HPIPM:Damping Off / Seedling Blight SC

Taxonomy

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

Scientific Name

Pythium

Common Name

Pythium diseases

Author: Howard F. Schwartz and David H. Gent

Identification (and life cycle/seasonal history)

Damping-off is a disease of seeds (pre-emergence damping-off) and seedlings (post-emergence damping or seedling blight) that can be caused by many fungi, primarily Pythium spp. and Fusarium spp., but also Penicillium spp., Rhizoctonia spp., Aspergillus spp., Alternaria spp., and others. These fungi are common soil inhabitants in soils worldwide and have a broad host range. They survive between crops as dormant resting structures (oospores, sclerotia), in crop debris, saprophytically, and pathogenically on weeds and other hosts.

Plant Response and Damage

Pre-emergence damping-off results in seed rot and seedling that never emerge. Initial root rot symptoms appear as elongated water-soaked areas on roots one to three weeks after planting. The cortex of severely infected plants will rub off, leaving the white stele. The pathogen will extensively prune roots, reduce overall plant growth, and can destroy much of the main root system. The water-soaked region may extend several inches above the soil line, with little, if any, visible evidence of the fungus. The water-soaked area eventually dries out, becomes somewhat sunken, and tan to brown in color. Above ground symptoms include stunting and yellowing; eventually plants wilt and die. Damage usually is most common when seed quality is poor and/or seed has been damaged by freezing, herbicides, or the presence of other pathogens. Slow germination and poor drainage typically result in damping-off and seedling blight.

Biological Control

Bio-Ag 22G (Trichoderma harzianum) and Kodiak (Bacillus subtilis) are registered for use on sweet corn, but their efficacy in the High Plains is unknown.

Cultural Control

Plant corn seed of high quality into well prepared seedbeds under conditions that promote rapid seed germination and seedling emergence. Avoid compaction, poor drainage, herbicide injury, and other stresses that delay germination and thus increase the chance for seed and seedling infection. Very little or no information is available on resistant varieties. Crop rotation may provide some control of some of the pathogens involved in the damping-off complex, but may not suppress pathogens such as Pythium spp. that have very broad host ranges. Increases seeding rates will partially compensate seedlings that are killed.

Chemical Control

Treat seed with a broad-spectrum fungicide to suppress damping-off pathogens. Seed treatments provide early season suppression of damping-off fungi, but often lose their effectiveness as the plant grows.

Product List for Damping-Off and Seedling Blight:

Pesticide	Rate per 100 lb seed	Application Frequency (days)	Remarks
Azoxystrobin
Amistar	0.125-0.25 oz/1000 feet	In furrow	Suppression of Rhizoctonia solani
Protégé	0.153 fl oz	Seed treatment	Broad spectrum
Quadris	0.4-0.8 fl oz	In furrow	Suppression of Rhizoctonia solani
Captan and Captan Combinations
Agrox Premiere	3.6 oz	Seed treatment	Broad spectrum
Captan 30-DD	6.5 fl oz	Seed treatment	Broad spectrum, but weak against Pythium and Phytophthora spp.
Captan 400	5-8 fl oz	Seed treatment	Broad spectrum, but weak against Pythium and Phytophthora spp.
Captan 400-C	5-8 fl oz	Seed treatment	Broad spectrum, but weak against Pythium and Phytophthora spp.
Nu-Grow Captan 4000	5-8 fl oz	Seed treatment	Broad spectrum, but weak against Pythium and Phytophthora spp.
Carboxin: various formulations and mixtures available
KICKSTART VP	3.75 oz	Seed treatment
Vitavax-34	2-4 oz	Seed treatment	Suppression of Rhizoctonia and head smut
Vitavax 200 Flowable	3-4 fl oz	Seed treatment
EBDC
mancozeb	Varies	Seed treatment.	Various formulations available such as Manzate and Dithane
Fludioxonil
Maxim 4FS	0.034-0.068 fl oz	Seed treatment	Broad spectrum, but weak against Pythium and Phytophthora spp.
Metalaxyl/Methoxonam
Apron XL LS	0.64 fl oz	Seed treatment	Suppression of Pythium and Phytophthora spp.
Allegiance-FL	0.75-1.5 fl oz	Seed treatment	Suppression of Pythium and Phytophthora spp.
Allegiance LS	1.2-2.4 fl oz	Seed treatment
Ridomil Gold EC	¼ to ½ pint	Pre-emergence soil drench	Suppression of Pythium and Phytophthora spp.
PCNB, Metalaxyl, and Bacillus subtilis
System 3	3.3 - 5.0 oz	Seed/planter box treatment.	Broad spectrum
Thiram
42-S Thiram	8 fl oz	Seed treatment	Broad spectrum
Thiram 50WP	8 oz	Seed treatment	Broad spectrum
42-S Thiram	1.5 fl oz/bu	Seed treatment	Broad spectrum

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.