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
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.
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 pesti-
cides 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;
Keywords: Biological control, biopesidus, IPM, pesticide, plantprotection, resistant varietive
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•
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
Fig. 1.
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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).
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). It has dropped from 15.4%
in 1979 to 3.7% in 1994. The summarized results of
Working system used to prevent pesticide residue
problems on vegetables and fruits
Fig. 2.
The percentage of samples violating the tolerance law before
and after the establishment of working stations
Table 1. Summarized results of residue analysis during the fiscal year 1997
residue analysis during the fiscal year 1997 (from
July 1996 to June 1997) are given in Table 1 (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 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.
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Fig. 3.
Method for multi­residue determination (Taiwan)
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 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.
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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 antiresistance 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
Table 2. Risk assessment of pesticide exposure of litchi growers
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 resis-
tance 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
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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
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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
Table 3. Natural enemies used for pest control in Taiwan
been tested for the control of insect pests (Table 2).
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 shortterm 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 special-
ists 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.
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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 monocrotophos. 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 concen-
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trated 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 broadspectrum 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 develop-
ment 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
9
Fig. 4.
System for monitoring plant pests in Taiwan
Table 4. Pests under constant monitoring
10
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., monitor-
ing).
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. 5). 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 5).
It is hoped that by the year 2000, a sound
IPM program will be developed as a result of this
monitoring system.
11
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