4.2. PLANT PROTECTION METHODS
Various methods are applied to protect cultural
plants from diseases, pests and weeds. The methods are agrotechnical,
biological, chemical, physical-mechanical and others.
Agrotechnical method is cultivation of
agricultural crops under optimal conditions that induce plants to grow and
develop rapidly, stimulate natural resistance of plants towards pathogens,
hinder spread of harmful organisms in crop fields and decrease their harmful
effect on yield and its quality.
Agrotechnical plant protection measures
cover right crop rotation, stubble cleaning and autumn ploughing, optimal time
of sowing, seed sowing depth, seed rate, balanced fertilisation, and choice of
varieties that are more resistant to pathogens.
Biological method is the use of natural
enemies, i.e. entomophages or parasitic insects, ticks, nematode, bacteria,
fungi or viruses to stop or to limit spread of harmful organisms and their
harmful effect. Biological method includes care of natural enemies in
agrocenosis, which are harmful for pests, artificial reproduction and use for
plant protection.
Physical-mechanical method is collection
of pests by hand or by special equipment and their elimination, annihilation of
pests by heating, cooling or drying of grains, thermal dressing of seeds,
removal of damaged plants from crop fields (e.g. removal of potatoes infected by
viruses or black leg) and eradication of weeds by mechanical means.
Chemical method is the use of chemical preparations, i.e. chemical compounds
having one or some active matters, called pesticides in general, for
annihilation of plant diseases, pests and weeds, for limitation of their amount
and harm, and for regulation of plant growth.
Integrated plant protection is the complex use of all plant protection methods
valuable for a particular case giving preference to non-chemical plant
protection measures.
Integrated plant protection measures
allow to reduce use of pesticides and at the same time to reduce expenditure for
plant protection operations and possible danger of pests to environment. When
applying the integrated plant protection method, not only various plant
protection measures are used, but also measures that are less harmful towards
environment are chosen, e.g. selective preparations that decompose quickly and
eradicate only particular species of harmful organisms. Chemical preparations
are applied only when real danger for the amount and quality of yield exists
(i.e. when the amount of harmful organisms exceeds economic threshold of harm).
Chemical plant protection method, use of pesticides, has the potential of doing
harm on environment and health. Therefore, this area of farmers' activity is
strictly regulated and continuously controlled.
4.1
Every activity of Lithuanian citizens with respect to plant protection from
diseases, pests and weeds with help of chemical or biological plant protection
measures has to be performed in compliance with Republic of Lithuania Plant
Protection Law and Rules on Use of Plant Protection Measures.
Republic of Lithuania. Law on Plant
Protection (Lithuanian). 1998 06 04 No. VIII-769
Rules on Use of Plant Protection Means
(Lithuanian). - V., 1999. - P.29.
All land users are obliged to follow this requirement in the territory of
Lithuanian Republic. Both mentioned documents are prepared according to the
requirements of corresponding documents of European Union (Council
Directive 91/414 EEC, Commission Directive 93/71 EEC)
especially in the fields of human health
protection and reduction of hazardous pollution.
4.3. DANGERS IN PESTICIDES USE
Chemicals (pesticides) for the
protection of plants from diseases, pests and weeds may be not only poisonous
for humans and fauna, but they may also pollute water bodies, ground water and
soil with hazardous pollutants. Some of the pesticides have phytotoxic
properties and they may injure vegetation, which grows besides treated fields.
Pesticides are dangerous for humans not only during application, but they may
get into our food by the way of treated plants. Stable, slow decomposing
pesticides are especially dangerous for environment. They may accumulate in one
of the food chains of agrocenosis and going through the chains they may
penetrate into human organism through food and water.
4.2
Abundant use of pesticides for plant protection from diseases, pests and weeds
should be avoided. Alternative methods for plant protection should be used
instead of them.
Reduction of pesticides application is possible only when there is a real
economic need, switching to new, more effective technologies, improving
pesticides spraying equipment and technologies, changing old preparative to new
ones more effectives that are to be used in smaller doses.
4.4. REDUCTION OF PESTICIDES
NEED BY ALTERNATIVE MEASURES
4.3
Reduction of expenditure for plant protection and in the same time reduction
of environmental pollution should be achieved by selection of plant varieties,
which choke weeds and are more resistant to diseases and pests. Not the most
fertile but more resistant for harmful organisms crop varieties should be
selected.
There are possibilities to choose plant
varieties for garden and kitchen garden that are more resistant to pathogens.
There are available potato varieties resistant to nematodes, less disease
susceptible cereal varieties. National Plant Varieties Analysis Centre publishes
list of plant varieties most favourable to grow in Lithuania and indicates
species resistance to the most harmful pathogens every year.
4.4
Plant resistance to harmful organisms should be increased growing it under
better conditions especially during germination when plants are most
vulnerable to diseases, pests and weed competition.
Good soil preparation for sowing, optimal sowing
terms, proper depth of seed sowing, seed rate and good seed quality offer
possibilities for plant to establish and grow quickly shortening the period when
plants are attacked intensively by harmful organisms (Fig.4.2). The newest
research data on this subject can be found in annually published book of the
Lithuanian Institute of Agriculture “Recommendations for Agriculture” and
other publications. Recomendation for
Soil Cultivation//LIA. - Akademija (Lithuanian). - 1999. -P.58
Fig. 4.2. Early sowing of spring crop increases
yield, reduces harm made by pests and need of pesticides
4.5
In order to increase natural plant resistance for plant diseases and pests
they should be fertilised supplying with all needed nutrients.
Fertilisation with only nitrogen fertilisers
diminishes plant resistance to diseases and pests usually.
4.6
Crop varieties in crop rotation should be laid out in such a way that crop
seeded in every field would have as less as possible common diseases and pests
remained in soil with a plantation grown in the same field before.
Properly organised crop rotation decreases the
amount of soil-borne diseases, harm of some weeds and pests stayed for the
winter in soil and on the same time need of pesticides. It is very important
that plants of the same or related species vulnerable to the same harmful
organisms would come back to the same field after as long as possible time
period. During planning of plant location in crop rotation, proper choice of
plants growing in neighbourhood is very important for plant protection.
4.7
One should avoid growing such crops in neighbourhood if pests or diseases that
survived the winter or propagated in early spring in one crop can easily
spread to neighbouring crop field.
Pea and bean weevil attacks peas and
beans early if to seed them next to clover field. Leaf diseases from winter
barley spread very early to closely planted spring barley. Late blight appearing
first of all in the early potatoes spreads very fast in neighbouring fields of
late potatoes. Therefore, pesticides have to be urgently used for plant
protection from pests and diseases that spread early and abundantly. Meanwhile,
pesticides are to be applied later or use of pesticides could be avoided at all
in the fields located further from source of infection.
4.8
There should be established 10 m a no-spray boundary zone towards plants that
have plenty of beneficial insects and territories of vulnerable environment,
i.e. water bodies, karst sinkholes, preserves, etc., if plans of land use or
designs of the territory do not determine higher requirements.
The scale of herbicide use may be reduced if
using mechanical measures for weeding, like cleaning of stubble, deep autumn
ploughing and intensive cultivation. It is very important that there would
remain no empty, set aside areas in the zones of intensive agriculture, because
weeds ripen and spread seeds in such areas. If such areas exist they have to be
mowed before ripening of the weed seeds.
4.5. WHEN PESTICIDES MUST BE
USED
of the opportunities to reduce the scale of
pesticides application is the right decision about need of pesticides in every
crop field. According to current order valid in Lithuania regional plant
protection and quarantine posts of National Plant Protection Agency and
Agricultural Advisory Service provide information about possible time of
appearance of plant diseases and pests and suggest pesticides. But this
information is only tentative.
4.9
Land user himself should make an estimate of a real need for plant protection
measures when he has evaluated situation in every field. Farmers without
agronomic education should take such decisions after consultation with
specialists.
The most right decision about feasibility of the
pesticides use may be taken using special computer programmes, which
systematically utilise data collected from automatic meteorological stations and
information about phytosanitary situation in a particular crop field provided by
the specialists. These programmes allow choosing not only the optimal time for
application of pesticides, but also the lowest feasible pesticides rate and
sometimes the programme even suggests not using pesticides at all. Application
of such programmes has already started in Lithuania.
Taking decision about feasibility of pesticides use in separate crop field, the
economic thresholds of harm of harmful organisms have to be considered in every
case.
Information about economic thresholds of harm can be found in prognosis on
abundance of plant pests and diseases published by the National Plant Protection
Agency every year, in recommendations prepared by Lithuanian Institute of
Agriculture and other publications.
4.10
Pesticides should be used only when the amount of harmful organisms in crop
field has reached thresholds of harm determined by scientific investigations.
4.6. TECHNOLOGIES OF PESTICIDES
USE
Danger of different pesticides for humans and
nature depends a lot on chemical as well as on physical characteristics of the
pesticides. If there is a possibility to choose, then one should avoid using
those pesticides that are very toxic, persistent and harmful for aquatic fauna
and beneficial insects.
4.11
It is forbidden to use those pesticides in Lithuania that are not registered
and written in the Lists of Professional or Individual Use of Plant Protection
Measures, regulating pesticides use in the country.
List of Professional Use of Plant
Protection Measures (Lithuanian). - V., 1999. - P. 72.
List of Individual Use of Plant
Protection Measures (Lithuanian). - V., 1999. - P.16.
The most dangerous for humans are the
preparations in a form of powder. They sprinkle during weighing and preparation
of solutions. More secure preparations are suspensions, emulsions and
water-soluble granular.
The less dangerous way of pesticides use from an environmental point of view is
seed dressing with fungicides, insecticides and sometimes even with mixture of
nutrients and germination stimulants. Seed dressing is usually performed in
special room using work safety measures. Seed dressing requires small quantity
of preparations and they are spread directly on seeds. Preparations used for
dressing are very effective – they protect plants from harmful organisms
during germination and establishment. If the seeds of beets, rapes and some of
the vegetables are treated in this way, the crop fields do not need to be
sprayed against pests and diseases attacking the sprouts.
Much more harmful from environmental point of view is application of pesticides
in the way of spraying. Using pesticides in this way only a part of preparations
fall on treated plants. Other part falls on soil or they are carried out by air
masses to neighbouring fields or water bodies. Because of that quality of
spraying of crop fields with plant protection products is an important index of
good agriculture.
4.12
Farmers' sprayers have to undergo a regular test and certification in order to
ensure their efficient function. Sprinklers of a sprayer should be of equal
discharge regulated to spray the needed amount of solution. Pesticides should
be sprayed on crop field evenly applying the determined amount of solution and
preparation. As big as possible part of pesticides should fall on treated
plants and there should be left any non-sprayed or double-sprayed bands of
crop field.
The type of sprayer, its preparation for operation, skills of operator and the
quality of performed operations determine the quality of spraying (Fig. 4.3 and
Fig. 4.4).
Spraying efficiency and work quality are
determined also by meteorological conditions, i.e. temperature, relative air
humidity and especially wind speed (Fig. 4.6)
| Fig. 4.6. Crop fields may be sprayed
while wind speed is less than 4 m/sec. |
 |
The meteorological conditions have to meet requirements for
the sprayer, which is available. If weather is windy, crop fields should be
sprayed in the early morning or late evening when the wind falls. Then
probability that the preparation will be carried over the boundary of field is
smaller and risk for beneficial insects is lower. It is not allowed to spray
crop fields before rain or straight after rain (Fig. 4.7).
 |
Fig. 4.7. Do not spray crop fields
before rain |
4.7.SAFE WORK AND ENVIRONMENTAL
PROTECTION USING PESTICIDES
All preparations used for plant
protection are biologically active substances, more or less dangerous for humans
and natural environment.
4.14
Every operation with plant protection preparations has to be carried out
exactly following work safety and environmental requirements that are
described in detail in the “Rules on Use of Plant Protection Means”. The
most important requirements are the following:
- Only trained persons who have
acknowledged with the characteristics of preparations and requirements of
work safety may work with pesticides.
- Only healthy persons who have
health examination certificates can work with pesticides.
- It is necessary to use personal
safety precautions and to follow rules of hygiene during operations.
- Use only correct, calibrated and
checked prior to operations machines and equipment for spraying of
pesticides on crop fields and for dressing of seeds. New sprayers must be
certified and sprayers in use must be checked by technical inspection.
- It is forbidden to apply
pesticides on blooming plants. The blooming plants could be sprayed only
in exception, following special recommendations.
Rules on Use of Plant Protection Means
(Lithuanian). -V., 1999. -P.29.
Badly stored pesticides are very
dangerous for humans and environment. A special store that meets sanitary
requirements should be assigned for the storage of pesticides in large farms.
Small farmers should not pile up big reserves of pesticides, but they should
keep minimal quantities of the pesticides correctly packed in their original
packages and store them in purposely arranged locked cupboard or box in store
place of machinery.
4.15
In large as well as in small farm it is necessary to have a record book of
pesticides and to register all operations related to the use of pesticides.
Rules on Use of Plant Protection Means
(Lithuanian). -V., 1999. -P.29.
Not only application of preparations for seed
dressing and spraying of crop fields should be registered in the record book of
plant protection measures but also date of purchasing of preparation, price and
other useful information should be written in a separate section (Annex 4.1).
Exact record of purchase and use of plant protection products not only
facilitates organisation of plant protection operations and their economical
assessment, but also allows correction of mishandling and liquidation of
consequences.
Personal precaution means are required for work with pesticides, they have to be
used and properly taken care of.
