Pest, disease and weed management

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Research outcomes: A comprehensive RD&E program that addresses existing and emerging pests, diseases and weeds, allowing sugarcane growers to manage their crops efficiently with minimal environmental impacts. An enhanced industry capacity to deal with incursions of exotic pests, diseases and weeds.

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Author: search.filters.author.Scalia, GStart date: 2020

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    Solving YCS : final report 2014/049
    (ASSCT, 2021) Scalia, G; Joyce, P; Powell, K
    Yellow canopy syndrome (YCS) is a sporadic condition presenting as golden-yellowing of the mid canopy in sugarcane during the peak growing period of December to March. The key driver of YCS is growth rate and symptoms usually exhibit after rainfall. YCS can be induced or mitigated by altering sink strength and sugarcane can recover from a YCS event. Abiotic or biotic stress has a serious effect on the photosystems and the physiological fitness of the crop. There is a strong correlation between YCS expression, leaf sucrose and sink strength, independent of crop age. YCS symptomatic leaves always have high leaf sucrose and ?-glucan content. Under experimental conditions the pyrethroid bifenthrin supresses insect stress, promotes increased sink growth and maintains low leaf sucrose and ?-glucan levels. Induced senescence causes YCS plants to have a lower number of attached leaves. Yield loss precedes YCS expression and there is no correlation between YCS severity and cane yield or CCS. Lamina starch staining is a useful tool to assist in YCS identification. There is no strong evidence of genetic predisposition for YCS susceptibility. Industry-wide incidence and severity of YCS is too difficult to accurately assess due to its episodic nature, no single causal agent and the link to climate change and severe weather events. The data does not support the cause of YCS being a pathogen, specific insect or mite, soil borne agent, poor root health, nutrient deficiency, or heavy metal toxicity. YCS is a physiological disorder visualised as the terminal expression of metabolic perturbances caused by growth disruption.
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    Leaf sucrose: The link to diseases, physiological disorders such as YCS and sugarcane productivity : final report 2015/016
    (Sugar Research Australia Limited, 2020) Scalia, G; Wathen-Dunn, K; Marquardt, A; Botha, F
    Yellow canopy syndrome (YCS) is a physiological disorder expressing as yellowing of the mid-canopy. Rapid growth following a stress period where growth rate of the top internodes has been compromised creates a supply demand imbalance. This results in high sucrose accumulation in the leaf which triggers yellowing. Accumulation of sucrose past an upper tolerance level causes partial stomatal closure, overheating, disruption to photosynthetic machinery, chloroplast destruction and leaf yellowing. Gene expression, protein and metabolite data all support a disruption to leaf metabolism as well as a strong association with abiotic stress. The data collectively shows that the metabolism of YCS-affected plants is compromised throughout the mid-canopy and occurs well before the onset of visual yellowing. Repartitioning of carbon to starch and other pools is an attempt to lessen the sucrose load within the source leaf, while also reducing oxidative stress. High levels of starch accumulation in the midrib veins of YCS leaves can be easily stained and viewed. This method can be used to reduce misdiagnosis when coaligned with correct symptom development and expression. There is no CCS penalty association with YCS, and crops can grow out of a YCS event. Management options to mitigate YCS involve best practice farming to reduce stress on the crop prior to and during the peak growing season. This will increase the sink capacity in the stalk and prevent a supply and demand imbalance. The data does not support a single cause and may therefore be either biotic, abiotic, or a combination of both.