Weed management in sugarcane using a combination of imazapyr followed by velvet bean as a break crop

Campbell, Peta L; Beckett, Richard P; Leslie, Graeme W

Weed management in sugarcane using a combination of imazapyr followed by velvet bean as a break crop

2019

Campbell, Peta L | Beckett, Richard P | Leslie, Graeme W

While farmers have used glyphosate to control the growth of weeds such as Cynodon dactylon (cynodon) in sugarcane fields for many years, its use has problems which include poor persistence in the soil and the development of tolerance. Here the potential of a class of persistent herbicides with an alternative mode of action to improve weed control in sugarcane was investigated. The main aim was to determine the amount of rainfall and waiting period required to dissipate enough imazapyr to enable safe planting of a sugarcane crop under South African field conditions. Results presented here indicate that imazapyr has good persistence, and effectively controls cynodon until ∼470 mm of cumulative rainfall has occurred, corresponding to a waiting period of ∼16 weeks. While this is also the time required before safe planting of sugarcane can occur, imazapyr-tolerant break-crops, in particular Mucuna pruriens (velvet bean), can be planted after as little as 70 mm of cumulative rainfall. In glyphosate-treated fields, cynodon recovers quickly, before sufficient break-crop development has occurred, necessitating expensive and time-consuming spot-spray control. Taken together, results presented here strongly suggest that under many South African conditions imazapyr may be a superior choice to glyphosate for weed control in fallow sugarcane fields.

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