Conditions typical of an Arizona monsoon were mimicked in the field to inoculate cotton plants withAspergillus flavus. Spores, mixed with autoclaved local soil, were blown onto cotton plants having bolls at all stages of maturity, using a modified commercial leaf blower. Half the plants were sprayed with water following inoculation. After one month, plants were pulled and the position of bolls mapped. All bolls were examined for bright‐green‐yellow fluorescence (BGYF) of lint, and ginned seeds from each boll were assayed for aflatoxin. Control non‐wetted, non‐inoculated bolls had no BGYF lint and no aflatoxin‐containing seed. In contrast, 15% of the bolls from wetted, inoculated plants exhibited BGYF; 18% of these BGYF bolls had toxin. Only 3% of the non‐wetted bolls had BGYF lint and none contained toxin. Lower bolls (fully fluffed at inoculation) were not infected, nor were upper bolls (flower stage at inoculation). Infection occurred only in bolls that had opened during the 30 days following inoculation. While the position of BGYF bolls on naturally contaminated plants was the same as for the inoculated, the ratio of toxic bolls to BGYF bolls was different. All BGYF bolls from plants naturally contaminated withA. flavus contained aflatoxin.

No abstract

Aflatoxin accumulation in Deltapine 16 cottonseed, grown in Yuma, Ariz., in a 3-year study, was significantly influenced by the timing of irrigation terminations and by level of pink bollworm infestations. In 1971 and 1972, termination of irrigations by early August resulted in significantly less aflatoxin than in plots where two additional irrigations were applied. Significantly less aflatoxin also was found in the 1971 and 1973 plots where low levels of pink bollworm infestations were maintained.

and Summary Samples of aflatoxin‐contaminated stored ginned cottonseed and of freshly harvested seed cotton and companion ginned seed were examined under long wave ultraviolet (UV) and visible light to develop physical criteria for separating aflatoxin‐contaminated seed from sound seed. Seed locks characterized by bright greenish‐yellow, or cateye, fluorescence when viewed under long wave UV light were separated from samples of 12 varieties of freshly harvested seed. As a result, 80–100% (mean 96%) of the aflatoxin contamination that was concentrated in 2–9% (mean 6%) of the seed weight was effectively removed. The cateye fluorescence separation technique was slightly less effective for removing aflatoxins from companion freshly harvested, ginned samples, but most of the aflatoxins were concentrated in only 0.5–3% (mean 2%) of the seed weight. This approach was relatively ineffective for stored ginned seed, probably due to deterioration of the cateye fluorescence.