Just prior to and during wheat harvest each year, the Plant Disease Diagnostic Laboratories at Princeton and Lexington receive many samples with questions about severe head molding. This condition is known as black or sooty head mold. Sooty molds are caused by a large number of weakly parasitic and saprophytic fungi, especially species of Cladosporium and Alternaria. Sooty mold fungi colonize wheat heads when wet, humid weather occurs during the latter stages of grain development and crop maturation.
Molding is frequently most severe when harvest is delayed.
In addition, heads that are shaded, weakened, undersized, or prematurely ripe are frequently affected by sooty molds. Head molding is also prevalent when plants are deficient in nutrients, lodged, or damaged by insects or other diseases. Severe sooty mold, thus, is a red flag that other production problems may also be affecting the crop. However, this is not always the case as many high yielding crops ca be affected by sooty mold in any given year. Sooty molds colonize and develop on scenescing and damaged tissues when weather conditions are favorable for fungal growth.