Rm. Davies et Jj. Nunez, Influence of crop rotation on the incidence of Pythium- and Rhizoctonia-induced carrot root dieback, PLANT DIS, 83(2), 1999, pp. 146-148
The influence of various crop rotations on population densities of Pythium
spp. and Rhizoctonia solani, subsequent carrot yields, and incidence of car
rot root dieback was investigated. Carrots followed crops of alfalfa, barle
y, carrots, cotton, onions, or fallowed soil in two independent trials. Pop
ulations of Pythium spp. were greater following alfalfa and barley than oth
er crops in one of the 2 years of the study. Populations of R. solani were
generally greater following alfalfa and cotton than other crops in each of
the 2 years of the study. In 1 year, yields of marketable carrots were redu
ced following the alfalfa crop; no other cropping pattern influenced carrot
yields. The incidence of root dieback, which resulted in mature carrots wi
th misshapen or multiple taproots, was generally greater following alfalfa
and barley than other crops in one trial, and greater following alfalfa and
cotton in the other trial.