Pathological anatomy of carrot root scab and some factors affecting its incidence and severity

Abstract does not appear. First page follows.

Introduction

Root scab of carrot has been a serious disease in California since at least 1937, when it was first observed in the state by (Ark and Gardner (1942; 1944))5 in the Santa Maria Valley. They described the disease and reported the cause to be direct root infection by Xanthomonas carotae (Kendrick) Bergey et al. originally described by Kendrick (1934), as the cause of a blight of the leaves and umbels of seed carrots. A similar disorder was reported by (Ramsey (1937)) and (Ramsey and Wiant (1941)) as occurring on California carrot roots shipped to the Chicago market. They isolated Fusarium spp. from the lesions, and concluded that the disease was caused by Fusarium.

From experimentation and observations the present paper evaluates the effect of several factors on the prevalence and severity of the disease and describes its pathological anatomy.

The Disease

Distribution in California

Carrot root scab in California occurs commonly in the Salinas Valley, from Chualar south to King City, and in the Lompoc and Santa Maria valleys. In 1955 it also occurred in a late fall crop near Patterson, but did not recur there the following year. The disease has not been observed in the carrot-growing areas of the lower Salinas Valley, near the Pacific Ocean, although as many as 18 carrot crops in twenty years have been grown in some fields there.