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 xananassa 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 runners, 18% smaller fruit, and 46% lower yields than did plants on fumigated soil. They also had an average of 27% fewer crowns, 49% more root discoloration, significantly fewer fine roots, and showed symptoms of the black root 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 of all genotypes was enhanced by fumigation, although the F, virginiana hybrids performed comparatively better than the other cultivars on nonfumigated soils.