RESUMEN
It is difficult to develop control strategies for grain mold of sorghum because of the limited information on the epidemiology of grain mold in Mexico. The objectives of this study were to identify the fungi associated with grain mold in Morelos, Mexico, and to explore the relationship among planting dates, disease development, and relative humidity and temperature. Fusarium thapsinum was isolated from 97% of the grains from field samples of infested sorghum grains in Morelos, Mexico. The influence of planting dates on the development of sorghum grain mold was determined at Tlayca, Morelos, Mexico, during the rainy seasons of 1998, 1999, and 2000. Incidence of grain mold varied annually, but disease incidence and severity were highest in 1998. Planting dates from 1 June to 13 July had the highest incidence of grain mold during the 3 years. Throughout the study, disease severity was generally low, and yield was not affected. The late planting dates in 1999 and 2000 had reduced yields due to terminal drought of the crop. Increase of disease was predicted by mean temperature, but not by mean relative humidity.
RESUMEN
The effects of 11 plant essential oils for maize kernel protection against Aspergillus flavus were studied. Tests were conducted to determine optimal levels of dosages for maize protection, effects of combinations of essential oils, and residual effects and toxicity of essential oils to maize plants. Principal constituents of eight essential oils were tested for ability to protect maize kernels. Essential oils of Cinnamomum zeylanicum (cinnamon), Mentha piperita (peppermint), Ocimum basilicum (basil), Origanum vulgare (origanum), Teloxys ambrosioides (the flavoring herb epazote), Syzygium aromaticum (clove), and Thymus vulgaris (thyme) caused a total inhibition of fungal development on maize kernels. Thymol and o-methoxycinnamaldehyde significantly reduced maize grain contamination. The optimal dosage for protection of maize varied from 3 to 8%. Combinations of C. zeylanicum with the remaining oils gave efficient control. A residual effect of C. zeylanicum was detected after 4 weeks of kernel treatment. No phytotoxic effect on germination and corn growth was detected with any of these oils.