Soil sterilization for disease contol

Soil sterilization of nursery beds

The aim of soil sterilization is to destroy soil fungi that cause diseases especially damping off disease, bacteria, insets, nematodes and weed seeds.

Methods of sterilization

Burning

·         Prepared nursery beds should be watered well before burning.

·         Put some materials for burning (Hey, Rice husk, dried weeds, coconut leaves, and coconut husk).

·         Several layers can be put on the soil. Selected Material for burning should give slow and complete burning for better results.

·         Start burning against wind direction. If burning is done in wind direction, materials burn rapidly and soil is not get heated enough to destroy of pathogens.

·         Leave two days after burning for cooling before seeding.

      Soil covered with hey rice husk

Solarization

      Use of solar energy to heat the soil for sterilization

• Prepared nursery bed should be wet.
• Use polythene sheet to cover the nursery bed and cover the margin of the sheet with soil to air tight. Keep about 3 to 4 cm in between soil and polythene by using few stones on the inside the polythene.

                                             Nursery bed covered with polythene

Steaming

• This is done by pumping of steam in to the soil of nursery bed by small tubes. Nursery bed should be covered with canvas cloth.
• For small scale nurseries steaming can be done by steaming soil in closed container for about one hour. This sterilized soil could be used to the top layer of nursery bed.
• Applying boil water to the nursery bed might partial sterilization.

Fumigation

The chemical Basomid is used for sterilization of soil.

• Prepare nursery and wet the soil.
•  Apply Basomid evenly on the soil (Use a glove).
• Collect soil about 1 meter height and cover with a polythene sheet and allow about 7-15 days.
• Remove cover and supple several times to remove all the gas.

Control of purple blotch of onion

Purple blotch of Onion

This is a fungal disease distributed in many countries and it can attack other crops like shallots, leeks, garlic and chives.

Disease is severe during wet and warm weather condotion.

Causal organism: Alternaria porri

Symtoms and damage

At the initial stage small water soaked lessions appear on the leaves and flower stalks.These lesions turn in to brown color with reddish purple margins and enlarged .Later these leaves will die.Older leaves are more susceptible for the disease.When thrips damage is present onion plants are more easily attacked by the purple blotch fungi.During harvet fungi can infect onion bulbs and bulb rot can occur during storage.

Control

• Crop rotation with other cros that are not attacked by the purple blotch fungi.
• Control of onion thrips may reduce disease infection.
• Avoid wet season specially when sed production is done.
• Avoid close planting and practce the recommmeneded spacing.
• Do not apply excessive Nitrogen.
• Use recommended fungicides.Protective application of fungicide is recommended when conditions are fevourble for dieases infection. Common fungicides are effective but repeated application is needed when conditions are favorable for the disease.

Control of Onion thrips

Onion Thrips

Onion thrip is a common pest in most countries and pest can attak some vegetables like tomato, cucumber, cabbage, beans and other crops like chrysanthemum and carnation.

Causal organism: Thrips tabaci

Life cycle

Takes 10-30 days depending on the environmental factors especially temperature.When temperature is over 30⁰ C, life cycle complete within 10-11 days.About 6-10 genaratins can occur in one onion crop depending on the temperature.

Egg: Eggs laid by unmated female and number of eggs varies (20-200).rearly reproduce sexually.About 0.2 mm, kidney shapedand white.

Larvae: 10-14 days.First larvae instar0.3 mm, and second instar larvae 0.8mm

Pupae: 5-9 days.Simmilar to second larvae.

Adult: Live about 30 days. 1.0 mm long,  yellowish insect.

Adult, larvae and pupae can over winter in the soil and litter on the ground.

Damage

Adults suck leaves by piercinng and rasking of the outer cover of the leaf. White color blotches could be seen on the leaves.When pest incidence is high leaves rolled and dry, plant become stunted.They feed on flowers alsocausing severe damge when seed production is done.

Control

• Use healty and vigorus seedlings.
• As pest population is high during dry season pay attention to take necessary steps to control the pest.
• Use overhead irrigation to simulated rainfall to reduce pest population.
• Do not use high levels of nitrogen
• Place yellow color plastic or polythene sheets smeared with grease in the field.
• Remove weeds as they may be alternate hosts for the pest.

Stem borer problem in corn

Stem borer (Chilo partellus) in Corn

The pest is widely distributed and is a major pest of corn and sorghum. This pest can infest some other crops like sugarcane, millets.

Damage

The pest can infect any stage of the crop. When infestation occurred during seedling stage, damage is severe as it can kill the plant. When young plants are infested dead hearts are produced due to the boring stems by larvae.

Life cycle

Adults- Female adults are 20-30 mm long when wings are opened. Hind wings are white .Male adults are smaller than female and darker. About 100 eggs are laid in 3-5 rows near the mid rib of the underside of leaves. Egg is about 0.8 mm flat and oval shaped.

Larvae-After 7-10 days time larvae come from eggs and when they mature they are about 25mm long.

Pupa- Pupate inside the stem about 7-10 days.

Control

Novaluron 10 EC

Etofenfox 10 EC

Thiodicarb 375 SC

Diazinon 5G

Fipronil 3 G

Thiocyclam hydrogen oxalate 0.4 g

Adding of granular insecticides to the center of plant apex at 3-5 weeks after crop establishment is very effective in controlling the pest.

Control of Violet Color Seed Disease of Soybean

Violet Color Seed Disease of Soybean

Causal organism- Cercospora kikuchi

Symptoms of the disease

When mature plants are infected reddish violet color patches are observed on the older leaves.Dark red spots are found in young leaves. When disease continues patches of leaves enlarge and join together. Finally these patches dry and whole leaf may dry. Violet color parts can be seen on the seeds. Usually color change begins at the scar of seeds. When these seeds are planted cotyledons become violet and drops.

Control

• Use healthy seeds.

• Treat seeds with fungicides. Suitable fungicides are Thiram, Thiophanate -methyl and Captan.

• Application of fungicides should begin at pod initiation stage and continue up to seed development stage. Mancozeb and Chlorothalonil are recommended for the disease control.

Produce your own papaya seeds it is easy

Seed production is by selfing (pollination in same plant) of papaya variety except hybrids give seeds plants similar to mother variety.

Types of plants:

Male plants- Produce only male flowers.

Female plants- Produce only female flowers.

Bisexual plant- Produce bisexual flowers and male flowers.

Usually flowering occurs after 4-6 months of planting of seeds. Only after flowering we can distinguish the plant types .Therefore, planting of unknown seeds create two problems.

1 Give plants having different fruit characters due to cross pollination.

2 Occurrence of male plants.

Usually this problem is overcome by planting few seed in one planting hole and removing male plants when they are flowering .However this is not acceptable as we have to maintain plant about 6 months giving all the inputs like water and fertilizer and crop protection practices.

How selfing is done

Select bisexual flowers that are close to open.

Cover few bisexual flowers with oil paper bags. (9x6 cm size bag is suitable)

Remove bags after 5-7 days and label them to indentify.

If selfing is occurred fruit will be developed.

Fruits mature after 3-4 month and after ripening harvest and take seeds.

Remove gelatinous outer cover of seeds and wash thoroughly and allow drying under shade.

Sufficiently dried seeds can be stored in polythene bags of aluminum foil bags.

Papaya Mealy Bug(Paracoccus marginatus) Control

Mealy bug: Paracoccus  marginatus                  

Family: Pseudococcidae

Mealy bug of Papaya is a widely distributed pest. There are about 60 species of are found around the world.

Other host plants: Cassava, Jak, Bread fruit, Egg plant, Capsicum, Ornamental plants, and many weeds.

Adult female light yellow and body is covered wax like substance. Several filaments about 3mm are present around the margin of the body. Eggs greenish yellow and laid in egg sac. First nymph can move to other places and pest distribution occurs by other means like wind, birds and human activities. This mealy bug sucks the plant.

Damage

Mealy bug suck sap so that plant becomes weak.

The excretions of mealy bug result black color fungal growth on the surface of leaves that cause low productivity due to low sunlight availability.

Toxic compounds enter to the leaves and make abnormal growth of leaves. Chlorosis and stunting of plat is also observed.

Fruits, flowers and younger leaves are covered with thick wax like substance. Clusters of cotton like masses are observed in different organs. Fruits are not edible when infestation is severe,

Control

·         Remove severely infested braches of the plant and destroy by burning.

·         Keep good sanitation by removing dropped leaves and other debris.

·        Use of polythene tape smeared with grease around the trees can stop pest from the 

          soil If  having only few plants.

• Biological control has been effective which has to be done by 

         the professionals in the regions affected severely.

• Use shampoo or soap spray for the ornamentals and flower plants. Mix soap with kerosene oil (Soap 2 teaspoon, Kerosene oil 1 teaspoon and one liter of water).

·        White mineral oil also effective.

·       Use insecticides:

Imidacgloprid 200g/l SL

Acetamiprid 20 % SP

Thiomethoxam   25% WG – Apply to the soil at the base of plant or to the pest.

                                Chlorofyrifos

                Single application might not control pest completely so, other application may be needed.

Control Soil Acidity for Better Yield

Control Soil Acidity for Better Yield

PH value gives a measure of acidity and alkalinity in soil. This value theoritically varies from 0-14 and value 7.0 is neutral .However pH value of soil in lands used for cultivation varies from 3.8-7.8.The optimum pH varies with the crop usually 5.0- 7.0

Here are some optimum PH valus for different crop species

5.5 -6.5: Potato

5.5 -7.0: Cucurbits, Egg plant, Bean, Carrot, Pepper, and Tomato.

6.0-7.0: Cauliflower, Shallot, Raddish.

6.0-7.5: Beet, Cabbage, Spinach mn 

The most commonly observed problem is the low pH or the acidity of soil. Acidity can be due to several reasons.

• Higher rainfall
• Regular cropping removes Calcium and Magnesium from the soil.
• Water logged condition.
• Higher microbial activity release carbon dioxide that creates acidity in soil.

When soil pH is less than 6.0, availability of Calcium, Magnesium and Phosphorus is less and increse the avilability of Boron, Zinc, Iron and Alluminium which is toxic to many plant species

How do you know soil pH?

Take soil sample from the land and give it to soil testing laboratory for testing.

Three are some soil testing kits are available for testing soil in the field.

Alleviate the problem

Add lime (1 t/ha). Action is rapid but short term.

Add ground Dolomite (Calcium carbonate and Magnesium carbonate) .Slow release and active for 2-3 years.

Apply 1 t/ha to increase 0.5-1.0 of pH value of soil. Based on pH value of your soil you can decide the amount needed for your land.How ever the amount is varied wit the type of soil.Sandy soil need less lime compared to clay and high organic matter soils.

Pot plants

Use 500 g lime for 10 kg of soil and organic matter mixture.

Ash can also be applied to increase soil pH.

Bordeaux mixture for fungal disease control

Bordeaux mixture

Bordeaux mixture is easily prepared cheap fungicide that could be used to control different fungal diseases of crops. This mixture first discovered by Millardet in France more than 100 years ago is still used to control fungal diseases.

Bordeaux mixture is suitable to control coffee rust, downy mildew in grapes, panama disease of banana, blight in tomato and potato, and various fungal diseases of many crops.

Bordeaux mixture act as a persistent fungicides and not easily washed away by the rain.

There are different ratios of ingredients used for the preparation of Bordeaux mixture as 5:5:50, 4:4:50, 2:2:50 (e.g. 5:5:50 – 5 lbs Copper sulphate, 5 lbs lime and 50 gallons water).

One present of Bordeaux mixture is suitable for many diseases.

Preparation of Bordeaux mixture

Copper sulphate- 500 g

Lime                     - 500 g

Water                   - 45 liter

Dissolve copper sulphate in 1-2 liters of water.

Dissolve lime in 1-2 liters of water.

Use wooden, plastic or clay vessels for preparation of mixtures.

Then add lime mixture little by little to the copper sulphate solution and stir continuously

After preparation of Bordeaux mixture use the same day and take precautionary steps as done when other pesticides are applied.

Management of Panama Disease(Fusarium Wilt) in Banana

Panama Disease (Fusarium wilt) of Banana

This fungal disease is common and serious disease in banana. Disease is distributed in all parts of the world like Australia, America, Asia and Africa.

Causal agent- Fusarium oxysporium

Symptoms

Marginal yellowing of older leaves and these leaves turned brown and dry out. The infected leaves collapse at the base and latter plant gets wilted and dies .However suckers seems to be healthy but if these suckers are planted disease symptoms show later. The fungus infect through the roots and enters to the xylem the tissue conducting water and affect to the movement of water in the plant that make plant to be wilted.

The disease mainly introduced by the planting material, as suckers do not show symptoms of the disease. The fungus can persist in the soil for long period.

                              Leaves collapse at the base and healthy sucker

                                     

Infected plant

                                              Cross section of pseudostem of intected plant

Control methods

·        Use resistant varieties (Indian varieties Poovan, Rajabale ,Moongil and Vamanakeli are resistant to disease) .Consult local agriculture authorities to find out resistant varieties.

·        Use disease free suckers or issue cultured plants.

·        Do not use poorly drained soil for banana cultivation.

·        Avoid runoff water from diseased area as funs can be distributed with the water.

·        Infected soil can move to other areas through implements or by foot wear so that disinfect them before moving to uninfected area. Methylated sprit, Formalin or Sodium hypochlorite may be used for disinfection purpose.

·        Cut and chop up all planting materials including the gouged out corm and place them in a large polythene bag to decompose. Application of urea in to the bag may be used for rapid decomposition of the material.

·        If diseased plant is observed, remove this plant with surrounding plants. Isolate the infected area. Herbicide injection can be used to kill the diseased plants.