An Assignment Of

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 S.D.A.U

Submittef by: Dineshkumar G. Dalvaniya M.Sc.(Agri) In Entomology 1st Sem.-C.P.College of Agriculture S.D.A.U .

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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:

Aloe Rust

Sooty MoldBacterial soft rot of aloe

Basal Stem rot

Aloe Rust C.O.: Phakopsora pachyrhizi

Host plants

Beans, Allium, corn, sorghum, rice, banana,

coffee, and a wide range of agricultural crops

Affected plant stages

Vegetative stage

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

Symptom: 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

leave black spots on the branches of aloe plant.

The Aloe Rust

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 of leaves.

Disease Cycle

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 hosts (heteroecious).

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 season.

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 aloe rust.

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 from germinating.

Spray with a solution of 1 tsp. baking soda in 1 qt. water to fight rust.

Basal Stem Rot

C.O.: Fusarium sp.

Symptoms: 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.

Management: 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 diseased.

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 diseases.

Bacterial soft rot

C.O. : Pectobacterium chrysanthemi

Host plants Potato, sweet potato, cassava, onion, cabbage and

other crucifers, carrot, tomato, beans, corn, cotton, coffee, banana, and many other succulent agricultural crops

Affected plant stages All growth stages Affected plant parts Whole plant

Conditions that favor developmentInfected 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.

Symptoms:

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 in color.

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 dieback.

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

Preventive control 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 tissues

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

Sooty Mold

Common Name:Sooty Mold LatinName:Cladosporium, Aureobasidium,

Antennariella, Limacinula, Scorias, and Capnodium.

Size:Tiny Spores Colour:BlackTransfer:Wind, Human and Pets in the

greenhouse, ants, Aphids.

Overview 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

Cause 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.

Effects 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.

Aphid Damage 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.

Treatment 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

.

Prevention 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