Fumigants in stored product protection

Abstract

Since man began to store huge amounts of harvested cereal grains and other products in large bulks the application of fumigants was the method of choice for thorough disinfestations. Only these molecules are suitable to meet all the stages of pests even hidden within the products and kill them without moving the stored produce. Some boundary conditions are linked to effective use of fumigants for pest control:

• The product of premise must be sealed to a high degree of gas tightness – for instance by use of tarpaulins, glue, sticky tapes, poly urethane foam, silica glue or other appropriate materials – to keep the concentration of the gas for some length of tome sufficiently high.
• The temperature must be sufficiently high to allow penetration of the poison into the insect body and reaction at the target site within the insect.
• The concentration must be sufficiently high for a considerable length of time to control all stages or the target stage of the pest at a mortality rate of at least 99.9% (to avoid selection for resistance).

Only a few fumigants remain as registered compounds for this purpose:

• metal phosphide products for the release of phosphine gas
• carbon dioxide as inert atmosphere for replacement of oxygen; also under high pessure
• nitrogen [as inert atmosphere without need for registration as plant protection product]
• [hydrogen cyanide as gas for use as biocide]

The specific features of the fumigants including the efficacy against pests and fields of applications will be discussed.