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FACT
SHEETS>PEST MANAGEMENT>DAMPING-OFF OF BEDDING PLANTS AND VEGETABLES
Damping-Off of Bedding Plants
and Vegetables
Introduction
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Rhizoctonia Damping-Off of Catharanthus Seedlings
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Damping-off is a disease of germinating seeds and seedlings caused primarily
by fungi. Within days, hundreds or thousands of seedlings can become colonized
resulting in plant losses and delayed planting or shipping. Healthy appearing
plants selected from flats with damping-off may develop root rot or stem
canker several weeks later. With some damping-off fungi, foliar blight
may also occur. Pythium, Phytophthora, Rhizoctonia and Alternaria
are fungi that commonly cause damping-off. There are many other species
of fungi that occasionally cause this disease.
Symptoms
Fungi may attack germinating seeds or young seedlings. If poor plant emergence
occurs, inspect the soil. If the seed has not germinated it may have been
subjected to unfavorable environmental conditions or it may be old. If
germination has occurred and the hypocotyl (emerging shoot) is water-soaked
in appearance or visibly decayed, fungi are the most likely cause.
Seedlings often develop a darkened or shriveled "wire stem" appearance
at the base of the stem. The top of the plant may appear h ealthy when
it falls over but quickly wilts and dies. The roots may or may not be
decayed. When seeds are germinated in flats or beds, the disease often
occurs in a roughly circular pattern. This is because of the tendency
of fungi to grow radially from the point of origin. If there is a lot
of fungal contamination, a circular pattern will not be apparent. In plug
trays, spread occurs by splashing irrigation water resulting in a more
random distribution of disease. The plug cells inhibit the radial growth
pattern seen in flats of soil.
Unfavorable environmental conditions and cultural practices can result
in seedling death that resembles damping-off. Hot water from sun-baked
pipes and hoses, over-fertilization, low temperatures, drought, heat stress
and chemical injury can all kill seedlings. However, in most of these
cases initial symptoms occur on the foliage or upper part of the seedlings.
When the seedlings collapse, the stem at the soil line is usually firm
and healthy and the root system is unaffected. An exception to this would
be over-fertilization which usually causes roots to appear desiccated
and shriveled.
Sources of fungi
Some fungi such as Alternaria are typically seed-borne rather
than soil-borne. Alternaria may cause foliar blights on plants
as well. Soil-borne fungi such as Pythium, Phytophthora, Rhizoctonia
and Sclerotinia may be present in untreated or improperly treated
field soil. While not impossible, it is unlikely that soil-less media
are contaminated when purchased. However, these fungi can easily be transferred
to the growth medium by soiled tools, hands, or hoses and splashing water
from infested soil.
Management
Prevention is most important. Avoid contamination of the growing medium
and purchase quality seed. Use a soil-less medium. Keep flats off of dirt
floors. Hang up the hose ends. When disease occurs, have the cause determined.
Drench the medium with a broad-spectrum fungicide or a mixture of fungicides.
When damping-off occurs in a flat, discard the entire flat. Healthy appearing
plants may carry contaminated soil and may develop root rot or blight
at a later date.
The fungicides listed below are registered for Damping-off and/or Root Rot of Bedding Plants and Vegetables
Fungicides for Pythium and Phytophthora |
Common name |
Trade name |
Rate |
Comments |
*Crops |
fosetyl-Al |
Aliette® WDG |
0.4 to 0.8 lb/100 gal; 2 pts/sq ft. |
Drench; however, foliar applications of 2.5-5 lb/100 gal will control root rot of some plants. |
Ornamentals |
etridiazole |
Truban® WP and EC |
--------------- |
Rates vary depending on the formulation. Irrigate immediately with additional water equal to at least half the volume of the fungicidal drench. |
Ornamentals |
mefenoxam |
Subdue Maxx |
--------------- |
Rates vary depending on the plant. Subdue has broad crop clearance for ornamentals. |
Ornamentals |
dimethomorph |
Stature |
3.2-6.4 oz per 50-100 gal. |
Apply when plant roots are well established on a 10-14 day interval. Use enough solution to wet root zone. Avoid irrigation for several hours before application. |
Ornamentals |
Potassium salts of phosphorous acid |
Alude |
6.25-12.75 fl oz/100 gal |
Apply 25 gallons to 100 sq ft. Follow application with irrigation. Repeat as required. Limit to one application per month. |
Ornamentals |
thiophanate methyl plus etridiazole |
Banrot® 40WP |
4-12 oz/100 gal; apply to 400 sq ft (about 0.5 pt/6" pot). |
Irrigate immediately with additional water equal to at least half the volume of the fungicidal drench. Also controls Rhizoctonia, Fusarium, Thielaviopsis and Cylindrocladium . |
Ornamentals |
propamocarb |
Banol |
20-30 fl oz/100 gal; see label for details. |
Drench at 3 to 6 week intervals. May be tank mixed with thiophanate methyl for control of Rhizoctonia. |
Ornamentals |
etridiazole |
Terrazole 35 WP |
3.5-10 oz/100 gal; drench with enough to saturate the soil such as 0.5 pt/6 inch pot. |
Repeat at 4-12 week intervals. Drench with enough to saturate the soil such as 0.5 pt/6 inch pot. |
Ornamentals |
Streptomyces griseovirdis |
Mycostop |
------------- |
Suppression of Pythium that can cause seed, root and stem rot. Contains a beneficial bacterium. Repeat applications may be needed. Use as soil spray or drench. Acts as a preventative. Will not cure diseased plants. |
Ornamentals,
Vegetable Plants,
Herbs |
Trichoderma virens |
SoilGard |
------------- |
Contains a beneficial fungus. Acts as a preventative. Will not cure diseased plants. Do not use other soil fungicides with SoilGard at time of incorporation. |
Ornamentals,
Vegetable Plants,
Herbs |
Trichoderma harzianum |
RootShield |
------------- |
Contains a beneficial fungus. Avoid applications of fungicides a least one week before or after application. Acts as a preventative. Will not cure diseased plants. |
Ornamentals,
Vegetable Plants,
Herbs |
Hydrogen dioxide |
Oxidate, ZeroTol |
--------------- |
Contact, oxidizing sanitizer. |
Ornamentals,
Vegetable Plants,
Herbs |
Fungicides for Rhizoctonia and some other fungi |
thiophanate methyl |
Cleary's 3336
Fungo Flo |
--------------- |
See label for seedlings and transplants. Cleary's has broad crop clearance for ornamentals. Use experimentally for plants not on the label. Rates vary depending on the formulation. |
Ornamentals |
iprodione |
Sextant
26 GT |
--------------- |
See label for rates. Active primarily against Rhizoctonia . Apply 1 to 2 pints of solution per sq. ft. and repeat at 14 day intervals. Do not use as a drench on impatiens. |
Ornamentals |
PCNB |
Terraclor® 75WP or 400F |
--------------- |
See labels for rates. Broad crop clearance for ornamentals. Active primarily against Rhizoctonia and Sclerotinia . |
Ornamentals,
Vegetable Plants |
thiophanate methyl plus etridiazole |
Banrot® 40WP |
see above |
see above |
see above |
fludioxonil |
Medallion |
1 to 2 oz packets/100 gal. |
For Rhizoctonia , apply sufficient water to wet the top half of the growing medium. For other pathogens, completely drench the growing medium. Medallion can be mixed with Subdue for broad spectrum control. |
Ornamentals |
triflumizole |
Terraguard 50W |
4-8 oz/100 gal; 4 fl oz/6 inch pot. |
For best results do not irrigate with additional water until 24 hr after application. Apply at 3-4 week intervals as needed. Do not use on impatiens plugs. On impatiens transplants, do not exceed 2 oz/100 gal. |
Ornamentals |
iprodione plus thiophanate methyl |
26/36 Fungicide |
13.5 fl oz per 100 gal; apply 1-2 pints per sq ft. |
Rhizoctonia, Cylindrocladium, and Fusarium. Do not use on Impatiens, Pothos, or Spathiphyllum. |
Ornamentals |
azoxystrobin |
Heritage |
0.2-0.9 oz per 100 gal. 1-2 pt per sq ft at 7-28 day interval. |
Do not make more than two sequential applications of Heritage. Do not rotate with Compass. Use caution applying to small bedding plants as phytotoxicity can occur. |
Ornamentals |
trifloxystrobin |
Compass |
0.5 to 1 oz per 100 gal. Drench to wet upper ½ of growing medium. |
Active against Rhizoctonia, Cylindrocladium, and Phytophthora parasitica. Do not make than two sequential applications. Do not rotate with Heritage. Do not apply to vegetable transplants. |
Ornamentals |
flutolanil |
Contrast |
3 to 6 one oz packets/100 gal. |
See label for volume of drench. |
Ornamentals |
Streptomyces griseovirdis |
Mycostop |
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Suppression of Rhizoctonia that can cause seed, root and stem rot. Contains a beneficial bacterium. Repeat applications may be needed. Use as soil spray or drench. Acts as a preventative. Will not cure diseased plants. |
Ornamentals,
Vegetable Plants,
Herbs |
Trichoderma virens |
SoilGard |
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Contains a beneficial fungus. Acts as a preventative. Will not cure diseased plants. Do not use other soil fungicides with SoilGard at time of incorporation. |
Ornamentals,
Vegetable Plants,
Herbs |
Trichoderma harzianum |
RootShield |
------------- |
Contains a beneficial fungus. Avoid applications of fungicides a least one week before or after application. Acts as a preventative. Will not cure diseased plants. |
Ornamentals,
Vegetable Plants,
Herbs |
Hydrogen dioxide |
Oxidate, ZeroTol |
--------------- |
Contact, oxidizing sanitizer. |
Ornamentals,
Vegetable Plants,
Herbs |
Key
*Crops: Crops registered for use.
See labels for rates and a complete explanation of precautions and restrictions.
Note: More than half of Pythium isolates cultured from greenhouse grown plants have been found to be resistant to Subdue Maxx. Do not use the same fungicide repeatedly, and rotate outside of a fungicide group.
1998 Prepared by Dr. Robert L. Wick, Department
of Plant Pathology, Fernald Hall, University of Massachusetts, Amherst,
MA 01003. Tel. (413) 545-1045 Fax (413) 454-2532
Tables revised 10/06 by M. Bess Dicklow, UMass Extension Plant Diagnostic Lab
Links to Further Resources on the Web
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