Agronomic Crops Disease Update

Alyssa Koehler, Extension Field Crops Pathologist; akoehler@udel.edu

Small Grains
The cool weather delayed flowering in wheat across much of the region. To date we have seen limited symptoms of Fusarium Head Blight (FHB). Bleached florets or bleached portions of the head are typically visible 18-24 days after flowering, but cool weather can delay symptom development. Foliar lesions along with floret discoloration from glume blotch have been observed in barley and wheat. Barley Yellow Dwarf Virus has been noted at low levels across multiple fields.

Corn
The cold weather and rain delayed corn planting across much of the region. As corn begins to emerge, environmental conditions may favor Pythium Root Rot, especially in low-lying areas of the field. Symptoms can include stunted, slower growing plants, to severely infected, dead plants (Figure 1). Infected plants typically have brown, rotted roots and mesocotyl (Figure 2). Once root systems have developed, seedlings can usually survive mild to moderate Pythium infections. Seed treatments with oomycete activity can provide some protection within 10-14 days after planting, and can be helpful for improving seedling emergence and reducing pre-emergent damping off. Multiple species of Pythium are able to infect corn, with each species having a different optimal temperature. We have ongoing research projects to collect diseased samples and identify which species are most problematic in the Mid-Atlantic.

Corn seedlings with post-emergent damping-off caused by Pythium spp

Figure 1. Corn seedlings with post-emergent damping-off caused by Pythium spp.

Corn seedling with necrotic, brown mesocotyl following infection by a Pythium spp

Figure 2. Corn seedling with necrotic, brown mesocotyl following infection by a Pythium spp.

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