GENERAL OVERVIEW
6.5 FUTURE PERSPECTIVES
A number of microbes with the potential for disease control and plant growth promotion have been isolated and screened by the Department of Plant Pathology, University of Natal, South Africa. More research is being undertaken in this field and it seems likely that more efforts will be needed to diversify the potential applications of beneficial microbes. There is a possibility of utilizing molecular technologies to promote biological control that will be effective in disease control strategy.
There is a need to investigate the interactions among pathogens,the plant and the antagonists in different agricultural systems (Kerry, 2000). It is by means of thorough research that one will be able to determine whether biocontrol will replace or supplement existing crop protection strategies. Moreover,although a market exists for biocontrol products, considerable progress is still needed on the technical, agronomic, socio-economic and political issues. Still more studies on the practical aspects of mass-production and formulation need to be undertaken to make new biocontrol products stable, effective, safe and more cost-effective. In addition, the successful utilization of a b iocontrol product requires adequate knowledge 0n how, when and where to apply it. For this purpose, the user (farmer) must be trained or be made fully aware of storage requirements and the safe and effective use ofthe product.
Pesticide bans (Whipps and Lumsden, 2001) and grower's interest in alternative disease control measures (Finch, 1992) suggests that the market potential of biocontrol products will increase in coming years. However, the future success of the biological control industry will entirely depend on innovative business management, product marketing, extension education and research (Mathreet al., 1999).
Based on the findings of the research and the foundations laid out in various parts 0fthis thesis, a forecast on the research needsin various areas of the field is as follows:
6.5.1 Isolation of beneficial microorganisms from the soil
• Initially, microbes must be isolated from an area where they are going to be re-inoculated, e.g.,from a sorghum rhizosphere if sorghum is the target crop;
• Where isolation of antagonists with a wide-spectrum of action is needed, suppressive soils are ideal sources and therefore, isolation from such soils can ease the screening procedures;
• Heat treatment that was used in this thesis may be a quick method to select only endospore forming-Bacillus sp. However, spores in a natural environment may posses different heat sensitivities from those which have been cultured following such treatment. Therefore, a more precise technique is needed to isolate antagonists without affecting their characteristics. This may be done by the use of selective media.
6.5.2 Screening of biocontrol agents
• Screening is needed for competence and induction of host resistance;
• Where screening for biocontrol agents is required to be exerted via hyphal interactions, it should be carried out under nutrient conditions that at least approximate the existing environment in which biocontrol is to be used;
• There is a need to develop an in vitro screeningprotocol that includes interactions of the pathogen, antagonist and the host;
• When assessing the effect of the antagonist on the target pathogen, information should be sought on the susceptibility of the biocontrol agent to attack by major components of the soil microbial populations;
• There is a need to develop a discrete screening approach for microorganisms intended for growth stimulation.
6.5.3 Biocontrol trials in greenhouse
• Good disease control potential was observed when Bacillus and Trichoderma were tested againstR. solaniandPythium sp. especially on sorghum;
• I therefore, suggest diversified trials against a number of pathogens on various crops in other controlled growth conditions such as hydroponics and growth chambers;
• Research is needed to investigate the possibility of mixing antagonists or with chemicals for disease control and growth stimulation under controlled environmental conditions.
6.5.4 Biocontrol trials in the field
• Detailed information on the history of the field, especially on cropping sequences and on physical and chemical characteristics of the soil are needed before attempting trials;
• Knowledge is required on the behaviour of the biocontrol agent in the field. In particular, the short- and long-term population dynamics of the antagonist and the pathogen;
• Assessment is needed on levels of pathogen inoculum and concentrations of the antagonist that should be applied in the field to demonstrate disease control efficiency;
• More fieldwork is needed to demonstrate efficiency and cost effectiveness of biocontrol agents in disease management;
• Consideration should be given for possible integration of biocontrol strategies with existing crop management programs;
• Following appropriate cultural practices (soil preparation, time of planting, irrigation regime.. fertilization, etc) often has a significant impact on disease severity and control efficiency of the antagonist. Therefore, consideration should be given to cultural practices to maximize biocontrol efficiencies of introduced antagonists.
6.5.5 Production and marketing of biocontrol products
Before developing an effective biocontrol product the following points must be fulfilled.
• Crops are grown under a variety of climatic and environmental conditions including temperature, rainfall and soil type.Additionally, crop variety and pathogens change from
farm to farm or sometimes even within one field. Therefore, for effective field performance, formulations must have the ability to tolerate a wide range of climatic and biotic factors;
• Assessments on different formulations, packaging and storage conditions are needed to stabilize and extend the shelf-life of the product;
• Production costs need to be reduced to market the product at a price competitive with standard fungicides;
• Many failures in the u se of biocontrol products for disease control have been linked to strong pressure to market biocontrol agents before they are fully tested for their efficacy.It is therefore recommended that biocontrol agents be adequately investigated before they are released. Itwould be advisable if growers test the product and use their feedback so that unexpected problems and failures can be avoided;
• Users need to understand the limitations ofbiocontrol agents. It is important to realize that biocontrol agents are not like chemicals, and the user should not expect fast, complete disease control, and that accepting certain levels of crop damage is a given;
• Scientific, regulatory and marketing issues must all be assessed effectively for a biocontrol product to be successful in the market.