Effect of Herbicides on the Development of Root Rot on Navy Bean

Application of EPTC (S-ethyl dipropylthiocarbamate) at 3.4 and 4.5 kg/ha in 1972 increased root rot severity and reduced navy bean (Phaseolus vulgaris L.) yields in soil with an artificial root rot [Fusarium solani (Mart.) Appel and Wr. f. Phaseoli (Burk.) Snyd. and Hans.] inoculum level. EPTC at 3.4 kg/ha and chloroamben (3-amino-2,5-dichlorobenzoic acid) at 3.4 kg/ha in 1973 caused the greatest root rot severity and greatest decrease in yield. Dinoseb (2-sec-butyl-4,6-dinitrophenol) and fluorodifen (p-nitrophenyl α,α,α-trifluoro-2-nitro-p-tolyl ether) at 5 kg/ha interacted with root rot less than the other herbicides assayed. In the growth chamber at 23 C, EPTC at 3.4 kg/ha and alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl) acetanilide] at 2.8 kg/ha applied to navy bean grown in soil infested with F. solani reduced plant growth. Root rot injury was most severe in plants treated with EPTC at 20 C ambient temperature. Navy bean growth was reduced as the level of F. solani chlamydospore inoculum increased in the presence of EPTC.