The effect of Sirex spp. woodwasps and their fungal associates on Alabama forest health

Abstract

Forestry is an industry in the Southeastern United States that provides products and jobs to people throughout the region. These forests, while are mostly well managed for various outcomes, are susceptible to a variety of pests and pathogens that have the potential to do great ecological and economic damage. One pest species that has been studied extensively in the Southern Hemisphere is Sirex noctilio. This is a species of woodwasp, native to Eurasia, which has become invasive in many parts of the world. This insect, along with its mutualistic fungal pathogen, Amylostereum areolatum, is a cause of concern because they have the potential to attack healthy pine stands, ending in the mortality of vast amounts of trees. In the southeast, no S. noctilio have been detected. A survey was undertaken to gain a better understanding as to which species of woodwasps are found in Alabama forests. Traps were deployed in three localities throughout the state, and were visited year-round for at least one year. Woodwasp and other insect species of concern were morphologically identified and cataloged from all sites. Woodwasp species were dissected and sampled for nematode infestation and for associated fungal species. These samples (wasp, nematode, and fungi) were all molecularly analyzed, and then phylogenetic relationships were determined. A novel relationship between S. nigricornis and Deladenus siricidicola was observed. Isolates of Amylostereum from Alabama and other localities around the world were subjected to chemicals emitted by the pine substrates in which they grow. Certain defense chemicals were shown to significantly reduce growth rates of Amylostereum spp. hyphae compared to a dH2O control treatment. Amylostereum spp. tended to be poor competitors to Leptographium spp. fungi when plated in direct contact with each other. One isolate of A. chailletii, 15B from Alabama, outcompeted both L. terebrantis and L. procerum. A VCG study also was performed, where isolates of the same species of Amylostereum were plated together to determine if isolates were clonal. Two distinct vegetative compatibility groupings of A. chailletii were determined from S. nigricornis captured in Alabama.