Influence of Fungicides and Irrigation Practice on Aflatoxin in Peanuts Before Digging

Peanuts grown under dryland conditions where drought stress occurred accumulated more aflatoxin before digging than peanuts grown under irrigation. Kernels became more susceptible to Aspergillus flavus and A. parasiticus invasion when the soil moisture in the pod zone approached levels at which moisture moved from the pod into the soil and the kernel moisture dropped below 31%. Isolation frequencies of these aspergilli from fresh-dug kernels were lowest in 1968 (maximum of 3%). In 1967 and 1969, maximum percentages of 100 and 74, respectively, were noted. Kernel infestation was correlated with degree of aflatoxin contamination. Dryland fresh-dug kernels contained a maximum of 35,800 parts per billion aflatoxin while a maximum of 50 parts per billion was detected in kernels from irrigated plots. In 1969 A. flavus infestation was as high as 59% in peanuts from irrigated plots; however, no aflatoxin was detected. Absence of aflatoxin in these samples is attributed to the higher kernel moisture content which reduced the aflatoxin-producing potential of A. flavus. Statistical analysis of the data revealed no significant differences in degree of fungal infestation, production levels, and grade factors between any fungicide treatments.     

Aflatoxin-producing Potential of Isolates of the Aspergillus flavus-oryzae Group from Peanuts (Arachis hypogaea)

Seventy-eight samples of farmer stock peanuts, representing peanuts grown in nine different geographical areas during 1964, were assayed for aflatoxin and examined for associated microflora. Only two samples contained more than 50 ppb of aflatoxin. Infestation by members of the Aspergillus flavus-oryzae group varied from 35 to 100% of the kernels per area and from 1 to 100% of the kernels per sample. Aflatoxin production by individual isolates ranged from 0 to 349,143 ppb under the test conditions employed. In general, the isolates produced 8 to 10 times more B₁ than B₂, and no isolate producing aflatoxins G₁ or G₂ was found. The importance of proper postharvest handling of peanuts is emphasized by the prevalence of isolates of A. flavus-oryzae capable of producing aflatoxins on farmers stock peanuts.     

Color mutants of Aspergillus flavus and Aspergillus parasiticus in a study of preharvest invasion of peanuts.

A comparison of the invasion of flowers, aerial pegs, and kernels by wild-type and mutant strains of Aspergillus flavus or A. parasiticus along with aflatoxin analyses of kernels from different drought treatments have supported the hypothesis that preharvest contamination with aflatoxin originates mainly from the soil. Evidence in support of soil invasion as opposed to aerial invasion was the following. A greater percentage of invasion of kernels rather than flower or aerial pegs by either wild-type A. flavus or mutants. Significant invasion by an A. parasiticus color mutant occurred only in peanuts from soil supplemented with the mutant, whereas adjacent plants in close proximity but in untreated soil were only invaded by wild-type A. flavus or A. parasiticus. Aflatoxin data from drought-stressed, visibly undamaged peanut kernels showed that samples from soil not supplemented with a mutant strain contained a preponderance of aflatoxin B's (from wild-type A. flavus) whereas adjacent samples from mutant-supplemented soil contained a preponderance of B's plus G's (from wild-type and mutant A. parasiticus). Preliminary data from two air samplings showed an absence of propagules of A. flavus or A. parasiticus in air around the experimental facility.     

Color mutants of Aspergillus flavus and Aspergillus parasiticus in a study of preharvest invasion of peanuts

A comparison of the invasion of flowers, aerial pegs, and kernels by wild-type and mutant strains of Aspergillus flavus or A. parasiticus along with aflatoxin analyses of kernels from different drought treatments have supported the hypothesis that preharvest contamination with aflatoxin originates mainly from the soil. Evidence in support of soil invasion as opposed to aerial invasion was the following. A greater percentage of invasion of kernels rather than flower or aerial pegs by either wild-type A. flavus or mutants. Significant invasion by an A. parasiticus color mutant occurred only in peanuts from soil supplemented with the mutant, whereas adjacent plants in close proximity but in untreated soil were only invaded by wild-type A. flavus or A. parasiticus. Aflatoxin data from drought-stressed, visibly undamaged peanut kernels showed that samples from soil not supplemented with a mutant strain contained a preponderance of aflatoxin B's (from wild-type A. flavus) whereas adjacent samples from mutant-supplemented soil contained a preponderance of B's plus G's (from wild-type and mutant A. parasiticus). Preliminary data from two air samplings showed an absence of propagules of A. flavus or A. parasiticus in air around the experimental facility.     

Increased susceptibility and reduced phytoalexin accumulation in drought-stressed peanut kernels challenged with Aspergillus flavus.

Three genotypes of peanut (Arachis hypogaea L.), with ICG numbers 221, 1104, and 1326, were grown in three replicate plots and drought stressed during the last 58 days before harvest by withholding irrigation water. Within each plot there were eight levels of stress ranging from 1.1 to 25.9 cm of water. Kernels harvested from the plots were hydrated to 20% moisture and challenged with Aspergillus flavus. Fungal colonization, aflatoxin content, and phytoalexin accumulation were measured. Fungal colonization of non-drought-stressed kernels virtually ceased by 3 days after inoculation, when the phytoalexin concentration exceeded 50 micrograms/g (fresh weight) of kernels, but the aflatoxin concentration continued to rise exponentially for an additional day. When fungal colonization, aflatoxin production, and phytoalexin accumulation were measured 3 days after drought-stressed material was challenged, the following relationships were apparent. Fungal colonization was inversely related to water supply (r varied from -0.848 to -0.904, according to genotype), as was aflatoxin production (r varied from -0.876 to -0.912, according to genotype); the phytoalexin concentration was correlated with water supply when this exceeded 11 cm (r varied from 0.696 to 0.917, according to genotype). The results are discussed in terms of the critical role played by drought stress in predisposing peanuts to infection by A. flavus and the role of the impaired phytoalexin response in mediating this increased susceptibility.     

Increased susceptibility and reduced phytoalexin accumulation in drought-stressed peanut kernels challenged with Aspergillus flavus

Three genotypes of peanut (Arachis hypogaea L.), with ICG numbers 221, 1104, and 1326, were grown in three replicate plots and drought stressed during the last 58 days before harvest by withholding irrigation water. Within each plot there were eight levels of stress ranging from 1.1 to 25.9 cm of water. Kernels harvested from the plots were hydrated to 20% moisture and challenged with Aspergillus flavus. Fungal colonization, aflatoxin content, and phytoalexin accumulation were measured. Fungal colonization of non-drought-stressed kernels virtually ceased by 3 days after inoculation, when the phytoalexin concentration exceeded 50 micrograms/g (fresh weight) of kernels, but the aflatoxin concentration continued to rise exponentially for an additional day. When fungal colonization, aflatoxin production, and phytoalexin accumulation were measured 3 days after drought-stressed material was challenged, the following relationships were apparent. Fungal colonization was inversely related to water supply (r varied from -0.848 to -0.904, according to genotype), as was aflatoxin production (r varied from -0.876 to -0.912, according to genotype); the phytoalexin concentration was correlated with water supply when this exceeded 11 cm (r varied from 0.696 to 0.917, according to genotype). The results are discussed in terms of the critical role played by drought stress in predisposing peanuts to infection by A. flavus and the role of the impaired phytoalexin response in mediating this increased susceptibility.     

Effects of soil moisture and temperature on preharvest invasion of peanuts by the Aspergillus flavus group and subsequent aflatoxin development

Four soil temperature and moisture treatment regimens were imposed on Florunner peanuts 94 days after planting in experimental plots in 1980. At harvest (145 days after planting), the incidence of the Aspergillus flavus group and the aflatoxin concentration were greatest in damaged kernels. Extensive colonization of sound mature kernels (SMK) by the A. flavus group occurred with the drought stress treatment (56% kernels colonized); colonization was less in the irrigated plot (7%) and the drought stress plot with cooled soil (11%) and was intermediate in the irrigated plot with heated soil (26%). Aflatoxin was virtually absent from SMK with the last three treatments, but it was found at an average concentration of 244 ppb (ng/g) in drought-stressed SMK. Colonization of SMK by the A. flavus group and aflatoxin production were greater with hot dry conditions. Neither elevated temperature alone nor drought stress alone caused aflatoxin contamination in SMK. When the ratio of SMK colonized by A. flavus compared with A. niger was greater than 19:1, there was aflatoxin contamination, but there was none if this ratio was less than 9:1. Irrigation caused a higher incidence of A. niger than drought did. This may have prevented the aflatoxin contamination of undamaged peanuts.     

Effects of soil moisture and temperature on preharvest invasion of peanuts by the Aspergillus flavus group and subsequent aflatoxin development.

Four soil temperature and moisture treatment regimens were imposed on Florunner peanuts 94 days after planting in experimental plots in 1980. At harvest (145 days after planting), the incidence of the Aspergillus flavus group and the aflatoxin concentration were greatest in damaged kernels. Extensive colonization of sound mature kernels (SMK) by the A. flavus group occurred with the drought stress treatment (56% kernels colonized); colonization was less in the irrigated plot (7%) and the drought stress plot with cooled soil (11%) and was intermediate in the irrigated plot with heated soil (26%). Aflatoxin was virtually absent from SMK with the last three treatments, but it was found at an average concentration of 244 ppb (ng/g) in drought-stressed SMK. Colonization of SMK by the A. flavus group and aflatoxin production were greater with hot dry conditions. Neither elevated temperature alone nor drought stress alone caused aflatoxin contamination in SMK. When the ratio of SMK colonized by A. flavus compared with A. niger was greater than 19:1, there was aflatoxin contamination, but there was none if this ratio was less than 9:1. Irrigation caused a higher incidence of A. niger than drought did. This may have prevented the aflatoxin contamination of undamaged peanuts.     

Interrelationship of kernel water activity,soil temperature,maturity, and phytoalexin production in preharvest aflatoxin contamination of drought-stressed peanuts

Samples of Florunner peanuts were collected throughout a period of late-season drought stress with mean geocarposphere temperatures of 29 and 25 °C, and determinations of maturity, kernel water activity (a_w), percent moisture, capacity for phytoalexin production, and aflatoxin contamination were made. Results showed an association between the loss of the capacity of kernels to produce phytoalexins and the appearance of aflatoxin contamination. Kernel a_w appeared to be the most important factor controlling the capacity of kernels to produce phytoalexins. Mature peanuts possessed additional resistance to contamination that could not be attributed solely to phytoalexin production. Kernel moisture loss was accelerated in the 29 °C treatment compared to the 25 °C treatment, and data indicated that the higher soil temperature also favored growth and aflatoxin production by Aspergillus flavus in peanuts susceptible to contamination.Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.     

Regional differences in production of aflatoxin B1 and cyclopiazonic acid by soil isolates of aspergillus flavus along a transect within the United States

Soil isolates of Aspergillus flavus from a transect extending from eastern New Mexico through Georgia to eastern Virginia were examined for production of aflatoxin B1 and cyclopiazonic acid in a liquid medium. Peanut fields from major peanut-growing regions (western Texas; central Texas; Georgia and Alabama; and Virginia and North Carolina) were sampled, and fields with other crops were sampled in regions where peanuts are not commonly grown. The A. flavus isolates were identified as members of either the L strain (n = 774), which produces sclerotia that are >400 micrometer in diameter, or the S strain (n = 309), which produces numerous small sclerotia that are <400 micrometer in diameter. The S-strain isolates generally produced high levels of aflatoxin B1, whereas the L-strain isolates were more variable in aflatoxin production; variation in cyclopiazonic acid production also was greater in the L strain than in the S strain. There was a positive correlation between aflatoxin B1 production and cyclopiazonic acid production in both strains, although 12% of the L-strain isolates produced only cyclopiazonic acid. Significant differences in production of aflatoxin B1 and cyclopiazonic acid by the L-strain isolates were detected among regions. In the western half of Texas and the peanut-growing region of Georgia and Alabama, 62 to 94% of the isolates produced >10 microgram of aflatoxin B1 per ml. The percentages of isolates producing >10 microgram of aflatoxin B1 per ml ranged from 0 to 52% in the remaining regions of the transect; other isolates were often nonaflatoxigenic. A total of 53 of the 126 L-strain isolates that did not produce aflatoxin B1 or cyclopiazonic acid were placed in 17 vegetative compatibility groups. Several of these groups contained isolates from widely separated regions of the transect.     

Effect of geocarposphere temperature on pre-harvest colonization of drought-stressed peanuts by Aspergillus flavus and subsequent aflatoxin contamination

Florunner peanuts grown in research plots were subjected to 5 soil temperature and moisture treatment regimes resulting in A. flavus infestation and subsequent aflatoxin contamination in drought-stressed peanuts. Treatments imposed beginning 85 days after planting were drought, drought with heated soil and 3 drought treatments with cooled soil. The incidence of A. flavus in drought-stressed, unshelled, sound mature kernels (SMK) decreased with decreases in the mean 5 cm deep soil temperature. The incidence of A. flavus was greater in inedible categories and in damaged kernels than in SMK. The mean, threshold, geocarposphere temperature required for aflatoxin development during the latter part of the peanut growth cycle was found to be between 25.7° C and 27° C.     

Aspergillus flavus and other mycoflora of groundnut kernels in Israel and the absence of aflatoxin

More than 300 groundnut (peanut) samples collected from different regions of Israel were examined by ELISA for aflatoxin contamination. Samples were designated for export, local consumption or for sowing. None of the samples were contaminated with the toxin. However, when kernels were kept at high humidity (RH?99%), aflatoxin could be frequently detected seven days after incubation and the toxin was not uniformly distributed among kernels.Aspergillus niger, A flavus, Penicillium citrinum andP pinophilum were the dominant fungi and no differences were observed among cultivars. Almost half of the commercial samples examined were devoid ofA flavus. Other fungi identified wereA tamaril, A amstelodami, P rubrum, Rhizoctonia solani, Macrophomina phaseolina, Rhizopus spp., Sclerotium rolfsll, Fusarium andAlternaria spp; the two last ones comprising a group of low incidence. Although groundnut samples that containA flavus—infected kernels are moderately common, the local climate and agrotechniques In use in Israel are not conducive to aflatoxin accumulation. Nevertheless infected kernels may become a threat to health if stored under inadequate conditions.     

Survey of aflatoxin concentrations in wild bird seed purchased in Texas.

The use of backyard feeders to attract avian wildlife is a common practice throughout the United States. However, feeding wildlife may create a problem due to aflatoxin, a harmful fungal metabolite, which can affect wildlife that are fed contaminated grain. Our study was initiated to determine if songbirds were being exposed to aflatoxin-contaminated feed throughout Texas. Bags of wild bird seed (n = 142) were purchased from grain cooperatives, grocery stores, and pet shops located in the panhandle, central, south, east, and west regions of Texas during spring and summer 1999. Aflatoxin concentrations in bird seed ranged from non-detectable to 2,780 micrograms/kg. Overall, 17% of samples had aflatoxin concentrations greater than 100 micrograms/kg, of which 83% contained corn as an ingredient. Retail establishment effects were noted in the southern and western regions of Texas, with average concentrations of aflatoxin greater from bags of bird seed purchased from grain cooperatives, followed by pet shops, then grocery stores. Regional differences in aflatoxin levels were not apparent from bags of seed purchased at pet shops: however, regional differences were noted in aflatoxin levels from seeds obtained at grocery stores and grain cooperatives. Average aflatoxin concentration from seed purchased at grocery stores was greatest in the panhandle region, followed by the remaining regions. Within grain cooperatives, the panhandle, south, and west regions of Texas exhibited higher levels of aflatoxin-contaminated bird seed than cooperatives within the east and central regions of Texas. Granivorous songbirds in Texas are exposed to aflatoxins at backyard feeders, which may be a significant morbidity and mortality factor.     

Effect of climate and type of storage container on aflatoxin production in corn and its associated risks to wildlife species

The effects of grain storage containers on aflatoxin production, and the relationship between the level of aflatoxin and the number and weight of fluorescing kernels were determined in corn (Zea maize) stored in controlled climate regimes. Two hundred and forty 100-g samples were held up to 3 mos using four types of storage containers placed in four climates. Storage containers included corn placed in metal cans, paper bags, plastic bags, and paper bags placed in plastic bags. Climates were constant during the duration of the project and included a combination of temperatures and humidities. Temperatures were 29-32 C and 14-18 C; relative humidities were 85-88% and 35-40%. In addition, corn was exposed to environmental conditions conductive for aflatoxin production and 100 g samples were randomly collected, examined under ultraviolet light for fluorescence, and then quantified for aflatoxin levels. Corn samples tested negative for aflatoxin at the beginning of the project. Main (i.e., container, climate, and month) and interactive effects were not observed. Mean levels of aflatoxin ranged from 0 to 151 microg/kg. Aflatoxin was produced regardless of type of storage container, time of storage, and climatic conditions; however, only 8% of the samples produced aflatoxin levels that exceeded 50 microg/kg. Fluorescing corn ranged from 0 to 19 kernels per sample, while aflatoxin levels ranged from 0 to 1,375 microg/kg for the same samples. No relationships were found between the number and weight of fluorescing kernels of corn and aflatoxin levels. The black light test yielded a false negative rate of 23% when in fact the aflatoxin concentrations exceeded 50 microg/kg. Therefore, quantifying fluorescing grain under UV light should not be considered a feasible alternative for aflatoxin testing of grain intended for wildlife.     

Evaluation of biological control formulations to reduce aflatoxin contamination in peanuts

A two-year study was conducted to evaluate the efficacy of three formulations of nontoxigenic strains of Aspergillus flavus and Aspergillus parasiticus to reduce preharvest aflatoxin contamination of peanuts. Formulations included: (1) solid-state fermented rice; (2) fungal conidia encapsulated in an extrusion product termed Pesta; (3) conidia encapsulated in pregelatinized corn flour granules. Formulations were applied to peanut plots in 1996 and reapplied to the same plots in 1997 in a randomized design with four replications, including untreated controls. Analysis of soils for A. flavus and A. parasiticus showed that a large soil population of the nontoxigenic strains resulted from all formulations. In the first year, the percentage of kernels infected by wild-type A. flavus and A. parasiticus was significantly reduced in plots treated with rice and corn flour granules, but it was reduced only in the rice-treated plots in year two. There were no significant differences in total infection of kernels by all strains of A. flavus and A. parasiticus in either year. Aflatoxin concentrations in peanuts were significantly reduced in year two by all formulation treatments with an average reduction of 92%. Reductions were also noted for all formulation treatments in year one (average 86%), but they were not statistically significant because of wide variation in the aflatoxin concentrations in the untreated controls. Each of the formulations tested, therefore, was effective in delivering competitive levels of nontoxigenic strains of A. flavus and A. parasiticus to soil and in reducing subsequent aflatoxin contamination of peanuts.     

Studies on the biocontrol of aflatoxin in maize in Thailand

Aflatoxins in maize and peanuts remain a major cause of liver cancer and other human and animal health issues. The principal causal fungi are Aspergillus flavus and A. parasiticus. Relatively little attention has been paid to reducing aflatoxin formation before harvest. The most promising approach is biocontrol by competitive exclusion. This project aimed to demonstrate the efficacy of locally isolated strains of A. flavus for biocontrol of aflatoxin in maize in Thailand. After a rigorous process utilising molecular methods was used to select non-toxigenic A. flavus strains, field inoculum was produced by using hulled rice coated with A. flavus spores in molasses. Field experiments were conducted over two years in two districts, one of light sandy soil (Chokchai), the other a heavy, close textured, soil (Pakchong). Postharvest treatments representative of local practice were also undertaken. Crops 1 and 2 were not significantly contaminated with aflatoxin at the time of harvest, so any impact of biocontrol could not be assessed. However, wet shelling plus storage before drying resulted in increased aflatoxin contamination; biocontrol had no impact on this increase. In crops 3 and 4, biocontrol had a beneficial impact in some freshly harvested maize. Biocontrol treatments also significantly reduced aflatoxin contamination in samples from some treatments stored for two or four days after shelling, but had minimal effect in others. These experiments demonstrated that biocontrol can be highly effective in reducing aflatoxin contamination in maize in Thailand, both at harvest and during poor postharvest crop handling. However, results were inconsistent.     

The presence of aflatoxin in kernels from five years groundnut crops and ofAspergillus flavus isolates from kernels and soils

Summary In T.L.C. tests for 605 samples of groundnut kernels from 5 years' yield, the percentage of fresh kernels in which aflatoxin was present was very low (up to 6.4%), while that of stored kernels ranged from 0 to 32.0%. But the intensity of toxicity was invariably very low (up to 125 ppb). Of 1626Aspergillus flavus isolates from groundnut kernels rhizosphere and geocarposphere, and from soil in which groundnuts grew, about 90% were found capable of forming aflatoxin. In quantitative tests with 750 isolates 60% of the isolates produce aflatoxin in excess of 25,000 ppb. This research is supported by Grant Number FG-Is-161 of the United States Department of Agriculture to whom the author is indebted.     

Regional Differences in Production of Aflatoxin B1 and Cyclopiazonic Acid by Soil Isolates of Aspergillus flavus along a Transect within the United States

Soil isolates of Aspergillus flavus from a transect extending from eastern New Mexico through Georgia to eastern Virginia were examined for production of aflatoxin B₁ and cyclopiazonic acid in a liquid medium. Peanut fields from major peanut-growing regions (western Texas; central Texas; Georgia and Alabama; and Virginia and North Carolina) were sampled, and fields with other crops were sampled in regions where peanuts are not commonly grown. The A. flavus isolates were identified as members of either the L strain (n = 774), which produces sclerotia that are >400 μm in diameter, or the S strain (n = 309), which produces numerous small sclerotia that are <400 μm in diameter. The S-strain isolates generally produced high levels of aflatoxin B₁, whereas the L-strain isolates were more variable in aflatoxin production; variation in cyclopiazonic acid production also was greater in the L strain than in the S strain. There was a positive correlation between aflatoxin B₁ production and cyclopiazonic acid production in both strains, although 12% of the L-strain isolates produced only cyclopiazonic acid. Significant differences in production of aflatoxin B₁ and cyclopiazonic acid by the L-strain isolates were detected among regions. In the western half of Texas and the peanut-growing region of Georgia and Alabama, 62 to 94% of the isolates produced >10 μg of aflatoxin B₁ per ml. The percentages of isolates producing >10 μg of aflatoxin B₁ per ml ranged from 0 to 52% in the remaining regions of the transect; other isolates were often nonaflatoxigenic. A total of 53 of the 126 L-strain isolates that did not produce aflatoxin B₁ or cyclopiazonic acid were placed in 17 vegetative compatibility groups. Several of these groups contained isolates from widely separated regions of the transect.     

Possible relationship of succinate dehydrogenase and fatty acid synthetase activities toAspergillus parasiticus (NRRL 5139) growth and aflatoxin production

Fatty acid synthetase (FAS) activity measured over time corresponded to aflatoxin B₁ biosynthesis byAspergillus parasiticus grown in minimal salts sucrose medium. Succinate dehydrogenase (SDH) activity, our primary metabolism indicator, decreased as FAS activity increased demonstrating that as primary metabolism slows, secondary metabolism and subsequently aflatoxin production begins. Fungal biomass, as measured by chitin, increased up to day 13 then stabilized. Calcium, potassium, magnesium, manganese, zinc, and a combination of these minerals were tested to determine their effect in culture on FAS and SDH activities. Cultures grown in broth supplemented with zinc had greater FAS activity and produced more aflatoxin B₁ when compared to the unsupplemented control. To determine if enzyme activity in a complex substrate is altered due to mineral composition, peanuts were cultivated with gypsum (calcium sulfate) supplementation. The peanuts grown had higher calcium content but less zinc. All peanuts grown in gypsum treated fields had less aflatoxin produced on them when compared to unsupplemented peanuts. Also, FAS activity was lower and chitin content was less when compared to the unsupplemented control peanuts. The FAS activity observed in these experiments indirectly suggests that the FAS complex may be responsible for producing the precursor for aflatoxin synthesis. However, additional information is needed to validate this hypothesis.     

Aflatoxin variability in pistachios.

Pistachio fruit components, including hulls (mesocarps and epicarps), seed coats (testas), and kernels (seeds), all contribute to variable aflatoxin content in pistachios. Fresh pistachio kernels were individually inoculated with Aspergillus flavus and incubated 7 or 10 days. Hulled, shelled kernels were either left intact or wounded prior to inoculation. Wounded kernels, with or without the seed coat, were readily colonized by A. flavus and after 10 days of incubation contained 37 times more aflatoxin than similarly treated unwounded kernels. The aflatoxin levels in the individual wounded pistachios were highly variable. Neither fungal colonization nor aflatoxin was detected in intact kernels without seed coats. Intact kernels with seed coats had limited fungal colonization and low aflatoxin concentrations compared with their wounded counterparts. Despite substantial fungal colonization of wounded hulls, aflatoxin was not detected in hulls. Aflatoxin levels were significantly lower in wounded kernels with hulls than in kernels of hulled pistachios. Both the seed coat and a water-soluble extract of hulls suppressed aflatoxin production by A. flavus.