Insect-Fungal Complex Associated with Loblolly Pine Decline in Central Alabama

Abstract

Abstract Loblolly pine decline, characterized by an expanding area of declining and dead trees, is becoming increasingly prevalent in loblolly pine (Pinus taeda L.) forests in central Alabama. A 3-year study was conducted to determine the fungal, root, and lower stem-infesting insect, and/or soil parameters associated with this decline. Hylastes salebrosus, Hylastes tenuis, Pachylobius picivorus, and Hylobius pales were significantly more abundant in declining plots than in asymptomatic plots. Root- and lower stem-infesting insects consistently carried Leptographium terebrantis, L. procerum, and L. serpens. Sampled roots had high levels of root damage, mortality, and staining typically associated with Leptographium species. Root damage and mortality preceded aboveground symptoms of short chlorotic needles, sparse crowns, reduced radial growth, and tree mortality. A sequence of biotic and abiotic factors is proposed as the cause of loblolly pine decline complex.