Effect of Time of Inoculation on Diplodia Stalk and Ear Rot of Maize in South Africa. K. R. Chambers, Senior Plant Pathologist, Grain Crops Research Institute, Private Bag X1251, Potchefstroom, 2520, Republic of South Africa. . Plant Dis. 72:529-531. Accepted for publication 11 October 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0529.

The effect of time of inoculation of maize (Zea mays) stalks and ears with Diplodia maydis on the severity of infection was studied. There was no significant difference between stalk pith rot ratings resulting from inoculations at midsilk and 18 days later. Similarly, there was no significant difference in yield loss (grain weight per plant and grain fill). This was explained in terms of vascular bundle distribution. Correlations between stalk pith rot ratings and yield indicated a nonsignificant relationship between these variables. Ear rot decreased sharply with a later inoculation date after midsilk. This was associated with a corresponding decrease in kernel moisture. A negative linear relationship existed between ear rot and yield loss (grain weight per plant) (r = –0.977, P = 0.001). Yield loss (grain weight per plant) was as high as 97% from inoculations made 10 days after midsilk. Plant attributes possibly involved in ear rot development showed a significant correlation between ear rot and starch accumulation in the kernels (r = –0.854, P = 0.05) and kernel moisture (r = 0.974, P = 0.001). No significant levels of Beta-glucoside (DIMBOA) were found in the kernels, nor were there significant correlations between ear rot and sugar concentration.

Keyword(s): premature death.