Pest, disease and weed management

Permanent URI for this collectionhttp://elibrary2.sugarresearch.com.au/handle/11079/13843

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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Pachymetra root rot surveys of the Tully district update 2018 : ASSCT peer-reviewed paper
(ASSCT, 2019) Shannon, GJ; Magarey, RC; Macgillycuddy, L; Stringer, JK; Lewis, M
Pachymetra root rot is a soil-borne disease that impacts all sectors of the Australian sugar industry. The disease attacks the root system of sugarcane crops, affecting yields and leading to stool loss and shortened crop cycles, thus impacting the farming, harvesting and milling sectors. Monitoring the disease is, therefore, important so that optimised management practices are adopted, so bringing benefits to the entire value chain. A survey of the Tully district conducted in 2004 showed that pachymetra root rot was widely distributed across the Tully mill area; a second survey undertaken in 2013 sought to determine trends in disease incidence after some significant changes occurred in the cultivar mix. Crop resistance had shifted significantly with a change in cultivar resistance and there was a consequent increase in disease severity. Financial losses from reduced yield were estimated at $5.5 million in 2013; this compares to just under $1.0 million in 2004. This paper reports on a third survey in 2018 that is a five-year update to provide snapshot of the status of this disease in the Tully sugar industry. While the disease is still widespread, its severity has decreased with financial losses estimated to be $3.5 million.
The bacterial biocontrol agent pasteuria penetrans can help control root-knot nematode on sugarcane
(ASSCT, 2018) Bhuiyan, SA; Stirling, GR; Garlick, K; Anderson, J; Wickramasinghe, P; Wong, E
ROOT-KNOT NEMATODE (Meloidogyne javanica) is one of the most damaging pests of sugarcane, often causing heavy losses in coarse-textured sandy soils. The bacterial parasite Pasteuria penetrans is a potentially useful biocontrol agent and in a 2015–16 survey it was found at relatively high levels in three of the 126 sugarcane fields surveyed. Soil was collected from one of the heavily-infested fields and a pot experiment established to compare root-knot nematode multiplication in naturally infested soil and in soil where the endospores of P. penetrans had been killed by autoclaving. After 37 weeks, the root-knot nematode population was very high in the autoclaved soil but numbers of root-knot nematode eggs and second-stage juveniles were 99% lower in the soil that was naturally-infested with P. penetrans. A subsequent pot experiment with mass-produced endospores showed that when soil contained more than 6 000 endospores/g soil, root galling was not as severe as in non-infested soil and the number of root-knot nematode eggs was reduced by 71–82%. These results indicate that when high endospore concentrations are continually maintained in the root zone, P. penetrans will markedly reduce populations of one of the most important nematode pests of sugarcane.
Plant-parasitic and free-living nematodes associated with sugarcane in North Queensland
(ASSCT, 2018) Bull, J; Stirling, GR; Magarey, R
SURVEYS OF NORTH Queensland sugarcane soils indicated that root-lesion nematode (Pratylenchus zeae) was the most important nematode pest because it occurred in most fields and was often present at high population densities. However, the presence of root knot nematode (Meloidogyne spp.) in sandy soils and the relatively widespread distribution of moderately pathogenic nematodes such as stunt nematode (Tylenchorhynchus annulatus), stubby root nematode (Paratrichodorus minor), ring nematode (various Criconematidae) and dagger nematode (Xiphinema elongatum) suggested that in most fields, several nematode species were feeding on roots and contributing to root health problems. With regard to the free-living nematode community, survey results showed that bacterial-feeding nematodes were much more common than fungal-feeding nematodes and numbers of omnivorous and predatory nematodes were relatively low. Collectively, these findings suggest that the biological status of many north Queensland sugarcane soils is relatively poor. In addition to having high numbers of plant-parasitic nematodes they have low numbers of fungal-feeding nematodes. This indicates that fungi are not an important component of the detritus food web and this has implications for the ecosystem services they provide: decomposition of recalcitrant forms of organic matter; aggregation of soil particles; enhancement of plant nutrient uptake; improvement of disease resistance in plants; and suppression of pests and pathogens. The lack of omnivorous and predatory nematodes also has implications for pest suppression, as these nematodes help regulate populations of plant-parasitic nematodes.
Sugarcane streak mosaic; researching a relatively new disease in Indonesia
(ASSCT, 2018) Magarey, RC; Kristini, A; Achadian, E; Thompson, N; Wilson, E; Reynolds, M; Sallam, N; Goebel, R; Putra, L
SUGARCANE STREAK MOSAIC occurs in the south and south-east Asia regions and was first identified in Indonesia in 2005. Its relatively recent recognition means that much remains to be learnt about this viral disease. ACIAR-funded research has been investigating molecular and serological assays for the virus, yield losses, important modes of transmission, and an integrated disease management strategy to manage and minimise losses. So far our findings include: molecular variation in the virus around its geographic range; yield losses amount to approximately 20% in a susceptible variety; transmission may occur via application of infested sap to leaves; mechanical transmission (as on infested machinery surfaces) is unlikely to be significant. Surveys have shown the disease to be present in various parts of Indonesia (Java, Sumatera, Sulawesi and probably West Papua). Much remains to be learnt about its epidemiology.
Genetic diversity among populations of soldier flies : ASSCT poster paper
(ASSCT, 2019) Braithwaite, K; Lindsay, K; Jennings, J
Soldier flies are a serious pest in several regions of the industry. Because they were often considered a localised problem, their impact has largely gone unrecognised. However, in recent years there has been a concerted research effort to gain more understanding of the biology of the pest and to develop better management solutions.
Innovation in disease management; where to next : ASSCT peer-reviewed paper
(ASSCT, 2019) Magarey, RC
New technologies offer considerable scope for the refinement of disease management in the Australian sugarcane industry. While resistant cultivars, disease-free plant sources, crop termination and quarantine have provided a strong foundation for good disease management, the development of new technologies offers the possibility to make changes to data accumulation, analysis and application to industry. DNA- and NIR-based assay technology, remote sensing, drones, data digitisation, GIS and information databases offer the ability to capture huge additional amounts of relevant field data, enabling a better understanding of disease issues and the management required to minimise losses. This will also enable targeted extension of management strategies to individual farmers and industry sectors. Automated pathogen assays may also be possible, centred on the sugar factory. Step changes in disease management are likely in the next 5-10 years.
Effects of pachymetra root rot and nematodes on some elite sugarcane clones in Australia
(ASSCT, 2016) Bhuiyan, SA; Croft, BJ; Wong, E; Ogden-Brown, J; Turner, M; Parfitt, R; Magarey, RC; Bull, J; Cox, MC
PACHYMETRA ROOT ROT and nematodes are the two most important soil-borne pathogens of sugarcane in Australia. An experiment was established in Yandaran, Queensland in grey forest soil with high Pachymetra spore counts (>100 000 spores/kg). Fifteen elite varieties and one advanced clone, from pachymetra root rot susceptible, intermediate and resistant categories, were planted in the experiment. The experiment was maintained until the second ratoon crop and Pachymetra and nematode populations were assessed in each crop. In addition, the incidence of smut was recorded before harvesting. Cane yield (TCH), commercial cane sugar (CCS) and sugar yield (TSH) were also measured in each crop. Pachymetra spore counts remained significantly lower in resistant varieties compared to susceptible and intermediate varieties until the second ratoon. In intermediate and susceptible varieties Pachymetra spore counts increased substantially, in particular, in second ratoon. In intermediate varieties such as Q232A and Q208A Pachymetra spore counts increased more than three times from plant crop to second ratoon. Numbers of nematodes, in particular root-lesion nematode, more than doubled in the second ratoon crop compared to the plant and first ratoon crops. Only Q248A had significant levels of smut, with 25% and 30% infected plants in the first and second ratoon crops, respectively. Yield reduction was substantial in the second ratoon compared to the plant and first-ratoon crop. Sugar yield decreased by 45% in the second ratoon compared to the first ratoon. Mostly, poor or negative correlations were observed between both Pachymetra spore counts and nematode numbers and yield.
How do current ratings of sugarcane varieties for resistance to smut relate to natural infection
(ASSCT, 2018) Bhuiyan, SA; Cox, MC; Croft, BJ
SUGARCANE SMUT, CAUSED by a fungus Sporisorium scitamineum, is an important disease of sugarcane in Australia. Sugarcane smut can be managed effectively through the propagation of resistant varieties. In Sugar Research Australia’s (SRA) smut screening experiments, stalks of varieties from various stages of breeding programs are cut into one-eye setts and then dipped into a smut spore suspension (5 × 106 spores/mL water) for 10 min at 31 °C. After germination, the plants are transplanted to the field and disease incidence is measured in the plant crop and first and second ratoon crops. This method is effective for screening of a large number of varieties in a relatively short period (10–12 months) and is used in other countries. Although this method is widely accepted, it has some drawbacks: i) test plants are subject to very high disease pressure; and ii) it does not replicate natural infection. Three experiments were established in 2007, 2008 and 2009, to determine if the ratings obtained by artificial inoculation technique predict field resistance of varieties. All experiments were planted with 10 or 5 replicates of the test varieties planted between rows of infected Q205A, and maintained until second ratoon. Highly susceptible varieties Q205A and Q157 had >40% infected plants in plant crops whereas little smut was observed in intermediate and resistant varieties. Average % of smut infected plants increased in all experiments from the plant crop (5–12%) to first ratoon (21–46%) and second ratoon (26–59%) crops. The correlation coefficient values between smut incidence in the natural infection experiments and the historical ratings obtained using dip-inoculation methods ranged from r = 0.82 to 0.72, indicating a good agreement between natural infection trials and dip inoculation ratings.
Chlorotic streak resistance screening in the Tully district
(ASSCT, 2016) Magarey, RC; Sevntek, K; Bull, JI; Stringer, JK; Zamora, R
CHLOROTIC STREAK DISEASE (CSD) was first recognised more than 85 years ago and is present in most cane-growing countries around the world. An important management strategy is the use of resistant varieties; past research has shown there is significant variability in resistance in the Australian sugarcane germplasm. Data are reported from a variety resistance screening trial conducted in the Tully district (2013–2015 period) that was subjected to at least five flooding events over a two-year period. Maximum ‘% stools diseased’ infection levels were over 60% in the most susceptible variety. Several current commercial varieties appear very susceptible, including Q241A and Q251A. The data show that a much higher disease incidence is evident when data on ‘% stools diseased’ are recorded rather than ‘% stalks diseased’. Recording data on a stools basis therefore may provide a shorter time frame for assessing varietal susceptibility. Crop inspections are also significantly easier using this parameter, especially in mature crops where symptom expression is often higher (and therefore desirable to undertake at this time). Major flooding events provide optimum conditions for disease transmission in field trials, as long as shoot survival is not unduly affected.
Does rotating cultivars with intermediate resistance influence pachymetra root rot of sugarcane : ASSCT peer-reviewed paper
(ASSCT, 2019) Jensen, AS; Croft, BJ; Parfitt, RC; Brown, PH
Concerns have been raised by industry members over lower than expected cane yields associated with high oospore levels in sugarcane cultivars rated to have intermediate resistance to pachymetra root rot. This is a significant issue, as intermediate cultivars represent more than 70% of the sugarcane grown in Australia. It is possible that planting the same intermediate cultivar in successive crop cycles could lead to increased yield losses due to pachymetra root rot. This paper examines the residual soil-borne effect of the current major sugarcane cultivars on the following sugarcane crop in three field trials, located in the Herbert, Central and Southern growing regions. Levels of oospores of Pachymetra chaunorhiza and cane yields were assessed in ratoon crops of replicated cultivar-assessment trials and in subsequent crops of intermediate resistant Q208A (planted on the sites of previous cultivar trials). The relationships between Pachymetra oospore levels and cane yield in Q208A crops and pre-plant oospore levels were examined. High oospore levels occurred in plots planted to some intermediate cultivars, as well as susceptible cultivars. In the following crop of Q208A, which was planted into plots of the previous cultivar trial, Pachymetra oospore levels at harvest were related to oospore levels prior to re-planting at all trial sites. Cane yield (t/ha) of Q208A was significantly related to pre-plant oospore levels at a site near Bundaberg (P=0.0049). Yield losses of 21% were incurred at 120 oospores/g soil in Q208A. Cultivation of Q208A following a crop of Q208A did not result in higher Pachymetra oospore populations or yield losses compared with planting Q208A after other cultivars of similar resistance rating. In the Herbert and Central field trials, Pachymetra oospore levels were lower and there were no significant relationships between oospore levels and yield in Q208A planted at these sites. We demonstrate that significant yield losses in Q208A are associated with high Pachymetra oospore levels that occur under intermediate and susceptible cultivars in the previous crop. There was no evidence to support the hypothesis that repeatedly planting the same intermediate cultivar could lead to host-cultivar-specific virulence in P. chaunorhiza. Greater emphasis should be placed on breeding and selecting highly resistant cultivars that are suited to soil types conducive to Pachymetra

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