Diseases of Vegetable, Ornamental and Spice Crops

Exercise 15: FUNGICIDES AND THEIR APPLICATION

The chemicals applied to control plant diseases are broadly called fungicides. These chemicals either inhibit growth, sporulation or are lethal to causal organism. According to their mode of action, they may be protectants (effective if applied before infection) or chemotherapeutants (effective if applied after infection). On the basis of mobility, chemotherapeautants are either eradicants (absorbed but not translated) or systemic (translocated in plant system to the site of action). Fungicides are formulated as dust, wettable powder, liquid or emulsion (Table 1). Some common fungicides are given below:
Table 1: List of diffetrent fungicides used to control plant diseases
1. Seed treatment fungicides

Common Name	Common trade name (s), Dose	Remarks
Captan	Captaf, Hexacap (3g/kg seed)	Used chiefly as seed dresser. Also widely used against Pythium, Rhizoctonia and other soil fungi causing damping-off and seedling diseases
Carbendazim	Bavistin, Derosal, Bengard (2g/kg seed)	Used as seed treatment against internally seed borne pathogens like Rhizoctonia, Ascochyta, Fusarium etc.

2. Soil treatment chemicals/ fungicides

Common Name	Common trade name (s), Dose	Remarks
Formaldehyde	Formalin (5% or 1: 7)	Mostly applied as soil treatment particularly for disinfection of nursery bed soil. Prepare a raised bed and after mixing with FYM treat the soil with Formalin solution and cover it with polythene sheet for 7 days. After 7 days remove the sheet. Rake the soil well at least twice a day till the soil is free from the fumes.
Captan	Captaf, Hexacap (0.3%)	Can be applied as dry or soil drench or furrow application for the control of soil borne pathogens like Pythium, Rhizoctonia and other soil fungi causing damping-off and seedling diseases

3. Foliar spray fungicides

Common Name	Common trade name (s), Dose	Remarks
Non-systemic fungicides
Wettable sulphur	Sulfex, Thiovit (0.2%)	Effective against powdery mildew diseases
Copper oxychloride	Blitox, Fytolan (0.3%	Effective against downy mildew fungi, bacterial diseases and other leaf spot diseases
Mancozeb	Dithane M-45, Indofil M-45 (0.25%)	Mostly used against foliar diseases
Dinocap	Karathane (0.05%)	Effective against powdery mildew diseases
Systemic fungicides*
Carbendazim	Bavistin, Derosal, Bengard, Agrozim (0.05-0.1%)	Commonly used systemic fungicide for the control of leaf spots, powdery mildews, Rhizoctonia, Fusarium diseases etc.
Metalaxyl + mancozeb	Ridomil MZ -72 (0.25%)	Used for the control of diseases caused by Phytophthora, Pythium and downy mildews
Hexaconazole	Contaf (0.05%)	Used against powdery mildews, rusts and leaf spots

* All systemic fungicides to be used once or twice alone and then use in combination with non-systemic multisite fungicides because there continuous use may develop resistance in the pathogen.

Application of Fungicides

Fungicides are applied on host surface with the help of various devices. For example, seed treating drums are used for seed treatment, sprayers for carrying out spray on foliar parts, and dusters for dusting fungicides on aerial parts of plants. The sprayers are of various types. These may be manually or power operated. The quality of spray can be maintained with the help of nozzles and other automizing devices. Knapsac sprayer is commonly used for applying fungicides on crop plants (Fig. 1).

Fig. 1: Knapsac sprayer