Group Title: ARC-A mimeo - Agricultural Research Center-Apopka ; RH-71-2
Title: Suggestions for the control of some common diseases of foliage plants
Full Citation
Permanent Link:
 Material Information
Title: Suggestions for the control of some common diseases of foliage plants
Series Title: ARC-A mimeo
Physical Description: 20 leaves : ; 28 cm.
Language: English
Creator: Knauss, J. F ( James Frederick ), 1938-
Agricultural Research Center (Apopka, Fla.)
Publisher: University of Florida, IFAS, Agricultural Research Center
Place of Publication: Apopka Fla
Publication Date: 1971
Subject: Foliage plants -- Diseases and pests -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: J.F. Knauss.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00065997
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 71194044

Full Text


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida



Agricultural Research Center Apopka (ARC-A... --"-""
IFAS, Univ. Florida, Apopka LM 3I BRfi.
ARC-A Mimeo 71-2 HU L

Introduction: 'AUG 71976

The following information is an outline which is intended to serve

as a guide for the control of some of the more common LFeAsl s 1n&9Qa

plants. The chemical control measures suggested must not be misinterpreted

as a formal recommendation nor is the use of trade names intended to dis-

criminate against products sold by other producers which might be just as

effective or may be the same but sold under other trade names.

The disease-causing organism (pathogen) in the list that follows is

given first with some of the plants it commonly attacks listed directly

beneath. A brief description of the disease symptoms, the conditions

conducive to disease development and the method of spread of the disease-

producing pathogen may be included. In considering the control measures,

the'reader must keep in mind the importance of certain cultural practices

which will greatly assist in the prevention of foliage plant diseases and

growers are strongly advised to consider the following suggestions.

1. Use the healthiest stock material available for propagation.

Replant new stock areas only with the best plants available.

2. If a certain stock source continually develops disease problems

change to another source. Never knowingly purchase propagative

material which is consistently poor.

3. Use clean (sterilized) media in new or sterilized pots and

on sterilized or disinfested benches.

4. Since most pathogens require water for spread and infection,

disease may be kept to a minimum if foliage is kept dry by

-~ 1'~.


.providing adequate ventilation and air movement in conjunction

with careful watering practices.

5. Remove and destroy any badly infected plants as soon as detected.

These plants, if not eliminated, will serve as disease centers

(sources) from which further infections may get their initial


'6. If chemical pesticides must be applied, ,do so only under

conditions not conducive to plant injury. Sprays should be

applied on a 7 day schedule and only when needed. Drenched

areas should be watered lightly to remove the pesticide from the

plant foliage.

The following codes placed behind the chemical concentration on a

100 gallon basis represents the status of the information to date:

a = chemical, at concentration stated, found at ARC-A to be safe

and effective for disease control on plants mentioned.

b = chemical, at concentrations stated, found at ARC-A to be safe

on plants mentioned.

c = chemical, at concentration stated, found elsewhere to be safe

and effective on plants mentioned.

d = chemical, at concentration stated, found elsewhere on crops

other than foliage, to be effective for control of the pathogen.

e = chemical effective but safety not determined for all plants

listed; use with caution.


1. Alternaria actinophylla

Plant(s) attacked Schefflera

Disease symptoms and control

Disease may occur at any time of the year and appears as

brown to black leafspots usually circular at first but often

enlarging to cover most of the leaf. A yellow halo is often

seen around the margin of the spot and when severely infected,

the affected leaves drop from the plant. The pathogen usually

spreads in splashing water and may be completely controlled

if the foliage is kept dry at all times. If impossible, the

following is suggested, Control at first symptoms of the disease

with weekly sprays of Zineb 75 WP (1 1/2 Ib)ac, M-45 (Fore) 80 WP

(1 1/2 Ib)a or Manzate D (1 1/2 lb)a

2. Ascochyta necans

Plant(s) attacked Leatherleaf Fern, Native Bracken Fern

Disease symptoms and control

This disease is only a problem during the late winter and

spring months that are cool and wet. The pathogen spreads

and causes disease only during rainy periods and may move

into new plantings from infected native bracken fern bordering

the fernery. The disease affects only immature fern fronds

and may vary from scattered reddish-brown leaf spots to a

complete brownish-black collapse of the total fern frond.

The most common symptom, however, is the severe distortion

of affected fronds often with a one-sided development of the

diseased leaves. Control may be effected by planting new

ferneries with clean stock and establishing them away from

areas surrounded by native bracken fern. Should the disease

become established in the fernery, apply weekly sprays of
Daconil 75 WP (1 1/2 lb) during cool, rainy periods.

3. Cephalosporium spp.

Plant(s) attacked Dieffenbachia spp., Nephthytis varieties.

Disease symptoms and control

Symptoms are most notable on the foliage and begin as small

reddish-brown spots that usually have a yellow border. On

Nephthytis,numerous lesions may be present on infected tissue

during hot, wet periods such that'many growers refer to the

problem as "The Shotgun Fungus Disease". Although the pathogen

will not spread if the foliage is kept dry, present watering

practices and open slat shed culture of stock beds makes

this impossible. Chemical control may be achieved during

periods of disease development with weekly sprays of Daconil

75 WP (1 1/2 b)ac, M-45 (Fore) (1 1/2 lb)a or Benlate 50 WP (1/2 Ib)a

4. Cercospora spp.

Plant(s) attacked Peperomia spp., Ficus spp.

Disease symptoms and control

On Ficus, minute, slightly raised, circular areas appear on

the leaf undersurface. These appear dark green and have a

P chlorotic margin. Infected leaves may turn yellow often with

healthy green leaves above and below them. On Peperomia,

infections appear initially as pin-point swellings on the


leaf undersurface which enlarge progressively into noticable

pimple-like growths then to very prominent raised areas which

appear dark green with a limited amount of necrotic tissue at

the apex. On the upper leaf surface the infected areas may

be seen as chlorotic (yellow) spots. Control during periods

of disease development with weekly sprays of Daconil 75 WP

(1 1/2 lb)c, M-45 (Fore) (1 1/2 Ib)c, Benlate 50 WP (1/2 lb) or

Mertect 60 WP (1/2 lb)d

5. Cylindrocladium pteridis, Cylindrocladium spp.

Plant(s) attacked Leatherleaf Fern

Disease symptoms and control

This is undoubtedly the most important and severe foliar

disease of leatherleaf fern. It is most active in the hot,

wet months. Infection appears on leaves as reddish-brown

pin-point spots which rapidly enlarge and fuse causing large

dead areas. The disease in severe cases often spreads so

fast and gives the infected tissue such a scorched appearance

that growers often refer to it as "Fire". Although sanitation,

care in watering, and wider spacing of new plants may aid in

the control of this disease, weekly sprays with Daconil 75 WP
d d
(1 1/2 Ib) or Benlate 50 WP (1/2 lb) during the hot, wet months

are a necessity.

6. Dactylaria humicola

plant(s) attacked Philodendron oxycardium, Philodendron spp.

Disease symptoms and control

For years foliage growers have mistaken this disease for insect

injury caused by thrips feeding. It is common to all open slat

shed cordatum beds and is only active during the hot, wet

months. Only young leaves are attacked and symptoms appear

initially as pin-point, water-soaked spots. Spots occur on

both leaf surfaces but generally are more numerous on the

lower. As the leaves mature, the spots enlarge slightly

and become yellowish-green to yellow in color often with a

brown water-soaked center. The most prominent symptom, however,

is the collapsed scooped-out appearance of the infected area

which is responsible for its being mistaken for thrips injury.

Although the disease does not appear to economically limit

the production of this crop, it may be controlled by sprays

used to control other leafspots of Philodendron oxycardium

or, if such sprays are not being applied, with weekly

applications of Daconil 75 WP (1 1/2 Ib)a, Benlate (1/2 Ib)a

M-45 (Fore) 80 WP (1 1/2 Ib) or Captan 50 WP (1 1/2 lb)a.

7. Fusarium moniliforme

Plant(s) attacked Dracaena spp., Pleomele spp., Sansevieria spp.

Disease symptoms and control

Any grower that has grown any of these crops under open slat

sheds with overhead irrigation has seen and been confronted

with the disease. Dracaena marginata is particularly

susceptible and.a few infected plants may serve as the

"infection source" that could and often does result in a

high proportion of diseased plants within a planting. In

all three groups of plants mentioned, infection only occurs

down in the young growing point often resulting in its complete

rot and collapse. Infection is facilitated and assisted in

this area by the water that collects there from rainfall or

overhead hose or sprinkler irrigation. The leafspots in all

three groups mentioned generally initiate as pin-point, water-

soaked spots that enlarge and usually take on a reddish color.

Under conditions conducive to active disease development the

cream-colored infective spores of the fungus may be seen

within the infected areas. As with practically all foliar

disease, COMPLETE CONTROL of this disease may be obtained

if the foliage can be kept dry. 'If this is impossible weekly

sprays (directed into the growing point area) of Daconil 75 WP

(1 1/2 Ib) c, M-45 (Fore) 80 WP (1 1/2 lb)b or Benlate 50 WP

(1/2 Ib)d will stop further development.

8. Leptosphaeria sp.

Plant(s) attacked Dieffenbachia spp.

Disease symptoms and control

In ground bed, slat shed stock plantings, this disease may

become very prevalent and severely mar the appearance of

extracted cuttings. The spots may be very numerous on the

affected leaves and appear yellowish to a more grayish-brown

color. The spots may vary in size and may occur also on

leaf-midveins, petioles and the flower spathe. Often,

severely affected leaves become chlorotic and die. This

disease, too, can be controlled by keeping the foliage dry.

If this is not possible, however, weekly sprays of M-45 (Fnre)

80 WP (1 1/2 Ib)bc may provide control.

9. Rhizoctonia spp.

Plant(s) attacked Ferns (including Leatherleaf)

Disease symptoms and control

This disease is common wherever ferns are grown. Its development

is dependent upon warm, wet and humid conditions that arise

when plants are watered overhead, are crowded together and

where poor drying conditions exist. Infection usually initiates

within the center of the plant at the tips of the leaflets.

Under wet, humid conditions the fungus spreads rapidly within

and among plants causing a wet brown-black rot. Positive

identification of the disease may be made by observing the

prominent spider web-like reddish-brown threads of the pathogen

that grow among and between the affected leaflets and fronds.

Changes in culture which promote rapid drying of foliage or

even better eliminate foliar wetting will greatly assist in

the control of this disease. If needed, weekly sprays of

Benlate 50 WP (1/2 lb)a, Daconil 75 WP (1 1/2 Ib)a or Mertect 60

WP (1/2 lb)a will prevent establishment or further spread of the


10. Phytophthora sp.

Plant(s) attacked Philodendron oxycardium

Disease symptoms and control

This is the leafspot observed within cordatum stock beds

that is most common along walkways or other areas where

,excessive splashing occurs and leaf tissue is injured by

contact with workers, tools or equipment. It is most common


during rainy periods. Initially it appears as a water-

soaked spot which may enlarge to encompass a good portion

of the leaf. In later stages, it becomes brown and may,

during dry weather, change to be tan in color. Although

often mistaken for a bacterial disease, it is truly fungal

in nature. Chemical control may be achieved with weekly

sprays of M-45 (Fore) (1 1/2 b)bc or Daconil 75 WP (1 1/2 b)bd


1. Rhizoctonia spp.

Plant(s) attacked Schefflera seedlings and young plants,

Pothos cuttings, P. oxycardium cuttings, Dieffenbachia spp.

cuttings and young plants, Nephthytis seedlings and cuttings,

Scindapsus pictus cuttings, Philodendron selloum seedlings,

Hoya spp. cuttings and young plants, "Purple Passion" cuttings

and many others.

Disease symptoms and control

As may be noted from above, this fungus.has a wide host range

and is one of the most important pathogens attacking foliage

plant crops. It is active all year round but seems to be

particularly active during the spring and early summer months.

Wet and crowded plants, cuttings or seedlings are extremely

susceptible to this pathogen. One infected plant may serve

as an infection spot that may rapidly enlarge (if unchecked)

P in several days to include a great many plants or propagative

units. If several such spots are interspersed within a crop,

severe losses may occur. Although the disease symptoms do not

appear identical on all crops mentioned, the disease should

be suspected when rapid rot and collapse of leaves touching

the soil surface occurs or when plants fall over and show a

distinct brown lesion right at the soil line. Seedlings

attacked by this pathogen often will be matted together and

will be difficult to pull apart. In most cases the prominent

reddish-brown, spider-web like threads of the fungus may be

observed either on the leaves or stems and often can be seen

growing on the soil media. If the disease becomes established,

control may be effected with a soil drench* of.Benlate 50 WP

(1 Ib)e or Terraclor** 75 WP (1 1/2 Ib)e. If disease is isolated

to a small area, remove and destroy infected plants and drench

the infested area and a 1 foot border.

2. Sclerotium rolfsii

Plant(s) attacked Schefflera seedlings and young plants,

P. oxycardium cuttings, Nephthytis seedlings and cuttings,

Dracaena godseffiana cuttings, Peperomia spp. cuttings and

young plants and others.

Disease symptoms and control

This disease is generally called "Southern Blight" but ismore

commonly referred to by foliage growers as the disease caused

All soil drenches for all soil fungicides mentioned, applied at rate

ofrl/2 pint/6" pot or 1 pint/sq. ft. of bed or bench. Also, fungicide

should be washed after drenching from foliage with a light watering.

** Terraclor should be applied only once a year to the same soil, and at

the concentration stated only to soils consisting totally or largely

of peat.


by the "web fungus". Although it may be active throughout

the year whenever growing temperatures are high, it is most

prevalent during the hot, wet summer months. In propagative

beds containing susceptible-plant material, this disease may

rapidly spread and cause severe losses if left unchecked. It

may be identified by the prominent, thick, white threads of

the fungus usually found on the infected,plants and the soil

surrounding them. Usually the tan to brown, mustard seed-

sized resistant structures (sclerotia) of the fungus are also

present. Chemical control may be obtained with a soil drench*

of Terraclor** 75 WP (1 1/2 lb)e or Fermate*** 70 WP (3 lb)e. If

disease is isolated to small areas, remove and destroy infected

plants and drench infested area and a 1 foot border.

3. Pythium spp.

Plant(s) attacked Philodendron spp., Aglaonema spp., Maranta

spp., Dieffenbachia spp., Schefflera seedlings and young plants,

and many others.

Disease symptoms and control

Diseases caused by this pathogen often occur under extremely

wet conditions. Damping-off of young seedlings may occur but

most often this pathogen attacks propagative cuttings and

roots of growing plants. The rot it produces on tissue other

than roots is usually a wet brown to black collapse of infected

tissue. In root infections, the color may vary from a water-

Refer to Page 10.

** Refer to Page 10.

*** Definitely not safe on Schefflera at this concentration.

soaked gray to brown to black. Occasionally only the root

tips are affected but most often a wet rot occurs which results

in the sluffing off of the covering of the root leaving only

the thin inner core. Although keeping the soil on the dry side

may restrict pathogen development, effective disease control

may usually be obtained with a drench* of Dexon 35 WP (1/2 lb)d

for potted plants and (1-1 1/2 Ib) for benched or ground beds or

Truban 30 WP (8-12 oz)ce. Applications of Truban to seedlings

should be made on a trial basis only and then at 1/2 the high


4. Phytophthora spp.

Plants) attacked Dieffenbachia spp., Peperomia spp., Zygocactus

sp. and others.

Disease symptoms and control

This pathogen is closely related to Pythium and causes disease

under conditions which are similar. Phytophthora, however,

often attacks and rots seemingly mature plant stems whereas

Pythium usually restricts its attack to more immature tissue

such as roots and young seedlings. Attack of the plant tissue

usually results in a rapid, wet rot that may vary from a normal

water-soaked appearance to a brown or black in color. Control

of the pathogen may be achieved with a soil drench* of Dexon****

35 WP at the concentrations stated previously, Truban 30 WP

(8-12 oz)cde or M-45 (Fore) (2 Ib)ce

Refer to Page 10.

**** Some reports indicate conflicting results, and Dexon may not be as

effective for this pathogen as against Pythium spp.

5. Sclerotinia sclerotiorum

Plant(s) attacked Pothos cuttings, Nephthytis cuttings,

Gardenia cuttings and others.

Disease symptoms and control

This pathogen generally does not cause a great deal of damage

but may do so in isolated cases. It is most severe in green-

house propagating beds during the late winter and spring

months. It is easily identified by its abundant white

growth which could be mistaken for Sclerotium rolfsii except

that it is finer and more fluffy and does not have the tan

sclerotia typical of the "web fungus". Disease centers do

not spread rapidly and effective control may be achieved by

keeping the propagative units as dry as possible and applying

a drench* of Benlate 50 WP (1 Ib)de. If disease is isolated

to small areas, remove and destroy infected plants and drench

infested area and a 1 foot border.


1. Xanthomonas dieffenbachiae

Plant(s) attacked Philodendron oxycardium

Disease symptoms and control

This disease is presently the most important foliar problem

occurring in the foliage plant industry. Very few stock

areas are now free of this problem. Its ability to move so

rapidly among the foliage plant industry has been facilitated

by the movement of infected P. oxycardium from one grower to

* Refer to Page 10.

another, a practice common within the industry. It is

characterized generally by a marginal yellowing of the leaf,

occasionally with yellow spots or streaks within the interior

of the leaf. As the disease progresses, the leaf turns

yellow and drops from the stem, thus making the node use-

less as a propagative unit. Severe leaf drop within stock

plantings severely limits the number of cuttings produced per

area. Often leaves appearing free or nearly free of the

disease are stuck into propagative beds and turn yellow and

die during the first weeks of propagation. The disease is

most active during the wet summer months. Once established,

it is often extremely difficult and costly to control. If

a new stock area is to be planted, plant only "clean"

cuttings and establish the bed far away from any diseased

plantings. Prevent any contamination of the clean beds.

Since the pathogen only attacks the leaves and needs wet

foliage to gain entranceinto the leaf, any cultural change

which will keep the foliage dry will help control the disease.

Where the disease is present and chemical control is a

necessity, weekly applications of a combination of Kocide

101 86 WP (1 1/2 lb)a and M-45 (Fore) 80 WP (1 1/2 lb)a alternating

every third week with streptomycin (100 ppm)a.

This combination may leave a heavy residue and should not be used

wherethis is definitely undesirable.

* ;

2. Erwinia chrysanthemi and Erwinia spp.

Plant(s) attacked Philodendron spp., Nephthytis varieties,

Pothos, Aglaonema and others.

Disease symptoms and control

This pathogen group causes a very rapid wet, mushy rot of

leaves, stems and cuttings. Any grower that has grown

Philodendron panduraeforme has experienced the leaf rot

caused by this bacterial group. Its speed of attack and

the mushy, water-soaked appearance is a dead give-away for

this disease. Although weekly sprays of streptomycin

(100-200 ppm)c will assist in the control of the disease,

keeping the plants or cuttings as dry as possible and providing

adequate ventilation and air movement will probably assist in

its control even more.

3. Xanthomonas vitians

Plant(s) attacked Nephthytis varieties

Disease symptoms and control

This disease is the most common foliage problem of Nephthytis

during the warm, wet months. It is characterized by water-

soaked lesions along the leaf margin which are initially dark

green, gradually turning yellow to brown. The affected

tissue eventually dies and appears papery thin. The lesions

are often bordered by a bright yellow zone and white flakes

of the dried numerous bacterial cells are often visible on

the lower surface of the leaf. Effective control may be

accomplished if culture allows the foliage to remain dry

(100 ppm)c has also been shown to be effective as a foliar

spray for the prevention of the leafspot phase of the disease.



BENLATE is probably the most interesting fungicide to

come along in a long time. It is produced by THE E. I. DUPONT

DE NEMOURS & CO., WILMINGTON, DELAWARE and sold in a 50% wettable

powder form.* Although it is rather expensive per pound when

compared to most other fungicides, it displays activity at

concentrations 1/2 to 1/3 of that usually recommended for

other fungicides thus bringing the cost per pound within an

acceptable range. The material has several advantages such as:

a) Locally systemic the chemical moves into or is

absorbed by the plant.

b) Extensive spray tests at ARC-A at the manufacturer's

recommended concentration-have shown the material to

be safe for foliage plants.

c) Spraying to plant foliage, leaves only a slight

noticeable residue.

d) It has shown in experimental tests in Florida and

elsewhere to have a miticidal activity, thus providing

a degree of mite control while controlling disease.

BENLATE is not, however, effective against several of the

pathogen groups (Pythium, Phytophthora, Alternaria) which may

attack foliage plants.


The material is most effective when applied in conjunction

with a spreader-sticker and appears to have a good residual

protective activity.

As with all chemical pesticides, BENLATE should be stored

where it will keep dry and the container kept tightly closed.


Since a great many of the root rot problems experienced

by foliage plant growers are the result of attacks by the water

mold fungi (Pythium spp., Phytophthora spp.), a soil fungicide

exhibiting activity against this group would find a definite

place within the industry. TRUBAN, marketed by MALLINCKRODT

CHEMICAL WORKS, ST. LOUIS, MO. in a 30% wettable powder form

appears to be such a material. In comparative tests carried

out in many parts of the country (particularly Florida and

California), TRUBAN employed as a pre-plant soil mix or as a

post-plant soil drench has proven in most cases to be superior

to Dexon 35 WP for the control of the water molds. Its activity

appears to be longer lasting (thus fewer applications required)

and it is not light sensitive. Its cost also is less when

compared to Dexon. It has been shown to be safe and effective

on a variety of foliage plants when incorporated in or drenched

on media consisting largely or totally of peat. It must be

stressed, however, that TRUBAN should only be used according to

label recommendations and any other intended usage should be

performed only on a trial basis to a small number of plants.


If, however, you have already achieved good control of

the water mold fungi with another soil fungicide, it would be

wine to continue as is but also set up a small comparative

test with TRUBAN to evaluate its effectiveness against your

present program.

Although label recommendations are made for use on organic

soils in bench plantings or in pots, use on an area where you

may be experiencing your greatest loss, the slat shed, stock

beds, is not specified. This is because little research has

been done with TRUBAN on these sandy soil beds where Pythium

spp. often severely reduce cutting production by constant

attack and rotting of roots. Use of TRUBAN in these areas

should be restricted to small trials until enough time has

elapsed so that safety and effectiveness is determined.

3. KOCIDE 101

KOCIDE 101 is a bactericide-fungicide manufactured by


of a stable copper hydroxide in an 86% wettable powder form.

It is characterized by an extremely fine particle size that

aids in its dispersion in the spray tank and application to

foliage. In tests conducted at ARC-A during 1970 it was shown

when combined with a maneb-type compound (M-45) to be an

effective protectant against Xanthomonas dieffenbachiae,

the cause of "Bacterial Leafspot and Tipburn" of Philodendron

oxycardium. It is at present under further investigation at

ARC-A to determine the minimum concentration which will provide


effective control. Because of its small particle size it

often provides as good or better protection than other wettable

powder-type coppers applied at higher concentrations. When

used to control Xanthomonas dieffenbachiae on P. oxycardium,

its concentration and that of M-45 should not be allowed to

exceed 1 1/2 lb/100 gallons water and then this mixture should

be alternated every 3rd week with 100 ppm streptomycin.

University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs