Period of susceptibility of almonds to aflatoxin contamination during development in the orchard

Picot, Adeline; Ortega‐Beltran, Alejandro; Puckett, Ryan D; Siegel, Joel P.; Michailides, Themis J.

doi:10.1007/s10658-016-1108-2

Cited by 18 publications

(9 citation statements)

References 29 publications

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“…flavus . This occurred regardless of continuous experimental release of both atoxigenic and toxigenic Aspergillus fungi during previous cropping seasons [ 22 , 33 ] and relatively high natural Aspergillus densities throughout California’s Central Valley [ 5 , 6 , 16 ]. Low (< 3%) frequencies of Aspergillus spp.…”

Section: Discussionmentioning

confidence: 99%

“…Our results indicate that Aspergillus species contaminate almond kernels more frequently during the final development stages, i.e. from hull split until almonds are mature, the most susceptible period for fungal infection and aflatoxin formation [ 33 ], which occurs throughout August. That is the period in which navel orangeworm is associated with almond crops and creates larval boring wounds that facilitate infection by aflatoxin-producing fungi that the insect typically carries; when navel orangeworm is not properly controlled, high aflatoxin contamination occurs [ 16 ].…”

Section: Discussionmentioning

confidence: 99%

“…Atoxigenic application during the proposed pre-hull-split (middle of July) period should be sufficient for the atoxigenic strain to reproduce on the delivery substrate (i.e. sterile wheat or sorghum grain), colonize organic matter sources present in the orchard, and then move to the maturing almond fruit to colonize the substrates that otherwise fungi residing in orchard soils and/or neighboring areas would do during the most susceptible period to aflatoxin contamination, second week of August and until harvest [ 33 ].…”

Section: Discussionmentioning

confidence: 99%

“…flavus and A . parasiticus strains), occurs on a yearly basis in this plot, including in both 2014 and 2015 (the immediate previous years in which the different samples evaluated in the current study were collected), as part of different experiments that include evaluation of atoxigenic strains to decrease aflatoxin content [ 22 ], determining period of almond susceptibility to aflatoxin contamination [ 33 ], or assessing influences of both fungicides and insecticides in decreasing aflatoxin content, among others.…”

Section: Methodsmentioning

confidence: 99%

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Fungal communities associated with almond throughout crop development: Implications for aflatoxin biocontrol management in California

et al. 2018

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Interactions between pathogenic and nonpathogenic fungal species in the tree canopy are complex and can determine if disease will manifest in the plant and in other organisms such as honey bees. Seasonal dynamics of fungi were studied in an almond orchard in California where experimental release of the atoxigenic biopesticide Aspergillus flavus AF36 to displace toxigenic Aspergillus strains has been conducted for five years. The presence of the vegetative compatibility group (VCG) YV36, to which AF36 belongs, in the blossoms, and the honey bees that attend these blossoms, was assessed. In blossoms, A. flavus frequencies ranged from 0 to 4.5%, depending on the year of study. Frequencies of honey bees carrying A. flavus ranged from 6.5 to 10%. Only one A. flavus isolate recovered from a blossom in 2016 belonged to YV36, while members of the VCG were not detected contaminating honey bees. Exposure of pollinator honey bees to AF36 was detected to be very low. The density of several Aspergillus species was found to increase during almond hull split and throughout the final stages of maturation; this also occurred in pistachio orchards during the maturation period. Additionally, we found that AF36 effectively limited almond aflatoxin contamination in laboratory assays. This study provides knowledge and understanding of the seasonal dynamics of Aspergillus fungi and will help design aflatoxin management strategies for almond. The evidence of the low levels of VCG YV36 encountered on almond blossoms and bees during pollination and AF36’s effectiveness in limiting aflatoxin contamination in almond provided additional support for the registration of AF36 with USEPA to use in almond in California.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Fungal communities associated with almond throughout crop development: Implications for aflatoxin biocontrol management in California

et al. 2018

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“…In California, over the last decade, there has been an increase in unacceptable aflatoxin levels in pistachio, almond, and fig (Donner et al 2015;Doster et al 1996Doster et al , 2014Picot et al 2017). This has resulted in rejection of tree crop lots, preventing entry into European markets (Bui-Klimke et al 2014;RASFF 2017).…”

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confidence: 99%

AtoxigenicAspergillus flavusIsolates Endemic to Almond, Fig, and Pistachio Orchards in California with Potential to Reduce Aflatoxin Contamination in these Crops

et al. 2019

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In California, aflatoxin contamination of almond, fig, and pistachio has become a serious problem in recent years due to long periods of drought and probably other climatic changes. The atoxigenic biocontrol product Aspergillus flavus AF36 has been registered for use to limit aflatoxin contamination of pistachio since 2012 and for use in almond and fig since 2017. New biocontrol technologies employ multiple atoxigenic genotypes because those provide greater benefits than using a single genotype. Almond, fig, and pistachio industries would benefit from a multi-strain biocontrol technology for use in these three crops. Several A. flavus vegetative compatibility groups (VCGs) associated with almond, fig, and pistachio composed exclusively of atoxigenic isolates, including the VCG to which AF36 belongs to, YV36, were previously characterized in California. Here, we report additional VCGs associated with either two or all three crops. Representative isolates of 12 atoxigenic VCGs significantly (P < 0.001) reduced (>80%) aflatoxin accumulation in almond and pistachio when challenged with highly toxigenic isolates of A. flavus and A. parasiticus under laboratory conditions. Isolates of the evaluated VCGs, including AF36, constitute valuable endemic, well-adapted, and efficient germplasm to design a multi-crop, multi-strain biocontrol strategy for use in tree crops in California. Availability of such a strategy would favor long-term atoxigenic A. flavus communities across the affected areas of California, and this would result in securing domestic and export markets for the nut crop and fig farmer industries and, most importantly, health benefits to consumers.

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Augmenting sanitation with insecticides to improve control of navel orangeworm (Amyelois transitella Walker) (Lepidoptera: Pyralidae) in California tree nuts

Siegel

Gilcrease

2022

Pest Management Science

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BACKGROUND Sanitation, consisting of eliminating unharvested nuts (mummies) that serve as both harborage and food source for navel orangeworm (Amyelois transitella), is the foundation for control in almonds and pistachios. Sometimes sanitation is ineffective and needs to be augmented. Trials in almonds and pistachios were conducted early October 2005–2006 to determine if insecticides applied postharvest could augment sanitation, and in almonds late March to early May 2016–2020 to establish their duration of control. RESULTS Early October sprays reduced adult emergence by as much as 81.5% in pistachios, but reduction was only 32.4% in almonds. Trapping before almond hull split revealed that 55% of adult emergence occurred between 15 April and 1 June, indicating that an insecticide with a six week duration of control could reduce successful oviposition and neonate establishment. Five insecticides applied from late March to early May belonging to four Insecticide Resistance Action Committee (IRAC) groups decreased survival for at least six weeks, and some lasted as long as 10 weeks. By contrast, the duration of control in contact bioassays was far shorter. CONCLUSION Insecticides applied from late March to early May successfully reduced the survival of A. transitella in almond mummies for as long as 10 weeks postapplication, and there was a positive relationship between reduction in survival and kernel damage. If these insecticides are applied during mid‐ to late April, postbloom and before hull split, they can substantially eliminate almond mummies as a resource for 55% of the spring flight of A. transitella.

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Period of susceptibility of almonds to aflatoxin contamination during development in the orchard

Cited by 18 publications

References 29 publications

Fungal communities associated with almond throughout crop development: Implications for aflatoxin biocontrol management in California

Fungal communities associated with almond throughout crop development: Implications for aflatoxin biocontrol management in California

AtoxigenicAspergillus flavusIsolates Endemic to Almond, Fig, and Pistachio Orchards in California with Potential to Reduce Aflatoxin Contamination in these Crops

Augmenting sanitation with insecticides to improve control of navel orangeworm (Amyelois transitella Walker) (Lepidoptera: Pyralidae) in California tree nuts

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