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Many corn (Zea mays L.) growers in Ohio delay harvest as a management strategy for reducing grain drying costs. However, this practice increases the risk of yield loss due to extended crop weathering. Field studies were conducted at three Ohio locations in 2002 to 2004 to determine effects of three harvest date periods, early to mid-October (HD1), early to mid-November (HD2), and early to mid-December (HD3), and four plant densities (59,000; 74,000; 89,000; and 104,000 plants ha-1) on the agronomic performance of four corn hybrids differing in maturity and stalk strength. Interactions between harvest date, plant population, and hybrid indicated that decreases in grain yield and increases in stalk rot and lodging associated with harvest delays were influenced by plant population and hybrid characteristics. Significant yield losses due to delayed harvest were evident only after HD2. When harvest was delayed until HD3, yields decreased at the higher plant populations, especially at 104,000 plants ha-1. Stalk rot and lodging increased at the higher plant populations, and this effect was magnified by late harvesting. Hybrids with lower stalk strength scores exhibited greater stalk lodging and yield loss when harvest was delayed beyond HD2. Stalk rot showed a greater increase between HD1 and HD2, whereas stalk lodging generally showed a greater increase after HD2. Harvest delays after HD2 achieved little or no additional grain drying. Results of this study indicate that harvest delays should be avoided when using plant populations above 74,000 plants ha-1, especially if planting hybrids that are not highly rated for stalk strength. [ABSTRACT FROM AUTHOR]

Greenhouse experiments were conducted to determine the effects of inoculation methods on incubation period, lesion length, percentage leaf area affected and sporulation of Cercospora zeae-maydis on young maize ( Zea mays L.) plants inoculated at V3 growth stage. Seedling plants were inoculated by four methods: (i) application of conidial suspension while puncturing the leaves within the whorl several times, (ii) spraying conidial suspension on leaves, (iii) placing colonized agar into lateral slits in leaves and (iv) placing colonized agar into whorls. Analysis of variance revealed a significant effect of genotype and inoculation method on several components of resistance and overall disease severity. Application of conidial suspension while puncturing the whorl was found to be the least laborious method, and it produced characteristic symptoms of gray leaf spot. Consistent trends were observed in classification of inbreds to resistant, susceptible and intermediate classes. Increasing the duration of exposure to high humidity by placing plastic bags over plants for 5 days significantly increased disease severity (P ≤ 0.001). Cercospora zeae-maydis produced conidia in all the lesions examined. Spore production was generally most abundant in lesions on susceptible inbreds that displayed necrotic lesion types (LT) and least abundant in lesions on resistant inbreds that were characterized by chlorotic and fleck LTs. The results demonstrated that inoculations in the greenhouse can provide an indication of inbred responses to C. zeae-maydis and may be useful in evaluating resistance and in studies of host–pathogen interactions. [ABSTRACT FROM AUTHOR]