Integrated Pest Management and their Management | Agriculture Optional Notes for UPSC PDF Download

Introduction

Storage plays a crucial role between the harvest and processing or consumption of food grains. In developing nations, on-farm storage is of particular importance, especially for small and medium landholding farmers. However, India faces an annual storage loss of 14 million tons valued at around 7,000 crores due to post-harvest pest damage, according to the Integrated Grain Management Portal. The economic losses from storage pests are not just due to grain consumption but also the contamination and spoilage caused by pest body parts, excreta, and hoarding. The primary reasons for these significant losses are the lack of knowledge about storage pests and their damage, as well as improper storage techniques. To mitigate these losses, two critical actions must be taken: the construction of suitable storage structures that are well-equipped and effectively managed, and the implementation of stringent hygiene standards in storage facilities, along with efficient pest control measures.

Types of control measures

Physical and mechanical methods

• Drying and Disinfestation:
  • Agricultural commodities typically need to be dried to a safe moisture level, usually below 11-12%, before storage.
  • Crops are often harvested at higher moisture content to avoid shattering losses.
  • Solar drying can be done on various surfaces like cemented platforms, mats, jute cloth, or metal sheets.
  • Elevating grain temperature to around 60°C and maintaining it for 10-15 minutes can kill all live stages of pulse beetles present in pulses.
  • Solar absorbent surfaces can effectively raise grain temperature and aid in disinfestation.
• Reducing Intergranular Space:
  • Adult pulse beetles are weak and have a short lifespan, so they cannot move effectively within the grain mass and are typically restricted to the top 15 cm layer.
  • Placing a 7-10 cm layer of dry sand or dry activated clay at the top of the grain mass can prevent adult pulse beetles from moving and mating.
  • To prevent mixing of sand or clay with the material, a paper or polythene sheet can be placed on top of the pulse grain, followed by sand or clay.
• Coating with Clay or Oil:
  • Small quantities of pulse produce kept at the farmer's level for consumption or seed purposes can be treated with clay or vegetable oil.
  • Coating with 1-2% clay uniformly mixed with whole grains and keeping them in a closed container can be effective.
  • Non-drying oils like castor, niger, sesame, etc., can also be used to prevent pulse beetles.
  • A dose of 0.5-1.0% is mixed with the whole grains to be stored, preventing egg-laying and larval hatching on the grain surface, ultimately killing the insects.
• Use of Improved Storage Structures:
  • Moisture-proof, airtight, low-cost, and low thermal fluctuation structures have been designed as improvements over traditional structures.
  • Examples of such structures include Pusa bin, Pusa kothar, Pusa cubicle, and improved bamboo baskets.
  • These structures have been found effective for storing chickpea, lentil, pigeonpea, and mungbean in various regions.
  • Metal bins of up to 1 tonne capacity are used for storing seed legumes in dry regions.
  • Bamboo baskets pasted with mud and placed at elevated locations can serve as storage containers.
  • Polythene-lined bags are used to retain low moisture in storage.
• Airtight Storage:
  • Subjecting infested mungbean to airtight conditions can check insect population build-up.
  • Accumulation of carbon dioxide and depletion of oxygen levels adversely affect insect growth.
  • Incorporating eucalyptus and mint oil in airtight conditions can quickly arrest infestation and ensure better protection for small quantities of legumes.

Chemical methods

• Treatment of Grain with Contact Insecticide:
  • Physical methods may not always provide complete insect control, making the application of chemicals necessary for total insect mortality and prevention of insect growth.
  • Treatment by contact insecticide involves covering the grain with an insecticide film that acts on contact with insects, with varying rapidity and persistence of effects.
  • Contact insecticides come in various forms such as powders for dusting, powders to be mixed with water, liquid concentrates, or fumigants, each dictating their application techniques.
  • For bulk storage, insecticide is incorporated directly into the grain by spraying before filling silos.
  • For bag storage, cleaned grain can be mixed with powder or sprayed before bagging. To prevent re-infestation in bag storage, additional dustings or sprayings are carried out while stacking bags and during the storage period.
  • Equipment for dusting grain ranges from simple mechanical dusters to motorized ones, but uniform treatment can be a challenge.
  • Spraying can be mechanical (pressure sprayer), pneumatic, or thermal, and provides better distribution of the product over the grain.
  • Contact treatments are effective on fully developed insects but have little or no effect on eggs or larvae. Some residues of the product may remain in foodstuffs, although they are not highly toxic.
• Treatment of Grain by Fumigation:
  • Fumigation is a method that eliminates stored grain pests using a poisonous gas known as a fumigant.
  • Fumigants are produced and concentrated as gases and are lethal to specific living species.
  • Unlike contact powders, fumigants penetrate the interior of the grain mass, reaching even the invisible incipient forms like eggs and larvae.
  • Fumigants are used in completely sealed enclosures, and their effectiveness depends on the concentration of the gas and the duration of fumigation.
  • For bulk grain storage, the bins must be perfectly airtight for fumigation.
  • In bag storage, the typical approach is to cover the bags with a tarpaulin, sealing its edges to the ground or walls to create an airtight environment.

Which fumigants to use?

There are two types of fumigants commonly used in grain storage programs:

• Methyl Bromide:
  • Methyl bromide has quick action, and grains can be aerated after 12-24 hours of its application.
  • However, it is highly toxic, colorless, and odorless.
  • It leaves a residual effect in the grain and accumulates in the human body.
  • Due to its toxicity and health risks, methyl bromide should not be used as a fumigant in grain storage programs.
• Magnesium or Aluminum Phosphide (Phosphine Gas):
  • Gas released from magnesium or aluminum phosphide is known as phosphine.
  • Phosphine has a small molecular weight (34.04) and excellent penetration capacity.
  • It has a similar weight to air, allowing it to mix easily with air and spread throughout the stored grains, eliminating the need for re-circulating fans to circulate the air.
  • Phosphine is very effective against most pests and does not affect the taste or smell of the fumigated grain.
  • It leaves no residues on the grain, making it safe for use with food grains and seeds.
  • Phosphine does not affect the germination of seeds and is suitable for seed storage.
  • However, phosphine is inflammable at normal temperatures, so care should be taken during its application.
  • Phosphine has a delayed release, requiring a longer fumigation period than other fumigants.

The duration of fumigation depends on whether methyl bromide or phosphine is used. For methyl bromide, the fumigation period should be 24-48 hours, while phosphine fumigation typically requires a minimum of five days. Phosphine, in the form of pellets spread throughout the grain mass, is a more common choice due to its ease of application. However, it's important to note that fumigants are highly toxic to humans, so proper training and strict adherence to recommended protective and safety measures (e.g., masks, gloves, hand-washing, hermetic sealing of phosphine containers) are crucial for those handling these chemicals.

Conditions for application of phostoxin

When applying Phostoxin for fumigation of grains, there are several important factors and conditions to consider:

• Location: Any enclosed space that can be made airtight can be used for fumigation of grains.
• Temperature: The effectiveness and duration of the fumigation treatment are highly dependent on ambient temperature conditions. Generally, higher temperatures are more conducive to effective treatment.
  Here are some important temperature-related guidelines:
  • Fumigation is more effective at higher temperatures.
  • The duration of fumigation treatment is influenced by the ambient temperature. Higher temperatures require shorter treatment durations, while lower temperatures necessitate longer treatments.
  • Fumigation is typically carried out in warmer weather, as the heat helps in the diffusion of phosphine gas into the grain mass.
  • In colder conditions, the fumigation period needs to be extended to ensure thorough penetration of the gas.

IPM strategies against pulse beetle

Relative Humidity: Humidity of the ambient air influences the rate of release of phosphine gas. Higher the RH, higher is the rate of release of gas. There is no release of gas below 30% RH. Under this condition, water containers should be placed below the fumigation sheet.

Right concentration: It is essential to maintain the required concentration of fumigant in the sealed space and for sufficient time in order to have effective control of all stages of the pest. The fumigation sheet, therefore, should be air-tight and properly sealed with the floor with the help of paper tape. The floor should preferably be of concrete.

Proper hygiene: Fumigants are not persistent and therefore, the possibility of re-infestation should be avoided. This can be done with carrying out surface treatment of the storage area with Malathion. This has a volatile action and is effective against flying insects.

Some do’s and don’ts
After fumigation, the grain storage should be aerated and thoroughly cleaned. The collected trash should be removed away from the storage area to prevent further breeding of insects and re-infesting the grains.
Before carrying out fumigation operation, it is important to know how to detect and measure the concentration of released gas in the air and the precautions to be taken to avoid hazards.

Do's:

• Keep fumigants safely stored and out of reach of untrained individuals. Only trained personnel should handle fumigation.
• Use a gas mask with the correct filter to protect yourself from fumes.
• After fumigation, wash and, if possible, take a bath to remove any potential residue.
• Display a board indicating the type of fumigant used, the date of application, and the responsible person.
• Have gas monitoring devices on hand to measure gas concentrations during fumigation.
• Aerate the storage area after uncovering to remove any residual gas.
• Conduct fumigation away from office or residential areas.
• Collect any residues left after fumigation and dispose of them in water. Bury used containers.
• Keep a first-aid treatment box nearby to address accidental exposures to fumigants.

Don'ts:

• Never work alone during fumigation.
• Avoid eating, drinking, or smoking during fumigation or immediately afterward.

Limiting values of fumigants
Gas concentration in the air which is safe for human being is known as threshold limit value of the fumigant. Threshold limit values of the two commonly used fumigants are: