Protection of stored grains against pests

The production of food grains in India is not in proportion to the country’s increasing population that has crossed the 110-crore mark. Again, out of the total quantum of food grains produced, what is made available for consumption is after deducting the required quantities for seed, feed and post harvest losses due to various reasons, including pest infestation at different stages of storage and transport. If the wastage at different levels especially due to pest infestation is reduced significantly, we can fill the gap in shortage to a substantial extent.

There are different methods of protecting stored grains from insect pests. Fumigation is one method while “controlled atmosphere” or “Hermetic storage” technology is the other method that can substantially reduce losses incurred by stored insect pests.

What is fumigation?

Fumigation is a method of using a lethal gas to exterminate insect pests within an enclosed space. Amongst all the chemical control methods, fumigation is the only one by which infestation within stored grains or consumable items can be controlled.

Effective fumigation can be carried out only by properly equipped and trained personnel in appropriately prepared fumigation enclosures. Stringent safety precautions are required as the process could be both dangerous and expensive. Fumigation treatments are to be executed by licensed fumigators only and treatments are not to be executed in residential premises.

General Overview

Even though fumigation continues to play a valuable role in many pest control operations, both the concepts and the procedures for controlling insects are changing. With increased public concern over the adverse effects of pesticides on human health and the environment, greater emphasis is being given to methods that can exclude the use of fumigants. Nevertheless, the need for chemical pesticides, particularly fumigants, is likely to continue for many years to come, as they have unique properties and capabilities that necessitate their use in situations where other methods are not feasible or practical.

In many cases, treatments can be carried out on infested material without disturbing it in any way. Use of lightweight plastic sheets or materials has made the fumigation process easier and more effective. Several modern technological developments like measurement & analysis of fumigant concentrations, improved formulations as well as increased demand for effective and economic pest control measures, have done much to improve fumigation procedures.

In India, there are two registered fumigants – Methyl Bromide and Aluminium Phosphide (Phosphine Gas).

Some of the fumigation processes are as follows:

• Cover Fumigation –at warehouses, etc.
• Freight Container Fumigation
• Ship Fumigation – for Cargo Holds
• Chamber Fumigation
• Structure Fumigation
• Vacuum Fumigation
• Store & Silo Fumigation
• Mill Fumigation
• Aircraft Fumigation

Fumigation Standards & Regulatory Authorities

Since the use of fumigant is restricted, it is regulated by Plant Protection Quarantine & Storage Department under Ministry of Agriculture, Government of India. Standards for fumigation include National Standards for Phytosanitary Measures No. 11 & 12 which are popularly known as NSPM 11 & 12 and refer to Methyl Bromide Quarantine treatments and guidelines for accreditation of fumigation agency respectively. Apart from Methyl Bromide, use of Aluminium Phosphide is also described by PPQ & S. Apart from these standards, International Standards for Phytosanitary Measures No. 15 also exists and is applicable for treatment of wooden material which is being used for packing along with export consignments. Since India is a signatory to Australian Fumigation Accreditation Scheme (AFAS), all the export to Australia is covered under AFAS and fumigation treatments must be performed by accepted treatment providers by this stipulated process.

Over all, these regulations play an important part in:

• Setting guidelines that establish safe working environment where treatment providers can perform effective treatments (through legislation, regulation & licensing).
• Establishing international standards for treatments that are practical, safe & effective and can be undertaken with confidence by treatment providers.
• Establishing standards for specialised treatment applications and enforcing quality assurance programmes to ensure they are maintained.
• Ensuring that treatment providers meet the requirements for performing safe & effective treatments.
• Making information available, such as national & international legislation, industry codes and requirements for certification to help raise awareness of the standard of competence at which treatment providers must work.
• Providing training & certification to allow treatment providers to achieve, maintain and demonstrate their ability to work at established standards of competence.

Monitoring of stored grain pests

Storage and processing industries should ensure that grains and consumable items are insect-free at consumer end and proper checks for infestations are carried out. If commodities are infested, then supplier needs to carry out fumigation treatments before packing. Also, it is important on the part of the industry to check the stocks during storage for development of any infestation. At times, this process could be time consuming and newer technologies like pheromone traps could be used for easy detection of infestation within the pantry or storage areas or in processing units. When the infestation is detected, the stocks can be sent for fumigation.

‘Green’ technology in grain storage

Restrictions due to adverse effects of pesticide residues in food and the environment has resulted in the imposition of strict limitations on pesticide registrations and its usage. Consumer demand for chemical & insect free products increased the focus on organic technologies. Among the new technologies that have successfully replaced fumigants are Modified Atmosphere Systems (MAS).

The premise of such a system is based on modifying the content and quality of air to reduce or remove oxygen which pests need to breathe without which they die from suffocation. The oxygen is replaced by other gases such as nitrogen or carbon dioxide, either by direct infusion of these gases or by allowing the grain to “breathe” the remaining oxygen and replace it with carbon dioxide. This novel system of “hermetic storage” obviates the use of toxic fumigants and can preserve the quality and sanctity of the grain for very long periods of time.

Consequently, hermetic storage is a sustainable, cost effective, user-friendly and environmentally “Green” technology that makes use of pesticides and fumigants in post harvest and seed storage, redundant. The technology has already been adapted for the protection of many different commodities in quantities ranging from that of conventional grain bag size to many thousands of tonnes. Applications of hermetic storage are likely to expand more rapidly in the future, as the available forms of hermetic storage continue to increase and more users experience and understand the advantages of this “green” technology.

Hermetic storage technology products are now available from small capacity bags to bigger size “Cocoons” or “Bunkers” and thus makes possible for us to use at household as well as at commercial premises for large storage. Hermetic storage “Cocoons” can also be used for CO² treatments of organically produced food grains.