Chemotherapy and Fungicides

                                               Chemotherapy and Fungicides

Chemotherapy refers to the chemical treatment which is applied to eradicate the pathogens from tissues of the diseases plant and thus curing it. Chemical treatment act as a chemical defence mechanism either by destroying the pathogen or by inducing temporary resistance.

 

Tropical and systemic fungisides :-

       The chemical which are use to kill pathogenic fungus are called fungisides. Fungisides maybe of 2 types-

(a) Tropical fungisides and

(b) Systemic fungisides.

 

       The 3 tropical fungisides are-

i) Bordeaux mixture, ii) Ferric dimethyl-dithiocarbmate, iii) Tetrachloro-ρ-benzoquinone.

      

       The 3 systemic fungisides are-

i) Benomyl, ii) Thiabendazole, iii) Bavistin.

 

Advantages and disadvantages of systematic fungiside :-

       A systematic fungiside is one which is taken and translocated with in the plant and later become fungi toxic. On the basis of function it resembles to antibiotic. The systemic fungisides may be spread on the leaves or may be given to the soil and thus they are absorbed by the leaves and also by the roots.

Advantage :-

(i) The systemic fungisides may be spread on the leaves or may be given to the soil because it is not harmful to the plants. Thus exposure of systemic fungisides does not reduce the plant growth or the plant yield.

(ii) Systemic fungisides may be absorbed with in plant through their roots and leaves. Thus use of systemic fungisides is very easy and need not require so much skill for its use.

(iii) The uptake of systemic fungisides is passive. It is absorbed alo0ng with the absorption water.

(iv) The systemic fungisides act where the fungus is present and is also develop a temporary resistant power.

Disadvantages :-

(i) It is costly in compare to other fungisides.

(ii) After absorption it should come into the stream of sap; so that it may be spread through out the body and interfere in other physiological process of plant.

(iii) When a systemic fungisides is applied to root, they become active and passes intercellularly into xylem vessel in which it is swept along by the saps stream towards the foliage. When applied to foliage the fungiside gets into the xylem and spreads to distral parts of the leaves. But not in the opposite direction in both cases.

 

Reason behind the preference of biofungicide:-

       For control of plant diseases various chemical compounds are used such chemical compounds may cause side effects to the host and sometimes cause toxicity to the host plants. To overcome this problem pathologists developed a fungisides which is biological in origin and name as biofungiside. Biofungisides are only toxic to other pathogen but not to the plant. They also have no side effects on physiological process of plant. Thus biofungisides are always favoured. On common biofungiside is- Agrobacterium radiobacter                                                                                                                    k84, showed activity against crown gall. Another biofungiside is Trichoderma viridis. It acts as fungiside as well as insecticide.