Determining appropriate parameters for optimization of biocontrol success

Abstract

Increased economic and environmental pressures have led to the requirement for a more accurate and safe crop protection method. Although Avogreen® (Bacillus subtilis) offers an environmental friendly alternative to the use of pesticides; few growers have opted for this approach mainly due to uncertainty regarding the success of the biocontrol program. Biocontrol success may be influenced by biological, ecological, scientific, economic, political, social, legal and marketing factors. Investigations showed that delivery of the antagonist to the plant surface was equally effective employing a mistblower application method and a handgun application method. On the leaf, the leaf carrying capacity influenced survival of the antagonist and the optimal application concentration of Avogreen®. Increased application frequency and a pre- harvest spray showed potential to increase biological control efficiency. Foliar fertilizers and oils enhanced antagonist counts, while spreaders, stickers and copper containing fungicides inhibited antagonist growth. Social factors that influenced farmer acceptability towards biological control programs included educational level, land owner status, generation of farming, land claim status and food safety system certification. Marketing hurdles facing the South African avocado industry included frustrations with the registration procedure of new products in South Africa and a lack of biocontrol knowledge demonstrated by sales staff. Two disease assessment methods were also evaluated. The conventional assessment method involving a rating scale was compared to a disease incidence and severity assessment method. The disease incidence and severity assessment method allowed a more detailed assessment of disease control effectiveness. To evaluate the overall success of the biocontrol program a Biocontrol Assessment Scheme (BAS) was also developed. BAS identified orchard management, antagonist application practices and technical knowledge and assistance during marketing as potential restrictions for successful biocontrol.