Thursday, March 28, 2024
General Agriculture

Physical Methods of Pest Control

Physical methods of pest control refer to methods of mechanical removal or destruction of the pest and are usually unimportant in most countries owing to the high cost of labour. They are still of use in some countries and for particularly valuable crops.

Physical control techniques involve the use of mechanical or structural means to manage and prevent pest infestations, minimizing the reliance on chemical interventions and promoting environmentally friendly pest management practices.

These methods offer effective and sustainable solutions for controlling pests across a range of agricultural settings.

Physical Methods of Pest Control

Physical Methods of Pest Control

1. Mechanical Methods

Hand-picking of pests was probably one of the earliest methods of pest control and is still a profitable method for the removal of some caterpillars from young fruit trees.

In cases where pests can be easily identified and accessed, manual removal is a practical and effective method of control. This method involves physically removing pests, such as caterpillars, snails, and eggs, from plants by handpicking or using specialized tools.

Manual removal can be particularly beneficial for managing small-scale infestations and maintaining the health and integrity of crops without resorting to chemical interventions.

The killing of longhorn beetle larvae boring in branches of some bushes is recommended by pushing of a springy wire (e.g. bicycle spoke) up the bored hole and spiking the insect.

The use of mechanical drags, which crush insects on the ground, has been made against armyworms (Spodoptera larvae), but this practice is now generally outmoded.

Banding on fruit trees is particularly effective against caterpillars and ants, which gain access to the tree by crawling up the trunk.

Spray-banding of the apple trunks is practised against the wingless females of Winter Moth and other Geometridae which typically climb the lower parts of the trunk from the soil.

An earlier method of locust control was to herd the hoppers into a large pit which was afterwards filled in with soil.

Armyworms when on the move can often be trapped in trenches dug across their line of marching, and when trapped they are easily destroyed by burning, filling the trench or spraying with chemicals.

Read Also: Legislative Methods of Pest Control

In parts of Asia, especially in gardens and on smallholdings, it is common practice to place bags around large fruits (e.g. grapefruit, pomelo, pomegranate and jackfruit) to deter fruit flies (Tephritidae) from oviposition.

In rural areas and in the forests the bag is usually woven from grass or raffia, but in more suburban situations paper bags and polythene may be employed. Occasionally a single fruit may be left unprotected so that the local fruit flies will concentrate their egg-laying upon this one fruit which can later be destroyed.

In temperate smallholdings and gardens, it is a common practice to build a large cage of wire or string (now often plastic) netting over a fruit bed, but this protection is usually against fruit-eating birds rather than insects; such a cage may be portable and temporary or maybe a permanent construction.

This idea is now being developed on quite a large scale throughout the world, particularly for the protection of seed beds and also for particularly valuable crops that may be at risk locally Greenhouses in temperate situations provide complete physical protection for a crop, but the main purpose is to modify the temperate climate to provide a suitable hot/moist microclimate for the cultivation of exotic crops or local crops out of season.

Nowadays the use of polythene tunnels has become very widespread as these are effective and much cheaper to erect than traditional glasshouses. The cultivation of protected crops has now become very sophisticated and in many respects is a separate branch of horticulture.

Barriers: Implementing physical barriers, such as nets, screens, and fences, can serve as an effective deterrent against pests. These barriers create a protective shield around crops, preventing pests from gaining direct access and causing damage.

For instance, covering plants with fine mesh nets can effectively shield them from insect pests, while installing fences around fields can help keep larger pests, like rodents and deer, at bay.

Traps: Utilizing traps is an essential physical control method that aids in capturing and eliminating pests. Various types of traps, including pheromone traps, sticky traps, and light traps, are strategically placed in fields to attract and capture pests, preventing them from causing extensive damage to crops.

Traps offer a targeted and environmentally friendly approach to pest control, minimizing the need for chemical pesticides and promoting the preservation of beneficial organisms.

Read Also: Different Recommended Methods of Pest Control

2. Use of Physical Factors

The use of lethal temperatures, both high and low, for insect pest destruction, is of importance in some countries. (Often high temperatures are lethal for temperate pests, and low temperatures for tropical pests.)

The use of cool storage in insulated stores for grain is practised in Asia and Africa. The purpose of this method is not the actual destruction of the pests, which may occur when lethal temperatures are employed, but the drastic retardation of development following the reduction of the metabolic rate.

Kiln treatment of timber for control of timber pests is very widely practised in many countries. Plant bulbs are often infested with mites, fly larvae (Syrphidae) or nematodes, and hot-water treatment (dipping) can be a very successful method of control if carefully carried out.

The drying of grain, which is widely practised for a reduction in moisture content, usually results in lower infestation rates by most pests. The heating of cotton seed to kill the larvae of Pink Bollworm (Pectinophora gossypiella) is an effective control.

In different parts of the World hermetic storage of grain is being developed as a standard long-term storage method.

The stores are now of several different basic types and generalization is not feasible; the principle involved is that only a small quantity of air is enclosed within the sealed bin, the oxygen which is quickly used up by the respiration of the pests and the subsequent carbon dioxide accumulation quickly results in the death of all contained pests, both arthropod and microbial.

On-farm storage of grain is being carried out in some areas using butyl silos; the addition of small quantities of diatomite fillers increases the effectiveness of this control, as the abrasive effect removes the outer waxy covering of the epicuticle of the insects, resulting in greater water loss (and possible dehydration) and greater ease of insecticide penetration through the cuticle.

Read Also: Disease and Pest Control of Plantain

3. Use of electromagnetic energy

The radio-frequency (long wavelength radiations) part of the spectrum has been extensively studied in the development of radio communications, radar, etc., and it has been known for a long time that the absorption of radio-frequency energy by biological material results in the heating of the tissues.

Exposing pests or infested materials to high temperatures can effectively eradicate or control pest populations. Heat treatments, such as hot water treatments and steam treatments, are commonly used to eliminate pests in stored agricultural products, grains, and seeds.

By subjecting these materials to specific temperatures for a determined duration, farmers can successfully eliminate pests without compromising the quality of the harvested produce.

Control of insect pests by such heating is only practicable in enclosed spaces of small or moderate size (food stores, warehouses, timber stores). The nature of absorption of radiofrequency energy by materials in a high-frequency electrical field is such that for certain combinations of hosts and insect pests their dielectric properties are favourable for differential absorption of energy, hence the insects can be killed without damaging the host material.

Timber beetles in wood blocks have been killed in this manner, but whether this treatment offers any real advantage over normal kiln treatment is doubtful. The use of infrared radiation for heating purposes is very much in its infancy.

Many insects show distinct preferences for visible radiation of certain wavelengths (i.e. certain colours), as well as the long-recognized attraction of ultra-violet radiation for various nocturnal insects, especially Lepidoptera.

Ultra-violet light traps have, on occasion, significantly lowered pest populations in various crops, but have also failed when used against other pests. Mercury vapour lamps are mostly used for pest monitoring, especially for various night-flying

Lepidoptera (Codling Moth, Pea Moth, rice stem borers, etc.), and for this purpose their use is now very widespread. In some countries, such as China, electricity lines are laid extensively throughout agricultural areas and ultra-violet light traps are used in large numbers.

Aphids and some other plant bugs are attracted to yellow colours; this is possible because most aphids feed either on young or senescent leaves, presumably because these are the plant parts where active transport of food material occurs.

The young leaves are photosynthesizing rapidly and the sugars formed are transported away in the phloem system to be stored as starch grains in older leaves, tubers, etc. As leaves become senescent, the stored starch is reconverted into soluble sugars for transportation prior to leaf dehiscence.

Senescent leaves are usually yellowish in colour and young foliage is often a pale yellowish-green. So the attraction of aphids to yellow colours seems fairly obvious, but why so many flies (especially Anthomyiidae) and some months are similarly attracted to yellow is not obvious.

This attraction for the colour yellow by so many insects is exploited in the use of many different types of traps; yellow water traps consistently catch more aphids and more Cabbage Root Fly adults; sticky traps coloured yellow, and even pheromone traps for Tortricoidea and Tephritidae, are often more effective than white ones.

In a monitoring programme, it is of course necessary to make allowance for any enhanced trapping effect due to the colour of the trap. Conversely, many flying insects are repelled by blue colours and by reflective material.

This has been exploited by using strips of aluminium foil, or metallicized plastic, between the rows and around the periphery of the crop, the result being that fewer flying aphids and other insects settle in the crop than would otherwise.

Thus, reflective strips also result in crops having far fewer aphid-borne virus diseases. Another effective method is to surround the seed- beds with flooded furrows, as practised in S. China with vegetable crops.

The ionizing radiations (X-rays, γ-rays) are sterilizing at lower dosages but lethal at higher. The use of these radiations in controlling stored product pests, particularly in grain, is being quite extensively studied in various countries.

Read Also: How to Control Pests and Diseases in a Pineapple Farm

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Agric4Profits

Benadine Nonye is an agricultural consultant and a writer with over 12 years of professional experience in the agriculture industry. - National Diploma in Agricultural Technology - Bachelor's Degree in Agricultural Science - Master's Degree in Science Education... Visit My Websites On: 1. Agric4Profits.com - Your Comprehensive Practical Agricultural Knowledge and Farmer’s Guide Website! 2. WealthinWastes.com - For Effective Environmental Management through Proper Waste Management and Recycling Practices! Join Me On: Twitter: @benadinenonye - Instagram: benadinenonye - LinkedIn: benadinenonye - YouTube: Agric4Profits TV and WealthInWastes TV - Pinterest: BenadineNonye4u - Facebook: BenadineNonye

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