The effect of applying prophylactic measures on the post-planting survival of Pinus patula in South Africa : scientific paper

Abstract

The observed survival of Pinus patula seedlings and cuttings has, on many occasions, been inadequate in nurseries and after field planting in South Africa. There have however, been several reports that survival can be improved if a fungicide is applied at planting, indicating that mortality is partially related to pathogenic activity. This paper summarises the results from two trials established to investigate the effects of the fungicide, Benlate (a.i. Benomyl), and biological control agents, Trichoderma harzianum and Bacillus subtilis, on P. patula survival and growth. During the nursery raising period, the pathogen Fusarium circinatum was isolated from all dying material. Field results from the trials indicate that initial (<180-day) post-planting survival is improved if the fungicide Benlate, and to some extent the biological agent T. harzianum was applied at planting. This improvement was, however, no longer significant at 360 days after planting. Reasons for this are not fully explained by the trial data but it is suggested that as fungicide efficacy declines over time, young trees may succumb to disease attack. Given the virulent nature of F. circinatum, it is assumed that mortality in the nursery was principally due to this pathogen, and that mortality in the field may be related to nursery infection. Due to the world wide restriction on the use of Benlate, future research should concentrate on identifying alternative fungicides and/or biological control agents that can be used in nurseries and when establishing disease susceptible species such as P. patula.


Keywords: Biological control, Benlate, Fusarium circinatum, Pinus patula, Post-planting survival


Southern African Forestry Journal No.200 2004: 51-58