Biopesticides and its use
What is Plant Protection?
A Good plant protection practice (GPPP) is the basic strategy in plant protection and means the application of plant protection measures that:
- are safe for humans, animals and the environment from a scientific point of view,
- have been recognized by the competent authorities as suitable, appropriate, and necessary in practice,
- are recommended by official extension services or recognized and qualified consultants, and
- are practised by skilled users.
The principles of good plant protection practice constitute a framework of action for those concerned with plant protection measures in agriculture, horticulture and forest trees. Together with the national law on the placing on the market and use of plant protection products, namely:
- Pesticides Control Act XI of 2001,
- the Plant Protection Products Regulations
The principles of good plant protection practice guarantee to the consumer safe plant production by means of established plant protection measures. Possible risks to man, animal and environment are at the same time reduced to a minimum.
GPPP is therefore a process of a wider concept known as Good Agricultural Practice. Good plant protection practice does not selectively concern solely the usage of plant protection products but all those other aspects that lead to plant protection.
General principles:
The following principles apply in general:
- Plant protection measures shall be carried out so as to fit the site, the crop, and the situation and the use of plant protection products shall be reduced to what is absolutely necessary.
- Proven cultural, biological and other non-chemical measures to reduce damage from pests and diseases shall be used as far as possible wherever practical and economically feasible.
- The aim shall be not to eliminate harmful organisms, but to reduce infestation so that there is no economic damage. There may be cases, however, which require zero tolerance for a pest organism.
- Growers shall use the diverse assistance of official and other extension services; look for advanced training and any other decision aids.
Principles of measures to prevent infestation by harmful organisms: The growers should consider the possibility of prevention of infestation by harmful organisms through choice of adequate cropping systems, crops and crop rotation.
Conservative tillage suitable for the site, the crop and the phytosanitary situation can help to reduce the use of chemical plant protection products, particularly herbicides. Tillage is mainly determined by soil properties, its humidity, previous crops, and the crop plant’s demands to its site. The danger of soil erosion by wind and water must be considered. Conservative methods of tillage require rather good tilth and are not feasible at certain periods of the year. Only the grower, who knows his site and has experience, can decide on the appropriate tilling method depending on the situation. The way of tillage depends on the demands of the crop and is often indispensable to control weeds.
Cultivars and origins which are resistant or have at least a certain tolerance of important site specific pest organisms should be considered especially in known cases of soil-borne diseases.
Hygienic measures in agriculture and horticulture have the aim to reduce the potential of harmful organisms and to prevent or delay as much as possible the first infection with harmful organisms. This is done by preventing the introduction and spread of harmful organisms, such as nematodes and virus diseases through seeds, planting stock, contaminated soil, substrates, propagation containers, tools or diseased plants.
The most important hygienic measure to be taken by the grower is to use healthy seed and planting material. This means regular purchase of certified seeds and planting stocks and confining replanting to seed and planting material from healthy and vigorous stocks.
If several growers share agricultural machinery, this must be carefully cleaned. Important hygienic measures in glasshouses and propagating centres are regular cleaning, steaming of substrates, disinfection of cultivation facilities if necessary, and clearing of weeds, crop residues and decayed plants. Newly imported plants should be quarantined for some time if necessary.
Principles of evaluation of infestation and/or damage that may be caused by pathogens, pests and weeds: Growers should not resort to calendar spraying; instead regular monitoring should be carried out on the crops to determine the degree of infestation before a decision is made on what method is used to control any possible harmful organism.
Growers can apply control threshold values for a number of harmful organisms. In any case this requires that the infestation in a field or crop be quantified by sampling. For some pests, there are also specific methods for estimating extent of infestation; such as yellow/blue sticky traps, pheromone traps, warning systems using weather data for late blight of potato.
The grower has to make his own decision about the control measure and he bears the sole responsibility for it. On the other hand he bears the risk of losses when necessary measures have not been taken. In assessing the need for a particular control measure, growers have to use their experience and observations from previous years, consider advice by official and other extension service, and use other extension aids if available.
In making a decision on what control measures to apply, growers should be aware of the availability of other official information included in informative leaflets, information by the meteorological office, grower meetings, radio broadcasts, training courses and laboratory/ extension office advice.
Principles of application of non-chemical plant protection measures: Non-chemical measures of plant protection can be very special methods, which are often expensive and difficult to handle. They must be adapted to the site and to the situation.
Biological methods, which have a selective effect and are environmentally friendly, are often very expensive, require adequate training prior to introduction and are practicable only for use under protected cropping.
Mechanical weeding techniques are examples of non-chemical plant protection measures in agriculture and horticulture.
Principles of correct and intended use of plant protection products: Authorized plant protection products, suitable equipment and competent users are the fundamental conditions for use of plant protection products. In principle, plant protection products must only be introduced, distributed or used if they are authorized in Malta after registration and authorization by the Department of Plant Health.
With the authorization, the Department of Plant Health, Ministry for Rural Affairs and the Environment, stipulates the use, conditions and instructions to protect man, animal; and the environment so that any requirement of correct and intended use of good plant protection practice becomes clear from the label. Plant Protection Products should only be used on listed crops approved for that product.
The operator has an obligation of particular care when handling, storing or disposing of plant protection products. Operators who misapply plant protection products, e.g. applications other than for their intended purpose, can be forbidden to use these products. Defective equipment should be put out of service.
Plant protection products are chosen after consideration of the target organism their efficacy and costs, the site, and the crop. The most suitable products for the specific circumstances should be chosen.
If various products are suitable for one intended use, the grower should prefer those, which are less toxic, spare beneficial organisms, e.g. harmless to bees, and not restricted by special use conditions. Selective products should be preferred to broad spectrum ones unless several pests occur simultaneously or are likely to occur. Selective Plant Protection Products are ecologically less damaging.
Using a product as a general precaution without prior ascertainment (as is calendar spraying) of the need of control is not good plant protection practice. Products which are most suitable for the crop and to control the pest in question must be used according to the situation with preference to opt for the lower indicated dosage rates. Site and weather conditions should be carefully noted to avoid drift of pesticide products. Measures to reduce the frequency and rate of application at the same time reduce the cost of crop protection and contribute to minimizing the general risk arising from use of plant protection products.
Treatments and dose rates should be adapted to the given conditions. The grower should be aware of the possibility of reducing the maximum indicated number of applications and application rates. This is carried out following careful monitoring of pest infestation, collection of other reliable information, including advice from official extension service and grower experience; all of which help in the decision making.
Resistant pest populations develop through selection pressure caused by repeated application of pesticides belonging to the same family. How often and how fast resistant populations develop depends on the active substance’s mode of action and on the harmful organism (its life cycle, feeding habits, natural spread and so on).
Appropriate strategies of resistance management, namely use of different families of active substances, combination of active substance and other chemicals e.g. mineral oil, shall be used to try and prevent development of resistance.
The use of plant protection products containing active substances with different modes of action during the vegetation period can be a suitable measure to prevent development of resistant pest populations. Whichever measures are to be taken should be clarified with official extension services, case by case.
Principles and instructions for correct and intended use of plant protection equipment: Plant protection products can be applied in various ways using various technologies depending on the purpose and field of use. It is known that the majority of plant protection products are applied by spraying using motorized back sprayer equipment and water as the carrier medium.
Only suitable and in good working order plant protection equipment should be used. During applications of Plant Protection Products, smoking, eating and drinking should not be permitted.
These principles must be followed when employing field sprayers:
- Spraying equipment serves the purpose of evenly depositing plant protection products on target areas in exact doses and with as little losses as possible. Possibly loss-reducing technology should be used (for example drift-reducing nozzles). The water rate application per hectare must be determined before starting operation. The water application rate depends on the walking speed of the operator, the growth stage of the crop and on the weather.
- When mixing the spray liquid, the instructions on the product label with regard to product application rates, miscibility and necessary precautions and measure of operator protection must be followed. For measuring and filling chemicals into the sprayer tank or into the chemical introduction bowl, only suitable calibrated measuring containers and appropriate methods reserved for that purpose must be used.
- Attention must be paid to the filling of sprayers. Tanks must not be over-filled above the indicated level and must not foam over. It must be ensured that no spray liquid can return when the tank is filled with water from a water pipe.
- Empty pesticide containers must be thoroughly rinsed. The wash water is added to the spray liquid. Empty pesticide containers must be perforated, crushed and safely disposed of in an appropriate site.
- To avoid having any spray liquid leftover at the end of treatment, the spray liquid consumption is to be estimated from the rate of application, and the size of the area to be treated. The number of tank fillings is calculated from the spray liquid consumption and the tank size. The last filling must be metered correctly or even so as to fall a bit short of the needed amount. The grower should consider the possibility of allocation of a small field patch that will remain untreated. Such field patch shall be used for the spraying of pesticide mix left over that will inevitably remain in the tank after every treatment.
- To achieve even horizontal distribution, the walking speed should be uniform and not more than 1km/h. In the case of tractor operated spraying, the driving speed should be 6km/h. With a higher speed distribution problems are growing more than proportionately.
- Spraying during strong wind spells; very hot temperatures or relatively low humidity under 30% Relative Humidity will entail high losses through drift and volatilization and should therefore be avoided.
- If objects neighboring the treatment area might be endangered, the current wind direction must be considered. When treating the nearest lengths along a body of water (for example a stream valley), in addition to following the label instructions, drift reducing measures, namely slowing down the speed, and applying coarser drops should be taken. The same measures should be taken when spraying in the vicinity of residential areas, gardens, amenity and sports grounds and tourist areas. If pesticide spray drifts to neighboring areas, in spite of all precautions, the user of these areas must be immediately contacted and informed. Special precautions such as waiting periods or a ban on consumption if necessary should be applied.
- Spraying equipment must be regularly calibrated and nozzles checked before every use.
- After finishing spraying, the spray residue in the tank is diluted by 1:10 with clear water and sprayed over the remaining untreated area. In the case of tractor-operated sprayers, the water should also be used to clean the tank from inside.
- Small residues, which have been repeatedly diluted, may be left in the tank and applied with a later spray if this is compatible with the product being used.
- The outside of the sprayer should be cleaned somewhere in the field that is treated.
- Sprayers should be carefully cleaned and maintained on a regular basis.
Principles of storage and other handling of plant protection products: Storage of plant protection products requires particular precautions to preclude dangers to man, animal and the environment. Storage and disposal of plant protection products by the user is often unavoidable and is subject to particular legal prescriptions. There are special legal regulations on that.
Storage of plant protection products should be limited to the necessary minimum in time and amount and is subject to a legal duty of particular care.
Common means of transport and traffic routes are used when plant protection products are transported from distribution centres to stores and from there to the fields. Therefore special precautions must be taken to prevent damage to containers and contamination of man, animal or the environment.
If an accident occurs and pesticides leak from transport containers, the Plant Health Department, Ministry for Rural Affairs and the Environment, and if necessary the distributor must be immediately informed.
The preparation of the spray mix and the handling of the concentration of plant protection products can cause dangers both to the user and to the environment and are a critical phase in the handling of these products. Special safety precautions must be taken to protect the user and the environment when preparing the spray liquid.
To avoid dangers, the safety precautions described in the user instructions in particular with regard to protecting skin absorption and respiratory organs must be followed when handling the concentration and preparing the spray mix. The operator bears full responsibility for observance of the safety precautions. Leakage and contamination during the preparation of the spray mix must be avoided by competent handling and appropriate wear of protective garment. Prepared spray mixes, pesticide residues, containers, and tools, which have not yet been cleaned, must not be left unattended to preclude risks to third persons. Contaminated containers and tools must be protected from rain. Appropriate hygiene at work helps to keep risks to the user as low as possible, for example washing gloves thoroughly before removing them.
Principles of verification of success and documentation of plant protection measures: Every plant protection measure should be followed by an inspection to see whether it was successful. This allows competent decision about further steps and gathering experience about the effect of plant protection measures in certain situations.
The success of plant protection measures should be verified by suitable means. Growers should inspect treated crops and assess infestation some time after treatment to verify the efficacy of a plant protection measure and its effect on the crop.
If the treatment was not sufficiently effective, it has to be carefully weighed what caused the loss in effectiveness or even damage, and whether repeated treatments are possible and make sense. Plant protection experts should be consulted for that decision.
If there is some particular concern about the efficacy of a spray application or a grower has applied pesticides while not being sure about its success, it is recommended to leave an untreated patch for comparison. This allows for the monitoring of the natural development of
infestation/infectivity and assesses the advantage of the measure over time after treatment in comparison with the rest of the field. However, leaving untreated patches cannot be recommended for all plant pests and diseases because they may represent a focus of reinfection/infestation, which would later, require additional treatments. Potato late blight would be such a case.
The usage of plant protection products must be documented by the growers as a minimum for all edible crops: Documenting plant protection measures serves to critically analyse and in the long run optimize plant protection applications in the location concerned. Growers may document plant protection measures in different ways in the framework of general book-keeping, for instance, in a kind of logbook or in a computer database.
It is recommended to record at least the following:
- name of product,
- justification for application,
- date and time of application,
- name of user,
- details of spray quantity and dose,
- equipment used,
- prevailing weather conditions. (for the above section got to www.planthealth.gov.mt)
What are the ways of protecting the plants from their enemies?
There are some ways by which plants can be protected from their enemies. The ways are like as follows:
a) Prevention,
b) Eradication,
c) Physical,
d) Cultural,
e) Mechanical,
f) Biological, and
g) Chemical methods.