Predicting Phenology of Pear Thrips Emergence in Pennsylvania Sugar Maple Stands

Abstract

Spring emergence of adults of Taeniothrips inconsequens was monitored with traps in 5 sugar maple (Acer saccharum) stands in Pennsylvania in 1990 and at 6 sites in 1991 and 1992. Arnold's least variability method and the standard error of prediction method were used to estimate the best start date X base (air) temperature combination among all combinations of 0-15°C and 1 January to 1 March for heat day degree (HDD) requirements to 1st and 50% emergence. The results suggested that HDD's predict emergence no better than average Julian date and that emergence is not temperature dependent. It is likely that the relevant measure for thermal summation is soil temperature near the surface, rather than air temperature. Also, cessation of overwintering may depend on a chilling requirement followed by thermal summation.