Sclerotia of Aspergillus flavus produced in preharvest maize are dispersed into soil with debris during combining. Overwintered sclerotia germinate sporogenically and produce yellow-green conidial heads. Germination occurred prior to the silking date for maize in southern Georgia. The presence of a maize canopy indirectly promotes germination via shading, so providing a microclimate at the soil surface with sufficient moisture. Soil micro-arthropods consume the conidia from germinated sclerotia, , dispersing inoculum throughout the soil. The aflavinines are major components of A. flavus sclerotia with substantial antifeedant activity against Carpophilus hemipterus (Nitidulidae), a detritivorous beetle that commonly encounters fungal sclerotia in crop residues.

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Relationships among toxigenic fusaria, their associated toxins and climate were examined for cereal crops grown in diverse locales. Fusarium sporotrichioides, F. poae, F. semitectum, F. equiseti, F. culmorum, F. graminearum, F. moniliforme, F. subglutinans and F. oxysporum were examined. F. culmorum occurred in cool northern Europe as the producer of deoxynivalenol and zearalenone, but was replaced in this role by F. graminearum in the warmer climates of southern Ontario, Canada, in the north central U.S.A., and mid and southern Japan.

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In a three year survey of cottonseed mycoflora gathered from across the southeastern and south central USA, A. flavus was present in very low levels in most years. Occurrence in these areas was greater only during hot drought years. In the hot irrigated desert growing areas in the southwest, A. flavus contamination of cottonseed is a chronic problem. However, macro-environmental factors are not the only ones involved in cottonseed contamination. Experiments in which plant parts were inoculated with A. flavus demonstrated that the fungus could enter seedlings, flowers and developing bolls early in the season, and infect bolls maturing in August and September. Among the early season inoculated bolls, those on plants with minimum daily water potentials of -1.6 to -1.9MPa on the day of anthesis were most susceptible to infection. Microenvironmental parameters influencing physiological factors in the plant strongly affect the susceptibility of cottonseed to A. flavus infection.

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The contamination of maize by Aspergillus flavus was investigated from farmers' fields through middlemen storages. Maize ears (moisture content 24.8%) were stored in farmer's storage straightly from the field without sun drying nor grading. A. flavus contamination of these ears in the field was low (0%) and was remained at low level (0.5-1%) even after 67 days since harvest. Maize ears (m.c.=28.6% and 26.6%) which were contaminated by A. flavus in the field (10% and 1%) were able to be stored with low contamination of A. flavus (2% and 0.5%) for 76 days if ears were sun dried (m.c.=17% and 22.3%) and graded properly before storage. Grain which were sun dried immediately after mechanical shelling on concrete drying floor with moisture content less than or around 15% was abled to be stored with low contamination of A. flavus (1.5%-8%) for 56 days in middlemen's storages. Those grain which were not dried after mechanical shelling, A. flavus contamination prevailed quickly if moisture content was over 20%. However if moisture content was less than 17% the spread of A. flavus was suppressed.

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Plant species that were reported to have fungicidal properties on other fungal genera and have of medicinal value was collected and extracted using water. Crude water extracts of 6 out of 97 plant species screened for their fungicidal properties in vitro showed inhibitory activity against Aspergillus flavus and A. parasiticus.
The crude extracts of garlic (Allium sativum) was found to be the most effective against Aspergillus flavus and A. parasiticus. In their decreasing order the following plant extract; Kalachuchi (Plumiera acuminata) >Bulakmanok (Ageratum conyzoides) > Sampa-sampalukan (Phyllantus nirure L.) while Talisay (Terminalia catappa L.) >Kakawati (Gliricidia sepium Jacq.) were quite effective on Aspergillus flavus and A. parasiticus, respectively. Also, aflatoxin formation was not detected on potato dextrose broth with the above mentioned crude extracts inoculated with aflatoxin-forming organisms.

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Addition of chitosan, either native (from crab) or a chemically-derived derivative (N-carboxymethyl chitosan), to liquid fungal culture at certain concentrations markedly reduced growth of Aspergillus flavus and A. parasiticus. The effect of chitosans on aflatoxin production varied based on the type and concentration of the material. Reduced levels of native chitosan inhibited fungal growth, whereas the chitosan-derivative stimulated synthesis of the toxin. After 8 days, A. flavus treated with the chitosan derivative produced 345.96μg aflatoxin B₁/g mycelia, whereas control cultures without chitosan produced 10μg toxin/g mycelia. Elevated concentrations of either chitosan inhibited aflatoxin production. Chitosan exhibited the greatest effect on fungal growth when it was added to culture flasks during the early fermentation phase. Aflatoxin production by both Aspergillus species was inversely related to fungal growth in cultures containing lower concentrations of chitosan-derivative.

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Cell lines from four Baccharis plant species have been grown in cell suspensions and tested, by two different bioassays, for their sensitivities toward the macrocyclic trichothecenes roridins A and E and baccharinoid B4. The two Brazilian species which were shown to contain macrocyclic trichothecenes were considerably less sensitive to these toxins than were the non-trichothecene-containing North American Baccharis species.

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Macrocyclic trichothecene roridin E, produced in culture or in plant host tissue by a strain of Myrothecium roridum pathogenic to muskmelon (Cucumis melo L), and roridin A and myrotoxin A+B, trichothecenes from M. roridum strains nonpathogenic to muskmelon were investigated for their role in pathogenicity of M. roridum. Roridin E did not affect the growth of the pathogen in vitro but significantly increased sporulation and lesion diameter on inoculated muskmelon leaves whereas roridin A and myrotoxin A+B did not affect sporulation and lesion size. All trichothecenes induced phytotoxic reactions in muskmelon and increased electrolyte leakage from muskmelon leaf tissue. Muskmelon cultivar rankings with respect to the phytotoxic responses and level of electrolyte leakage induced by roridin E were similar to cultivar rankings after inoculation with M. roridum. Roridin A and myrotoxin A+B did not elecit cultivar-specific responses.
Characteristic lesions caused by the pathogen were similar to lesions caused by roridin E. These results suggest that roridin E is involved in the establishment of pathogenicity by M. roridum in muskmelon tissue.

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On the basis of data obtained from an one-grain analysis, the distribution of deoxynivalenol (DON) and nivalenol (NIV) in wheat and barley is considered to be heterogeneous. Fusarium graminearum strains capable of producing either DON or NIV were found in cereal grains harvested from the same field, indicating that both types of F. graminearum simultaneously occur in crop fields and independently produce the individual toxins in cereals. NIV-producing F. graminearum was proved to be able to convert DON into NIV and its acetate not only in liquid media but also in solid media. From these results, it is likely that the microbial transformation of DON to NIV by NIV-producers may be an alternative route for the generation of NIV in cereal grains.

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