Etiology of Parsley Damping-off and Influence of Temperature on Disease Development

Abstract

Lumsden et al (12) and the taxonomic Hershman, D. E., Varney, E. H., and Johnston, S. A. 1986. Etiology of parsley damping-off and criteria of Middleton (15). The key and influence of temperature on disease development. Plant Disease 70:927-930. methods described by Toussoun and Nelson (22) were used to identify Damping-off of seedlings resulted in extensive stand reductions of parsley in southern New Jersey Fusarium species. during the 1981-1982 growing seasons. The fungi most frequently isolated from field-grown Rhizoctonia anastomosis grouping. seedlings with symptoms of postemergence damping-off were Fusarium oxysporum, F. solani, Thirty-two randomly selected isolates of Pythium irregulare, P. ultimum, and Rhizoctonia solani (AG-4, AG-l, and AG-2, type 2). In R y y pathogenicity tests, most isolates of P. irregulare and P. ultimum were highly pathogenic and grolani were asig to anastmosi caused extensive preemergence and postemergence damping-off. Similarly, most isolates of R. groupings (AG), using the precedure solani AG-4 and AG-2, type 2, were highly pathogenic. Isolates of AG-2, however, varied described by Burpeeetal (1). Each isolate considerably in pathogenicity. No other fungi tested for pathogenicity incited disease in parsley. In was paired with two isolates of each sand bed studies, a combination of P. irregulare and P. ultimum isolates was highly pathogenic at anastomosis group (obtained from D. K. 15, 23, and 30 C. R. solani, however, was much less pathogenic at 15 C than at either 23 or 30 C. A Bell, University of Georgia). Two testers similar response was obtained in experiments in environmental chambers. of each group were used because it is known that some isolates may anastomose with one tester and not with another withParsley (Petroselinum crispum (Mill.) The objectives of this study were to in the same group (D. K. Bell, personal Nym.) is an important crop in southern sample the major parsley-growing communication). All isolates were New Jersey. It is typically grown from regions of southern New Jersey for maintained on the PDYCA medium (39 g March through September, although it is postemergence damping-off of seedlings, of Difco dehydrated PDA, 0.5 g of yeast frequently overwintered to provide for determine the etiology of the disease, and extract, 0.5 g of casein hydrolysate, 2 g of the early spring market. Plain- and curl- investigate the relationship between agar, and 958 ml of deionized water) leaved cultivars are grown in New Jersey temperature and disease development in developed by Sumner and Bell (20). and are marketed primarily as bunches controlled environments. Pathogenicity of isolates. Before