Harrell's Compendium of Tropical Plant Diseases & Disorders

A COMPENDIUM of TROPICAL DISEASES AND DISORDERS

A Valuable Resource for Commercial Growers and Interiorscapers

The compendium describes each disease and disorder, including photos of symptoms and signs, conditions that favor or induce development, and science-based management recommendations when available.

COMPILED BY

+ AARON J. PALMATEER + A.R. CHASE (retired) + LYNN P. GRIFFITH JR.

A COMPENDIUM OF TROPICAL PLANT DISEASES AND DISORDERS

ALGAL LEAF SPOTS

SYMPTOMS

Circular to oblong leaf spots with or without a yellow or reddish border (halo) Signs of yellow to reddish orange sporulation on the leaf spot surface ( C. verescens ) C. parasiticus causes brown leaf spots with a red border andorange tufts of spores on the underside (resembling rust)

Algal leaf spots caused by Cephaleuros species are often mistaken for rust, powdery mildew, various leaf spots, and a bacterial canker. This resulted in some of the cases misleadingly named “red rust”. Cephaleuros virescens appears to be the most common and widespread species in the genus, but diseases caused by C. parasiticus are more severe and damaging to the plant.

FAVORABLE CONDITIONS

Poor air circulation

Warm temperatures typical of summer months

High relative humidity

ALGAE LEAF SPOT

ALGAE LEAF SPOT OF GUAV

ALGAE LEAF SPOT SPORULATIN

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BROWN SPOT WITH RED HALO

REDDISH ORANGE SPORULATION

BROWN SPOT

TROPICAL PLANTS COMMONLY AFFLICTED BY ALGAL LEAF SPOTS Cephaleuros parasiticus

MANAGEMENT RECOMMENDATION

Cephaleuros virescens

Aglaonema Anthurium Bouganvillea Bromeliads Croton English Ivy Eugenia Ficus Gardenia Ginger Heliconia Hibiscus Philodendron Sansevieria Spathiphyllum

+ M inimize plant stress with proper nutrition and irrigation. Space plants to apart to increase air flow to reduce humidity.

FUNGICIDES FOR CONTROLLING ALGAL LEAF SPOTS Tradename

FRAC Group

Chlorothalonil

Daconil Ultrex®, Daconil Weatherstik®

Phosphorus acid

Oxiphos®

P07

Copper octanoate, copper oxychloride

Camelot® O, Grotto®, COC DF

M01

Bacillus amyloliquefaciens *

Triathlon® BA, Double Nickel®

BM02

- - - -

Sodium carbonate peroxyhydrate

Phycomycin®, GreenClean® Pro

Reach out to your Harrell’s rep for more information.

Quaternary ammonium (DDAC)

KleenGrow TM

Hydrogen peroxide + peroxyacetic acid

Zerotol®

Potassium bicarbonate *

MilStop®

Follow the product label and rotate between FRAC groups to reduce resistance development * May not perform well under high disease pressure.

A COMPENDIUM OF TROPICAL PLANT DISEASES AND DISORDERS

ALTERNARIA AND CLOSELY RELATED FUNGI

SYMPTOMS

Spots of different sizes scattered across leaves

Spots can have a reddish, purple, or yellow border (halo)

Spots on leaves mainly but can occur on flowers and stems

Alternaria, Bipolaris, Corynespora, Drechslera, Exserohilum, Helminthosporium, and Stemphylium . These fungi form dark- colored spores with more than one cell. This results in causing very similar diseases in similar ways. They can all be controlled with the same range of fungicides. They are common on some crops grown in greenhouses, nurseries, and landscapes.

FAVORABLE CONDITIONS

Overhead irrigation or exposure to rainfall

Poor air circulation

Temperatures in the mid 70’s to low 80’s

ALOE ALTERNARIA

EXSEROHILUM PALM

SEDUM ALTERNARIA

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BROMELIAD BIPOLARIS

CORDYLINE BIPOLARIS

STRELITZIA BIPOLARIS

TROPICAL PLANTS COMMONLY AFFLICTED BY ALTERNARIA AND ITS RELATIVES Alternaria Bipolaris

MANAGEMENT RECOMMENDATION

Corynespora Drechslera Exserohilum Helminthosporium Stemphylium

African Violet Aloe Aralia Bromeliads Cacti Calathea Cordyline Desert Rose Ficus Grasses Kalanchoe Lipstick Vine Mandevilla Palms Schefflera Zebra Plant

+ E liminate overhead irrigation. Insecticidal soaps and oxamyl (IRAC 1A) both provide control of Alternaria leaf spot equivalent to the fungicides. Acephate (IRAC 1B) can also reduce disease severity. Adequate plant nutrition including micronutrients are very important and can reduce the severity of disease. Some of the minor element sprays mimic leaf spot symptoms caused by Helminthosporium (Bipolaris, Exserohilum) on palms.

+ U sing infected plugs or cuttings

FUNGICIDES FOR CONTROLLING ALTERNARIA AND RELATED FUNGAL LEAF SPOTS Tradename FRAC Group

Chlorothalonil

Daconil Ultrex®, Daconil Weatherstik®

Iprodione

Chipco® 26019 Flo, Chipco® 26019 WP

DMI

Avelyo®, Eagle®, Terraguard®

DMI + SDHI

Postiva TM

3 + 7

Reach out to your Harrell’s rep for more information.

Compass®, Heritage®, Empress® Intrinsic®, Fame®

Strobilurin

Strobilurin + SDHI

Broadform®, Orkestra® Intrinsic®, Mural®

7+11

Fludioxonil

Medallion®, Emblem TM

Follow the product label and rotate between FRAC groups to reduce resistanace development * Fungicides containing thiophanate methyl can increase the severity of Alternaria leaf spot ** Broad spectrum products including copper and mancozeb are somewhat effective

A COMPENDIUM OF TROPICAL PLANT DISEASES AND DISORDERS

ANTHRACNOSE

SYMPTOMS

Leaf spots tan to dark brown, circular and sunken containing dark brown to black fruiting bodies Fruiting bodies often form in concentric rings appearing as a bull’s eye target on the upper surface of leaves Symptoms differ by host including needle necrosis, blights, dieback, cutting rot and stem rot

Anthracnose diseases of tropical plants are caused by a variety of fungi including Colletotrichum, Gloeosporium and Glomerella . They are common on some crops grown in greenhouses, nurseries and are often found in many landscapes. Anthracnose diseases can start in propagation where they present as leaf spots and sometime cutting death. Unfortunately, if they are present in propagation they usually carry through and cause losses throughout the remainder of the production cycle, even showing symptoms as long as 2-3 years after the cutting was rooted.

FAVORABLE CONDITIONS

Overhead irrigation or exposure to rainfall

Long periods of high relative humidity and warm temperatures

Mechanical damage or wounding and poor air circulation

AGLAONEMA ANTHRACNOSE

CACTUS ANTHRACNOSE

DRACAENA ANTHRACNOSE

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YUCCA ANTHRACNOSE

HEDERA ANTHRACNOSE PHILODENDRON ANTHRACNOSE

FUNGICIDES FOR CONTROLLING ANTHRACNOSE

MANAGEMENT RECOMMENDATION

Common Name

Tradename

FRAC Group

chlorothalonil

Daconil Ultrex ® , Daconil Weatherstik ®

chlorothalonil + DMI

Concert ® II *

M5 + 3

DMI

Avelyo ®

DMI + SDHI

Postiva TM

3 + 7

+ E liminate overhead irrigation or exposure to rainfall + A dequate plant nutrition including micro nutrients are very important and can reduce disease severity + U sing infected plugs or cuttings should always be avoided

strobilurin

Heritage ® , Fame ®

Broadform ® , Orkestra ® Intrinsic ® , Pageant ® Intrinsic ® , Mural ®

strobilurin + SDHI

7 + 11

fludioxonil

Medallion ® , Emblem TM

fludioxonil + cyprodinil

Palladium ®

9 + 12

Follow the product label and rotate between FRAC groups to reduce resistance development * May not perform well under high disease pressure.

TROPICAL PLANTS COMMONLY AFFLICTED BY ANTHRACNOSE

Anthurium

Hosta

Artillery Plant

Kangaroo Vine

Cyclamen

Mandevilla

Croton

Norfolk Island Pine

Dieffenbachia

Sansevieria

Dracanea

Sedum

English Ivy

Spathiphyllum

Euonymus

Succulents

Ficus

Venus Flytrap

Reach out to your Harrell’s rep for more information.

A COMPENDIUM OF TROPICAL PLANT DISEASES AND DISORDERS

Crown gall is caused by a plasmid carried by the bacterium Agrobacterium tumefaciens . Crown gall is generally more common in woody plants and the disease is more prevalent in field grown nurseries and landscapes than in soilless media free of the bacterium. Olive knot is caused by Pseudomonas savastonoi and was originally found on olives. It has been found on several tropical plants, some of which also can have crown gal. BACTERIAL GALLS - CROWN GALL AND OLIVE KNOT

SYMPTOMS

Crown galls are usually corky appearing tan in color, with a dryish texture.

They form on stems, petioles and leaves of infected plants.

Galls on leaves usually appear at a point where the main vein was damaged Aerial galls are quite common on Ficus benjamina which is not unique for crown gall.

On some crops (like roses) galls can be found on roots.

Symptoms of olive knot are very similar and telling the two apart by sight is not possible.

Galls often form on cutting ends and stem tips where cuttings were removed

FAVORABLE CONDITIONS

Disease outbreaks are favored by environmental stress (i.e., cold, heat, drought)

FICUS CROWN GALL

MANDEVILLA CROWN GALL

OLEANDER OLIVE KNOT

The bacterium infects stems and roots through wounds

The bacterium can be easily spread on tools

Scan for enlarged images and additional information

ROSE CROWN GALL

ROSE ROOT AGRO

PHOTINIA CROWN GALL

TROPICAL PLANTS AFFLICTED BY GALL-FORMING BACTERIA

MANAGEMENT RECOMMENDATION CONTINUED

Crown Gall

Olive Knot

Croton

Dwarf Schefflera

Euonymus

Sedum

Ficus

Succulents

Mandevilla

Loropetalum

+ A void introducing the pathogen by closely inspecting new plant material for galls + A ll plants with galls should be removed and discarded + C ontrol of crown gall requires sanitation and exclusion

Photinia

Mandevilla

Rose

Oleander

Schefflera

MANAGEMENT RECOMMENDATION + Biological control of crown gall has been possible on some woody ornamentals with Galltrol- A® ( A. radiobacter , strain K84) and NoGall ( Agrobacter radiobacter , strain K-1026). + Significant work has been done for control of olive knot in olives. In this case, use of copper spray timed for 2 days after leaf fall has been most effective. Use of copper sprays at other times was not significantly effective.

+ U se of disinfectants such as quaternary ammonium and

sodium hypochlorite to clean the production area including tools, benches, pots, etc., will help reduce disease

+ Considering ornamental production and Florida conditions, copper sprays may not be helpful.

+ Immediate use of a copper spray after pruning may be helpful but no work has been reported to demonstrate this

Reach out to your Harrell’s rep for more information.

A COMPENDIUM OF TROPICAL PLANT DISEASES AND DISORDERS

CERCOSPORA

SYMPTOMS

Leaf spots have diffuse margins (lacking definite borders)

Most often appear as bright yellow or purplish red spots

Translucent yellow borders are most obvious when viewed with back-lighting

Cercospora and Pseudocercospora leaf spots are common on a wide variety of tropical plants grown in greenhouses, nurseries and are often found in landscapes. Some of these leaf spots are not seen for years until an unusual amount of rainfall occurs and they suddenly show up.

Leaf spots vary in shape and color depending on the plant

FAVORABLE CONDITIONS

Overhead irrigation or exposure to rainfall favors

Poor air circulation will make this foliar disease worse

CERCO RAPHIS

CERCOSPORA ON CORDYLINE

CERCOSPORA ON LIRIOPE

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CERCOSPORA SPATH

NANDINA LS

CERCOSPORA ON LIGUSTRUM

FUNGICIDES FOR CONTROLLING CERCOSPORA LEAF SPOT

Common Name

Tradename

FRAC Group

MANAGEMENT RECOMMENDATION

thiophanate methyl

3336, T-methyl

copper

Camelot® O, CuPRO®5000, Kalmor®, Kocide®, Phyton® 27

M01 M03 M05

mancozeb

Protect TM DF, Manzate®

chlorothalonil

Daconil Ultrex®, Daconil Weatherstik®

chlorothalonil + DMI

Concert® II *

M05 + 3

+ A void using infected seed or cuttings. Eliminate overhead

DMI

Avelyo®, Banner Maxx®, Eagle®, Terraguard®

DMI + SDHI strobilurin

Postiva TM

3 + 7

irrigation or exposure to rainfall. Water during the day when plant leaves have the greatest cache to dry quickly. Provide uniform spray coverage of both sides of the leaf for adequate control and add a wetting agent when leaves are very waxy.

Compass®, Heritage®, Empress® Intrinsic®, Fame®

Broadform®, Orkestra® Intrinsic®, Pageant® Intrinsic®, Mural®

strobilurin + SDHI

7 + 11

Follow the product label and rotate between FRAC groups to reduce resistanace development * Outdoor use only

FUNGICIDES FOR CONTROLLING CERCOSPORA LEAF SPOT

Common Name

Tradename

FRAC Group

mancozeb

Protect TM DF, Manzate®

M03 M05

chlorothalonil

Daconil Ultrex®, Daconil Weatherstik®

chlorothalonil + DMI

Concert® II *

M05 + 3

DMI

Avelyo®, Banner Maxx®, Eagle®, Terraguard®

DMI + SDHI strobilurin

Postiva TM

3 + 7

Compass®, Heritage®, Empress® Intrinsic®, Fame®

Broadform®, Mural®, Orkestra® Intrinsic®, Pageant® Intrinsic®

strobilurin + SDHI

7 + 11

fludioxonil

Medallion®

Broadform®, Orkestra® Intrinsic®, Pageant® Intrinsic®, Mural®

strobilurin + SDHI

7 + 11

Follow the product label and rotate between FRAC groups to reduce resistanace development * Outdoor use only

TROPICAL PLANTS COMMONLY AFFLICTED BY CERCOSPORA

Bord-of-paradise

Hydrangea Ligustrum

Cordyline

Ligustrum Peperomia

Reach out to your Harrell’s rep for more information.

Croton

Cordyline

Doryopteris

Philodendron Pittosporum Rhapis palm

Crape myrtle

Liriope

Ficus

Croton

Peperomia

Heliconia

Dryopteris Euphorbia

Philodendron Pittosporum Rhapis palm Spathiphyllum

Ficus

Heliconia

A COMPENDIUM OF TROPICAL PLANT DISEASES AND DISORDERS

MYROTHECIUM DISEASES

SYMPTOMS

Spots often form at wound sites

Fruiting bodies appear black with a white fringe on undersides (sporodochia)

Spots often merge and have wet margins

Myrothecium roridum attacks many tropical plants causing leaf spots generally and petiole rot on tissue-cultured plants like Spathiphyllum and Syngonium. Studies indicate that there is no host specificity, so an isolate from Aglaonema could cause disease on any other susceptible host such as Ficus.

Petiole rot occurs at the soil-line with the oldest petioles dying first

FAVORABLE CONDITIONS

Overhead irrigation or exposure to rainfall

Using infected plugs or cuttings

Tissue-cultured plants are especially sensitive

Shade houses covered with plastic (wintertime in south Florida)

Over-fertilizing plants

FICUS eLASTICA MYROTHECIUM

HIBISCUS MYROTHECIUM

AGLAONEMA MYROTHECIUM

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DIEFFENBACHIA MYROTHECIUM

FICUS MYROTHECIUM

MYROTHECIUM

TROPICAL PLANTS COMMONLY AFFLICTED BY ALGAL LEAF SPOTS Tradename

MANAGEMENT RECOMMENDATION

FRAC Group

chlorothalonil

Daconil Ultrex®, Daconil Weatherstik®

iprodione

Chipco® 26019 Flo, Chipco® 26019 WP

mancozeb

Protect TM DF, Manzate®

M03

DMI

Avelyo®, Eagle®, Terraguard®

+ A void using infected seed, plugs or cuttings. Eliminate overhead irrigation or exposure to rainfall. Water during the day when plant leaves have the greatest cache to dry quickly. Provide uniform spray coverage of both sides of the leaf for adequate control and add a wetting agent when leaves are very waxy.

DMI + SDHI

Postiva TM

3 + 7

Compass®, Heritage®, Empress® Intrinsic®, Fame®

strobilurin

strobilurin + SDHI

Broadform®, Orkestra® Intrinsic®, Mural®

7+11

fludioxonil

Medallion®, Emblem TM

Follow the product label and rotate between FRAC groups to reduce resistanace development

TROPICAL PLANTS COMMONLY AFFLICTED BY MYROTHECIUM DISEASES

Aglaonema Anthurium

leaf spot leaf spot leaf spot leaf spot leaf spot leaf spot leaf spot petiole rot

Dieffenbachia

Ferns

Gardenia

Ficus

New Guinea Impatiens

Spathiphyllum

Syngonium

petiole rot

Reach out to your Harrell’s rep for more information.

A COMPENDIUM OF TROPICAL PLANT DISEASES AND DISORDERS

PHYTOPHTHORA DISEASES

SYMPTOMS

Black or brown sunken lesions at the base of the stem or anywhere on leaves

Rapid death especially following water stress

Dead tops with little if any root damage

Diseases caused by Phytophthora are among the most aggressive and damaging as above ground plant tissue is often targeted resulting in stem rot, crown rot, aerial blight in addition to bud rot of palms. Phytophthora species also cause root rot.

FAVORABLE CONDITIONS

Overwatering and overhead irrigation

Drought stress or high temperatures

Ebb and flood irrigation systems

PHYTOPHTHORA BLIGHT ON ANTHURIUM

PHYTOPHTHORA BLIGHT ON MONSTERA

PHYTOPHTHORA BLIGHT PICHARA AQUATICA

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PHYTOPHTHORA CROWN ROT OF BROMELIAD

PHYTOPHTHORA CROWN ROT ON BROMELIAD

PHYTOPHTHORA BLIGHT PICHARA AQUATICA

FUNGICIDES FOR CONTROLLING DISEASES OF PHYTOPHTHORA

Host

MANAGEMENT RECOMMENDATION

Disease

Host

Disease

Calibrachoa

Crown and stem rot

Pachira (Money tree)

Aerial blight

Croton

Aerial blight

Palms

Bud rot

Ficus

Root rot

Petunia

Crown rot

Gardenia

Root rot

Poinsettia

Stem rot

+ M onitor irrigation to avoid saturated conditions.

Gerber daisy

Crown rot

Pothos

Aerial blight

Hedera (English ivy)

Aerial blight

Rosemary

Root rot

Thoroughly clean and disinfect pots and avoid reusing potting medium. Get an accurate diagnosis as many diseases can look alike and not all fungicides will be effective against Phytophthora.

Lavender

Crown and stem rot

Snapdragon

Crown rot

Lily (Asiatic and Oriental)

Bulb rot

Spathiphyllum

Aerial blight

Liriope

Crown rot

Vinca (annual)

Aerial blight

Mandevilla

Aerial blight

FUNGICIDES FOR CONTROLLING DISEASES OF PHYTOPHTHORA

Common Name

Tradename

FRAC Group

mefenoxam

Subdue Maxx®

phosphonates

Aliette®, TitlePhyte®

P07

fenamidone

FenStop®

etridiazole

Terrazole®, Truban®

cyazofamid

Cyazo, Segway® O

mandipropamid

Micora TM

dimethomorph

Stature®

amectoctradin + dimethomorph

Orvego®

45 + 40

fluopicolide

Adorn®

oxathiapipropalin

Segovis®

Follow the product label and rotate between FRAC groups to reduce resistanace development ** Broad spectrum products including copper and mancozeb are somewhat effective

Reach out to your Harrell’s rep for more information.

A COMPENDIUM OF TROPICAL PLANT DISEASES AND DISORDERS

Globisporangium and Phytopythium are new separate genera that previously were included in the genus Pythium. These water mold pathogens attack the roots and sometimes stems of many ornamental plants. They are among the most common root rot pathogens that spread easily by run-off, in an ebb and flood and in contaminated irrigation water and occasionally in potting media. They often escape notice completely causing roots to be badly rotted with no above ground signs of the infection. PYTHIUM, GLOBISPORANGIUM AND PHYTOPYTHIUM DISEASES

SYMPTOMS

Damping-off

Lower yellow leaves, stunting and wilting

Brown water-soaked roots and poor root growth

Roots disintegrate when handled

FAVORABLE CONDITIONS

Poorly draining potting medium and over-watering

Over-fertilization on some crops

Ebb and flood irrigation systems

PYTHIUM BLIGHT ON IMPATIENS

PYTHIUM ROOT AND CROWN ROT

PYTHIUM ROOT ROT ON GARDENIA

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IVY PYTHIUM

PYTHIUM ROOT ROT NG IMPATIENS

PYTHIUM ROOT ROT

TROPICAL PLANTS COMMONLY AFFLICTED BY PYTHIUM DISEASES

MANAGEMENT RECOMMENDATION

Host

Disease

Host

Disease

African violet

Root and stem rot

Leatherleaf fern

Root rot

Aglaonema

Root and stem rot

Peperomia

Root rot

Aloe

Root and stem rot

Philodendron

Root rot

Areca palm

Root rot

Poinsettia

Root rot

+ M onitor irrigation to avoid saturated conditions.

Begonia

Root rot

Pothos

Cutting rot

Caladium

Root and corm rot

Rosemary

Root rot

Thoroughly clean and disinfest pots and avoid reusing potting medium. Get an accurate diagnosis as many root and stem rot diseases can look alike and not all fungicides will be effective against Pythium. + Some cuttings may be infected with Pythium without showing symptoms.

Dieffenbachia

Root rot

Snapdragon

Crown rot

Echeveria

Root and crown rot

Umbrella tree

Damping-off

Fatsia

Root rot

Zebra plant

Root rot

FUNGICIDES FOR CONTROLLING DISEASES OF PYTHIUM

Common Name

Tradename

FRAC Group

mefenoxam

Subdue Maxx ®

phosphonates

P07

Aliette ® , TitlePhyte ®

fenamidone

FenStop ®

strobilurin

Fame ® , Empress ® , Heritage ®

etridiazole

Terrazole ® , Truban ®

cyazofamid

Cyazo, Segway ® O

fluopicolide

Adorn ®

Follow the product label and rotate between FRAC groups to reduce resistanace development

Reach out to your Harrell’s rep for more information.

A COMPENDIUM OF TROPICAL PLANT DISEASES AND DISORDERS

RUST DISEASES

SYMPTOMS

Yellow or reddish leaf spots that appear blotchy or angular on the upper leaf surface Rust pustules on the underside of leaves (and sometimes stems) occur when mature Rust pustules in concentric rings are common on some hosts like geranium and snapdragon

Rust diseases have been on the rise with a few new and economically important rusts entering the US. gladiolus rust, guava (eucalyptus) rust, white rust on chrysanthemum and most recently rust on Monstera. Very few of the rusts we see in ornamentals have the classic alternate host situation (common in wheat and other agronomic crops) as we are well able to maintain them in a single life stage by propagating them on our plant material year-round. Watch for rust diseases this fall and one some crops throughout the winter and spring.

Spores in pustules (whitish, yellow, orange, and brown, which is the most common color)

Sometimes leaves drop when the disease is severe

FAVORABLE CONDITIONS

High humidity and more than 6 hours of leaf wetness

Temperatures ranging from 60-85 and poor air circulation leading to prolonged leaf wetness

Using infected seedlings or cuttings and liners

PROSPODIUM RUST ON TECOMA

ROSE RUST

RUST ON FIG

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RUST ON SNAPDRAGON RUST ON SYZIGIUM

RUST ON MONSTERA

TROPICAL PLANTS COMMONLY SUSCEPTIBLE TO RUST

MANAGEMENT RECOMMENDATION

Puccinia thaliae

Canna

Puccinia horiana, P. chrysanthemi

Chrysanthemum

Cerotelium fici

Fig

Uredo dianellae

Flax lily

Puccinia pelargonii

Geranium

+ R ust diseases can be very hard to control since their spores are very easily spread via wind

Uromyces transversaalis

Gladiolus

Uromyces triquetrus

Hypericum

Phakopsora jatrophicola

currents on asymptomatic cuttings with rainfall and

Jatropha

Puccinia nakanishikii

Lemongrass

splashing irrigation water and they can last for years in the dry state. Do not allow condensation overnight. Do not spray fungicides more than once a week and be sure to rotate FRAC groups.

Puccinia menthae

Mint

Pseudocerradoa paullula

Monstera

Puccinia psidii

Myrtle, guava, eucalyptus

Coleosporium

Plumeria

Phragmidium

Rose

Puccinia antirrhini

Snapdragon

Coleosporium

Solidago

+ Using infected seedlings or cuttings and liners.

Uredo manilensis

Tabernaemontana

Puccinia tillandsiae

Tillandsia

Prospodium appendiculatum

Yellow Elder

FUNGICIDES FOR CONTROLLING RUST DISEASES

Common Name

Tradename

FRAC Group

thiophanate methyl

3336, OHP-6672®, T-methyl

DMI

Avelyo®, Terraguard®, Torque TM , Tourney®

strobilurin

Compass®, Heritage®, Empress® Intrinsic®, Fame®

Reach out to your Harrell’s rep for more information.

3 + 7

DMI + SDHI

Postiva TM

Broadform®, Orkestra® Intrinsic®, Pageant® Intrinsic®, Mural®

7 + 11

strobilurin + SDHI

M03

mancozeb

Mancozeb, Manzate®, Protect TM DF *

M05 + 3

chlorothalonil + DMI

Concert® II **

Follow the product label and rotate between FRAC groups to reduce resistanace development * Mancozeb is best applied preventatively or as a tank mix ** Outdoor use only and avoid drench applications as root damage is possible with chlorothalonil

A COMPENDIUM OF TROPICAL PLANT DISEASES AND DISORDERS

SOUTHERN BLIGHT

SYMPTOMS

The pathogen attacks all portions of the plant but is mostly found on stems and leaves. Symptoms on stems are water soaked, necrotic lesions at or near the soil line.

White, coarse mycelium grows in a fan like pattern on the soil surface, leaves or stems

Southern blight, caused by Athelia rolfsii (formerly Sclerotium rolfsii ), is known to occur on many agronomic, vegetable, and ornamental crops in the Southern United States, and Central and South America. The disease is most common in tropical and subtropical climates. Southern blight remains a continuing problem today on many foliage crops including most recently English ivy (Italy), Mediterranean fan palm (Italy) and Areca palm (California).

FAVORABLE CONDITIONS

Disease development is favored by wet soil conditions, acidic pH (3.0 – 5.0), and temperatures between 77 – 95℉ A cutting rot can develop on contaminated plant materials during the summer months

SCLEROTIA OF SOUTHERN BLIGHT PATHOGEN

SOUTHERN BLIGHT ON IMPATIENS

SOUTHERN BLIGHT ON ZZ PLANT

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SOUTHERN BLIGHT POTHOS

SOUTHERN BLIGHT ON MOSS

SOUTHERN BLIGHT ON ROTTEN STEM

SOME TROPICAL PLANTS COMMONLY AFFECTED BY SOUTHERN BLIGHT

African Violet

Pothos

MANAGEMENT RECOMMENDATION

Aglaonema

Rabbit's Foot Fern

Aloe

Spider Plant

Areca Palm

Staghorn Fern

Bird's-nest Fern

Umbrella Tree

+ C losely monitor and scout plants to avoid introducing the disease into the nursery or greenhouse. Fungicides that have demonstrated control include Heritage (FRAC 11), Medallion (FRAC 12), Mural, Orkestra, Pageant (FRAC 7 + 11), Postiva (FRAC 3 + 7), and Terraclor 400 (FRAC 14),. All products should be applied preventatively for best results.

Caladium

Velvet Plant

Chinese Money Plant

Xantheranthemum

Croton

Yucca

Dieffenbachia

Zebra Plant

Dracaena

ZZ Plant

Reach out to your Harrell’s rep for more information.

A COMPENDIUM OF TROPICAL PLANT DISEASES AND DISORDERS

BACTERIAL WILT (SOUTHERN WILT)

SYMPTOMS

Yellowing and browning of the lower leaves

Drooping of the tip of some of the lower leaves that resembles lack of water

Southern wilt is caused by the bacterial plant pathogen Ralstonia solanacearum . Ralstonia solancearum is divided into several different races and biovars. A biovar 3 strain of R. solancearum can infect and cause disease of Mandevilla, Geranium and Osteospermum. Vinca vine (V. minor) and Sutera were asymptomatic hosts. The biovar 3 strain is distinct from the strain classified as a select agent (race 3, biovar 2). The strict regulatory guidelines associated with the presence of race 3 biovar 2 do not apply to biovar 3.

Leaf petiole and lower leaf turn brown in between the veins

Roots of infected plants often appear healthy

FAVORABLE CONDITIONS

Disease is primarily spread from infected cuttings

Favors temperatures of 86 and higher

Overhead irrigation

GERANIUM- RALSTONIA

RALSTONIA MANDEVILLA

Scan for enlarged images and additional information

BACTERIAL WILT OF PANICLE HYDRANGEA

CORDYLINE BIPOLARIS

BACTERIAL STREAMING

SANITATION PRODUCTS FOR DISINFECTING TOOLS AND PRODUCTION AREAS

MANAGEMENT RECOMMENDATION

Common Name

Tradename

sodium carbonate peroxyhydrate

Phycomycin®, GreenClean® Pro

quaternary ammonium (DDAC)

KleenGrow TM

hydrogen peroxide/hydrogen dioxide

Perpose Plus®

hydrogen peroxide + peroxyacetic acid

Jet-Ag®

+ S ymptomatic plants should be tested for R. solanacearum. Testing can be done at a diagnostic lab or in the greenhouse with ImmunoStrip tests available from Agdia, Inc. Use pathogen-free cuttings, plugs and bulbs. Tools, equipment, containers and all surfaces should be properly cleaned of any organic debris and thoroughly disinfested with sodium hypochlorite or a less corrosive disinfectant containing quaternary ammonia or peroxide material. Eliminate overhead irrigation (or irrigate when the leaves dry quickly). Scout crops as they are received and once a week in production. Remove and discard plants with symptoms as soon as they are found. Research reported on geranium showed reduced root infections when plants were treated with phosphonates preventatively.

Follow the product label for sanitation and prevention

TROPICAL PLANTS AFFLICTED BY SOFT ROT BACTERIA

Achillea

soft rot of cuttings

Calla Lily

bulb rot, root rot

Cyclamen

soft rot of leaves, corms

Dieffenbachia

stem rot

Epipremnum

soft rot of cuttings

Euphorbia

stem rot

Orchids

stem and pseudobulb rot

Philodendron

leaf spot, stem rot

Osteospermum

soft rot of cuttings

Syngonium

leaf spot, stem rot

Reach out to your Harrell’s rep for more information.

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