GROWTH-RESPONSES IN OILSEED RAPE (BRASSICA-NAPUS L) TO COMBINED APPLICATIONS OF THE TRIAZOLE CHEMICALS TRIAPENTHENOL AND TEBUCONAZOLE AND INTERACTIONS WITH GIBBERELLIN

Crop height in the oilseed rape cv. Ariana was reduced more by the triazole retardant triapenthenol at 490 g ai ha-1, applied as a combined spray with the triazole fungicide tebuconazole at 250 g ai ha-1, than when triapenthenol was applied alone. The growth responses following combined treatment appeared to be additive of the component effects. Initial inhibition of stem extension and leaf expansion by tebuconazole was followed by compensatory growth; the pattern of responses was similar to that with triapenthenol applied at approximately one tenth of the rate. However, different mechanisms of effects on growth were indicated by competitive interaction with gibberellic acid.