Efficacy of Modified Atmosphere and Thermal Treatments for Disinfestation of Storage Pests Infesting Walnut Kernel

摘要

Walnuts are a potential export commodity from India.About 2,665.87 MT of walnuts worth of Rs.136.45 crores wereexported during 2014-15. However, the major concern in theirproduction, storage and marketing is pest infestation. Manyfumigants have so far been used for the post-harvest management ofstored pests infesting walnuts. But due to restrictions in their use andenvironmental concerns there has been a need to develop ecofriendlyand non-chemical approaches. These comprise high temperature andmodified atmosphere (MA) treatments. Disinfestation using MAinvolves the alteration of the atmospheric gases such as CO2, O2 andN2 to render the atmosphere in the stores lethal to pests. A bioassaywas conducted to investigate the efficacy of all MA treatments on theadults of important pests of walnut viz, Cadra cautella, Triboliumcastaneum, Trogoderma granarium and Oryzaephilus surinamensis.Exposure of walnut kernel infested with adults of these storage pestswere subjected to MA treatments of different gas compositions viz.,MA1 (40%CO2+60%N2); MA2 (50%CO2+50%N2) and MA3(60%CO2+40%N2) at two temperatures 28+10Cand35+10C. Thetreatment mortality data was then subjected to probit analysis toachieve time of 99% kill (LT99). The comparisons were made on thebasis of LT99 values, the susceptibility of all the test insects to the MAtreatments tested showed the following trend: C. cautella< O.mercator< T. castaneum< T. granarium. The times needed to achieve99% kill (LT99) of the least tolerant insect species i.e. C. cautellatreated with three MA treatments at 28oC were 21.07,12.57 and 15.47h, respectively, whereas at 35oC LT99 values were 19.09, 10.77 and9.34 h, respectively.