|Juzwik, J - USDA FOREST SERVICE|
|Gust, K - UNIVERSITY OF MINNESOTA|
Submitted to: Western Forest and Conservation Nursery Association
Publication Type: Proceedings
Publication Acceptance Date: September 15, 1998
Publication Date: N/A
Interpretive Summary: Many of the bareroot tree nurseries in the North Central Region of US depend on methyl bromide fumigation to control root diseases including those caused by Fusarium spp. Alternative chemical and/or cultural methods are needed because of the ban on the use of methyl bromide scheduled for 2001. Fusarium spp. saprophytically colonizes crop residue, so the pathogen nis located in the soil wherever the crop residue in a cover crop is incorporated. Those nursery managers who use a moldboard plow have deeply buried (30 cm) residue while those who use disk have crop residue and Fusarium pathogen in the upper 10 cm. In the former case more fumigant and a deeper incorporation is needed- chemical alternatives to methyl bromide are more likely to succeed when the pathogen is closer to the soil surface. Confirmation of these findings is needed to assure that nursery managers can use systems approach to link tillage with root disease control.
Technical Abstract: Field studies were conducted in North Central states nurseries to investigate the soil conditions resulting from operational tillage and their potential effect on root disease development. Compacted soil layers, or hard-pans, were found in pine fields of two nurseries that use rotary tillers after sub-soiling but prior to sowing and use moldboard plows for incorporating cover crop residue. Water flow through undisturbed soil in rotary tiller - associated pans (10 to 15-cm depth) was slower than in non- compacted soils above and below the pan and compared to non-compacted areas of the fields. Vertical distribution profiles of soil-borne Fusarium spp. at each of five nurseries reflected the type of tillage implement used to incorporate cover crop material that ultimately served as substrate for fungal population increase. When a moldboard plow was used for incorporation and soil fumigation subsequently conducted, depth of fumigation was found to be inadequate for reducing Fusarium levels below 1 cm in methyl bromide - chloropicrin, metam sodium, and dazomet (when incorporated by rotary tiller) treated fields. Implications of these results to management of root disease in pine fields are discussed.