contact fungicide

classification of contact fungicide defenition, mode of action,examples and uses

1. PAT 202 – PRINCIPLES OF INTEGRATED PLANT DIEASE MANAGEMENT (1+1 ) CLASSIFICATION OF CONTACT FUNGICIDE BY RATHIKA NATARAJAN 2017028067 RVS AGRICULTURAL COLLEGE THANJAVUR. Course Teacher: K. Ramalingam Assistant professor (pathology)

2. CONTACT FUNGICIDES Contact fungicides are not taken up into the plant tissue, and protect only the plant where the spray is deposited ; Transminar fungicides redistribute the fungicide from the upper, sprayed leaf surface to the lower,unsprayed surface . control Foliar disease

3. Mode of action and uses-Copper fungicides Copper as copper ions is readily accumulated by sensitive fungi. It forms couplexes with enzymes that possess sulphydryl , hydroxyl, amino or carboxyl groups by inactivating them and leading to a general disruption of metabolism and breakdown of cell integrity

4. Mode of action and uses- Sulphur compounds 1) Elemental Sulphur a) Oxidised sulphur theory So2 accounts for fungicidal activity . Sometimes ‘S’ oxidized to So3 is responsible for fungicidal activity. Some reports indicated that thionic acid, an oxidizes derivative of sulphur is important for fungitoxic action. Hydrogen ion concentration in the fungicide solution in water is highly toxic to pathogens .

5. b) Hydrogen sulphide theory H2S from elemental sulphur is responsible for fungicidal action c) Direct action theory Sulphur acts as a hydrogen acceptor in metabolic systems and doing so disturb the normal hydrogenation and hydrogenation reactions in cell. This theory is based on the presumption that sulphur is next to O2 and acts much like O2. Since fungal cells are permeable to O2 and hence the cells are permeable to sulphur also.

6. Some more reports indicates that oxygen and sulphur forms H2S instead of H2O in fermentation reaction and S2 mixed up in the compounds of Koch cycle causing thereby metabolic disturbance. Sulphur fungicides emits sufficient vapour to prevent the growth of fungus spores at a distance of several millimeter from deposits on leaves.

7. 2. Organic sulphur Interaction of Cu ions and dithio carbamates ions forms two complexes. i )Unsaturated positively charged 1:1 complex ii) Saturated charged 1:2 complex Attachment of 1:1 complex of metal and dithiocarbamate ions to enzymes reduces the fungal growth. Dithiocarbamate bearing free hydrogen at the nitrogen can split the hydrogen sulphide with the formation of Isothiocyanate groups. The Isothiocyanate and hydrogen sulphide formed are more antifungal and react’s with free sulphidal group.

8. Mercury fungicides Grouped as inorganic and organic mercury compounds. Highly fungitoxic and were used as seed treatment chemicals against seed borne diseases. Inorganic compound show bactericidal property also. Due to their residual toxicity in soil and plants and their extreme toxicity nature to animal and human beings, the use of mercury fungicides is beings discouraged.

9. Heterocyclic nitrogen compounds Mostly used as foliage and fruit protectants. Some compounds are very effectively used as seed dressers. Benzene compounds Many aromatic compounds have important antimicrobial properties and have been developed as fungicides

10. Quinone fungicides Quinones are naturally present in plants and animals and they exhibit anti microbial activity and some compounds are successfully developed and used in the plant disease control. Organo tin compounds Several other organic compounds tin, lead etc have been developed and successfully used in plant disease control

11. ORGANO PHOSPOROUS Common Name-Edifenphos ( organo phosphate) Trade Name- Hinosan Diseases controlled- Blast Miscellaneous Common Name- Chlorothalonil Trade Name- Daconil , Kawach Diseases controlled- Leaf spots, early and late leaf spot, downy mildews, rusts, anthracnoses Common Name- Dodine Trade Name- Cyprex Diseases controlled- Apple scab and Ascomycotina fungi