Physoderma Maydis

Physoderma Maydis

• Symptoms:
• Physoderma brown spot lesions occur mainly on the leaf, but may also occur on leaf sheath, stalks, outer ear husks and tassels
• As disease progresses, small lesions may coalesce to form larger affected areas

• Look-Alike Diseases:
• Eyespot disease caused by Aureobasidium zeae can look similar to Physoderma brown spot
• Eyespot is a leaf disease with small, yellow, mostly round lesions
• Main difference – lesions of eyespot do not usually occur in the banded pattern across leaf
• On the leaf blade, young Physoderma lesions can also resemble those caused by rusts, such as early southern rust (see arrow below). A higher magnification lens can help distinguish these diseases

• Facts on Physoderma Brown Spot:
• Fungal disease caused by Physoderma maydis
• Generally of minor importance in the U.S.
• Localized outbreaks may occur in years when weather favors disease development

• Disease Cycle:
• Overwintering fungal structures, sporangia, survive in infected corn tissue or soil
• Sporangia germinate to produce infective zoospores under conditions of moisture and light
• With the right conditions of water, light and temperature when leaves are in the whorl, infections often occur on a diurnal cycle

• Management:
• Crop rotation, as the fungus survives in infected crop residue
• STillage to encourage breakdown of crop residue
• Specific management for this disease is not typically required, as the occurrence is sporadic and the effect on yield should be minimal
• Pioneer does not rate its hybrids for resistance to this disease