Browsing by Author "Olsen, DJ"

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Effect of neonicotinoid, pyrethroid and spirotetramat insecticides and a miticide on incidence and severity of Yellow Canopy Syndrome : ASSCT peer-reviewed paper
(ASSCT, 2019) Olsen, DJ; Ward, AL
Yellow Canopy Syndrome (YCS) is a condition affecting Australian sugarcane that can lead to yield losses in excess of 30% in severely affected crops. The causal agent of this condition is unknown. Insect pests are well known causal agents of a wide variety of yield-limiting crop conditions, either as vectors of pathogens, directly through their feeding damage, or as transmitters of toxins, but little has been done to evaluate insects as a possible causal agent of YCS. This paper presents the findings of a one-year field trial in which insecticides from different chemical groups and an acaricide were tested to evaluate their effect on YCS incidence and severity. Results showed a delay in the onset of symptoms and a significant reduction in the severity of symptom expression following the application of neonicotinoid and pyrethroid treatments. These treatments also resulted in a significant yield improvement relative to cane in the untreated control. The acaricide treatment was ineffective. These findings suggest further work is warranted to determine which insects are being controlled and to identify the mechanism for the positive yield response.
Is magnesium deficiency a causal agent of sugarcane Yellow Canopy Syndrome? : ASSCT peer-reviewed paper
(ASSCT, 2019) Tippett, O; Olsen, DJ; Ostatek-Boczynski, Z
Yellow Canopy Syndrome (YCS) is a disorder affecting sugarcane in the Australian industry, the cause of which is unknown. This paper reviews YCS research focusing on magnesium imbalance as a possible cause of the condition. Four studies were undertaken to evaluate the role of Mg in YCS incidence and severity. In Trial 1 sugarcane leaves were collected at multiple locations in the Burdekin and Herbert with samples taken from sugarcane blocks with both YCS symptomatic and asymptomatic plants. Despite adequate soil-Mg, leaf-Mg concentrations were significantly lower (p?0.05) in leaves 2, 3, 4, 5 and 6 of YCS symptomatic plants in both regions suggesting an imbalance of this critical nutrient. Trial 2 measured Mg concentrations in sugarcane leaves before, during, and after YCS symptom expression. Symptomatic cane showed decreased leaf-Mg concentrations, but this returned to normal levels once the cane recovered. Trial 3 treated YCS symptomatic cane with foliar and soil applications of Mg in an attempt to mitigate the condition. Neither treatment resulted in alleviation of the YCS symptoms. Trial 4 treated sugarcane with foliar-Mg and soil-Mg prior to onset of symptoms. Despite elevating the Mg concentration in leaves, these pre-symptomatic treatments did not prevent YCS expression and plants exhibited YCS symptoms similar to that of the untreated control. We conclude that YCS affected cane is associated with reduced leaf Mg concentrations, but it is unlikely that this is the cause of YCS per se, as concentrations were well above critical thresholds for plant health. YCS occurs independently of Mg and low Mg is an indirect effect rather than a cause. Given that disruption to plant nutrient balance has been described as a symptom of some plant diseases, we speculate that these findings suggest a biotic causal agent.
The fast fluorescence kinetics; a sensitive tool for early detection of water stress in sugarcane : ASSCT peer reviewed paper
(ASSCT, 2016) Olsen, DJ; Shafei, R; Botha, FC
Water stress is a major constraint for sugarcane production in many regions of the world, including Australia. Sensitive and non-destructive early measurement of the crop response to water stress would be of great value for producers, advisors, and researchers. Chlorophyll-a (Chla) fluorescence is well established as a tool for measurement of photosynthetic efficiency. Changes in the kinetics of Chla fluorescence can provide valuable insight into the structure and function of the photosynthetic apparatus and chloroplast membrane integrity. The parameter Fv/Fm is often used to describe the effect of stress on the quantum yield of photosystem two (PSII). In this study the polyphasic OJIP fluorescence transient was used to evaluate the response of the sugarcane photosynthetic electron transport system. Chlorophyll fluorescence was measured on three leaves in the canopy of KQ228A over a five-day water stress period, and the response analysed using the OJIP-test. The results show that several of the parameters that can be derived from the OJIP test are more sensitive and a better reflection of water stress than the Fv/Fm ratio. Evidently PSII is much more sensitive to water stress than photosystem one (PSI). In late stages of stress there are signs of a loss in membrane integrity and a disruption of water splitting in PSII.