Anthracnose on seedlings

​Cold weather of temperate zone winters can be harsh on fungi in the previous crop debris left on the soil surface after harvest. Low temperatures kill most spores (conidia) capable of spreading and infecting new crop corn plants.  Although spring moisture can encourage production of new spores from infections in the old leaves, inconsistent temperatures and relative humidity plus sun exposure of the young seedlings can cause result in many potential fungal pathogens to fail infection of the young plants.
 
Colletotrichum graminicola (cause of anthracnose) produces spores on surface of infected leaves in mucilaginous matrix that offers protection of the spores on the infected debris from temperature fluctuations and dehydration. This allows survival of spores for quick distribution to seedling leaves.  Spores germinate and hyphae quickly form appressoria, allowing penetration in the first few seedling leaves.  Corn varieties vary in resistance to further spread of the fungus to the growing point or roots.  Killing of seedlings can occur in a few varieties but not in most. 
 
Most studies have shown that there is not a strong correlation among susceptibility to the anthracnose seedling disease, anthracnose on mature leaves and anthracnose stalk rot.  This fungus’ ability to overwinter in minimally tilled, continuous corn fields with anthracnose in the previous season are most vulnerable to this seedling disease.
 
An interesting study of this phenomenon can be found at:
https://www.apsnet.org/publications/phytopathology/backissues/Documents/1980Articles/Phyto70n03_255.PDF
 
Corn Journal 4/9/2019