The 2009 ASHS Annual Conference

Demand for biological control products has increased in recent decades due to problems associated with the use of chemical pesticides, including resistance, pest resurgence, environmental pollution and risks to human health. There is a growing interest in including biocontrol agents as part of integrated pest management systems to promote green technology. A bioassay has been developed to screen for an effective yeast inhibiting both the growth of the Aspergillus flavus and aflatoxin production.  The yeast, Pichia anomala strain WRL-076 was tested further for its ability to reduce spore production in pistachio flowers and fruits (nuts) as well as on almond and pistachio leaves. Assessment of the efficacy of P. anomala in orchard has been achieved by artificially wounding almond and pistachio nuts on the trees and then spraying the nuts  with the biocontrol yeast. The results clearly demonstrate that populations of A. flavus and other fungi were significantly reduced on wounded nuts. Several properties P. anomala make the species suitable as a biological control agent.  The yeast strain does not produce allergenic spores or mycotoxins. The yeast species is in the category of general regarded as safe (GRAS).  It is found naturally in the orchard. The yeast colonized the plant wound site effectively and inhibited growth of A. flavus on the wounds. Results from a number of labs indicated that the P. anomala can control several important fungal pathogens in post-harvest application. Recently it was shown that sprayed yeast on pistachio nuts inhibited the growth of a human pathogen, Burkholderia cepacia.  Several other species of yeast were reported to control the pathogenic bacteria, Ervinia amylovora, Xanthomonas campestris, Escherichia coli, Listeria monocytogenes, and Salmonella enterica. Further research to test the utility of P. anomala in horticutural production systems is warranted.