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.
