Fluctuating temperature and the longevity of conidia of Metarhizium flavoviride in storage

Conidia of Metarhizium flavoviride were hermetically stored at 13.7% moistu re content with four constant (20, 30, 40 and 50 degrees C) and six fluctua ting temperature regimes (20:30, 20:40, 20:50, 30:40, 30:50 and 40 degrees C:50 degrees C, all 24 h:24 h) for up to 119 days. Survival of conidia stor ed at both constant and fluctuating temperatures conformed to cumulative ne gative normal distributions and all 10 survival curves could be constrained to a common origin. The effect of constant storage temperature on conidia longevity was quantified satisfactorily by a negative curvilinear semi-loga rithmic relation developed previously, in which the estimates of the consta nts C-H and C-Q were 0.0176 (SE 0.0013) and 0.000703 (SE 0.000019), respect ively. The fitted relation at constant temperatures showed that Q(10) for l oss in conidia viability increased the warmer the temperature regime. The e ffect of the cooler temperature of each fluctuating temperature regime on c onidia longevity was small, since the effective temperature of each regime for loss in conidia viability was always much warmer than the mean. Conidia were also stored in two further regimes: at 30 degrees C for 21 or 35 days before transfer to 50 degrees C. The standard deviations of the conidia su rvival curves at 50 degrees C were unaffected by the duration of previous s torage at 30 degrees C. Thus change in temperature per se had no effect on conidia survival: conidia survival curve slopes were solely dependent upon the contemporary storage environment. Approaches are developed in order to predict loss of conidia viability in fluctuating temperature storage enviro nments, and the predictions compared against independent observations.