CRAZY TOP: The most characteristic symptoms of crazy top are distorted tassels with prolific leaf-like growths, or stunted plants with numerous tillers. Crazy top is caused by a soilborne oomycete that produces swimming spores (zoospores) in flooded conditions. The zoospores infect the growing points of young plants.

PHYSODERMA BROWN SPOT: This disease is most common when heavy rains occur when the corn is at growth stage V5 to V9. This article describes the characteristic symptoms of the two phases of the disease. The one pictured is Physoderma brown spot. Note that hybrids that are susceptible to Physoderma node rot rarely have Physoderma brown spot symptoms on the leaves.

PHYSODERMA NODE ROT: Meanwhile, hybrids that get Physoderma brown spot rarely have the Physoderma node rot that is pictured.

GOSS’S WILT: It’s been a few years since Goss’s wilt was prevalent in Iowa. However, I still hear reports of it each year. While most hybrids have good resistance to the bacterium, there are some hybrids that are susceptible.

TRANSLUCENT FRECKLES: Remember to look for dark “freckles” in the Goss’s wilt lesions, which become translucent when they are backlit.

BACTERIAL STALK ROT: We rarely see bacterial stalk rot in Iowa, but it’s possible to find this disease in areas where water sat, and where plants may have been wounded. This stalk rot often occurs midseason. Infected plants may be scattered across the field and die prematurely. The stalk is soft, slimy and brown; and perhaps the most characteristic symptom — infected plants stink.

BACTERIAL STALK ROT: We rarely see bacterial stalk rot in Iowa, but it’s possible to find this disease in areas where water sat, and where plants may have been wounded. This stalk rot often occurs midseason. Infected plants may be scattered across the field and die prematurely. The stalk is soft, slimy and brown; and perhaps the most characteristic symptom — infected plants stink.