What is the primary risk factor for FHB when planting wheat after corn?

The primary risk factor for Fusarium Head Blight (FHB) when planting wheat after corn is the residue from previous crops. This is because corn is a known host for the Fusarium fungi, which can survive in plant debris and infect subsequent crops. When wheat is planted in fields with leftover corn residue, the presence of these pathogens increases the likelihood of FHB outbreaks during the wheat growing season. The Fusarium fungi can thrive on decaying corn remnants, which can lead to higher infection rates in wheat both through direct contact with the residue and through favorable environmental conditions often following such crop rotation.

In contrast, low soil moisture, weed competition, and high soil temperature, while they can influence plant health and growth, do not have the same direct connection to the risk of FHB from corn residue as the presence of decayed or surviving pathogens does. Thus, it is essential for growers to manage crop residues effectively to mitigate the risks associated with FHB, particularly in rotations involving corn and wheat.