Diseases

Southern rust of corn has now been observed in different areas of Illinois.  Southern rust is one of two different rust diseases of corn that can be observed in the state (the other is known as common rust).  Because nearly every corn hybrid grown is susceptible to southern rust, yield reductions can occur if infection takes place early enough in the season.  Late-planted corn fields are at the highest risk for yield losses associated with southern rust and should be scouted for the presence of this disease. …

White mold of soybean (a.k.a. Sclerotinia stem rot), caused by the fungus Sclerotinia sclerotiorum, is a disease that can occur in the northern half of the state in cool, wet years.  The most recent white mold epidemic in Illinois occurred during the 2009 season, where several fields in the northern half of the state were affected.
The white mold fungus overwinters in the soil as, small, black, and dense structures known as sclerotia. …

Goss’s wilt of corn often is most severe after fields are exposed to high winds and/or hail damage, because the causal bacterium, Clavibacter michiganensis subsp. nebraskensis, readily infects corn leaves through wounds.  With the recent storm activity across the state, growers should be on the lookout for the appearance of Goss’s wilt symptoms.  Goss’s wilt lesions on the leaves generally have wavy margins with a water-soaked appearance on the edges of the lesions. …

Head scab of wheat (a.k.a. Fusarium head blight) is showing up in Illinois wheat fields.  Incidence is ranging from low (less than 10% of the heads affected) to moderately high (over 25% of the heads affected).  Affected wheat heads will appear “bleached” in color.  Heads often are partially affected, with both healthy green and affected bleached areas being present in the same head.  Although I have not been in all wheat production areas in the state,…

Stripe rust of wheat was observed in Champaign County, IL on May 10, 2013 (Fig. 1). The incidence of the disease was very low. The observation of this disease in Champaign County indicates that stripe rust likely is present in southern Illinois counties too.

Wheat producers will need to continue to scout their crop for stripe rust, and apply an effective fungicide if necessary (see this previous post for additional information about stripe rust and fungicides: http://bulletin.ipm.illinois.edu/?p=456).…