The efficacy of acibenzolar-S-methyl (ASM) in inducing resistance against Fusarium graminearum sensu stricto in wheat (Triticum aestivum L.)

Four ASM (acibenzolar-S-methyl) concentrations were applied on wheat plants at different growth stages prior to inoculation with 1x105 conidia/ml of Fusarium graminearum. Thereafter, disease severity was monitored and recorded over time. All ASM concentrations reduced disease severity compared to the control. The best treatment, providing the lowest Area Under the Disease Progress Curve (AUDPC) units, high average Hundred Seed Weight (HSW) and reduced average Percentage Seed Infection (PSI), was 0.075 g/L ASM applied at anthesis. A weak but significant positive correlation was observed between AUDPC and PSI (r = 0.33; p = 0.0001). However, a moderate and weak negative correlation was observed between AUDPC and HSW (r = - 0.41; p < 0.0001) and HSW and PSI (r = - 0.18; p = 0.04) respectively. Higher ASM concentrations were more effective when applied at anthesis and lower concentrations at late boot. Moreover, repeated applications (applied at both late boot and anthesis) did not improve disease reduction. A disease reduction and deoxynivalenol (DON) reduction of up to 28.97% (0.075 g/L ASM applied at anthesis) and 18.79% (0.0375 g/L ASM applied at anthesis) was observed. However, DON and zearalenone (ZEA) reduction did not always correspond with disease severity reduction of tested treatments. This accentuates the importance of the development of integrated control strategies for the improved and effective management of Fusarium head blight (FHB) in wheat

Qualitative evaluation of smallholder farmer decisions, support systems, knowledge and disease management tools

Rural South African smallholder farmers are deprived of knowledge, relying on eroded indigenous  knowledge to support crop production. Modern technology can play a role in supporting production  decisions and packaging knowledge so it is easily accessible to all levels of users. Information  Communication Technologies, such as Decision Support Tools (DST) play an important role in systematic dissemination of information in agriculture, thus improving the quality of farmer  decisions, especially in  rural areas. These tools are constantly developed, improved and evaluated to assess their applicability  and efficacy. The article is based on the study that aimed at evaluating the effectiveness of a recently developed DST, with a disease management component, to enhance production decisions and  crop-disease management, among organic and small-scale farmers. Due to resource-limitations of most smallholder farmers in South Africa, production  practices, including disease control could be much improved, using indigenous-based, local knowledge about cultural methods of controlling crop diseases. A group of 15 extension officers and 12 researchers were purposively selected for the study because they play a major role in organising and disseminating information to the farmers. Participatory workshop sessions were conducted with groups, where tools were presented, explored and critiqued. The DST was found to have the potential to benefit both organic and smallholder farmers, the study recommends that government should support the development of agricultural DSTs, building on and improving eroded indigenous knowledge, to help farmers improve production and address problems with extension officers and within their resource means.Keywords: Organic farming, small-scale farming, Decision Support Tool (DST), disease management

Progress in the management of Fusarium head blight of wheat: An overview

Fusarium head blight (FHB), also known as head scab, is a devastating fungal disease that affects small grain cereal crops such as wheat (Triticum aestivum L.). The predominant causal agent, Fusarium graminearum Schwabe (teleomorph: Gibberella zeae (Schwein.) Petch), is ranked the fourth most important fungal plant pathogen worldwide. Apart from yield and quality losses, mycotoxin production can occur from FHB infection, resulting in harmful effects on human and animal health. Some level of disease control may be achieved by using certain fungicides and agronomic practices plus host resistance. In South Africa, there are currently no registered fungicides or bio-fungicides, no resistant wheat cultivars and only limited control is achieved by cultural practices. Because effective disease reduction cannot be achieved by using a single strategy, the integration of multiple management strategies can enhance disease control. We review possible strategies for reducing the risk for FHB infections that are relevant to the context of South Africa and other wheat growing areas in Africa. Significance: The importance of the effect of FHB on wheat cannot be overemphasised. This review highlights and describes the various control options and their efficacies. It also describes the current state of research in an effort to control FHB and its associated mycotoxins. Wheat is one of the most produced crops worldwide and in South Africa, hence this review could promote and intensify research towards the development of more effective management strategies for FHB of wheat

Establishment of Beauveria bassiana isolates as endophytes in rice cultivars and their biocontrol efficacy against rice stem borer, Sesamia calamistis

Possible endophytic colonisation of rice cultivar parts (leaves, stem and roots) by Beauveria bassiana isolates and their potential as biocontrol agents against Sesamia calamistis Hampson (African pink stem borer) were investigated. Five promising B. bassiana isolates were evaluated for their endophytic colonisation, the effectiveness of the inoculation methods and the efficacy of the isolates as biocontrol agents against S. calamistis. The plant part colonised is often dependent on the inoculation method. Colonisation of plant parts was assessed at 30 and 60 days after seed inoculation and foliar spray. For the pathogenicity activity, third instar larvae of S. calamistis were fed with rice stems that were previously inoculated with endophytic isolates of B. bassiana. Both inoculation methods led to the colonisation of the rice cultivar tissues, but were affected by the interactions of cultivars x isolates x inoculation methods. The colonisation of the cultivar plant parts varied over time (30- and 60-day intervals), and was affected by the inoculation method used. For both inoculation methods, highly significant differences were observed in the roots and the leaves over time (p=0.0001). However, with seed treatment, there was no significant difference in levels of colonisation in stems by the isolates x time (p=0.32). The B. bassiana isolates were pathogenic on the third instar larvae of S. calamistis, causing mortalities of more than 50% at 28 days after treatment. However, the virulence of the isolates varied. According to the isolates and the inoculation methods, B. bassiana formed an endophytic relationship with rice plants, and produced various mortality rates. Significance: Beauveria bassiana could be a potential biocontrol agent of rice stem borer, S. calamistis as there is no report of endophytic isolates of B. bassiana for the control of rice borers. Currently there is no commercially registered biocontrol agent against rice borers; hence further studies into B. bassiana could lead to the registration and commercialisation of B. bassiana as a bio-pesticide for rice stem borers