HPIPM:Damping Off and Seedling Blight FC

Author: Howard F. Schwartz and Michael E. Bartolo

Taxonomy

Domain	Eukarya
Kingdom	Chromista
Phylum	Oomycota
Class	Oomycetes
Order	Peronosporales
Family	Pythiaceae

Scientific Name

Pythium

Common Name

Pythium diseases

Death of seedlings before and after emergence can be caused by various species of Pythium and Fusarium. Older reports also claim that Rhizoctonia can be involved. Plants are often infected at the soil line or slightly below; tissue turns tan to brown, watersoaked, and shrinks rapidly while aboveground parts wilt and fall over. Root systems of seedlings and transplants are rotted by these fungi or damaged by nematodes. Therefore, roots are killed directly or weakened and predisposed to additional damage by other stress factors such as cold, wet soil, compaction, herbicides, and salts from alkaline soil or fertilizer.

Disease management recommendations include crop rotation out of onions for three years; plant seed treated with a fungicide such as Thiram and/or metalaxyl (Ridomil); good seedbed preparation that promotes adequate drainage and rapid emergence; and reduction of other stresses such as cold soil, soil compaction and poor drainage, or improper fertilizer placement. A seven to ten inch banded fungicide such as Ridomil applied at planting provided an average increase in plant stand of 13 percent (range from five to 22 percent) in commercial fields of seeded onions.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.