An Evaluation of Dazomet Incorporation Methods on Soilborne Organisms and Pine Seedling Production in Southern Nurseries
The use of dazomet as a fall and spring fumigant for pine seedling production and control of soilborne pests was evaluated at two southern nurseries. Dazomet was applied at low (280-325 kg/ha) and high (493-560 kg/ha) rates and incorporated with a rototiller or spading machine. Comparisons were made with methyl bromide/chloropicrin (MBC) fumigation and nonfumigated control treatments. Dazomet incorporation method had no effect on seedling density at either nursery, and often did not affect seedling morphological characteristics. At the Georgia (GA) nursery, seedling density and morphological characteristics did not differ among fumigant treatments except in the spring study area where shoot weight was greater in the MBC treatment than the dazomet or nonfumigated control treatments. In the study area at the North Carolina (NC) nursery, seedling density was greater in the high-rate dazomet treatment than the nonfumigated control. Seedlings were generally larger in MBC and dazomet treatments than the control. Seedling density and morphological characteristics did not differ amongfumigation treatments in the spring study area. Fumigation with A4BC or dazomet generally reduced the percentage of roots with Pythium and Fusarium spp. compared to controls at the GA nursery and the fall fumigation area in the NC nursery. Plant parasitic nematodes were found infrequently at both nurseries and did not difSer among treatments. Nutsedge (Cyperus spp.) was the major problem at the GA nursery and was effectively controlled only with MBC. Compared to the MBC treatment, the abundance of soilborne fungi and the association of certain types of'lkichoderma with roots was ofren lower in the dazomet treatments. The importance of these differences for long term seedling production and management of soilborne diseases is not known at this time.