Plant-nutrient deficiency or heavy-metal toxicity as a cause of Yellow Canopy Syndrome

Yellow canopy syndrome (YCS) is a condition affecting Australian sugarcane crops. It causes characteristic yellowing of the mid-canopy leaves and can result in significant yield loss for badly affected crops. Many nutrient deficiencies and heavy-metal toxicities are well known to cause yellowing of sugarcane leaves. This paper explores the possibility of YCS being caused by a nutrient deficiency or heavy-metal toxicity. Soil and plant tissue were collected from healthy and YCS-symptomatic sugarcane in the Herbert and Burdekin districts during 2015– 2017 and analysed for nutrient content. Results show that YCS-symptomatic cane is not deficient in any of the necessary macro- or micro-nutrients and, therefore, nutrient deficiency per se is unlikely to be the cause of the condition. Further, test results indicated no significant increase in heavy-metal concentrations in samples of soil or plant from YCS-symptomatic cane compared to healthy asymptomatic cane and we conclude that, similarly, heavy-metal toxicity is an unlikely cause of YCS. Key words YCS, toxicity, heavy metals, macronutrient, micronutrient, nutrients