5.7 Enhancing of biocontrol efficacy by preharvest application of antagonists
Preharvest application of biocontrol agents as a stand alone treatment or combined
with a postharvest application of the biocontrol agent may also prove to be a useful
strategy in achieving improved performance against infections. This approach could
be used as a tool to manipulate epiphytic populations and change patterns of surface
wound colonization. Reports indicate the possibility of reducing postharvest decay
caused by C. gloeosporioides on avocado and mangoes by a preharvest spray with B.
subtilis, an antibiotic producing bacterium (Korsten et al., 1994). Koomen and Jeffries
(1993) have also demonstrated the feasibility of controlling anthracnose on mango
fruit with Bacillus cereus Frankland & Frankland and Pseudomonas fluorescensMigula.
Droby et al. (1999a) suggested the possible use of preharvest application of the yeast
antagonist P. guilliermondii to reduce the development of postharvest decay of citrus
fruit, and a reduction of postharvest Rhizopus rot of table grapes was also achieved by
a preharvest spray of the yeast P. guilliermondii. More recently, Benbow and Sugar
(1999) showed that preharvest application of the yeasts C. infirmo-ministus, C. laurentii
and C. oleophila provided control of postharvest decay on two pear cultivars. C. infirmoministus
gave the most consistent postharvest decay control in fruit treated 3 weeks
before harvest. Preharvest introduction of antagonists in conjunction with additional
postharvest applications may prove successful in providing acceptable levels of con-