Lecture 02 – Diseases of Mango (2 Lectures)

 

 

Lecture 02 – Diseases of Mango (2 Lectures)

Anthracnose: Colletotrichum gloeosporioides

Symptoms:

The disease appears on young leaves, stem, inflorescence and fruits. Leaves show oval or

irregular, greyish-brown spots which may coalesce to cover larger area of the leaf. The affected

leaf tissues dry and shred. Leaves on infected petioles droop and fall. On young stem, grey-

brown spots develop. These enlarge and cause girdling and drying of the affected area. The

disease appears on young leaves, stem, inflorescence and fruits.

Often, black necrotic areas develop on the twigs from the tip downwards causing a

dieback. In humid weather, minute, black dots develop on the floral organs. The infected flower-

parts ultimately shed resulting in partial or complete deblossoming. Latent infections of fruit are

established before harvest. The ripening fruits show typical anthracnose. Black spots appearing

on skin of the affected fruits gradually become sunken and coalesce.

Pathogen

Mode of survival and spread

Mycelium septate and coloured. Conidia Single celled, hyaline, small and elongated.

On dried leaves, defoliated branches mummified flowers and flower brackets. Contact with

diseased fruit during transport and storage. The secondary spread is through airborne conidia.

Favourable conditions

Disease cycle

Temperature of 25°C and Relative Humidity 95-97%

The survival of pathogen in detached diseased twigs and leaves lying on surface of soil

and in diseased twigs attached to the tree. They successfully reproduced the disease by

inoculating leaves, petioles, stems and fruits. The optimum temperature for infection was found

to be 25˚C. The disease spreads rapidly in the rainy season. Cloudy and misty weather during

flowering favors damage to the infected floral parts.

The pathogen causes severe leaf spotting. The appearance of spots in more concentration

at the stem-end and sometimes in stripes down the sides of the fruits suggested distribution of

spores by rain water over surface of the fruit. The fungus can enter the pores of green fruits. The

latent infection of mature fruits may take place through lenticels. The fungus apparently infects

the fruit while it is green and develops in flesh during ripening.

Management

Spray P. fluorescens (FP 7) at 3 weeks interval commencing from October at 5g/like on flower branches.

5-7 sprays one to be given on flowers and bunches. Before storage, treat with hot water, (50-55°C) for 15 minutes or
dip in Benomyl solution (500ppm) or Thiobendazole (1000ppm) for 5 minutes

Powdery mildew: Oidium mangiferae (Acrosporum mangiferae)

Symptoms

Pathogen

conidia.

Powdery mildew is one of the most serious diseases of mango affecting almost all the varieties.

The characteristic symptom of the disease is the white superficial powdery fungal growth on

leaves, stalk of panicles, flowers and young fruits. The affected flowers and fruits drop pre-

maturely reducing the crop load considerably or might even prevent the fruit set. Rains or mists

accompanied by cooler nights during flowering are congenial for the disease spread.

Mycelium is ectophytic. Conidiophores short, hyaline and conidia single celled -barrel

shaped, produced in chain. Fungus is odium type.

Mode of survival and spread

Survives as dormant mycelium in affected leaves. Secondary spread by air borne

Spores blown wind from infected areas readily adhere to hairy, unopened flowers near tip

of the inflorescence and germinate in five to seven hours. Fungus grows rapidly during cloudy

weather accompanied with heavy morning mist. Warm, humid weather and low night

temperatures favour dissemination of the pathogen. Overall disease development is favoured by

Disease Cycle

high humidity.

Management

Dusting the plants with fine sulphur (250-300 mesh) at the rate of 0.5 kg/tree. The first

application may be soon after flowering, second 15 days later (or) spray with Wettable sulphur

(0.2%), (or) Carbendazim (0.1%),(or) Tridemorph ( 0.1%),(or) Karathane (0.1%).

Mango malformation : Fusarium moliliforme var. subglutinans

Symptoms

Three types of symptoms: bunchy top

phase,

floral malformation and vegetative

malformation. In bunchy top phase in nursery

bunching of thickened small shoots, bearing

small rudimentally leaves. Shoots remain short

stunted giving a bunchy top appearance. In

vegetative malformation, excessive vegetative

and

branches of limited growth in seedlings. They are swollen with short internodes forming

bunches of various size and the top of the seedlings shows bunchy top appearance. In

malformation of inflorescens, shows variation in the panicle. Malformed head dries up in black

mass and persist for long time. Secondary branches are transformed into number of small leaves

Micro conidia are one or 2 celled, oval to fusiform and produced from polyphialides.

Macro conidia are rarely produced. They are 2 -3 celled and falcate. Chlamydospores are not

giving a witches broome appearance.

Pathogen

produced.

Mode of spread

Diseased propagatives materials.

Disease Cycle

Management

Diseased plants should be destroyed .Use of disease free planting material. Incidence

reduced by spraying 100-200ppm NAA during October. Pruning of diseased parts along the

basal 15-20 cm apparently healthy portions. This is followed by the spraying of Carbendazim

(0.1%) or Captafol (0.2%).

Stem end rot: Diplodia natalensis

Symptoms

The dark epicarp around the base of the pedicel. In the initial stage the affected area

enlarges to form a circular, black patch. Under humid atmosphere extends rapidly and turns the

whole fruit completely black within two or three days. The pulp becomes brown and somewhat

softer. Dead twigs and bark of the trees, spread by rains

Pathogen

The fungus produces brown to black, globose to sub globose, pyriform, erumpent

pycnidia that are ostiolate. They are 120-155×370-465 micron meter. Two types of conidia are

produced within a pycnidium. One is hyaline, thin walled and unicellular.Tha another one is

thick walled and bicelled with four to six longitudinal striations.

Mode of spread and survival

The fungus persists in infected plant parts which serve as source of inoculum.

Prune and destroy infected twigs and spray Carbendazim or Thiophanate Methyl(0.1%) or Chlorathalonil

Management

(0.2%) as fortnightly interval during rainy season.

Red-rust: Cephaleuros virescens

Symptoms

Algae attacks foliage and young twigs. Rusty spots appear on leaves, initially as circular,

slightly elevated, coalesce to form irregular spots. The spores mature fall off and leave cream to

white valvet texture on the surface of the leaves.

Pathogen

Cephaleuros virescens after a period of vegetative growth develops its reproductive

structures.Sporangia formed directly on the thallus are sessile and thick walled with orange

pigments. hey are formed singly on the vegetative filaments. When the sporangia are riped the

con tents are converted into Zoospores and liberated through an opening in the wall. The

Zoospores are orange in colour, ovoid and swim actively by means of cilia.

Management

Bordeaux mixture (0.6%) or Copper oxychloride 0.25%

Grey Blight : Pestalotia mangiferae

Symptoms

Brown spots develop on the margin and at the tip of the leaf lamina. They increase in

size and become dark brown. Black dots appear on the spots which are acervuli of the fungus.

Survive on mango leaves for over a year. Spreads through wind borne conidia. Heavy infection

is noticed during the monsoon when the temperature is 20-25˚C and high humidity.

Pathogen

Acervuli seen as minute black dots on affected portion. Mycelium is colored and septate.

Conidia five celled middle three cells are colored and the end cells are hyaline Slender 3-5

appendages are produced at the apex of the spore.

Mode of survival and spread

Survive on mango leaves for over a year. Spreads through wind borne conidia.

Heavy infection is noticed during the monsoon when the temperature is 20-25˚C and high

Favourable conditions

humidity.

Management

or Bordeaux mixture 1.0%.

Remove and destroy infected plant parts. Spraying copper oxychloride 0.25 Mancozeb 0.25%

Sooty mould : Capnodium mangiferae

Symptoms

The fungi produce mycelium which is superficial and dark. They row on sugary

secretions of the plant hoppers. Black encrustation is formed which affect the photosynthetic

activity. The fungus grows on the leaf surface on the sugary substances secreted by jassids,

The fungus grows on the leaf surface on the sugary substances secreted by Jassids,Aphids

aphids and scale insects.

Favourable conditions

and scale insects.

Management

Management should be done for insects and sooty moulds simultaneously. Controlling of

insect by spraying systemic insecticides like Monocrotophos or methyl dematon .After that spray

starch solution (1kg Starch/Maida in 5 litres of water. Boiled and dilute to 20 liters) .Starch dries

and forms flake which are removed along with the fungus.