Legislative Methods of Pest Control

November 4, 2023 Agric4Profits

The legislative methods of pest control includes those methods of control where government legislation (laws) has been passed so that certain control measures are mandatory, with failure to comply being a legal offense. These are extreme measures and only apply to certain very serious pest situations of national importance.

Legislative measures play a crucial role in regulating and managing pest-related risks at regional, national, and international levels. These laws and regulations are designed to ensure the prevention, control, and eradication of pests that pose a significant threat to agricultural production, environmental stability, and public health.

Legislative Methods of Pest Control

1. Phytosanitation (Quarantine)

When the major crops were distributed around the world from their indigenous areas, initially they may have been free of their native pests and diseases (particularly crops grown from seed).

But over the years many reintroductions have been made and gradually the native pests and pathogens have spread also, until now when some pests and diseases are completely sympatric with their host crops.

However, there is still a large number of pests and diseases that have not yet spread to all parts of the crops’ areas of cultivation.

Quarantine laws are implemented to prevent the introduction and spread of invasive pests across borders.

These regulations often mandate the inspection and certification of agricultural commodities, including plants, seeds, and produce, to ensure they are free from harmful pests and diseases before they are transported or traded internationally or within a country.

Strict enforcement of quarantine measures helps safeguard local ecosystems, preserve biodiversity, and maintain the integrity of agricultural industries.

For example, the early success of coffee in Brazil (S. America) was due to the absence of Coffee Rust, Antestia Bugs, and Coffee Berry Borer, which remained behind in E. Africa; but this advantage has now been lost in recent years both Rust and Berry Borer have become established in S. America.

Similarly, the success of rubber as a crop in S.E. Asia is due in part to the absence of its native South American Leaf Blight. FAO (Food and Agriculture Organization of the United Nations) has organized a system of international plant protection with respect to the import and export of plant material.

The world is divided into a number of different geographical zones on the basis of phytosanitation; each zone has its own regional organization for coordination.

There is now an International Phytosanitary Certificate, an essential document required for the importation of plant material into almost every country of the world.

Disease-free and pest-free plants can usually be imported, provided they are accompanied by appropriate documentation from the country of export, but certain plants (and fruits) are completely prohibited because of the extreme likelihood of their carrying specific noxious pests or pathogens.

Other categories of plants are allowed to be imported (and exported) after routine treatment to eradicate possible pests; such treatment usually consists of fumigation (e.g. fumigation of fruits using ethylene dibromide).

Sometimes the plants have to be kept in quarantine isolation for a period of time to check that no symptoms develop (as with domestic pets and rabies quarantine). Specific import regulations vary from country to country according to the nature of the main agricultural crops.

From time to time, the introduced pests/pathogens have devastated crops and even created famine conditions in different parts of the world. The Ireland famine of 1845 was the result of an almost total failure of the potato crop due to the introduction of the late blight pathogen (Phytophthora infestans) from Central America.

The introduction of powdery mildew (Uncinula necator), Phylloxera, and downy mildew (Plasmopara viticola) in quick succession about the middle of the 19th century from America virtually annihilated the grapevine industry of France.

The chestnut blight (Endothia parasitica) was introduced into the US on the nursery stocks imported from the Orient in about 1906. Within 25 years, the American chestnut was almost exterminated as a forest tree causing an estimated loss of 1000 million US dollars.

In Sri Lanka, coffee was replaced by tea as a plantation crop because of the widespread epiphytotic of coffee leaf rust (Hemileia vastatrix) in 1868. Also, about 20,000 hectares of coconut plantation were devastated by the introduced coconut leaf minor (Promecotheca cumingi) during the late 1960s.

In India also, several pests and diseases got introduced from time to time, some of which, like the late blight of potato, banana bunchy top, bacterial blight, and streak diseases of paddy, have since become widespread. Some others like golden nematode and wart disease of potatoes and downy mildew of onion are still localized in certain parts of the country.

The above examples only highlight the risks involved in the inadvertent introduction of serious pests/diseases along with the planting material imported without adequate safeguards. Plant quarantine can provide such safeguards.

Plant quarantine measures aim at providing protection to the agriculture of a country or region against the likely ravages of alien pests/pathogens should they get introduced and established.

These measures are of particular importance and relevance to countries like India whose economy is largely based on agriculture.

Quarantine not only helps to ward off the threats of exotic pests but also aims to eliminate and prevent the further spread of pests/pathogens (both indigenous and introduced) with restricted distribution within the country (domestic quarantine).

Government quarantine offers services that are beyond the capabilities of individual beneficiaries or that are difficult to obtain in some other way at a lesser cost. Thus, plant quarantine, in a real sense, serves as a national service by preventing the introduction of exotic pests/pathogens/weeds and their further spread.

However, such endeavors could succeed only with the active support of all-the administrators, the general public, farmers, scientists, communication media, customs, and others.

Pest/Pathogen Detection Techniques

The success or failure of plant quarantine measures would depend, to a great extent, on the ability of plant quarantine officials to detect pests and pathogens that may be associated with the introduced planting material.

For quarantine purposes, techniques should be sensitive enough to detect even trace infections. This is particularly important in the case of pests/pathogens with very high multiplication rates like certain pycnidial fungi, downy mildew, bacteria, and also viruses when the insect vectors are efficient.

A wide variety of pests and pathogens (insects, mites, nematodes, fungi, bacteria, viruses, viroids, piroplasm, etc.) and weeds are the objects for quarantine consideration. Similarly, planting material also may be introduced in a variety of forms, i.e., true seed, corms, bulbs, rhizomes, suckers, runners, budwood, scions, cuttings, and rooted plants.

Therefore, detection techniques would vary depending on the type of material, the host species, and the type of pests/pathogens involved. Many times, more than one technique would have to be used.

Detection Techniques

Detection techniques may broadly be classified into two groups:

Generalized tests would reveal a wide range of pests/pathogens; and
Specialized or specific tests are used to detect specific pests/pathogens.

1. Generalized tests

A very widely used method is the inspection of dry seed with the naked eye or under the low power of the microscope.

This method would reveal a wide range of free-moving insects, their eggs and larval stages, mites on or with the seed, weeds, soil, infected/infested plant debris, fungal fructifications like sclerotia, smut and bunt balls, nematode galls, discolored or deformed seeds mixed with seed; oospore or bacterial crusts, acervuli, pycnidia, sclerotia and even free spores of rusts, smuts and many other fungi on the seed surface.

Examination of dry seed under UV or NUV light may reveal infections of certain fungi and bacteria through the emission of fluorescence of different colors. Examination of seed washings may reveal surface contamination by rusts, smuts, downy mildew, and a large number of other fungi.

The most commonly used incubation methods for the detection of fungi are the common moist blotter and agar tests wherein seeds are incubated on these media for a specific length of time (generally about a week) at a suitable temperature under alternating light and dark cycles.

These two media reveal a wide range of internally seed-borne fungal and some bacterial pathogens in a wide variety of crops. The seedling symptom test and the grow-out test are quite versatile and reveal the symptoms produced by any category of plant pathogens including fungi, bacteria, and viruses.

Grow out test is the simplest of the tests extensively used for the detection of viruses. However, some viruses may be carried symptomlessly in the plant and, therefore, it should be used in combination with other tests like indexing on indicator test plants and serology.

Read Also: Introduction to Pest Management

2. Specialized tests Insects

X-ray radiography has been used very successfully all over the world for the detection of hidden infestation (with no apparent sign of infestation on the seed surface) of insects, particularly seed-infesting chalcids and bruchids.

A seed transparency test (boiling the seeds in lactophenol to make them transparent) may also be used for the detection of hidden infestation and extraction of the insects for identification. X-ray radiography is also very effective in salvaging infested seed lots.

2a. Nematodes

For the detection of seed-borne nematodes, seeds are soaked in water for about 24 hours. This makes the nematodes active, which then come out of the seed into the water, or the seeds may be teased out with the help of forceps and a needle and examined for detection of nematodes under a stereo microscope.

In rooted plants, the accompanying soil and plant debris may similarly be soaked in water and nematodes may be extracted for identification using nematological sieves or tissue paper.

2b. Fungi, bacteria, and viruses

Serological tests are very effective for the detection and identification of viruses and bacterial pathogens and are being used in various plant quarantine stations with great success.

Phage- plague technique is still more sensitive to bacterial pathogens as even strains of bacteria can be identified. Indicator test plants are also very helpful as they may reveal pathogenic races within a species of a fungus, bacterium, and specific strains within a virus.

Modifications of the generalized incubation tests (agar and blotter tests) have also been used for the detection of specific plant pathogens. Deep-freezing blotter test and 2,4-D blotter test are very efficient for the detection of the black-leg pathogen (Phoma lingam) in crucifer crops. Potato-dextrose-ox gall agar is useful for the detection of Septoria nodorum in wheat.

In the case of vegetative propagules, laboratory methods may suffice for the detection of insects and mites, nematodes, the majority of fungi, and certain bacteria.

However, for the detection of systemic fungal pathogens, bacteria, viruses, and viroids, isolation growing for a season or a year or more in quarantine glass-houses/net-houses is required.

The availability of glass houses/net houses in large numbers is an expensive proposition, but the quarantine safeguards afforded by them to any country are worth that expenditure.

Quarantine Regulations

Plant quarantine regulations are promulgated by the national and state governments to prevent the introduction and spread of harmful pests and pathogens.

Plant quarantine will be justified only when the pest has no natural means of spread and when they are based on biological considerations only, i.e., pest/pathogen introduction risks and the available safeguards.

In general, risks are more with the introduction of vegetative propagules than with true seeds. In the case of true seed, risks are more with deep-seated infections than with the surface-borne contamination of pests/pathogens.

Again, risks are far greater with pathogens like viruses, downy mildews, smuts, and many bacteria carried inside the seed without any external symptoms.

When vegetative propagules are introduced, rooted plants and other underground plant parts like rhizomes, suckers, runners, etc. carry higher risks than budwood, scions, and un-rooted cuttings.

In any case, bulk introductions are always risky as thorough examination and treatment in such cases is very difficult and the planting area is far too large to prevent the establishment and spread of the introduced pest/disease.

Based on these factors, plant quarantine regulates the introductions as follows:

1. Complete embargo/prohibition: When the pest risk is very high, the safeguards available in the country are not adequate and, therefore, import is prohibited.

2. Post-entry quarantine: The risk is very high but adequate safeguards in the form of post-entry isolation growing facilities are available.

3. Restricted: Pest risk is not high and an import permit is required stipulating conditions for entry, inspection, and treatment.

4. Unrestricted: An import permit is not required, and material may enter without restriction. While formulating quarantine regulations, local conditions like crop spectrum and environmental conditions are also to be considered.

Since quarantine regulations are designed to break the life cycle of the pest/pathogen involved, the presence of alternate or collateral hosts in the country of import and their introduction should also be taken into account.

2. Biosecurity Protocols

Biosecurity measures aim to safeguard agricultural systems from the introduction and proliferation of pests through strict protocols and guidelines.

These protocols may include the establishment of buffer zones, the implementation of hygiene practices, and the monitoring of pest populations to prevent the accidental or intentional spread of pests from one area to another.

By enforcing comprehensive biosecurity measures, authorities can effectively mitigate the risks associated with pest incursions and protect the long-term sustainability of agricultural production.

3. Pesticide Regulation

Legislation governing the use of pesticides is crucial for ensuring the safe and responsible application of chemical control methods.

Pesticide regulations typically include guidelines for the registration, labeling, and use of pesticides, as well as the establishment of permissible residue levels in food products.

These regulations aim to minimize the risks associated with pesticide exposure to human health, non-target organisms, and the environment while promoting the effective management of pest populations.

4. Integrated Pest Management (IPM) Policies

Legislative support for Integrated Pest Management (IPM) encourages the adoption of sustainable and eco-friendly pest control practices that prioritize the use of non-chemical interventions and the integration of multiple control methods.

IPM policies promote the implementation of cultural, biological, and mechanical control strategies, emphasizing the reduction of pesticide reliance and the preservation of natural ecosystems.

By integrating IPM principles into legislative frameworks, governments can promote sustainable agricultural practices that prioritize long-term environmental health and food security.