Post establishment survival of Pinus patula in Mpumalanga, one year after planting

Abstract

Recent evidence indicated that the pathogen Fusarium circinatum might be contributing significantly to post-planting mortality. Consequently, sixteen experimental sample plots, widely distributed over many localities in Mpumalanga, were established over two growing seasons to quantify the extent of pest and pathogen related in-field mortality. Survival in all treatments was extremely low. There was large variation in response to treatments and survival in the different trials. A single application of fungicide at planting improved survival by 13% on average, while a single application of fungicide and insecticide at planting improved survival by 29% on average. Most of the mortality occurred between 30 and 140 days after planting. Visual inspection of the dead plants indicated that White grubs and Hylastes angustatus caused most of the insect-related mortality. Pathogen isolation from a sub-sample of dying plants indicated that 49% of dying plants were pathogen-free, while F. circinatum was the prevailing fungus, isolated from 42% of the dying plants. It is estimated (95% confidence level) that F. circinatum was responsible for an 18.5% to 31.5% decline in survival in the monitored compartments, planted between November 2002 and March 2004 in Mpumalanga.