Methods of fungicide applications =" ¥* A large number of fungal pathogens are carried on or in the seed leading to their rotting, seedling mortality or produce diseases at a later stage. Seed treatment: Effective and economic method against soil and seed borne pathogens that infect embryos, cotyledons or endosperms under the seed coat.A)Wet seed treatment — | {> lt involves preparing fungicide | suspension in water, often at field rates and then dipping the Ea seeds or seedlings or propagative materials for a specified time. » Seeds cannot be stored and the treatment has to be done before sowing. | > Usually applied for treating vegetatively propagative materials like cuttings, tubers, corms, setts rhizomes, bulbs etc.a)Seed dip / Seed soaking * For certain crops, seed soaking is essential. * Seeds treated by these methods have to be properly dried after treatment. The fungicide adheres as a thin film over the seed surface which gives protection against invasion by soil- borne pathogens. * For e.g. Seed dip treatment in paddy.b.Seedling dip / root dip: The seedlings of vegetables and fruits are normally dipped in 0.25% copperoxychloride or 0.1% carbendazin solution for 5 minutes to protect against seedling blight and rots. c. Rhizome dip: The rhizomes of cardamom, ginger and turmeric are treated with 0.1% emisan solution for 20 minutes to eliminate rot causing pathogen present in the soil. d. Sett dip / Sucker dip: The setts of sugarcane and tapioca are dipped in 0.1 % emiasn solution for 30 minutes. The suckers of pineapple may also be treated by this method to protect from soil-borne diseases.B)Dry Seed Treatment - In this method, the fungicide adheres in a fine form on the surface of the seeds. A calculated quantity of fungicide is applied and mixed with seed using machinery specially designed for the purpose. * For e.g. Mix a required amount of fungicide with in a seed treating drum or polythene lined gunny bags, so as to provide uniform coating of the fungicide over the seeds. Treat the seeds atleast 24 hours prior to soaking for sprouting. Any one of the following chemical may be used for treatment at the rate of 2g/Kg: Thiram or captan or carboxin or trycyclazole. Seed treatment using rotary seed drumC)Slurry treatment (Seed pelleting): In this method, chemical is applied in the form of a thin paste (active material is dissolved in small quantity of water). The required quantity of the fungicide slurry is mixed with the specified quantity of the seed so that during the process of treatment, slurry gets deposited on the surface in the form of a thin paste which later dries up. * For Eg. Seed pelleting in ragi:Mix 2.5g¢ of carbendazim in 40 ml of water and add 0.6g of gum to the fungicidal solution. Add 2 kg of seeds to this solution and mix thoroughly to ensure a uniform coating of the fungicide over the seed. Dry the seeds under the shade. Treat the seeds 24 hrs prior to sowing.Il. SOIL TREATMENT iw — 2 * It is well known that soil harbours a large number of plant pathogens and the primary sources of many plant pathogens happens to be in soil where dead organic matter supports active or dormant stages of pathogens. In addition, seed treatment does not afford sufficient protection against seedling diseases and a treatment of soil around the seed is necessary to protect them. Soil treatment is largely curative in nature as it mainly aims at killing the pathogens. In soil and making the soil 'safe' for the growth of the plant. Soil treatment is done by two methods: * Physical method * Chemical methodChemical methods of soil treatment: It is| comparatively simple, especially when the soil is fallow as the chemical is volatile and disappears quickly either by volatilization or decomposition. Soil treating chemicals should be non-injurious to the plants in the soil adjacent to the area where treatment has been carried out because there may be standing crop in adjacent fields. The soil treatment methods involving the use of chemicals are : (i) Soil drenching, (ii) broadcasting, (iii) furrow application, (iv) fumigation and (v) chemigation.* (i) Soil drenching: This method is followed for controlling damping off and root rot infections at the ground level. Requisite quantity of fungicide suspension is applied per unit area so that the fungicide reaches to a depth of atleast 10-15 cm. For eg. Emisan, PCNB, Carbendazim, Copper fungicides, etc. * (ii) Broadcasting: It is followed in granular fungicides wherein- the pellets are broadcasted near the plant. ¢ (iii) Furrow application: It is done specifically in the control of some diseases where the direct application of the fungicides on the plant surface results in phytotoxicity. It is specifically practiced in the control of powdery mildew of tobacco where the sulphur dust is applied in the furrows.* (iv) Fumigation: Volatile toxicants (fumigants) such as methyl bromide, chloropicrin, formaldehyde and vapam are the best chemical sterilants for soil to kill fungi and nematodes as they penetrate the soil efficiently. Fumigations are normally done in nursery areas and in glass houses. The fumigant is applied to the soil and covered by thin polythene sheets for 5-7 days and removed. For example, Formaldehyde is applied at 400 ml/100 Sq. m. The treated soil was irrigated and used 1 or 2 weeks later. * (v) Chemigation: In this method, the fungicides are directly mixed in the irrigation water. It is normally adopted using sprinkler or drip irrigation system.oo A. Spraying * Most commonly followed method is done on leaves, stems arid fruits. * Wettable powders are most commonly used for preparing} spray solutions with water as common diluent or carrier. ‘ * Amount of spray solution required iam for a hectare will depend on the nature of crops to be treated. For trees and shrubs more amount of spray solution is required than in the case of ground crops.The different equipments used for spray application are: a) Foot-operated sprayer, rocking sprayer, knapsack sprayer, b) motorized knapsack sprayer (Power sprayer), tractor mounted c) sprayer, mist blower and aircraft or helicopter (aerial spray). * B. Dusting: Dusts are applied to all aerial parts of a plant as an alternative to spraying. Dry powders are used for covering host surface. Generally, dusting is practicable in calm weather and a better protective action is obtained if the dust is applied when the plant surface is wet with dew or rain drops.IV. POST-HARVEST APPLICATION Fruits and vegetables are largely damaged after harvest by fungi and bacteria. Many chemicals have been used as spray or dip or fumigation. Post harvest fungicides are most frequently applied as aqueous suspensions. Dip application has the advantage of totally submerging the commodity so that maximum opportunity for penetration to the infection sites. Systemic fungicides, particularly thiabendazole, benomyl, carbendazim, metalaxyl, fosety-Al have been found to be very effective | against storage diseases. In addition, dithiocarbamates and antibiotics are also applied to control the post-harvest diseases. Wrapping the harvested products with fungicide impregnated wax paper is the latest method available.V. PAINTING (SWABBING): 2 =e Sr a * This is practiced normally in most of the ornamentals and fruit trees after pruning. The fungicidal solution/paste is painted on the cut ends to prevent the entry of pathogens. Sometimes, the swabbing is done after removing the diseased portion of the| plants. ° Eg. Swabbing of Bordeaux paste in stem bleeding disease of coconut.VI. SPECIAL METHODS 1. Trunk Application / Trunk Injection: It is normally adopted in coconut gardens to control Thanjavur wilt-caused by Ganoderma lucidum. In the infected plant, a downward hole is made to a depth of 3-4 inches at an angle of 45 ° at the height of 3 feet from the ground level with the help of an auger. The solution containing 2g of aureofungin and 1 g of copper sulphate in 100 ml of water is taken in a saline bottle and the bottle is tied with the tree. The hose is inserted into the hole and the stopper is adjusted to allow the solution in drops. After the treatment, the hole is covered with clay. Root Feeding: Root feeding is also adopted for the control of Thanjavur wilt of coconut instead of trunk application. The root region is exposed; actively growing young root is selected and given a slanting cut at the tip. The root is inserted into a polythene bag containing 100 ml of the fungicidal solution. The mouth of the bag is tied tightly with the root.References 2 Books Fungicides in plant disease control 3° edition by y.L. Nene P.N. Thapliyal Principles of Plant Pathology by R. S. Singh Plant Pathology by G. N. Agrios 4" edition Web Resources http://agridr.in/tnauEAgri/eagri50/PATH171/inde x.html http://agriinfo.com