Impact of cold storage on the performance of entomophagous insects: an overview

Mass rearing for commercial production of high quality beneficial insects is considered as an important tool for biological control programmes worldwide, especially those based on augmentative releases. Low temperature storage is a valuable method for increasing the shelf life of entomophagous insects. Insect predators and parasitoids are used extensively in biological control programmes and, because of this, studies on cold storage started over 90 years ago. The ability to store reared biocontrol agents at low temperatures for certain duration provides an opportunity to accumulate or stockpile sufficient number of entomophagous insects for field release at proper weather conditions and make them available during high demand periods to the concerned farmers. Cold stored natural enemies can be synchronously released in the fields during critical stages of pest outbreaks. Cold storage also helps to keep viable stock of natural enemies when not needed and to minimize laboratory operations by prolonging their survival and delaying eclosion. Cold storage tolerance is highly plastic trait influenced by a range of biotic and abiotic factors experienced before, during and after cold exposure. These factors ultimately affect the development, longevity, fecundity, parasitization, sex-ratio and other fitness parameters along with morphology, behaviour and physiology of entomophagous insects. For the successful implementation of a cold storage project, knowledge of these diverse factors that cause storage and post-storage effects is essential. The potential of cold storage protocols in improving mass rearing and commercial production of bioagents is thus reviewed to access the strategies, innovations, techniques, devices and wisdom involved in the process of cold storage of entomophagous insects worldwide.