Several fields in Northern Illinois have ponded areas that have been replanted after the first plants were drowned. There are also seedlings in some fields in some parts of the northern belt that are dying in fields, some clearly infected with Pythium species. They grew from treated seed. There have been reports of strains of Pythium overcoming most common seed treatments but it is notable that many seeds were in cool wet conditions for 3 weeks before emergence. Did the seed treatment lose effectiveness over time?
Reports of Southern Rust in Louisiana reminds us of the corn crop vulnerability to Southern and common rust diseases during stormy June weather patterns. Puccinia polysora (Southern Rust) and Puccinia sorghi (common Rust) overwinter primarily in the Caribbean and Mexico areas before blowing north east with storms. Spores carried by wind that dump into the open whorls of young plants germinate in these moist chambers. Germinating spores quickly invade the cells and within a week pustules show up a few inches up on the new leaves in a band, indicating when the spore shower occurred. These become the inoculum source for spread elsewhere within the field, hybrid resistance and and weather for the rest of the summer determines the rest of the disease development.
About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.