The significant positive relationship between the amount of surface residue
and gray leaf spot severity is probably due to the fact the causal agent, C. zeae
mayd/s, is capable of surviving and sporulating on the previous season's maize
residue left on the soil surface. Investigating the relationship between residue
management and airborne conidia, Payne et al. (44) reported that significantly more
conidia were trapped in plots with residue left on the soil surface than in plots that
had the residue plowed under. These results were consistent with the findings made
earlier by Payne and Waldron (43). In the latter study, the authors observed that C.
zeae-mayd/s was better able to overwinter in maize residue left on the soil than in
residue buried in the soil. Maize residue left on the surface in November still
produced conidiophores in May of the following year. A study by de Nazareno et al.
(13) also showed that the fungus survived well in residue left on the soil surface in
Ohio and that infested residue produced viable spores throughout the winter and
spring. Residue buried early in the winter decomposed and did not produce spores
in the spring.