Articles
Field spread of the biological control agent Aspergillus flavus AF36 in Californian nut orchards
Article number
1406_51
Pages
359 – 366
Language
English
Abstract
Aflatoxins are potent carcinogens produced by Aspergillus species, which occasionally contaminate pistachio nuts in the field.
The international markets reject pistachio loads when aflatoxins exceed minimum levels, causing economic losses for the industry.
The massive release of atoxigenic strains of A. flavus stands out among the integrated management practices.
The products, AF36 Prevail® and Afla-Guard®, have been commercially used in pistachio in California since 2017 and 2018 respectively.
However, in nut orchards, the treatment application is still being optimized.
We studied the sporulation capacity of both AF36 Prevail® and Afla-Guard® grains, in diverse culture media.
Also, the effect of soil moisture on the percentage of sporulated AF36 Prevail® grains (SG) and the number of spores per grain using a sporulation index (SI) were evaluated under controlled conditions.
SG was higher than 85% when soil moisture was ≥13%; likewise, the SI increased with soil moisture from 8.4 to 21% and then decreased.
In-field, we studied the dispersal of the AF36 spores, the density of spores decreased markedly with the height and distance from the inoculum source.
After nut harvesting, there was an increase in the Aspergillus population in the tree canopy; in contrast, the summer rains reduced these population.
This work has contributed to optimizing the biocontrol application approach and understanding the pathogen inoculum dynamics in tree-nut orchards.
The international markets reject pistachio loads when aflatoxins exceed minimum levels, causing economic losses for the industry.
The massive release of atoxigenic strains of A. flavus stands out among the integrated management practices.
The products, AF36 Prevail® and Afla-Guard®, have been commercially used in pistachio in California since 2017 and 2018 respectively.
However, in nut orchards, the treatment application is still being optimized.
We studied the sporulation capacity of both AF36 Prevail® and Afla-Guard® grains, in diverse culture media.
Also, the effect of soil moisture on the percentage of sporulated AF36 Prevail® grains (SG) and the number of spores per grain using a sporulation index (SI) were evaluated under controlled conditions.
SG was higher than 85% when soil moisture was ≥13%; likewise, the SI increased with soil moisture from 8.4 to 21% and then decreased.
In-field, we studied the dispersal of the AF36 spores, the density of spores decreased markedly with the height and distance from the inoculum source.
After nut harvesting, there was an increase in the Aspergillus population in the tree canopy; in contrast, the summer rains reduced these population.
This work has contributed to optimizing the biocontrol application approach and understanding the pathogen inoculum dynamics in tree-nut orchards.
Authors
M.T. Garcia-Lopez, R. Jaime-Garcia, E. Meca, R. Puckett, T.J. Michailides, J. Moral
Keywords
AF36 Prevail®, biocontrol, tree nuts, sporulation, dispersal
Groups involved
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