Persistence of Beauveria bassiana (Ascomycota: Hypocreales) as an endophyte following inoculation of radiata pine seed and seedlings

Abstract

The entomopathogenic fungus Beauveria bassiana commonly causes disease on a range of insects, including bark beetle pests of plantation forest trees. However, using broadcast application of the fungus to control pest beetles in large scale plantation forests could be difficult to achieve economically. B. bassiana has also been found as an endophyte in plants, including the main commercially planted tree in New Zealand, Pinus radiata. In this study we investigated two methods to establish B. bassiana as endophytes of pine seedlings, seed coating and root dip. Two isolates previously isolated from within mature pines were used and the seedlings monitored for 9 months. Samples of unwashed, washed and surface sterilised roots, surface sterilised needles and soil were plated on semi-selective agar at 2, 4 and 9 months after inoculation. B. bassiana was successfully established in pine seedlings using both root dip and seed coating. The fungus was found in soil, non-sterile and sterilised samples at 2 and 4 months, but only one seedling of 30 was positive for fungus in surface sterilised samples after 9 months.