Disease Management

A. FUNGAL DISEASES

S.No.

Disease

Causative agent

Development

Distribution 

Symptoms

Control Measures

1.

Leaf Rust Disease

leafrust

Puccinia reconditatritici. 

(Fungus) 

Pathogen over-summers in low and mid altitudes of Hima-layas and Nilgiris.  Pri-mary infections develop from wind deposited urediospores in eastern Indo-gangetic plains in middle of January where it multiplies and moves westwards by March. Temperatures of 20 :t 5° C with free moisture (rain or dew) cause epidemics. Sev-ere infection causes upto 30 percent yield losses.

Throughout wheat growing regions of India.

Uredinia normally appear on the upper leaf surface, but with severe epidemics sheath infections can occur. Uredinia are brown in color and generally circular in shape. Uredinia seldom penetrate thr-ough the leaf.

1. The use of resistant cultivars.

2. Control of volunteer wheat and seeding dates.

3. The use of fungicide sprays.

2.

Stem Rust Disease

stemrust

Puccinia graminis tritici

Spreads through air-borne urediospores, when temp-erature are 10­20°C but the spread is checked above 25°c. Pathogen survives in the cool temperatures of hills (Himalayas and Nilgiris) and the primary infection takes places by middle of January in the foot hills and sub mountainous parts of north western India. Also, infection comes from across the western border, hence the probability of evolution of new races increases in this area. Yellow rust from Nilgiri hills cannot come out of the zone due to high temperatures in the Peninsular and Central India.

Hills, foothills and plains of north western India and southern hills zone (Nilgiri hills of Tamilnadu).

Uredinia generally appear as oval lesions on leaf sheaths, true stem, and spike. Uredinia can appear on the leaves if other diseases have not killed them. Uredinia are brick red in color and can be seen to rupture the host epidermis, on the leaves uredinia generally penetrate to sporulate on both surfaces. Infected areas are rough to the touch.

1. Farmers are advised to use the latest resistant varieties recommended for the area.

2. Chemical spray

Foliar spray of Tilt @ 0.1% for the control of brown and yellow rust

Foliar spray of Plantavax @0.2% for the control of yellow rust.

3.

Alternaria leaf blight

Alternaria

Alternaria triticina 

The fungus survives as conidia on seed or as mycelia within seed. Sporulation on lower leaves provides inoculum that can be dispersed by wind, leading to secondary spread of the disease. Seed-borne inoculum often results in spike infections late in the crop cycle. High humidity or irrigation, as well as warmer temperatures (20 to 25ºC) favor infection and disease development.

Parts in Indian Subcontinent where ever wheat is grown.

Initial symptoms of Alternaria leaf blight consist of small (< 1 mm), oval, yellow lesions, irregularly scattered on the leaves. As the lesions enlarge, they appear irregular and dark brown to grey, surrounded by a bright yellow margin.

At a later stage, the lesions coalesce, covering large areas of the leaf and sometimes causing plant death (Prabhu and Prasada 1966). Infection usually starts on the lower leaves, but symptoms can be found on all plant parts. Lesions are difficult to distinguish from spot blotch in the absence of C. sativus conidia. Alternaria triticina has often been reported as part of the foliar blight complex.

  • Seed-borne infection can be controlled by treating seed with Vitavax at the rate of 2.5 g per kg seed.
  • Apply adequate fertilizers and irrigation.
  • Alternaria leaf blight can also be controlled by 0.2 per cent Zineb or Mancozeb 75 WP sprays. It is beneficial to mix urea at the rate of two to three per cent with Zineb at first and second sprays.

4.

Black Point

blackpoint

Alternaria alternate

Disease causes blackening of embryonic region of the seed (black point), discoloration of area beyond the embryonic region (black discoloration (Caused by Aalternata, Curvularia lunate, Epicoccum sp., Bipolaris sorokiniana, etc.) and eye-spot symptom (B. sorokiniana). The warm and humid weather at grain filling or near maturity favors this disease.

In India the states Jammu and Kashmir, Punjab and  Uttar Pradesh are mainly effected by this disease

Glumes, other tissues covered with black, sooty-appearing mold; diseased kernels are discolored, weathered, black at seed ends, embryos often shriveled and brown to black in color

This disease is of minor importance. Only when the disease percentage is high, it causes concern to the trader and the consumer. The discolored seeds are mostly shrivelled and they are separated out during processing.

5.

Common bunt

(Stinking Smut)

commonbunt

 

Tilletia tritici,

Tilletia laevis

The disease is initiated when soil-borne, or in particular seed-borne, teliospores germinate and eventually produce hyphae that infect germinating seeds by penetrating the coleoptile before plants emerge. Optimum infection occurs when teliospore-laden seed is planted in soil at 5° to 10°C. Only slight infection occurs at 22°C (Purdy and Kendrick, 1963). The intercellular hyphae become established in the apical meristem and are maintained systemically within the plant.

Common bunt is limited to temperate climates

Spores lying dormant in the soil or on seed germinate and infect emerging seedings. Infection is favored by cool temperatures during germination. The disease develops systemically, with visible symptoms appearing after heading.

Control of common bunt includes using clean seed, seed treatments chemicals and resistant cultivars. Historically, seed treatment with organo-mercury fungicides reduced common bunt to manageable levels. Systemic seed treatment fungicides include carboxin, difenoconazole, triadimenol and others and are highly effective. However,in Australia and Greece, strains of T. laevis have developed resistance to polychlorobenzene fungicides.

6.

Dwarf bunt

dwarfbunt

Tilletia controversa

Grain kernels replaced with brown masses of spores known as smut balls; fishy smell; plants and heads are stunted/dwarfed

Dwarf bunt occurs in areas having prolo-nged snow cover.

Grain kernels replaced with brown masses of spores known as smut balls; fishy smell; plants and heads are stunted/dwarfed

  • Resistant cultivars
  • Systemic fungicide seed treatment
  • New seed source

7.

Flag smut

flagsmut

Urocystis agropyri

Germinating kernels or very young seedlings are infected by germinating spores on the seed or in the soil. The disease continues to develop systemically, and the black subepidermal strips of teliospores become visible near heading. Infection is favored by low soil moisture and cool soil temperatures.

Parts in Indian Subcontinent where ever wheat is grown.

Masses of black teliospores are produced in narrow strips just beneath the epidermis of leaves, leaf sheaths and occasionally the culms. Diseased plants often are stunted, tiller profusely and the spikes may not emerge. A severe infection usually induces the leaves to roll, producing an onion-type leaf appearance. The epidermis of older diseased plants tends to shred, releasing the teliospores

The disease is normally considered a problem on autumn sown wheat in countries with arid summers and mild winters. The disease is favoured by minimal cultivation practices which leave plant debris on the soil surface. Spring sown wheats are not affected by the disease. One to two year breaks from wheat can reduce inoculum levels and deep ploughing can help to remove to inoculum from the emerging seedlings.

8.

Ergot

(Ergot is toxic to humans and animals (ergotism))

ergot

Claviceps purpurea

 

The primary infection originates from ascospores in fruiting bodies produced by sclerotia from the previous year's crop. Ascospores infect the florets, which then produce the sticky exudate containing conidia. Insects are attracted to the sweet exudate, and carry conidia to healthy florets in the same spike or to adjacent spikes. Rainy or humid weather favors the production of exudate and spores. An ergot body develops in each infected floret; these fungal structures can survive in the soil from one season to the next, and under dry conditions they can remain viable for many years. Sclerotia require cold temperatures before they can germinate.

In Indian sub- continent south India is mainly affected.

Grain kernels replaced with solid purple-black mass of fungal hyphae called a sclerotia; if wet after flowering honeydew (sticky mass of fungal conidia) can be observed on infected heads

  • Crop rotation to non-grass crop;
  • tillage to bury sclerotia
  • clean seed

9.

Karnal Bunt

kamalbunt

 

Tilletia indica (Neovossia indica)

Seed and soil-borne; infection occurs at flowering by means of soil-borne inoculum. The degree of disease development depends upon the weather conditions prevailing during spike emergence to grain filling stage of crop. If the rains occur during the month of February in north Indian plains (disease - prone areas), the disease is likely to come with higher severity.

Parts of Northern Plains, especially Punjab, parts of northern Haryana, foot hills of J&K and HP., tarai area of Uttranchal, in lesser severity in Rajasthan, Bihar and UP. The states of Gujarat, Maharashtra, Karnataka and several parts of M.P. are free of KB

  • Karnal bunt symptoms are evident when the grains have developed. After harvest, diseased grains can be easily detected by visual inspection.
  • The grains are partially bunted. Black coloured spore mass replaces a portion of the grain and the pericarp may be intact or ruptured.
  • Black powdery mass of spores can be seen in the groove of wheat grain.
  • Diseased grains give off a foul fishy odour when crushed. It is due to the presence of trimethylamine in the diseased grains.

1. Sowing crops at night time.

2. Seed should be treated with Vitavax at the rate of 2.5g/kg of seed

3. Avoid excess irrigation at flowering time

4. Spraying of Indofil This email address is being protected from spambots. You need JavaScript enabled to view it. /ha in 1000 litres of water at the time of ear emergence stage.

5. Spray of Propiconzole (Tilt 25EC@0.1%) should be given at the time of anthesis.Integration of one spray of bio agent fungus,

10.

 

Loose Smut

loosesmut

 

 

Ustilago segatum

It is a seed borne disease; infection occurs during flowering through wind-borne spores. The infection remains dormant inside the otherwise healthy looking seed but the plants grown from such seeds bear infected inflorescence. Infection is favored by cool, humid conditions during flowering period of the host plant.

North Indian plains and northern hills zone.

Grain kernels replaced with green-brown masses of spores covered by a thin membrane; spores disperse within days of head emergence

Disease can be easily controlled through seed treatment with systemic fungicides hence resistance breeding has not attracted much attention. Treat the seed with fungicides like carboxin (Vitavax 75WP @ 2.5g / kg seed), carbendazim (Bavistin 50WP @ 2.5g / kg seed), tebuconazole (Raxil 2DS @ 1.25g / kg seed) if the disease level in the seed lot is high. If it is low to moderate, treat the seed with a combination of

11.

Powdery Mildew

powederymildew

Erysiphe graminis tritici

 

Powdery mildew can easily be diagnosed by the white, powdery patches that form on the upper surface of leaves and stem. With age, the patches turn dull dirty white and may have small black specks embedded. This disease can spread to all aboveground

Mainly in the cooler areas and hilly region; foot hills and plains of north - western India and the southern hills (Nilgiris).

White or gray-brown powdery or cottony patches of mycelium (fungal threads)

on the upper surface of lower leaves. Tiny, brown-black specks (cleistothecia) are visible in older gray-brown areas. Yellowing is usually visible on the undersides of leaves opposite the powdery patches.

  • Crop rotations, resistant cultivars, destruction of residues, proper
  • fertilization, foliar fungicides. Do not plant susceptible cultivar prior to fly-free date.

12.

Head Scab

headscab

Fusarium graminearum

Disease development is favoured by cool, moist weather with high humidity. Spores are produced on crop debris and reach the leaves through rain splash or wind. Apart from ear head infection, it can cause seedling blight and foot rot leading to lodging. In severe cases, it can cause shriveling of grains and low-test weights. At present, it is a disease of limited importance but has the potential to emerge as a major problem due to the production of toxins.

Parts of Punjab, especially in the sub mountainous regions. Bread wheat suffers lesser damage than the durum. It was first recorded in severe proportion in some parts of Punjab during 1995-96 crop season and again during 2004-05 crop season.

Spikelets appear bleached often with a pale pink tint, tombstone kernels, seed light weight, sometimes infected spikelets are barren, can produce mycotoxin, seedling blight.

  • Bread wheat are more resistant than durum. However, no resistant varieties are available. Hence, vigil is needed for this disease.

13.

Stripe Rust /Yellow Rust

yellowrust

 

 

 

 

 

 

 

Puccinia striiformis tritici

Develops from air-borne urediospores, needs free moisture and temperature above 20° C for spread. It can cause severe grain losses if infection is early. The pathogen perpetuates in Nilgiri hills during off season and becomes air­borne. If Peninsular and Central India experience rainfall during November then epidemics are severe. Late infections cause less damage in north India.

Mainly in Peninsular and I Central India, may occur in traces in Northern India too were the infestation comes late.

Citron-yellow uredia (spore masses) appear in long stripes on leaves and, rarely, on stems and heads. As the crop matures, black spores (telia) are produced in stripes which are covered by the leaf epidermis.

Ballad Plus at 1 to 4 quarts/A on 7- to 14-day intervals. Efficacy unknown in the Pacific Northwest. Can be applied up to and on the day of harvest. 4-hr reentry.

14.

Black Molds

(Sooty Molds)

scootymalds

 

Alternaria, Cladosporium, Stemphylium, Epicoccum and other species

When wet or humid weather occurs at or near crop maturation, or when plants are heavily infested with aphids, or when plants die prematurely, they may be invaded by one or more of these fungi. Technically, black molds do not constitute a disease, since the fungi are saprophytic and invade only dead or dying plant tissue.

Parts in Indian Subcontinent where ever wheat is grown.

The typical symptom is the blackened appearance of mature or dead spikes, caused by a superficial accumulation of mycelia and sporulating fungal tissue

Avoid moisture during crop storage

15.

Tan Spot

(Yellow Leaf Spot or Blotch)

tanspot

 

Pyrenophor tritici-repentis a

Initial infections come from diseased crop debris in the soil, or from diseased grass hosts. Usually the lower leaves are infected first, and the disease progresses to the upper leaves and leaf sheaths if conditions are favorable. This disease develops over a wide range of temperatures and is favored by long periods (18 hours or more) of dew or rain.

Parts in Indian Subcontinent where ever wheat is grown

The first sign of the disease is small yellow or dark spots on the leaf. These develop into yellow lesions or spots becoming oval in shape. As they grow the lesions turn tan in colour with a yellow border and a dark centre, best seen when held up to the light. As more lesions develop, they coalesce producing large irregular, dead patches on the leaves and leaf sheaths. All above ground tissue can be infected. After harvest under further wet conditions, infested stubble produce small black raised fruiting bodies that provide primary inoculum for the succeeding crop.

  • ·Avoid sowing wheat into infected stubble. Infected stubble can be identified by the presence of black fruiting bodies.
  • Rotate infested areas into non-host crops, eg barley, oats, chickpeas, faba beans.
  • • Reduce the amount of surface stubble prior to sowing.
  • • Resistant varieties Ellison and Leichhardt are the most resistant varieties currently available.

Fungicides registered for control of yellow spot in Australia include:

  • Propiconazole
  • Tebuconazole
  • Azoxystrobin + Cyproconazole
  • Propiconazole + Cyproconazole

16.

Sclerotium Wilt

(Southern Blight)

wilt

 

Corticum rolfsii (Sclerotium rolfsii)

Sclerotium rolfsii can attack the plant at any stage of development. Fungal mycelia on crop debris or sclerotia serve as primary inoculums. Infection and disease development are favored by warm (20C +) temperatures, excessive moisture, and acid soils.

Parts in Indian Subcontinent where ever wheat is grown

If infection occurs early in the crop cycle, pre- or post-emergence "damping off" of seedlings can result. Diseased tissues will frequently have white, fluffy fungal mycelia on the surface, which often permeate the soil surrounding the plant. Subsequent disease development results in rotted culms, crowns and roots, and the eventual death of the plant; this leads to the appearance of "white heads" or spikes in the green crop. Sclerotia are commonly found on the crown tissues, culms, or near the soil surface. Young sclerotia are whitish and turn brown to dark brown with age.

  • Always use certified or registered seeds.
  • Use mancozeb at 3g/l.OR Use carbendzim at 1.5g/l. or
  • Spray Copper oxychloride at the rate of 0.25 % at 10 to 15 days interval.
  • All infected plant debris should be destroyed.

 

B. BACTERIAL DISEASES

S.No.

Disease

Causative agent

Development

Distribution 

Symptoms

Control Measures

1.

Bacterial leaf blight

leafblight

Pseudomonas syringae 

The pathogens survive on crop debris, as well as various grass hosts. It is disseminated by splashing rain or by insects, and can be seed borne..

Throughout wheat growing regions of India.

Generally after boot stage, water-soaked spots develop which expand and progress from gray-green to tan-white. Spots may coalesce into irregular streaks or blotches, and entire leaves may turn brown and die while heads and glumes remain symptomless. Slimy droplets may develop on leaves in wet weather..

  • Avoid the disease by planting pathogen-free seed.
  • Irrigate less frequently to keep relative humidity lower.

2.

 

Tundu,

(Yellow Ear Rot) 

 

yellowear

Corynebacterium tritici 

The bacteria persists in organic material in the soil. It attacks wheat when it comes in contact with the plant apex within the leaf whorl, and this transmission is often facilitated by the nematode A. tritici.

Throughout wheat growing regions of India.

Yellow exudate on the spikes is indicative of bacterial diseases .When dry, the exudates is white to yellow white .often the spikes and necks will emerge as a distorted sticky The early leaves may also be wrinkled or twisted

  • Use of seeds free from nematode galls or certified seeds.
  • Temik 10G@20kg/hac or Aldicarb sulphon @2kg ai or Carbofuron @1.5kg ai/ hac at the time of planting or before planting needs to applied in severely infested fields.

3.

 

Black chaff

 

blackchaff

Xanthomonas campestris pv. translucens

The bacterium can be seed borne and persists on crop residues in the soil, tolerating warm as well as freezing temperatures. Free moisture is required for infection and spread of the broken epidermal tissue. The disease is spread by splashing rain, plant contact, and insects.

Throughout wheat growing regions of India.

Black chaff and bacterial stripe are both caused by the same organism; the site and extent of the symptoms depends on the strain of the bacterium, the affected cultivar and environmental conditions. "Bacterial black chaff" occurs primarily on the glumes; "bacterial stripe" occurs primarily on the leaves and/or leaf sheaths. Initial symptoms are narrow chlorotic lesions or stripes that have a water-soaked appearance; droplets of sticky yellowish exudate may appear with extended periods of rain or dew. The exudate dries to form crusty droplets or a translucent film on the surface of affected tissues. The film may crack and give a scaly appearance. If infection occurs early in the crop cycle, the spike may be infected, resulting in sterility; when the disease is severe, entire leaves or spikes may be killed.

  • Use of certified, pathogen-free seed.
  • Controlling volunteer cereals and grassy weeds can help reduce primary inoculum.
  • Irrigation management is critical in creating an environment that is less favorable for disease development and spread. Irrigation should be managed in such a way as to allow the plant canopy to dry completely between irrigations.