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Scope of Plant Protection - a Practical Point of View
Gwo-Chen Li
Taiwan Agricultural Chemicals and Toxic
Substances Research Institute
11 Kung-ming Road, Wufeng, Taichung Hsien,
Taiwan, ROC, 1999-05-01

Abstract

This bulletin describes plant protection in Taiwan, systems of farmer education and the monitoring of produce for pesticide residues. It describes the results of experiments to test the exposure of farmers to chemical pesticides during application, and the toxicity which resulted. It also discusses various tests of pesticide resistance among pest populations, using GPS and GIS. Resistance management and the breeding of pest resistant crops are also discussed.

Abstracts in Other Languages: 中文(991), 日本語(1169), 한국어(1072)

Introduction

Because of rapid population growth, it is expected that in the next three decades we must produce as much food as we have produced since the beginning of history. Maximizing the crop yield on a limited area of arable land is an absolute necessity.

It is estimated that weeds, plant diseases, and pre- and post-harvest pests currently destroy 45% of the potential yield of world crops. There are many methods of controlling diseases and insect pests, such as the application of pesticides, breeding and cultivation of resistant varieties, biological control etc. This paper will discuss the new technologies being incorporated into these control methods and the objectives of integrated pest management.

Pesticide Application

According to the recent survey on the production and utilization of pesticides carried out in 1997 by FFTC and APO, the use of pesticides still remains one of the most important control measures for plant protection. It is expected that this situation will continue in future.

It is the responsibility of the plant protection specialist, not only to ensure the effective use of pesticides, but also to ensure the safe use of pesticides in order to protect farmers' health, the safety of agricultural products, and preserve the environment. There are two main approaches to these issues. One is to obtain enough knowledge from the data requirement of pesticide registration under the Agricultural Chemicals Regulation Law. The other is the education and guidance of farmers and dealers, to encourage safe and proper handling and use of pesticides.

Knowledge Obtained from Pesticide Registration

Each country has its own data requirements for the registration of pesticides. The sale and distribution of any pesticide without such registration is usually prohibited. Registration is given only after all necessary data on the pesticide's effectiveness, physical and chemical properties, toxicity, residue tolerance and impact to the environment are evaluated under local environmental conditions, and the results found to be satisfactory.

Some valuable information can be obtained from these data. The information will help the plant protection specialist to design guidelines for field application. The information includes:

  • The physical and chemical properties which will help us to ensure the quality of the pesticide;
  • The toxicity to mammals, to ensure the safety of a pesticide;
  • The avian toxicity, and toxicity to aquatic organisms and to natural enemies of pests, to minimize the impact of pesticide on the environment;
  • The distribution and degradation in water and in soil, to reduce potential environmental pollution;
  • Residues on crops and in the human/livestock metabolism to limit over-application in the field;
  • The efficacy and phytotoxicity, to ensure the effectiveness of pest control.

The integration of this information forms the guidelines for field application. In Taiwan, these guidelines and summarized information can be seen on a computer in the form of a database. This makes it easier for the plant protection specialist to find the appropriate chemical for pest control.

Education and Guidance for Farmers

Education and guidance for farmers, so that they follow the guidelines, are an important way of ensuring the proper use of chemicals. Training courses will increase farmers' knowledge, but sometimes do not solve farmers' on-site problems.

An inspection and education program has been enforced by the government of Taiwan ( Fig. 1(1341)). Fifteen stations, located in different parts of Taiwan, are responsible for the analysis of pesticide residues on vegetables and fruits, and also for the education of farmers based on the results they obtain. For each vegetable sample, 77 commonly used pesticides are analyzed; and for each fruit sample, 24 - 42 pesticides are analyzed, depending on the type of fruit.

If the results of long-term and wide-area surveys indicate that pesticide residues violate the tolerance level, a follow-up investigation is undertaken to understand the possible causes, such as the cultural practices used and the method of pesticide application. The development of pest resistance to the pesticides used is also assessed. When the problem has been identified, farmer education follows.

Approximately 10,000 samples are analyzed annually. Since the establishment of the inspection-education program, the number of vegetable samples with high levels of residues has been greatly reduced ( Fig. 2(1294)). It has dropped from 15.4% in 1979 to 3.7% in 1994. The summarized results of residue analysis during the fiscal year 1997 (from July 1996 to June 1997) are given in Table 1(1163) (Residue Control Department 1998).

Multi-Residue Method Used by the Residue Control Program

Modern agricultural production depends heavily on the careful use of pesticides. The inspection - education program established in Taiwan has succeeded in educating farmers. Quick screening residue analysis methods are necessary to support such a program. The analytical method selected should give both qualitative and quantitative results. It is necessary to know what kind of pesticide residues are found and at what levels, before the educational program for farmers is initiated. The multi-residue method meets these requirements. A total of the 89 most commonly used pesticides were selected in developing a multi-residue analysis method for selected vegetables and fruits in Taiwan. This method is used for the support of the inspection - education program. Fig. 3(1196) gives a flow chart which shows how this method is carried out.

The multi-residue method used in California is able to detect 204 different pesticides, with a detection limit of 0.02 - 0.2 ppm. The method is the same as that used in Taiwan. The average number of samples analyzed by a single trained technician is about 15 - 20/day. The Canadian government is using a similar method for the screening of pesticide residues in crop samples.

Risk Assessment of Farmers' Exposure to Pesticides

Farmers working in litchi orchards near Wufeng, in the central part of Taiwan, were monitored for pesticide exposure. Alpha-cellulose pads were placed outside their regular working clothes to measure the exposure of their skin. Air was pumped through portable sampling tubes to measure the inhalation exposure when pesticides were applied by airblast sprayers. The percentage of the toxic doses in an hour (PTDPH) represented the acute level of exposure. The margin of safety (MOS) represented the chronic toxicity of exposure. The PTDPH was calculated by dividing the sum of skin exposure/10 and the inhalation exposure within one hour, with the LD50 of the pesticide investigated. MOS was calculated by dividing the "no observed effect" level with the sum of skin exposure/10 and inhalation exposure. The farmer is at risk if the MOS value of a pesticide is less than 100. Table 2(1190) gives the results of risk assessment of pesticide exposure of four litchi growers.

Data obtained from similar experiments on the growers of peanut, mango, cabbage, tea, grape, and citrus is now being analyzed in order to develop a prediction system. Hopefully, this system can be used to predict the safety of pesticides to farmers under recommended rates of application, before the pesticide is registered.

Pest Resistance to Pesticides

Pesticide treatments are likely to remain the most important component in crop protection for the foreseeable future. Their continuing use and increasing adoption in integrated pest management will be challenged, however, by the growing problem of resistance in pests, pathogens and weed populations. It has been estimated that in 1983, 504 species of insects and mites were resistant to insecticides (Ghiorgiou 1983) and over 100 species of fungi were resistant to fungicides (Ghiorgiou ibid), while by 1991, 81 species of weeds were resistant to herbicide (LeBaron 1991).

This problem can be avoided or minimized by using chemicals in combination with biological and physical controls in integrated resistance management programs. Future needs include improvements in the diagnosis, monitoring and prediction of resistance. Continuing research, training and extension are also required to protect future pesticide inputs.

It has been realized for some time that the ability to accurately predict the build-up of resistance to pesticides would be valuable. This information could be used, in particular, to formulate anti-resistance strategies for the commercial application of new materials. Attempts, though, to develop prediction systems applicable to field situations have not generally been successful.

Most mathematical models for predicting an increase in resistant forms of a pest are difficult to validate, and remain largely theoretical. Denholm et al. (1990) have emphasized the need for good experimental work to allow models to be adequately tested during development, and they advocate an integrated approach. With increasing availability of data and with the aid of computers, it is possible to produce more realistic resistance development models.

Predicting the risk of resistance to a particular pesticide under specific conditions is becoming easier. Prediction combines the mode of action of the chemical; the degree of pesticide use; the fecundity and ease of dispersal of the target organism, and ease of resistance development in controlled environment studies (Brent 1987). A good understanding of pest-pesticide-crop interaction is also required.

Simple techniques for determining the frequency of resistance, and the subsequent monitoring of any resistance build-up in pest populations, would be very useful as the basis for more rational resistance management. Knowing the background resistance in past populations before chemical selection is applied would be particularly helpful, together with information on regional differences.

For these reasons a great deal of research is being carried out on diagnostic techniques, in order to develop biochemical, immunological and bioassay tests. Bent et al. (1990) points out that such systems will respond to known resistance factors, but new resistances may not be so readily detected, and that this is important. Furthermore, the rapid development of resistance to certain fungicides may not be detected at an early enough stage to avoid control failure (Brent et al. ibid.).

As fewer "new chemistry" pesticides become available on the market for pest control, there is increasing pressure on existing materials used for crop protection. Where high-risk situations are identified, appropriate integrated resistance management strategies must be promoted through advice to, and training of, farmers. The economics of production of particular crops can sometimes encourage over-reliance on cheap pesticides, or conversely can encourage lower application rates. With increasing knowledge of the development of pesticide resistance, it is becoming increasingly possible to reduce control problems. Although it seems likely that pesticide resistance will continue to arise, the increasing adoption of IPM, (integrated pest management), together with more rational plant protection, should ensure that the impact will be less than in previous years.

A "Geographic Information System" (GIS) is a computer software system with which spatial information may be captured, stored, analyzed, displayed and retrieved. GIS has been used for detecting pest infestation and early stages of insect outbreaks on a regional or national level. GIS also makes it possible to quantify and evaluate relationships among pest distribution, climatic variables, topographic attributes, crop mortality and economic loss. With the help of GIS, farmers and extension services will be able to decide an acceptable response before pests have time to cause much damage. The Global Positioning System (GPS) provides full-time and rapid ground coordinates within a meter of accuracy, using signals from earth-orbiting satellites. GPS has been used to record latitude-longitude coordinate data of infested localities. Precise location data obtained from GPS fit nicely into GIS and, combined with other multiple data sets, allow a more accurate monitoring of pest dynamics.

Kuo (1998) studied the sensitivity of the mango anthracnose pathogen, Colletotrichum gloeosporioides, to the fungicide prochloraz in Taiwan. A monitoring program was established, using bioassay techniques combined with GIS and GPS. Forty-three mango orchards covering 4000 ha were surveyed. Global positioning system (GPS) was used to locate and retrieve the sites sampled. Of the locations surveyed, 23 sites were randomly selected. Twenty were orchards with a history of high prochloraz applications. The other three were orchards that were known to have 12 - 16 prochloraz applications each cropping season. A total of 545 isolates were surveyed. The results showed that the IC50s fell in a range between 0.009 - 0.14mg/L. No significant resistance was found, even in mango orchards with the highest frequency of prochloraz applications. One orchard located in the Yujing area, and known to have had a high frequency of prochloraz applications, showed on IC50s of between 0.02 - 0.14 mg/L. The average IC50 is 0.077 mg/L, which is about five times higher than the baseline population (0.015 mg/L).

The results indicate that a slight dose-response shift toward higher IC50 seems to occur over time. A further survey, using 10 mg/L as the threshold dosage, was conducted. The results of 1375 isolates obtained throughout this region showed no isolate could survive at this dosage. Since the registered dosage for field use is 83.3 mg/L, we concluded that there was no sign of prochloraz resistance in mango plantations 13 years after the registration of prochloraz in Taiwan.

This technique will be used to detect and follow the development of resistance in some common crops to newly registered pesticides.

Biological Control

Biological control is the use of living organisms as pest control agents. Many natural enemies have been used for the control of insect pests in history. The use of biological control in the early part of this century was dealt a severe blow by the advent of synthetic organic pesticides in the 1950s. Compared to these new products, natural enemies were seen as inefficient and unreliable. Mounting problems with pesticide resistance and environmental pollution led scientists in the 1970s to develop the concept of integrated pest management, or IPM. This was an attempt to free pest management from the domination of chemical control by adding other technologies, among them is the biological control.

Recently, many scientists have begun to acknowledge the potential value of biological control in IPM. However, relatively little thought has been given to what kinds of biological control we need to develop, or how we will truly integrate them with other control measures. More importantly, almost 40 years of preoccupation with chemical pesticides have left most scientists, industrialists, policy makers and farmers poorly informed about the role of natural enemies. Before biological control can be developed and implemented, it will be necessary to re-establish an understanding of the impact of natural enemies on crops. This is essential to the development of IPM. If we know which natural enemies are contributing the most to pest depression at critical times, we can select them for conservation or augmentation.

Conservation involves modifying cropping practices to improve the action of biological control agents. These practices may include the destruction of crop residues, cultivation, and the pattern and timing of planting. Increasing crop diversity improves pest control by enhancing the action of natural enemies.

In Taiwan, biological control has been practiced for many years. Many natural enemies have been tested for the control of insect pests ( Table 2(1190)). Studies on the conservation of these enemies in the field have been carried out. The experience of this recent effort is that the more we study the problem, the more complex it becomes.

Establishing a population of natural enemies in the open field seems to be impossible because of pesticide applications and the lack of diversity of crops. Further research is needed on how to modify patterns of pesticide use and select cropping systems, so as to enhance the action of natural enemies. In the future, efforts at conservation will be based on an understanding of important natural enemies in a crop, and targeted at improving their action, rather than increasing natural diversity and abundance in general.

On some occasions, the conservation of natural enemies is not sufficient to increase their useful contribution to pest management. This may be due to the lack of resources in modern monoculture, or the lack of continuity in resources such as seasonal crops. In such instances, methods are available for the augmentation of natural enemies, or the addition of natural enemies to crops for a short-term effect over, or within, a single season.

This approach also depends on an understanding of the action of natural enemies in crops, so that this can be predicted, and the right number of enemies introduced at the right time. It is another example of how ecological research will improve the cost efficiency and success of biological control in the decades to come.

Improvements in the mass production of insects, and possibly in artificial diets for parasitoids and predators, may also allow new species of insect natural enemies to be augmented commercially in future.

In the meantime, plant protection specialists in Taiwan suggest that biological control measures should be used only in agriculture under structures (greenhouses or net houses), where environmental conditions and pesticide applications are easily to be manipulated.

Natural Enemies of Planthoppers and Leafhoppers

Recently, the amount of data about the toxicity of pesticides to potential enemies has grown rapidly in Taiwan. Special attention has been paid to natural enemies of the brown planthopper and green rice leafhopper. These include the mirid bug ( Cyrtorhinus lividipennis Renter) and wolf spider ( Lycosa pseudoannulata Boesenberg and Stand). In terms of its capacity to control these rice insect pests while at the same time protecting their natural enemies, MTMC showed the highest selectivity, followed by undan and carbaryl. These are useful data for the implementation of IPM of rice pests (Ku and Wang 1981).

Kao and Tzeng (1989a), using the thin film method, studied the effect of pesticide residues on the time it took adult Trichogramma chilonis Ishii to kill cornborer. Among eighteen technical-grade pesticides tested, all proved highly toxic to adults of T. chilonis, while LT50 values were far less than control at 0 day post-spray. Although the LT50 values were less than non-treated, they increased over time. Ten days after spraying, MTMC, MPMC, mancozeb and demeton-S-methyl, had a LT50 > 5 hrs. At 21 days after spraying, MIPC, methamidophos and deltamethrin had an LT50 > 5 hours, while 35 days after spraying it was chlorpyrifos, EPN, endosulfan and acephate.

The effect of insecticide residues on the parasitoid wasps Trichogramma chilonis and T. ostriniae was also studied in the laboratory. Tests were carried out at 0-, 1-, 2-, 3-, 7-, and 21-days after spraying insecticides on corn leaves, using recommended rates of nine insecticides under field conditions. The insecticides tested were acephate, carbofuran, chlorpyrifos, deltamethrin, endosulfan, EPN, methamidophos, methomyl, and monocro-tophos. The parasitism rates of T. chilonis and T. ostriniae on cornborer eggs were greatly reduced by insecticide residues under field conditions. Of the insecticides tested, carbofuran was the most toxic (Kao and Tseng 1990).

Natural Enemies of Diamondback Moth

Similar work has been carried out on Apanteles plutellae, a natural enemy of the diamondback moth ( Plutella xylostella). Seventeen insecticides commonly used to control diamondback moth in Taiwan were evaluated. Carbofuran, cartap, mevinphos, quinalphos, methomyl, methamidophos and deltamethrin (Decis, E.C., 28 ppm) were found harmful (mortality > 99%) to adults of A. plutellae, while the remaining 10 insecticides were found harmless (mortality < 50%). The toxic ranking of these 10 insecticides to the parasitism of A. plutellae were in the following order: Fenvalerate (sumicidin W.P., 40 ppm) > acephate (orthene S.P., 500 ppm) > B.T. (San 415 ISC, 5.33 IU/mg) > CME-134 (nomolt F.P., 33.9 ppm) > permethrin (kestrel E.C., 50 ppm) > chlorflurazon (atabron E.C., 10 ppm) > acephate (orthene E.C., 312.5 ppm) > B.T. (dipel W.P., 16 IU/mg) > fenvalerate (sumicidin E.C., 33.3 ppm) > CME = 134 (diaract E.C., 25 ppm). The insecticides which were considered to reduce the parasitism by A. plutellae on the larvae of P. xylostella were fenvalerate (sumicidin W.P., 40 ppm), acephate (Orthene S.P., 500 ppm) and BT (San 415 ISC, 5.33 IU/mg) but all were classified as only slightly harmful. These results show that further selectivity can benefit the IPM of P. xylostella (9).

Biological Disease Control

Biological control is also an attractive alternative strategy for the control of crop diseases. It provides practices compatible with the goal of a sustainable agricultural system. It is a strategy for reducing disease incidence or severity by direct or indirect manipulation of microorganisms. The principle may be eradication or protection, depending on the specific target disease to be controlled. In recent years, plant pathologists in Taiwan have concentrated on the selection of highly virulent isolates of antagonistic microorganisms for the control of plant diseases. The microorganisms currently, studied include Trichoderma spp., Bacillus spp., Giocladium spp., Streptomyces spp. and Penicillium spp. These microorganisms are often applied in soil amendments, or mixed with organic fertilizer. In a few cases, foliar applications are used.

Development of Biopesticides for Plant Protection

Biopesticides are the most rapidly growing technology of argumentation, indeed of biological control in general. They rely on the action of pathogens of insects and plant diseases which, although highly virulent, do not spread through crops. This makes them appropriate for mass production and targeted release.

Biopesticides have many advantages. They are friendly to the environment, and fit well into IPM programs. In some cases, they provide long-term control. They should be easier to register and less expensive than chemical pesticides. Considering all the hidden cost of chemical agents, the public and farmers generally favor their use. Such agents should also be less resistant, should be easily mass produced, and may be the only available control strategy as chemical agents lose their efficacy.

A number of biopesticide products were developed in the 1970s, but these failed to survive in the marketplace. There were two reasons for their lack of success. First, the market was not easy to penetrate. IPM had not taken off as anticipated, and few niches were available where a biopesticide would not face competition from an established, conventional product. More important, insufficient work had been done on ensuring the field efficacy of these products, and they proved variable in their efficacy. This was largely because of the influence of the environment on the survival of formulations.

Recently, in the 1990s, we have seen a new surge of interest in biopesticides, and much greater prospects of success. Exciting new markets have been created by the reduction in use of broad-spectrum pesticides in many agricultural areas where the IPM concept has been implemented. Furthermore, companies are reluctant to register chemical pesticides for certain uses, because of their low profitability relative to their high cost of registration and environmental exposure. This has boosted the development of biopesticides.

The other impetus of biopesticide development comes from the advance of modern technology such as fermentation technology, formulation technology, and biotechnology. These not only increase the field efficacy of biopesticides, but also improve their persistence in their environment and the shelf life. The most important point is that modern technology reduces the cost of mass production of biopesticides.

In Taiwan, it has become government policy to speed up the development of biopesticides. Scientists form multidisciplinary teams and work together to develop these products. Microorganisms in which they are interested include Bacillus thurigiensis, Bacillus subtilis and Trichoderma spp..

Use of Resistant Varieties

Varietal resistance to diseases and insects plays a major role in pest management programs. Major advances have been made in developing cultivars with multiple resistance to diseases and insects. In the past, genetic improvement for pest resistance was achieved mainly through the application of classical Mendelian genetics and conventional plant breeding methods. Plant breeders relied upon crop germplasm, including wild species and induced mutants, as sources of resistance. However, recent advances in cellular and molecular genetics have led to the development of new tools for producing resistant cultivars.

It is now possible to introduce novel genes against pests or pathogens from unrelated plants, animals, or microorganisms into desired crops. Tissue culture has helped broaden the gene pool for resistance through the production of wide range of hybrids among distantly related species and genera, and through selection of useful mutants in vitro. Pest resistance genes, when tagged with isozyme markers, can be moved more rapidly from one cultivar to another. Nucleic acid probes allow the detection of pathogens in breeding materials and aid in the selection process. The resistant cultivar thus developed will form the backbone of pest management programs in the future.

In Taiwan, the breeding of horticultural crops resistant to insect pests has been emphasized in order to minimize the use of pesticides on vegetables and fruits. Current studies focus on the source of resistance, mechanisms and inheritance, interaction of resistance with crop morphology, biochemical analysis of resistance, and various breeding methods.

Papaya ( Carica papava L.,) is one of the most widely grown and economically valuable fruits of the tropics and subtropics. A destructive disease caused by papaya ringspot virus (PRV) is a major obstacle to wide-scale planting of this fruit. PRV has been reported as a major limiting factor for growing papaya in many countries. The virus was first recorded in southern Taiwan in 1975. Within four years, the virus had destroyed most of the papaya production in commercial orchards along the west coast of the island. The total yield of papaya dropped from 41,595 mt in 1974 to 18,950 mt in 1977. During the same period, the wholesale price increased sixfold, from NT$*3.67/kg to NT$20.70/kg. (In 1999, 1US$ = 33 NT$).

Wang et al. (1994) constructed the coat protein (CP) of a local mosaic strain of papaya ringspot virus (PRV YK) in the Ti-vector for generation of transgenic papaya resistant to PRV infection. The CP gene with a GUS marker as the PRV leader sequence was transferred to embryogenic tissues derived from immature embryos of papaya via Agrobactrium - mediated transformation that assisted by carborundum-wounding treatment. The plants of CP-transgenic lines were established by micropropagation. A total of 45 transgenic lines were tested for their resistance to PRV YK infection by mechanical inoculation. Among these, 16 lines showed some degree of resistance to infection, but there was no significant delay in development of severe symptoms. Ten lines were highly resistant, with a 4 - 7 week delay in the development of symptoms. Two lines did not show any symptoms over a test period of four months. Negative results in ELISA detection and bioassays indicated that the replication of the challenge virus was suppressed in these two lines.

The ten highly resistant lines and the two immune lines were selected for further evaluation against different strains of PRV under greenhouse conditions. The results revealed that the transgenic lines with a higher degree of resistance to the Taiwan strain YK also had a higher degree of resistance to the Hawaii strain (HA), the Thailand strain (TH), and the Mexico strain (MX). The two lines which were immune to YK were also immune to HA, TH and MX strains.

Results of field trials over eighteen months indicated that the CP transgenic lines have great potential for control of PRSV in Taiwan. Open-field trials in different locations of Taiwan will proceed after more tests under isolated conditions. It is expected that the transgenic lines will be deregulated for commercialization after the field experiments are completed. Based on the greenhouse evaluation, it is believed that these transgenic lines carrying the coat protein of the Taiwan PRV vs. PRSV strain can be used for control of PRV vs. PRSV in other areas.

Information Technology and Pest Management

To establish an integrated pest management program, the following basic guidelines should be followed. We must:

  • Understand the biology of the crop or resource, especially in the context of how it is regulated by the surrounding ecosystem.
  • Identify the key pests, know their biology, recognize the kind of damage they inflict, and initiate studies on their economic status.
  • Consider, and identify as far as possible, the key environmental factors that impinge (favorably or unfavorably) upon pest and potential pest species in the ecosystem.
  • Consider concepts, methods and materials that, individually and in concert, will help to permanently suppress or restrain pest and potential pest species.
  • Structure the program so that it will have the flexibility to adjust to change, i.e., avoid rigidity in a program which cannot be adjusted to variations from field to field, area to area or year to year.
  • Anticipate unforeseen developments, expect setbacks, move with caution.
  • Above all, be constantly aware of the complexity of the resource ecosystem and the changes that can occur within it.
  • Seek the weak links in the armor of the key pest species, and direct control practices as narrowly as possible at these weak links. Avoid broad impact on the resource ecosystem.
  • Whenever possible, consider and develop methods, which preserve, complement and augment the biotic and physical mortality factors that characterize the ecosystem.
  • Whenever possible, attempt to diversify the ecosystem.
  • Insist that technical surveillance for programs must be available (i.e., monitoring).

These guidelines are rooted in ecological thinking. Information gathering limits the progress of IPM programs. For the past 20 years, IPM has been slow to move from theory to practice. This failure might be caused by the lack of sufficient information to construct an IPM program. With the help of modern information technology, it is possible to speed up the information gathering process and the implementation of IPM.

Since September 1997, the Taiwan Provincial Government has worked on setting up a "Monitoring system for plant pests" ( Fig. 4(1070)). The system started to function in August 1998. An Information Center, Diagnosis Center, and eight district surveillance and monitoring centers, play a major role in the system. Twenty specialists from different research institutes, and ten working staff for the Information Center, have been recruited. The Information Center is responsible for the collection and analysis of information, and formulates the pest control strategies. The Diagnosis Center is responsible for the identification of plant diseases and insect pests. Hopefully, a museum of plant diseases and insect pests found in Taiwan will be set up as a result of this system.

District surveillance and monitoring centers are responsible for monitoring insect pests and plant diseases in their territories. District centers will dispatch specialists to undertake the field monitoring, with the help of contracted farmers. Each specialist will handle three to eight townships. In each county, a few well-trained farmers will carry out routine monitoring work under contract. A total of about 320 townships will be covered by the system.

All the components in the system communicate with each other by computer. Different levels of training classes are held for specialists and farmers. The plant protection data bank built up by the specialists in the Information Center provides information that can be easily accessed. Data obtained from the field research is also very rapidly transferred to the Center.

A total of about 74 insect pests and plant diseases will be under surveillance. The pests are classified into four categories i.e. quarantine pests, epidemic pests, endemic pests and pests which need further study. Of these 74 pests, 16 are being constantly monitored ( Table 4(1154)).

It is hoped that by the year 2000, a sound IPM program will be developed as a result of this monitoring system.

References

  • Brent, K.J. 1987. Fungicide resistance in crops - its practical significance and management. In: Rational Pesticide Use, K.J. Brent, and R.J. Atkin, (Eds.). Cambridge University Press, Cambridge, United Kingdom, pp. 137-151.
  • Brent, K.J., D.W. Hollomon, M.W. Shaw. 1990. Predicting the evolution of fungicide resistance. In: Managing Resistance to Agrochemicals: From Fundamental Research to Practical Strategies, M.B. Green, H.M. LeBaron, and W.K. Moberg (Eds.). American Chemical Society Series 421, Washington, D.C., U.S.A., pp. 303-319.
  • Denholm, I., M. Rowland, A.W. Famham and R.M. Sawicki. 1990. Laboratory evaluation and empirical monitoring of resistance - counting strategies. In: Managing Resistance to Agrochemicals: From Fundamental Research to Practical Strategies, M.B. Green, H.M. LeBaron and W.K. Moberg, (Eds.). American Chemical Society Series 421, Washington, D.C., U.S.A., pp. 92-104.
  • Georghiou, G.P. 1983. In: Pest Resistance to Pesticides, G.P. Georgious and T. Saito (Eds.). Plenum, New York, U.S.A., P. 14.
  • Georghiou, G.P. 1990. Over view of insecticide resistance. In: Managing Resistance to Agrochemicals: From Fundamental Research to Practical Strategies, M.B. Green, H.M. LeBaron and W.K. Moberg (Eds.). American Chemical Society Series 421, Washington, D.C., U.S.A., pp. 18-41.
  • LeBaron, H.M. 1991. Distribution and seriousness of herbicide-resistant weed infestation worldwide. In: Herbicide Resistance in Weeds and Crops, J.C. Caseley, G.W. Cussons and R.K. Atkin (Eds.). Butterworth-Heinemann, Oxford, United Kingdom, pp. 27-45.
  • Kao, S.S. and C.C. Tzeng. 1989a. Effects of pesticide residues on lethal time of Trichogramma chilonis Ishii adults. Entomol. Bull., National Chung Hsing Univ. 21: 35-42. (In Chinese).
  • Kao, S.S. and C.C. Tzeng. 1989b. Effect of insecticide residues on parasitism of the egg parasitoids Trichogramma chilonis and T. ostriniae. Entomol. Bull. National Chung Hsing Univ. 21: 43-50.
  • Kao, S.S. and C.C. Tzeng. 1992. Toxicity of insecticides to Cotesia plutellae, a parasitoid of diamondback moth. In Diamondback moth and other crucifor pests; proceedings of the second international workshop, Tainan, Taiwan, 10-14 December. AVRDC. p. 287-297.
  • on Apanteles plutellae, a parasitoid of Plutella xylostella. J. Ecol. Entomol.
  • Ku, T.Y. and S.C. Wang. 1981. Resistance of the major rice insect pests with the effect of insecticide on the natural enemies and non-target animals. Phytopath. Entomol., (National Taiwan University) 8: 1-17.
  • Kuo, K.C. 1998. Sensitivity of mango anthracnose pathogen, Colletotrichum gloeosporioides, to the fungicide prochloraz in Taiwan. Proceedings, 7 th International Congress of Plant Pathology. 5,5,10.
  • Cheng, Y.H., J.S. Yang and S.D. Yeh. 1996. Efficient transformation ringspot virus mediated by Agrobacterium following liquid-phase wounding of embryo genetic tissues with carborundum. Plant Cell Reports 16: 127-132.
  • Wang, C.H., H.J. Bau, and S.D. Yeh. 1994. Comparison of the nuclear inclusion B protein and coat protein genes of five papaya ringspot virus strains distinct in geographic origin and pathogenicity. Phytopathology 84: 1205-1210.
  • Residue Control Department. 1998. Report on the Pesticide Residue Analysis in/on Vegetables and Fruits During the Fiscal Year of 1997. Residue Report, Residue Control Department, Taiwan Agricultural Chemicals Testing and Toxic Substances Research Institute (TACTRI).

Index of Images

Figure 1 Working System Used to Prevent Pesticide Residue Problems on Vegetables and Fruits

Figure 1 Working System Used to Prevent Pesticide Residue Problems on Vegetables and Fruits

Table 1 Summarized Results of Residue Analysis during the Fiscal Year 1997

Table 1 Summarized Results of Residue Analysis during the Fiscal Year 1997

Table 3 Natural Enemies Used for Pest Control in Taiwan

Table 3 Natural Enemies Used for Pest Control in Taiwan

Figure 2 The Percentage of Samples Violating the Tolerance Law before and after the Establishment of Working Stations

Figure 2 The Percentage of Samples Violating the Tolerance Law before and after the Establishment of Working Stations

Figure 3 Method for Multi-Residue Determination (Taiwan)

Figure 3 Method for Multi-Residue Determination (Taiwan)

Table 2 Risk Assessment of Pesticide Exposure of Litchi Growers

Table 2 Risk Assessment of Pesticide Exposure of Litchi Growers

Figure 4 System for Monitoring Plant Pests in Taiwan

Figure 4 System for Monitoring Plant Pests in Taiwan

Table 4 Pests under Constant Monitoring

Table 4 Pests under Constant Monitoring

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