Major diseases and control measures of Potato:

Major diseases and control measures of Potato:

Fungal disease

A total of 57 diseases and disorders of potato have, so far, been recorded in

Bangladesh. Among them, late blight (Phytophthora infestans (Mont de Bary), stem

canker and Black scurf (Rhizoctonia solani) are the most important disease of potato

in Bangladesh.

Late Blight

Late blight is the major limiting factor to increase potato production. In Bangladesh,

the infection of late blight was first reported in 1922. It occurs every year under

favourable condition (High humidity, low temperature and

foggy weather) with varying intensities wherever potato is

grown in the country. More than 25% yield is reduced due

to late blight of potato every year. All the cultivated

varieties in Bangladesh are more or less susceptible to late

blight. Potato variety, Raja, Dheera and BARI TPS-1 and

2 showed tolerant reaction to late blight disease. In

general TPS progenies are more tolerant compared to

tuber varieties. Late blight infected stem

Late blight appears on leaves, petiole and stem as pale green and turns into brown to

black water soaked spots under favorable condition.White cottony mycelial growth

appears under the surface of infected leaf in the morning during high humidity and

leaf wetness condition. Under cool, foggy and wet conditions, whole plant of the field

rot and die rapidly within 4-5 days and tubers also rot and spread in storage. Under

severe condition, emits foul smell from rotted leaf in the field. The sections from

infected tuber appeared brown with necrotic tissues.

Control measures:

• Use disease free certified seeds.

• Follow early planting and early harvesting (15 Novto 15 Feb).

• Weed management.

• Haulm pulling at 80 DAP.

• Under cool, foggy and wet conditions, spray should be continued with fungicides

at 15 days interval. Any of the fungicides like Dithane M-45 or Indofil or Melody

duo or Hamancozeb @ 0.2% at 15 days interval should be done.

• When symptoms appear, spraying with fungicides or mixture of fungicides at 7

days interval

• Secure @ 1 g/ L water or

• Melody duo 2 g + Secure 1 g in 1 litre water or

• Acrobat MZ 2 g + Secure 1 g in 1 litre water or

• Acrobat MZ 2 g + Melody duo 2 g in 1 litre water or

• Melody duo 2 g + Dithane M-45 2 g in 1 litre water

• High ridge during earthing up.

• Restricted irrigation in the infected field.

• Do not cover the harvested tuber lots by infected potato debris.

• Sorting of infected tubers during storage.

Stem canker and Black Scurf

Causal fungus of this disease is Rhizoctonia solaniand now becoming a major disease

of potato in Bangladesh.

Aerial green tubers produce in the axes of petioles and branches.Sunken shallow

brown cankers affect stolons and stem at or below the soil line. Ultimately, infected

plant died and tuber size reduced.

Control measures:

• Use of disease free seed.

• Destruction of crop debris.

• Crop rotation with cereals or leguminous crop.

• Seed treatment with Boric acid (3%) before storage.

• Rogue out of diseased plant from the field.

• Spraying with Bavistin (0.1%) at the base of the plant.

• Avoid excessive irrigation.

Stem canker and Black

Scurf infected plant

Bacterial disease management

Bacterial wilt (Ralstonia solanacearum), Common scab (Streptomyces scabies) and Soft

rot (Erwinia spp.) are the most important bacterial diseases of potato in Bangladesh.

Bacterial Wilt

Initial symptoms of wilt may affect one side of a leaf first,

or one branch and not another. Later symptoms are severe

wilt and death. Vascular strands darken and in cross

section a gray to brown slime exudes, except in mild cases

which may be confirmed by the flow of milky white

strands from a stem section immersed in clear water.

Control measures:

• Rresistant source of bacterial wilt was not detected in Bangladesh.

• Use of certified seeds.

• Use of whole tuber.

• High ridge during earthing up.

• Crop rotation with non-solanaceous crop.

• Soil application with stable bleaching powder (SBP)@ 25-30 kg/ha.

• Intercropping with maize or wheat.

• Minimum irrigation should be maintained and irrigation should be stopped at the

moment of disease expression.

• Diseased plant should be removed including surrounding soil and apply SBP at the

rate of 20-25 kg/ha into the affected area.

Blackleg and Soft Rot

Black and slimy lesions most often progress

up the stem from the soft rotted mother tuber.

Young plants are commonly stunted and erect.

Yellowing and upward rolling of leaflets may

occur, finally wilting and death. Soft rot in

field or storage often follows any type of tuber

injury. Tissues become wet, cream to tan

colored and soft, and are easily separated from

healthy tissue. Emit foul smell.

Control measures:

• Use diseased free seed.

• Prohibit excess irrigation in the field.

• Early cultivation should be done to avoid high temperature.

• Maintain proper grading before storage.

• Soil amendment with SBP @ 20-25 kg/ha.

• Tuber should be treated with 3.0% Boric acid solution before storing as seed tuber.

Bacterial wilt infected plant

Black leg infected plant Soft rot infected tuber

• Crop rotation with cereals or leguminous crop.

• Harvest in dry weather and proper care during harvest, transit & storage.

• Potato should be storedin dry and well ventilated room.

• Destruction of crop debris.

Common Scab

Scab appears on tubers as circulate to irregular lesions as

corky-appearing, raised and pitted. They are variable in

size and shape.Periderm turns brown and rough. Under

severe condition, the periderm depressed and rotted.

Control measures:

• Application of ammonium sulfate (equally in three

installments) instead of urea as a nitrogen source

proved most effective in reducing common scab disease of potato.

• It was also found that the incidence of common scab can be minimized effectively

by maintaining proper soil moisture from 30 DAP to 60 DAP.

• Seed treatment with 3% boric acid before storage showed most effective in

reducing scab disease of potato.

• Crop rotation with cereals or leguminous crop.

• Green manuring crop should be used.

Virus diseases

Viruses are the main problem in our country to reduce potato production. It decreased the

production generation to generation of potato. There are several viruses remain in plant

and tuber in latent condition. However, major viruses of potato are described below.

Potato Leaf Roll Virus Disease (PLRV)

Leaves become upward rolled which initiates from lower

leaves. Rolled leaves are stiff and leathery and plant growth

often stunted. PLRV is transmitted by aphid. Spots appear on

leaves and defoliation occurred.

Potato Viruses Y (PVY)

Leaves became twisting and downward turning of leaflet

margin. Plant growth severely stunted. Leaf and tuber size

reduced markedly. Leaves look shiny.

Mosaics (Potato Viruses X, S and M) diseases

Mosaic symptoms may be caused in leaves of potatoes by

several different viruses singly or in combination. Normally

causes mosaic, crinkling, top necrosis, spotting or even leaf

drop. Sometimes necrosis of petioles and leaf veins are

occurred. Leaves are stiff and leathery and plant growth often

stunted. Yield is reduced.

Common scab infected tuber

PLRV infected tuber

PVY infected plant

PLRV, PVY and PVS

combinely infected plant

Control measures:

• Use disease free certified seed.

• Follow early planting and early harvesting (15 Nov to 15 Feb).

• Isolation distance maintains.

• Weed management.

• Virus eradication through tissue culture.

• Indexing viruses through ELISA.

• Production of breeder seed under net-house.

• Haulm pulling at 80 DAP.

• Grading, sorting and storing in cold storage maintaining proper temp.

• Rouging all virus infected plants.

• Spraying systemic insecticides as Admire (0.05%) to control vector.