Relative performance of strawberry cultivars and native hybrids on fumigated and nonfumigated soil in Michigan

The performance of four California and 11 eastern cultivars of Fragaria xan anassa Duchesne in Lamarck, and 12 elite F-1 hybrids of Fragaria x annnassa with F, virginiana Miller in their immediate background was evaluated in a producer's field with and without methyl bromide-chloropicrin fumigation, Averaged across all genotypes, plants in nonfumigated soils had 43% fewer r unners, 18% smaller fruit, and 46% lower yields than did plants on fumigate d soil. They also had an average of 27% fewer crowns, 49% more root discolo ration, significantly fewer fine roots, and showed symptoms of the black ro ot rot syndrome. The most commonly isolated pathogens from discolored roots were Pythium sp., Rhizoctonia sp., Idriella lunata P.E. Nelson & K, Wilh,, and the root-knot nematode (Meloidogyne hapla Chitwood), The performance o f all genotypes was enhanced by fumigation, although the F, virginiana hybr ids performed comparatively better than the other cultivars on nonfumigated soils.