Degree-Day Models for Predicting Levels of Attack by Slash Pine Flower Thrips (Thysanoptera: Phlaeothripidae) and the Phenology of Female Strobilus Development on Slash Pine

Abstract

Degree-day models were developed for predicting different levels of attack by slash pine flower thrips, Gnophothrips fuscus (Morgan), on female strobili (flowers) and for predicting the appearance of different morphological stages of flower development. The models were based on 5-yr data collected from a north Florida slash pine, Pinus elliottii Engelmann variety elliottii, seed orchard. Different starting dates and lower threshold temperatures for models were compared. Starting dates included the 1st annual incidence of temperatures below 4.4 degrees C (40 degrees F) and a range of biofix dates (20 November through 10 December). Lower threshold temperatures were compared over a range of -1.1-12.8 degrees C (30-55 degrees F). Degree-day models with a 4.4 degrees C (40 degrees F) lower threshold temperature appeared to be suitable predictors of the appearance of stage 2 flowers and the 50% level of attack by slash pine flower thrips. These models should facilitate implementation of insecticide application programs based on predicting levels of thrips attack and flower phenology.