Diseases of Aloe vera
Course: Pl.Patho.507- Disease of Field & Medicine Crops
Submitted to: Dr. S.M Chaudhary
Professor of Pl.Pathology
C.P.College of Agriculture
Submittef by: Dineshkumar G. Dalvaniya
M.Sc.(Agri) In Entomology
1st Sem.-C.P.College of Agriculture
Botanical Name: Aloe barbadensis
Common Name: Aloe vera Curacao Aloe, Barbados Aloe, Lily of the Desert
Plant Family: Liliaceae
History: The virtues of Aloe vera have been recorded for thousands
of years by many ancient civilizations, including Egypt, Persia,
Greece, India and Africa.
The name was derived from the Arabic alloeh meaning 'bitter'
because of the bitter liquid found in the leaves. It is also known
as 'lily of the desert',the 'plant of immortality', and the 'medicine plant'.
The Disease Of Aloe Vera:
Basal Stem rot
Bacterial soft rot of aloe
C.O.: Phakopsora pachyrhizi
Beans, Allium, corn, sorghum, rice, banana,
coffee, and a wide range of agricultural crops
Affected plant stages
Affected plant parts
Stems, leaves, petioles, and pods
Conditions that favor development
Frequent rains, drizzle, or dew with cool
temperature and high humidity
Poor quality seeds used for sowing
Poor field sanitation
Aloe rust is a fungal disease of succulents
that causes circular black or brown spots on
the leaves of aloes and gasterias. The fungal
disease is especially a concern in the
commercial production of aloe vera. The black
spots are created by the oxidation of the ph
enols in plant sap and are permanent once
they appear. Aloe rust is a fungus that may
black spots on the branches of aloe plant.
Aloe rust is a plant fungus that affects succulent
aloe plants. The fungus creates round black or brown
spots on the leaves. The fungus is self-limiting, and
does not spread beyond the spots that are affected.
The black colour is caused by oxidation of
phenolic substances in the sap which seals of the
affected area. The first symptom is small and pale-
yellow spots on the upper surfaces of the leaves.
As the spots increase in size, masses of orange
spores appear on the undersurfaces. The fungus
reproduces through the stomata rather than breaking
thrmost rusts do.
The powdery lesions on the undersides of the leaves can
be orange-yellow to red-orange in color, but colors vary
from one region to another.
While the lesions can develop anywhere on the
leaf, they tend to be concentrated around the
margins, where dew and rain droplets collect. The
centers of the spots eventually dry and turn brown,
while the margins of the lesions continue to expand
and produce spores. The first lesions usually appear
on the lowermost leaves and the infection slowly
progresses upwards. The infected leaves drop
prematurely, leaving long expanses of twigs devoid
rust is caused by the fungi Phakopsora pachyrhizi and P.
meibomiae. The host range of both species is quite broad,
with at least 41 and 34 natural hosts for P. meibomiae and
P. pachyrhizi, respectively. These additional hosts can
serve as overwintering reservoirs for the pathogen, as well
as build-up of inoculum. The pathogen is well adapted for
long-distance dispersal, because the spores can be readily
carried by the wind, making it an ideal means for
introduction to new, rust-free regions. The primary means
of dissemination are spores, which can be carried long
distances by wind or splashed by rain within fields. The
environmental conditions that favor disease development
are extended periods of leaf wetness accompanied by
temperatures of 59 to 82°F. Temperatures above 86°F
retard the development of disease.
Spores are generally produced 10 days after infection, and
are released after about three weeks. Spores are
continually released, as long as moist and moderate
temperatures are present disease severity depends on the
developmental stage of the plant at the time of infection.
If this pathogen arrives or becomes established in this
area, the role of overwintering or secondary hosts in the
survival of the rust is not known. However, current
epidemiological models or predictions indicate that it is
unlikely that this fungus will overwinter in the north
central part of the US. The leaf-infecting spores can only
survive in the presence of the host.
These life cycles may involve totally unrelated host
plants and may include up to four different spore
producing stages and five functionally different kinds of
spores. Some species complete their entire life cycle on
one host (autoecious) whereas other species require two
In order to understand symptoms caused by infections by
the rust fungi, it is necessary to understand the various
spore stages of the fungi. Infection by each spore stage
causes somewhat different symptoms. Spore stages useful
in identification of the disease include aecia, uredia, and
telia. The aecia are cup and blister like in appearance.
Light yellow to orange wind dispersed aeciospores are
produced in the aecia. Uredia are also blisterlike pustules
that produce masses of orange to rust-colored
uredospores. Telia are structures that produce masses of
teliospores. The telia follow uredia on the same host. The
teliospores are usually black in color.
Prevention and control
Select only diseased-free seeds for planting.
If there was a heavy infestation of rust on your farm
during the previous crop, practice crop rotation
by planting a different crop in the next cropping
Control weeds to facilitate air circulation and rapid
drying of the plants‘ canopy
Prune coffee plants properly. Pruning improves air
circulation and promotes rapid drying of the foliage,
thereby reducing the rust damage.
Aloe leaf extract
Papaya leaf extract
Leaf diseases, in general, are controlled by the use of
preventive foliar fungicides.
The use of resistant cultivars, and seed treatments
(some rust fungi are seed-borne) for control of certain
rust diseases is beneficial
When you see black spots on the aloe, reduce watering
immediately. If that does not solve the problem, you may
choose to pinch off the affected leaves or to take a cutting
and start over from scratch
To avoid this disease, do not let water stay on the leaves.
Water droplets left on leaves make the plant susceptible to
Rake up and dispose of all fallen leaves and debris from
under the plant. Rust spores are carried by water splashing
back up onto the and leaves.
Water in the early morning hours to give the plants time to
dry out during the daylight hours.
Provide air circulation by pruning and thinning the plant.
Avoid planting annuals or other type plants under roses;
this will provide maximum air circulation.
Remove and destroy infested foliage.
Dust plants with sulfur powder every one to two weeks,
starting when foliage begins to develop in the early spring
and continuing throughout the growing season. The sulfur
won't kill the rust, but it will prevent the next generation
Spray with a solution of 1 tsp. baking soda in 1 qt. water to
Basal Stem Rot
C.O.: Fusarium sp.
Basal stem rot is a fatal aloe vera disease
that is caused by cold, damp conditions. The
base of an aloe vera plant affected with basal
stem rot will turn dark red or black and then
quickly begin to rot.
Basal stem rot is a fungal disease that leads to the
rotting of the stem near soil level. This is often
caused by prolonged exposure of the stems near the
soil to excessively wet soil. As the tissue rots, it
change colors from reddish brown to black. The color
of the rot is determined by the type of the plant and
the nature of the fungus attacking it.
Basal stem rot attacks the lower area of the plant at
the soil level. Soil that is in contact with the base of
the plant should not be allowed to stay damp. plant
appears to be dying from the base upward.
Basal stem rot is a fatal aloe vera disease
Basal Stem Rot favorable condition
Aloe plants kept in conditions that are too cool or
damp are at risk for developing basal stem rot. The
stem of the plant starting at the soil become dark red
or blackish in color and begins to rot.
Monitor soil conditions to prevent basal stem rot
Basal stem rot is the result of cold or wet conditions.
This condition leads to rotting stems. The base of the
plant is usually affected. Rotted aloe tissues affected
by basal stem rot turn black or reddish brown. It is
possible to take a stem cutting above the rotten
portion to save pieces of the plant.
Discard affected plants and amend the growing conditions
before planting new aloe vera plants. . Grafts can be taken
from healthy parts of the plant and rerooted. Afterwards, the
diseased plant is generally disposed of.
Fungal diseases that affect aloe plants are treated with spray or
powder fungicides. If the disease is caught early, the plant is
usually saved. If the plant succumbs to disease, treat the soil
with fungicides to prevent future plants from becoming
rot should be cut out. Treat it with anti-fungus and leave to
dry. When an aloe looks sickly without any signs of
something wrong on the outside, the roots are rotting.
Remove the plant (it will probably be loose in the soil) cut off
the dying roots and leave the plant dry to form new roots. .
plant appears to be dying from the base upward, you can save
parts of the plant through grafting or rerooting.
This disease can be controlled by spraying
Dithane M-45. Another disease is tuber rot
which is a soil borne disease affecting the
underground rhizomes causing the death of the
plant. Drenching the soil with Bavistin@ 0.2%
is recommended to control the disease. Some
progressive farmers apply bio-pesticides and
bio-control agents for controlling pests and
Bacterial soft rot
C.O. : Pectobacterium chrysanthemi
Potato, sweet potato, cassava, onion, cabbage and
other crucifers, carrot, tomato, beans, corn, cotton,
coffee, banana, and many other succulent agricultural
Affected plant stages
All growth stages
Affected plant parts
Conditions that favor development
Infected plant debris left rotten in the field.
Presence of onion maggot as the vector for soft
rot in onion and garlic and root knot
nematodes that cause lesions on the roots.
Plant wounds and injuries.
Hot and damp weather with plenty of rainfall
trigger the disease to occur. Water is required
for the bacteria to invade.
An initial infection occurs on the outer petiole (leafstalk)
which is in contact with the soil, and then progresses . An
infected leaf is watery and often has a complete leaf rot. The
affected area becomes soft and mushy and generally turns dark
an infected leaves has a soft and watery decay. The bacteria
sometimes rapidly consume the entire leaves often leaving the
epidermis (the peel) intact.
an infested leaves rots internally resulting in the wilting of
young leaves which is then followed by tip collapse and
suddenly collapses and is usually twisted. The initial sign is
the premature withering and drying up of the tips of the
uppermost leaves, then the lower leaves, soon followed by the
appearance of a slimy soft rot at the base of the whorl. The
decay spreads rapidly downward until the affected plant
collapses. The diseased plant often has a foul odor.
The disease was serious when abundant moisture was
available through irrigation and/or rain. The symptoms started
as water soaked lesions at the base of the leaves (Fig. 1).
The rotting progressed very fast and the whole
plant died within two to three days. As the
rotting progressed, the leaf epidermis bulged
out due to gas formation and the leaf content
was converted to a slimy mass, that was
eventually released (Fig. 2).
Figure 1: Initiation of bacterial soft rot symptoms in aloe
Figure 2: Bulging of epidermis due to gas formation
during bacterial soft rotting in aloe
There is no known effective control measure of
bacterial soft rot. The following practices can lessen
its damage to the plant population;
Proper land preparation to have a well-drained soil
Control nematodes and other insect pests that serve as
vectors (carriers) of the bacteria to invade the plant
If possible, avoid plant injury during weeding
especially when the disease symptoms are observed
Aloe rot must be removed using sterile pruning tools
and the wounds should be treated immediately with a
liquid fungicide to prevent reinfection. Be sure to
dispose of all rotting pieces in a sealed bag and do not
allow any pieces to fall onto the soil of the plant.
Remove infected plants immediately
Remove plant residues after harvest
Practice crop rotation by using crops that are not
susceptible to the bacterial soft rot disease like
soybean, forage legumes, and small grains Fungicides
do not directly affect these bacterial pathogens, but
seed piece treatments with fungicides can reduce
invasion by other fungi and therefore reduce
opportunistic infection by Erwinia spp. Chlorinate
recirculated wash water with a concentration of 50 to
200 ppm, depending on potato variety
Common Name:Sooty Mold
Antennariella, Limacinula, Scorias, and
Transfer:Wind, Human and Pets in the
greenhouse, ants, Aphids.
The aloe vera plant is attractive, useful and easy to care for. With its thick,
uplifted arms in a shade of pale green, it tends to attract positive attention.
But some homeowners find their beautiful aloe plants beginning to develop
an ugly black fuzz. Even if they wipe it away, it comes back heavier than
before. Sooty mold is the problem, and it is related to insect infestation on
your aloe plant.
You can identify sooty mold by the presence of dark patches growing on
your aloe vera plant. These patches are actually composed of a complex of
fungi like Cladosporium, Aureobasidium and Antennariella
Sooty mold develops as a secondary infection caused by the presence of
certain insect pests that produce honeydew, a sticky, sweet substance that
adheres to the plant's leaves. Aloe vera plants are susceptible to the aloe
vera aphid. As the aphid sucks sap from the aloe plant, it excretes
honeydew. Resulting sooty mold infections can be extension, according to
the Florida Division of Plant Industry.
Honeydew, a sticky substance secreted by some plants or
by feeding insects, provides a prime environment for sooty
mold to form.
sooty mold resembles a covering of soot upon the plant that
may be light or heavy. You can easily scrape off sooty mold
with your fingernail, and during dry conditions, it may dry on
your aloe plant and dislodge from the plant. Sooty mold itself
is rarely harmful, according to the University of Wisconsin
Extension, although extensive infections may block access to
light and cause the leaves the yellow. If you observe it on your
aloe plant, your concern should focus on the insect pest
causing the problem and what you can do to treat it.
Although more unattractive than harmful, sooty mold can
cause damage to young or weak plants. Its dark film can also
block light, inhibiting your aloe's process of photosynthesis.
The aloe vera aphid that causes sooty mold, on the other hand, can damage
your plant. The bugs feed at the base of aloe leaves or sequester themselves
inside of the rolls formed by damaged leaves. Because they extract the
nutrient- and water-containing sap that the aloe plant needs to live, they
cause the leaves to wither and turn brown.
Treating sooty mold involves treating the insect problem that causes it.
Control aphids on houseplants by rinsing your aloe plant with a strong jet
of water to dislodge the insects or crush them by hand when you find them.
Sticky traps may capture winged adults. If these control measures don't
work, insecticidal soap is one of the most effective remedies against aphids
on houseplants, according to the University of Colorado Extension.
Always read the label carefully on any product that you use to be sure that
it is safe and approved for aloe plants.
Reducing populations of insects feeding on your plants will decrease
honeydew and thus sooty mold. Using a fungicide or getting rid of the part
with sooty mold can help if your plant already has been affected
If have aphid problems with aloe plants, check frequently for
bugs so that sooty mold doesn't have the chance to develop.
The Texas Agricultural Extension Service recommends using
sticky traps to monitor aphid populations. Periodically rinsing
houseplants also dislodges bugs and removes honeydew,
preventing sooty mold buildup