Several organisms like Fungi, Bacteria, Virus, Phytoplasma, Protozoa and Nematodes cause internal and external deformities in plants, which is referred as disease. The disease causing organisms produce definite symptoms in crop plants/seeds. The diseased crop does not attain its natural growth, thereby adversely affecting the crop yields. The soil and seeds are the main source of disease infection in crops. Apart from these, air, water and other sources also help in the spread of the diseases. The organism of seed borne diseases remains dormant inside/surface of the seed and infects the plant at any stage of the crop i.e. from germination to seed formation. The Smut and Karnal bunt of wheat, Collar rot of groundnut, green ear head of Pearl millet etc. are examples of seed borne diseases. The causal organisms of some of the diseases remain in soil and in the presence of favourable conditions, infect the seed and the germinating seedlings. The Pythium, Sclerotium, Rhizoctonia, Microphomina are the fungi which cause soil borne diseases in pulses and other crops. The spread of diseases in standing crops is also facilitated by air, water and other sources.
The chemical compounds or bio-agents used to kill or inhibit the fungi or fungal spores are termed as Fungicides.
Classification of Fungicides
Fungicides have been grouped into different categories on the basis of their chemical nature, and mobility in plants, as below:
- Inorganic – Sulphur
- Dithiocarbamate – Thiram, Ziram, Ferbam Mancozeb, Nabam
- Copper based – Copper oxychloride, Copper hydroxide
- Carbonic mercury – Ethyl mercuric chloride, Phenyl mercuric oxide
- Quinones – Chloranil, Dichlore
- Heterocyclic nitrogen – Captan, Folpet, Captafol
- Benzimidazole – Carbendazim, Benomyl, Thiabendazole
- Thiophanate – Thiophanate-ethyl, Thiophanate-methyl
- Oxathin – Carboxin, Oxycarboxin,
- Phenylamides – Metalaxyl, Oxadixyl, Benalaxyl
- Triazoles – Propiconazole, Flusilazole, Hexaconazole, Tricyclazole, Myclobutanil, Penconozole
- Morpholine – Tridemorph, Dodemorph
- Organophosphorus – Kitazin, Kitazin P., Fosetyl AL
- Acetamides – Cymoxanil, Chlorothalonil
- Others – Dinocap, Chinomethionate
- Contact Fungicides : These fungicides control the diseases by contact action and are not absorbed by the plant tissues and remain on the surface of the plant. Repeated application is needed to control new fungi growth, eg. Mancozeb, Thiram etc.
- Systemic Fungicides : These fungicides are absorbed by the plant tissues and translocated in whole plant, e.g. Hexaconazole, Flusilazole, Carbendazim
- Translaminar Fungicides : The fungicides redistributed from upper leaf surface to lower unsprayed leaf surface, e.g. Trifloxystrobin, Azoxystrobin