Ten Diseases of Herbaceous Plants 2008 Damping-Off/Seedling Blights Specialized Master Gardener Training • Pathogens: Ten Diseases of Herbaceous Plants – Pythium spp. – Rhizoctonia solani – Fusarium spp. Brian D. Hudelson • Hosts: Seedlings of virtually anything Department of Plant Pathology University of Wisconsin-Madison/Extension

Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Damping-Off/Seedling Blights Damping-Off/Seedling Blights

• Control: • Control: – Use a pasteurized soil mixture – Germinate seeds at higher temperatures – Use decontaminated pots, working surfaces and tools – Use fungicides to protect seedlings – Moderate soil moisture • Etridiazole, metalaxyl, mefenoxam, captan • Use a soil with adequate drainage • Applied as a seed treatment or drench • Don’t overwater

Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Root/Crown Rots Root/Crown Rots

• Causes: Pythium spp., Phytophthora spp., • Control: Rhizoctonia solani, Fusarium spp., – Moderate soil moisture Cylindrocarpon spp., Thielviopsis spp. • Grow ornamentals in well-drained sites • Hosts: Anything and everything • Use a soil with adequate drainage • Improve drainage in poorly drained soils – Add organic matter to improve drainage –Use raised beds • DO NOT overwater • DO NOT overmulch

1 Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Root/Crown Rots Root/Crown Rots

• Control: • Control: – DO NOT move contaminated soil or plants to non- – Decontaminate recycled water infested areas • Filtration – Decontaminate infested tools, pots, work areas • Irradiation – Pretest soils/mulches/composts for the presence of • Chemical treatment root rot fungi – Use a soil-less potting mix for containerized plants

Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Root/Crown Rots Southern Blight

• Control: • Pathogen: Sclerotium rolfsii – Use fungicides to prevent infections •Host: • Etridiazole, metalaxyl, mefenoxam, fosetyl-Al, – Many other herbaceous annuals and perennials PCNB, thiophanate-methyl, fludioxonil • Use granular formulations if possible – Some woody ornamentals • Use during periods of wet weather –Hosta – Use biopesticides to prevent infections – Bedding plants • Trichoderma, Gliocladium • Use in pot production

Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Southern Blight Powdery Mildews

• Control: •Cause: – Inspect plants prior to purchase and avoid infected – Erysiphe spp. – Microsphaera spp. – Oidium sp. plants – Uncinula spp. – Sphaerotheca spp. – Ovulariopsis sp. – Avoid cocoa mulch (????) – Phyllactinia spp. – Podosphaera spp. – Remove infected plants – Blumeria spp. – Brasiliomyces spp. – Use fungicides for control • Hosts: Virtually everything • triadimefon • 14 – 28 day intervals – Pray for a cold winter

2 Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Powdery Mildews Powdery Mildews

• Control: • Control: – Remove diseased plant material and debris – Use fungicides to prevent infections – Reduce humidity • Dinocap, dithiocarbamates, myclobutanil, triadimefon, • Plant less densely triforine, sulfur or thiophanate-methyl • Thin existing stands • Baking soda (1.5 T/gal) and horticultural oil (3 T/gal) • Apply when humidity >60-70% – Use resistant cultivars/varieties • 7-14 day application interval

Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Botrytis Blight/Gray Mold Botrytis Blight/Gray Mold

• Pathogen: Botrytis cinerea • Control: •Hosts: – Remove and destroy diseased plant material – Virtually everything (particularly flower parts) – Remove senescing plant parts – Hit list: roses, peonies, geranium – Plant less densely – Thin existing plant stands – DO NOT overhead watering – DO NOT overwater

Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Botrytis Blight/Gray Mold Aster Yellows

• Control: • Pathogen: Aster yellows phytoplasma – Use fungicides to prevent infections •Hosts: • Chlorothalonil, copper-containing fungicides, fludioxonil, – Many plants in the Asteraceae iprodione, mancozeb, maneb, thiophanate-methyl, triflumizole – Many other plants in many other plant families • 7-14 day application interval • Transmission: Aster leafhopper • Apply during periods of high moisture

3 Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Aster Yellows Foliar Nematodes

• Control: •Cause: Aphelenchoides spp. – Control leafhopper vector (?) •Hosts: – Remove infected plants – Many different plants – Houseplants: African violets, ferns, begonia chrysanthemum – Landscape plants: Hosta

Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Foliar Nematodes Hosta Virus X

• Control: • Cause: Hosta virus X virus – Start with clean propagation materials • Host: Hosta – Follow strict sanitation procedures when working –‘Gold Edger’ with plant materials –‘Gold Standard’ – Remove symptomatic plants – ‘Golden Tiara’ – Remove contaminated plant debris –‘Striptease’ – Avoid overhead irrigation – ‘Sum and Substance’ – Hot water treatments (10 minutes at 125°F)

Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Hosta Virus X Hosta Virus X

• Transmission: Mechanical • Control: – Pruning tools –Buy Hosta plants from reputable sources – String edgers – Inspect hostas prior to purchase for symptoms of – Shovels Hosta virus X – Touch – Request that plants be tested for Hosta virus X prior to purchase – Keep new Hosta plants isolated from established Hosta plants

4 Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Hosta Virus X Tobacco Rattle

• Control: • Cause: Tobacco Rattle Virus – Remove and destroy infected plants •Hosts: – Remove infested plant debris – Ornamentals – Disinfest tools (and other items) that come into • Astilbe, bleeding heart, columbine, coral bells, daffodils, contact with potentially infected plants epimedium, gladiolus, hyacinth, marigold, peony, tulip, • Sodium dodecyl sulfate (sodium lauryl sulfate) + vinca Alconox® (1% + 1%) – Vegetables • Trisodium phosphate • Beans, beet, pepper, potato, spinach • Alcohol dip followed by flaming

Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Tobacco Rattle Tobacco Rattle

• Transmission: Stubby-root nematodes • Control: – Trichodorus – DO NOT buy symptomatic plants – Paratrichodorus – Grow non-susceptible plants • Annual phlox, carnation, devil’s trumpet (downy thorn- apple), sweet William, zinnia, zombie cucumber – Remove and destroy infected plants

Ten Diseases of Herbaceous Plants Ten Diseases of Herbaceous Plants Tobacco Rattle Herbicide Injury

• Control: • Causes: – Disinfest tools (and other items) that come into – Growth regulator herbicides contact with infected plants (e.g., when dividing •2,4-D plants) • Dicamba • Sodium dodecyl sulfate (sodium lauryl sulfate) + – Other herbicides Alconox® (1% + 1%) • Trisodium phosphate • Affected plants: Anything and everything • Alcohol dip followed by flaming – Control of stubby-root nematode is not practical

5 Ten Diseases of Herbaceous Plants Plant Diseases Herbicide Injury Where to Go for Help

• Control: Plant Disease Diagnostics Clinic – Apply herbicides only when needed Department of Plant Pathology – Follow application directions exactly University of Wisconsin-Madison – Apply herbicides only when wind speed is low (< 5 1630 Linden Drive mph) Madison, WI 53706-1598 – DO NOT apply herbicides too close to nontarget plants (608) 262-2863 – Apply herbicides at low pressure [email protected] – Use amine rather than ester forms of herbicides http://www.plantpath.wisc.edu/pddc (http://wihort.uwex.edu)

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