The effects of soil fumigation on pine seedling production, weeds, foliar and soil nutrients, and soilborne microorganisms at a south Georgia (U.S.A.) forest tree nursery

Abstract

Pine seedling production and pest problems were evaluated in plots fumigated with methyl bromide and nonfumigated plots over a 6-year period at a Georgia nursery. Fumigation increased bed densities for loblolly pine (Pinus taeda L.) in 1996 and slash pine (Pinus elliottii Engelm. var. elliottii) in 1998; differences were not observed between treatments in other years. The root collar diameter, height, and root and shoot masses of loblolly pine seedlings were often greater in fumigated plots during the first 3 years. Morphological characteristics rarely differed between treatments for slash pine. The primary pest problem was nutsedge (Cyperus spp.); most other weeds were controlled with herbicides used operationally at the nursery. Plant-parasitic nematode populations did not increase over time and were not a problem. Although Fusarium and Pythium spp. were more common in soil and on roots in nonfumigated plots, evidence of disease was rare. Fumigation increased the abundance of and changed the composition of Trichoderma spp. in soil and on roots. Soil manganese and iron, and foliar manganese, phosphorus, and nitrogen were greater in the fumigation treatment in some years. A better understanding of the risks of soilborne diseases may facilitate the development of pest management programs that are more cost-effective.