WELCOME

“SUSTAINABLE MANAGEMENT OF SOIL-

BORNE PLANT DISEASES “

Sustainable management to be defined as the application of sustainable practice in the category of Agriculture, business, society ,environment and in personal life by manage them in the way that will be benefit current and future generation

It create the ability to keep a system running indefinitely without depleting resources the decision of making sustainable management help to sustain our immediate surrounding and environment.

One important result is that farmers are able to minimize their use of pesticides and fertilizers, thereby saving money and protecting future productivity, as well as the environment

INTRODUCTION

Intensive production in agriculture ,horticulture or forestry increases the opportunity for disease to develop comparing to other ecosystem,

As plants and soils become sickers, growers have responded with newer and more powerful chemicals in an effort to kill off the pathogens, chemical intervention only serves to make things worse over time.

In this condition sustainable management of soil borne plant disease is very important to minimize the activity that cause damage to our environment .

PREDOMINANT SOILBORNE PATHOGENS:

Fungi: Sclerotium rolfsii,Rhizoctonia solani,Fusarium sp,Pythium, Phytophthora etc.

Bacteria: Erwinia, Raltsonia, Rhizomonas, Agrobacterium, Streptomyces etc.

Virus: Wheat soil borne Mosaic virus

Nematodes: Meloidogyne, Heterodera, Longidorus, Paratrichodorus , Trichodorus etc.

Parasitic plants: Orobanche, striga

WHY THE PLANT DISEASE ?

PRINCIPLES OF PLANT DISEASE MANAGEMENT

• Avoidance of pathogen

• Pathogen exclusion

• Pathogen eradication and reduction of inoculum

• Plant protection

• Resistant Varieties

• Therapy

45 %

28%8%

4%

15%

Chemical method

Cultural methodPhysical methodBiological method

Practices for sustainable management of soil borne plant disease

Host resistance

1) CULTURAL METHOD

It is an integral part of subsistence agriculture in developing countries.Cultural practices are now being consider as essential back up procedure for management of resistant varieties and also for chemical protected crops.

Cultural practices involves the principles of :

Avoidance Eradication Exclusion

Cultural methods includes

Crop rotation

Date of sowing

Nutrient managem

ent

Organic amendme

nt

Cover cops

Depth of sowing

Management of top

soil

• Many diseases build up in the soil when the same crop is grown in the same field year after year. Rotation to a non-susceptible crop can help break this cycle by reducing pathogen levels.

• The susceptible crop, related plants, and alternate host plants for the disease must be kept out of the field during the rotation period.

• it help control pathogens that can survive long periods in the soil without a host.

• Example : Fusarium sp

CROP ROTATION AND DISEASE SUPPRESSION

VEGETABLES DISEASE YEAR OF ROTATION

Asperagus Fusarium rot 8

Beans Root rot 3-4

Cabbage Club root 7

Cabbage Black leg 3-4

Cabbage Black rot 2-3

Muskmelon Fusarium wilt 5

Parsnip Root canker 2

Peas Root rot 3-4

Peas Fusarium wilt 5

Pumpkin Black rot 2

Radish Club root 7

Rotation periods to reduce vegetable soil-borne diseases

BENIFICAL CROPS

PATHOGEN REDUCED PRECEDING CROP (host)

Rice Verticillium dahliae Cotton

Peas Gaeumannomyces graminis Wheat

Maize , Wheat, Sorghum

Ralstonia solanacearum Tomato and potato

Legume crops

Streptomyces scabis Potato

Ground nut Meloidogyne incognita Tomato

Effect of short term rotation on some pathogens

Date of sowing Early and delayed sowing of crops enables it

escape critical period of disease incidence.

Peas and chickpea sown in October usually suffer heavily from root rot and wilt (a complex of Fusarium, Rhizoctonia and Sclerotium). When these crops are sown late, the diseases are not so severe or almost absent.

Avoiding cool and cloudy days for planting will help to reduce red rot of sugarcane. Late sowing of winter wheat and barley is considered to be the most effective measures in reducing take all disease of wheat.

PLANT NUTRIENT AND DISEASE CONTROL

• All essential plant nutrients influence the health of plants and their susceptibility to disease. Plants suffering a nutrient stress will be more susceptible to diseases, while adequate crop nutrition makes plants more tolerant of or resistant to disease.

 •  The nutrient status of the soil and the use of

particular fertilizers and amendments can have significant impacts on the pathogen’s environment.

• One of the most widely recognized associations between fertility management and a crop disease is the effect of soil pH on potato scab.

• Potato scab is more severe in soils with pH levels above 5.2. Below 5.2 the disease is generally suppressed.

• Sulfur and ammonium sources of nitrogen acidify the soil, also reducing the incidence and severity of potato scab.

• Fungi penetrate the surface cells (epidermis), by passing between the cells or through them. The cell walls present a physical resistance to the fungus and stronger cell walls can prevent the infection. Certain nutrients, like Calcium, play a major role in the ability of the plant to develop stronger cell walls and tissues. 

 

Example

• Bacteria invade the plant tissue through wounds, sucking insects and through the stomata. Then they spread within the intercellular spaces. The bacteria release enzymes that dissolve the plant tissue. Calcium is known in its ability to inhibit such enzymes. 

 

How can mineral nutrition prevent plant disease?  Mineral nutrition can affect two

primary resistance mechanisms:

A) Formation of mechanical barrier (eg. Thickness of cell wall )

B ) Synthesis of natural defence compounds (eg: phytoalexins , antioxidants and flavanoids)

NUTRIENT SUPPRESSING DISEASE

CROPS

Calcium 1)Clubroot2)Fusarial wilt3)Damping off

1) Curcifiers2) Tomato,Watermelon

and cotton.3) Peanut ,Soybean,Peppe

r,Tomato, onion,Bean and Wheat.

Nitrate Fusarium wilt Tomato,Celery, crysanthimum and Carnation.

Sulfer Scab Potato

Pottassium Verticillum wilt Cotton

Phosphate Fusarial wilt Cotton and Muskmelon

EFFECT OF NUTRITION IN PLANT DISEASE SUPPRESSION

COMPOST AND DISEASE SUPPRESSION

Compost encourages healthy plants that are better equipped to fight off disease and increase in yield are often an added benefit of improving soil and plant health.

HOW DOES COMPOST SUPPRESS DISEASE?

• Adding compost to soil improves soil physical and chemical properties and increases the number and diversity(different types) of bacteria and fungi in soil.

• Root rots caused by Pythium and Phytophthora are generally suppressed by the high numbers and diversity of beneficial microbes found in the compost.

Vegetable Pathogen/Disease

Treatment Comments

Alfalfa .

“Clover tiredness” Four years of treating fields with high-quality compost

Stand thickness and yield doubled, weeds crowded out .

Barley/Wheat

Drysiphe graminis/Powdery mildew

Compost added to soil.

Disease incidence suppressed 95% when 1:1 soil:compost mixes used .

Beans (CA blackeye No. 5)

Rhizoctonia sp. Compost added to soil at varying rates (36-72 tons/acre).

Disease reduced 80% in areas with highest compost rates, 40% where intermediate rates applied. Control plots yielded 75 bushels/acre, compost plots yielded 200 bu/acre

Soybeans.

Phytophthora sp 40 tons of compost per acre.

Control achieved

Compost Treatment and Disease Management

Vegetable Pathogen/Disease

Treatment Comments

Cucumber Sphaerotheca sp./Powdery mildew

Young cucumber plants grown in soil/compost mix of variable rates.

1:1 soil:compost mix decreased PM by 20% over control; 1:3 mix decreased infection by 40%

Pea (Pisum sativum)

Pythium sp./Damping off

Seed treatment; seeds soaked in dilute compost extract, dried before sowing.

Peas seed-treated with compost extract germinated significantly better than untreated seed in soil artificially inoculated with Pythium ultimum

Peppers Phytophthora sp.

40 tons of compost per acre.

Compost in combination of hilling plant rows is best practice to reduce Phytophthora

Management of top soil

1. Covering of soil with organic residue helps in reducing plant diseases ,but it should be unrelated material to the host’

2. Shaping the top soil into ridges will be helpful to keeping the soil dry which is in direct contact with collar region it help to reduce the pathogens like sclerotium rolfsii, pythium fruit rot and sclerotiana sclerotium

Cover cropping

They are non-host crops sown with the purpose of making soil borne pathogens waste their infection potential before the susceptible main crop is grown.

Growing of cover crops: Mustard and Brassicasp (Broccoli) helps to reduce the

load of soilborne pathogens. Cover crops will increase soil microbial diversity by

enhancing the soil microflora. Create unfavorable conditions.

Depth of sowing:

The depth of sowing has important effect on pathogen that attack seedling .By delaying the emergence of seedling ,deep sowing may help to increase the resistance of a susceptible crop to pathogen .

Example : Deep sowing is advisable In case of diseases caused by Fusarium and Rhizoctonia sp

2) PHYSICAL METHODS

It aims to eradicate the pathogen propagules. It causes the inactivation and immobilization of the pathogen

The physical agents used most commonly in controlling plant diseases are temperature (high or low), dryair,unfavorable light wavelengths, and various types of radiation.

With some crops, cultivation in glass or plastic greenhouses provides physical barriers to pathogens and their vectors and in that way protects the crop from some diseases.

plastic or net covering of row crops may protect the crop from infection by preventing pathogens or vectors from reaching the plants.

Soil solarization

Soil solarization is a method of heating soil by covering it with transparent polythene sheeting during hot periods to control soilborne diseases. The technique has been commercially exploited for growing high-value crops in diseased soils in environments with a hot summer (maximum daily air temperatures regularly exceeding 35°C).

Examples include control of verticillium and fusarium diseases in vegetable crops in Israel, control of Verticillium dahlias in orchards in California, USA and control of chickpea and pigeonpea wilt in India.

Heat sterilization It is a process of heating up of soil . It can generally achieved by heat produced electically than supplied by steam or hot water

Example: At 50°C – Nematodes and some oomycetes are killed

At 60- 70°C – most plant pathogenic bacteria and fungi.

Flooding

• Flooding the field to eliminate soil borne plant pathogen is both a physical and cultural method.

• Prolonged water logging leads to lack of oxygen and accumulate of CO2.

Example : panama wilt of banana can be effectively controlled by flooding for 4 -6 weeks prior to planting.

Two ways of disease suppression:

3) BIOLOGICAL CONTROL

By Antagoni

stic associati

on

By

Symbiotic associatio

n

Antagonistic association

Bio control agents suppress disease causing organism in four main ways:

Competition :Beneficial organism out-compete disease causing plant pathogens in the search for nutrients or colonization space in specific habitats such as the root zones. Increased competition prevents pathogens from becoming established and multiplying to levels that cause plant disease.

Antibiotics and secretions : produced by some microorganisms inhibit the growth of plant pathogen.

Predation and parasitism of plant pathogen by bio control agents (where beneficial microbes use pathogen as a food)

Hyphae of the beneficial fungus Trichoderma wrap

around the pathogenic fungus

Rhizoctonia.

Symbiotic association

In this association beneficial microorganism protect the host plant from pathogen by keeping an association with the host plant of pathogen.

Example: MYCORRHIZA

It is considered as the most beneficial root-inhabiting organisms, which forms a fungal mat over the root and protect the root of plant from the attack of soil borne pathogen.

MYCORRHIZAL FUNGI AND DISEASE SUPPRESSION

MYCORRHIZA : consider to be an association between fungi and root of higher plants

IT PROTECT THE PLANT BY:

By providing antagonistic chemicals.

By competing with the pathogen.

By increasing the nutrient uptake ability of plants.

By changing the amount and type of plant root exudates.

It act as a barrier for invading pathogen.

1. Protection from the pathogen Fusarium oxysporum was shown in a field study using a cool-season annual grass and mycorrhizal fungi. In this study the disease was suppressed in mycorrhizae-colonized grass inoculated with the pathogen.

2. In field studies with eggplant, fruit numbers went from an average of 3.5 per plant to an average of 5.8 per plant when inoculated with Gigaspora margarita mycorrhizal fungi. Average fruit weight per plant went from 258 grams to 437 grams.

EXAMPLE:

4) Chemical method

Chemical pesticides are generally used to protect plant surfaces from infection or to eradicate a pathogen that has already infected a plant.

A few chemical treatments, however, are aimed at eradicating or greatly reducing the inoculum before it comes in contact with the plant. They include soil treatments (such as fumigation),disinfestation of warehouses, sanitation of handling equipment, and control of insect vectors of pathogens

• Chemicals in plant disease are used to create the toxic barrier between the host surface and pathogen.• These are applied in the soil as pre and post plant applications. Generally these treatments are being givenin high value cash crops.• Applied as soil fumigation, soil drenching and seed treatment.• Fungicides like prothiocarb, propamocarb and metalaxyl are useful to control the Oomycetes pathogens.• Fosetyl – Al is the fungicide which controls the soilborne pathogens when it is used as foliar spray.

• Suppressiveness is linked to the types and numbers of soil organisms, fertility level, and nature of the soil itself .• The response of plants growing in the soil contributes to suppressiveness. This is known as “induced resistance“ • The level of disease suppressiveness is typically related to the level of total microbiological activity in a soil.

Suppressive soil

• limiting available nutrients is a key for general suppression . • Virtually any treatment to increase

the total microbial activity in the soil will enhance general suppression of pathogens by increasing competition for nutrients.

5) Host Plant ResistanceGrowing of resistance plants is one of the most effective and economical method. Host plant resistance not only reduces the crop losses but lessens the expenditure incurred on disease control as well as reduces the pollution hazards.

• Resistance is of two types:

i) Monogenic (Vertical)ii) Polygenic (Horizontal):

General preventive measures to restrict soil-borne diseases occurrence Select resistant plant cultivars and certified disease-

free stock, then plant them at the right time of year. Avoid mechanical damage to plants Do not over-fertilize; doing so inhibits proper root

development Management of soil pH—raising the soil pH to 6.5–7

by using nitrate nitrogen in place of ammonical nitrogen, for example will decrease the development of Fusarial wilt.

Avoid contamination of the growing medium and purchase quality seed

Avoid use of low, poorly drained areas for nursery production

Restrict use of machinery in infested areas, particularly when soil is wet

Prevent movement of soil from infested to non-infested areas of nursery

Avoid over watering to puddle or run-off point

Avoid movement of infected trees within and between nurseries

Conclusion Management of soil-borne diseases is most successful and

economical when all the required information pertaining to the crop, disease affecting it, history of these in the previous years, resistant levels of the host and environmental conditions to prevail is available.

Combination of disease management practices may have additive or synergistic effects and such an approach is especially desirable in the case of soilborne diseases which are entirely different epidemiologically.

Hopefully, the present situation, which emphasizes the use of integrated disease management practices, will stimulate the development of non-chemical methods of disease management to better manage the soilborne pathogens.