Exploring Fungal Diversity and Interactions with Lecanosticta acicola in Brown Spot Needle Blight

Abstract

Brown spot needle blight is a foliar disease that affects loblolly pines. It is characterized by small, necrotic spots on the needles that expand into brown lesions surrounded by a yellowish halo, often culminating in defoliation when conditions are favorable. Loblolly pine is the most abundant pine found in the southeast U.S. It is of a high economic value, however in recent years it has been threatened by brown spot needle blight disease, thereby impacting the region’s forest economy. In this study morphological and molecular techniques were used to identify co-occurring foliar pathogens with Lecanosticta acicola, the causative pathogen of the disease. Twenty-one different fungi genera were recovered from these methods of which Pestalotiopsis, Cladosporium, Hendersonia, and Trichoderma were found to be the predominant fungi associated with L. acicola. The study further tested the susceptibility of seventeen different loblolly pine families to L. acicola. We ranked the best three families that had better tolerance to the pathogen, based on growth parameters such as mean height, disease rating root collar diameter and relative water content. Finally, we investigated how spore traps could be used to assess L. acicola spore loads in BSNB-infected plots. We found that climatic variables such as rainfall, relative humidity and temperature affected spore release throughout the sampling period, with rainfall having the best association with spore release. Keywords: Loblolly pine, foliar pathogens, Brown spot needle blight