recent years, this method has been widely applied in the control of crop diseases caused by nematodes. Kaohsiung DARES evaluated the effect of using a natural antagonistic plant, African marigold, for controlling root-knot nematode in guava. The results showed that growing African marigold around the rhizosphere of guava plants significantly reduced the density of infective second-stage juveniles of root-knot nematode (the density was reduced from 128 to 32 juveniles per 100g soil) (Figure 3). It has been confirmed that planting African marigold around the rhizosphere of host plants is an effective and eco-friendly way for controlling soil-inhabiting nematodes. With efforts on extension and outreach, growing African marigold is now a commonly used biocontrol measures for guava farmers.

Fig. 3. African marigold cultivation is effective in the control of root-knot nematode disease. The population of 2nd instar larvae was decreased from 128/100g soil to 32 /100g soil after 18 months.

 

Natural enemies: parasitoids and predatory insects

Beneficial microorganisms such as Bacillus thuringiensis, Streptomyces spp. and natural enemies, including parasitoids and predatory insects, have been commonly used as biological control agents. (10). Among these, Bacillus thuringiensis has been widely used for a long time in Taiwan. Utilization of natural enemies for pest control is advantageous for reducing pesticide use. In Taiwan, Miaoli DARES has a biological control station that focuses on developing mass rearing technology and application of natural enemies of insects. There are also some scholars in other DARESs and academies working on natural enemies related to research and extension.

In a wide variety of parasitoids, the utilization of an artificially mass-reared indigenous parasitic wasp, Trichogramma ostriniae, is a common method to control Asia corn borers (Ostrinia furnacalis) in Taiwan. (17) Predatory insects covering 18 orders and nearly 200 families are also popular in Insecta. Important and common predators include dragonflies, mantises, ladybirds, epomis, hover flies, green lacewings, stink bugs, robber flies, wasps, ants, mites, etc.

In the application of predatory insects, take Mallada basalis and Cantheconidea furcellata for example, a green lacewing, Mallada basalis (Neuroptera:Chrysopidae), is a predator of spider mites, aphids, whiteflies, scales, psyllids, and many Lepidoptera and Coleoptera larva or eggs. The experiments conducted at KDARES showed that releasing M. basalis larva significantly reduced the population of aphids and spider mites in both of cucumber and asparagus bean greenhouses. Cantheconidea furcellata sting bug (Hemiptera:Entatomidae) is a common predator for Lepidoptera larva and various insects in the order Coleoptera, Hemiptera, and Homoptera. The experimental results showed that releasing Cantheconidea furcellata nymph or imago significantly reduced the population of Diaphania indica, Maruca testulalis, and Euproctis taiwana in both of cucumber and vegetable soybean fields. Since the abovementioned predators can be mass-reared in a cost-effective manner, DARESs have been working on education and extension in mass production technologies and application models for farmers.

Sex pheromones and attractants

Insect sex pheromones have been widely used for pest monitoring and control in the field for over 20 years in Taiwan. To date, more than 10 insect sex pheromones are identified and synthesized. Using sex pheromones as a non-pesticide agent is environmentally friendly and can be concurrently applied to the field with other pest control methods, therefore it is one of the non-pesticide agents widely adopted by growers in Taiwan (24).

Insect sex pheromones have high bioactivity and specificity and remain attractive for long period of time even at a low dosage (21), therefore they are widely used for pest monitoring for timing insecticide sprays resulting in the reduction of insecticide use in the field (21). In Taiwan, insect species that are monitored using this technique include: Spodoptera litura (tobacco cutworm and armyworm), Spodoptera exigua (beet armyworm), Helicoverpa armigera (tomato fruit worm, corn earworm, cotton bollworm, and false tobacco moth), Plutella xylostella; (diamond-black moth), Chilo suppressalis (Asiatic rice borer), Adoxophyes sp., Homona magnanima (tea leaf-roller and tea tortrix), Cylas formicarius (sweet potato weevil), Eucosma notanthes (carambola fruit borer), and Lymantria xylina (casaurina tussock moth) (19,21,22).

Besides pest monitoring, insect sex pheromone traps can also be used to attract male insects in the field to reduce the population of the next generation. In Taiwan, the insect pests that sex pheromones are used for monitoring or mass trapping include: Spodoptera litura (tobacco cutworm and armyworm), Spodoptera exigua (beet armyworm), Helicoverpa armigera (tomato fruitworm, corn earworm, cotton bollworm, and false tobacco moth), Plutella xylostella, (diamond-black moth), Adoxophyes sp., Homona magnanima Diaknoff (tea leaf-roller and tea tortrix), Cylas formicarius (sweetpotato weevil), and Lymantria xylina (Casaurina tussock moth) (19,21,22). When using sex pheromone traps, insect behavior and the density of traps must be taken into account. In addition, the distance between 2 different sex pheromone traps should be greater to avoid interference with each other (21).

Oriental fruit fly (Bactrocera dorsalis, OFF) which can infest 117 different plants is one of the major limiting factors for fruit production in Taiwan(3). Even though the government and growers have put lots of efforts in the control of OFF, the population density of the insect is still high in fruit-producing areas in Taiwan as suitable environmental conditions and available host plants grown perennially favor its survival and infestation. Methyl eugenol, an attractant of male Oriental fruit flies, added with proper insecticide is used to trap and kill male OFF, and therefore reduces the population of offspring (2,3). The long-efficacy trap for OFF invented by Kaohsiung KDARES consisting of 90% methyl eugenol and 5% Naled (EC) remains effective over six months in the field. It is normally deployed at a density of 4~6traps per hectare. The use of long-efficacy traps accompanied with field sanitation, fruit bagging and protective facilities provides the best pest control and yield benefit and drastically reduce the use of insecticides as well. It has been widely adopted by fruit growers in Taiwan (13,14).

Economical and safe use of pesticides

Pesticides are essential materials for plant protection. However, inappropriate and excessive use of pesticides can cause harm to humans, agricultural products, and the environment. To ensure quantity and quality of agricultural crops as well as environmental sustainability, the academies and government institutes in Taiwan especially emphasize the research and extension of economical and safe use of pesticides. The main points for farmers’ education include (1) Choosing the right pesticides: Only use approved pesticides, diagnose problems correctly, apply proper pesticides rationally, and alternate pesticides with different modes of action to prevent or postpone pest resistance to pesticides, (2) Proper Timing: Apply pesticides when pests in its early stages and use the minimum amount of pesticides to control pests, (3) Proper amount: Use application rates, intervals, and concentrations recommended by the Plant Protection Manual to avoid ineffectiveness or residual pesticides problems, (4) Identify pests-infested sites and apply pesticides on the main targeted sites for best protection, (5) Complying with safe duration between pesticide application and harvest and use safe materials the duration of which is either short or waived when crops are near harvest.

Taking Kaohsiung DARES as an example, in order to promote economical and safe use of pesticides, we not only provide free pest diagnostic and technical services, but also intensively monitor important crop pests and deliver the pest status information to farmers through multiple communication channels. Furthermore, our research focuses on developing safe pest control materials, evaluating efficacy of approved pesticides, screening safe and effective pesticides that can prevent multiple pests. Through education course, workshops and demonstration in the fields, farmers learn how to reduce the variety, amount, and application frequency of pesticides.

Farmers education and training

In recent years, the agricultural labor force is shrinking in the rural areas of Taiwan because young people are moving away from farming while the aging farmers are increasing. To ensure agricultural sustainability, our government especially focuses on the establishment of lifelong learning programs for farmers, including regular technical workshops and field demonstrations which emphasize crop health management technology, application for Ji-Yuan-Pu safe fruit and vegetables (GAP) label, and pesticide-safety related knowledge. A variety of training programs have also been designed to meet specific needs. To date, the COA has held the “The Farmers’ Academy Program”, a systematic education and training program mainly conducted by DARESs for the general public, particularly for young farmers. The courses include crop health management technology, good agricultural practices, and agricultural business management aiming to cultivate young farmers and strengthen agricultural competitiveness (30,36).

To take Kaohsiung DARES for example, 13 classes for the Farmers Academy Program and more than 60 workshops related to crop health management and agricultural production and marketing technology were held in 2013. We also compile the approved pesticides in the Plant Protection Manual and posted it on our official website for farmers’ reference.

The hard copies are directly given to farmers in the workshops. Technical brochures of crop health management for important crops, agricultural newsletters, and agricultural journals containing abundant useful information about rational fertilization and health crop management are periodically published, delivered to farmers, and posted on the official website and on Facebook. We also provide farmers and consumers with updated information and consultation services via telephone, fax, and internet. By developing digital learning materials and making research/extension reports and other resources freely accessible online, we have greatly increased the efficiency of information dissemination and promoted the implementation of good agricultural practices for production of safe fruit and vegetables in Taiwan.

CONCLUSION

Located in the subtropical region, Taiwan’s temperature and humid climate makes it susceptible to the spread of pests and hence the common use of chemical pesticides. How to strike a balance between crop production, safety of agricultural products and environmental conservation has long been a serious challenge for governing authorities in agriculture. For a long time, administrative and technical governing agencies have endeavored to build a system to promote healthy agricultural practices while at the same time, engage in research and promotion. Some of these practices include building a more comprehensive Agro-Pesticide Act, finding best practices and validation for agriculture, and research and development in pest prevention. The aim is to develop technologies and to promote the safe use and better management of chemical pesticides to balance the safety of agricultural products and environmental conservation. After years of hard work, chemical pesticide abuse has been significantly improved, and there is better safety of agricultural products.

Taiwan’s production area spans across approximately 80 hectares, with a total of 779,375 farm households. On average, each household holds 1.1 hectares of farmland. Farmers on average are 63 years old, highlighting the issue of an ageing farmer population in Taiwan. Against this backdrop, governing authorities of agriculture have been proactive in establishing agricultural production and marketing groups to facilitate the education and training of farmers. Currently, the number of agricultural production and marketing groups has reached 6,271, with around 2,000 groups GAP-certified. However, most farmers are still not members of agriculture-related organizations, making communication relatively difficult. This creates a gap in the education and promotion of healthy agriculture practice. Therefore, improving the organization and education of farmers to practice healthy agriculture is an important work that needs to be completed in the future.

GAP, TAP, and CAS ORGANIC systems are the three agricultural product certification systems which are currently in place. However, the relatively complexity generates difficulties or confusion for farmers in applying the certification systems. Inspection and management measures of certification systems still need to be better developed, and this has resulted in certified products bearing residual pesticide higher than standards or even fraudulent use of the GAP labels. In this light, it is necessary to conduct a through review and to design an integrated and more efficient system to be better adopted by farmers. At the same time, an agricultural and food traceability system that is aligned with international practice is also needed. In terms of the technical development, Taiwan needs to further improve R&D in bio-agents and safe crop-protection products and to facilitate the producers to obtain permits for legal sale of such products so that chemical pesticides can be partially replaced. Furthermore, Taiwan also needs to reduce the use of chemical pesticides and fertilizers and to gradually develop its organic farming. It is hoped that through these practices, Taiwan will become a nontoxic agricultural island in the future.

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