Biological agents against plant pathogens

  • Biological agents against plant pathogens
  • Biological agents against plant pathogens
  • Biological agents against plant pathogens

Biological agents against plant pathogens

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Arbuscular Mycorrhizal Fungi (AMF)

Inoculation with AMF at the time of planting in the nursery or main filed improves the growth and tolerance of crop against root pathogens, particularly Phytophthora, Pythium, Rhizoctonia and root nematodes of black pepper, cardamom, ginger, turmeric, cowpea, upland rice and transplanted vegetables.

On-farm production of Trichoderma

Bio-control of soil borne plant pathogens involves mass introduction of antagonistic microorganisms in the soil. Trichoderma spp. Is a group of broad-spectrum antagonists subjected to detailed studies for their potential as bio-control agents. They are effective against the foot rot of pepper (T. viride, T. longibrachiatum), rhizome rot of cardamom (T. longibrachiatum, T. virens) and ginger (T. viride). A mixture of neem cake-cow dung mixture is used as food base for Trichoderma spp.

Dry neem cake and cow dung are to be powdered and mixed at 1:9 ratio to get a coarse texture and then moistened by sprinkling water. Add the commercial preparation of Trichoderma spp. (available I polythene packets) @ 1-2 kg per 100 kg of neem cake-cow dung mixture. After thoroughly mixing, cover it with a perforated polythene sheet or ordinary newspaper and keep it in shade for 4-5 days for multiplication. Again, mix well and keep for three more days for further multiplication. This preparation is ready for incorporation in the soil. Cow dung alone can also be used as the food base; but, since neem cake is found to be a better substrate, a mixture of the two is found better than using cow dung alone. If cow dung alone is used, mixing has to be done at 5 days interval and it will be ready for use only on the 15th day. This Trichoderma incorporated neem cake-cow dung mixture can be used in the potting mixture in nursery beds and in the field.; i.e. wherever cow dung is used as a manure.

For the management of foot rot of black the above-mentioned mixture of Trichoderma neem cake cow dung can be applied @ 2.5 kg per vine. The mother culture in liquid formulation can be incorporated with sterilized coir pith compost @11 per 20 kg and apply @ 1 kg per wine as above.

Prophylactic application of Trichoderma is effective for the management of sheath blight of rice. T. viride as Seed treatment (10 g per kg seed) + Soil application (2.5 kg/ha) one week after transplanting + Foliar spray (10 g/l) after one month is effective for the management of sheath blight of rice under upland condition. Seed treatment can be recommended for submerged rice.

Pseudomonas fluorescens

Pseudomonas fluorescens are a group of bacteria very effective against disease incited by species of Phytophthora, Pythium, Phizoctonia, Fusarium, Colletotrichum, Ralstonia and Xanthomonas in various crop plants in the nursery as well as in the main filed.

Isolates of Pseudomonas fluorescens have been developed by the Kerala Agricultural University for the disease management and growth promotion of crop plants. This is found highly effective for the management of foot rot and fungal pollu of black pepper, sheath blight and bacterial leaf blight of paddy, bacterial leaf spot and Phytophthra infestation in betel vine, bacterial wilt of solanaceous vegetables, bacterial leaf blight of anthurium, Colletotrichum and Phytophthora infestation in vanilla and rhizome rot of ginger. The organism significantly improves the growth and biomass production of crop plants.

Application of Pseudomonas fluorescens @ 10 g formulation mixed with 2 kg of well decomposed farmyard manure or compost can be applied in the basin of pepper wine in the field for the control foot root of black pepper.

PGPR mix II

It is a consortium of highly compatible rhizobacteria having broad spectrum of inhibitory property with different mechanisms. Bacteria promote plant growth and have better ability to multiply and persist in varying soil conditions. Effective against all fungal and bacterial plant pathogens of crop plants. Application method and schedule are similar to that of P. fluoresces. If not compatible, apply Trichoderma as enriched organic manure and Pseudomonas fluorescens separately as spray and drench.

Method of application

The time and the frequency of application vary depending on the crops. The application may be repeated based on the intensity of the disease incidence. The talc-based formulation at 1-2 per cent level may be used for soil drenching and spraying. For transplanted crop, seedlings/cuttings are treated with Pseudomonas fluorescens culture by dipping the root/tip of cuttings in slurry of Pseudomonas fluorescens (250 g in 750 ml) for 20 min.

For seed treatment on paddy, the talc-based culture may be added to the water used for sprouting @ 10 g per kg of seed. For transplanted crop, root dip treatment at the time of transplanting, followed by a spray30 days after transplanting can be recommended.

For black pepper, the nursery plants can be drenched immediately after planting, followed by one or two sprays of Pseudomonas fluorescens depending on the intensity of disease. For managing foot rot of pepper in the main field, drenching the base of the wine and spraying the plant with Pseudomonas fluorescens culture @ 10-20 g per liter at the onset of monsoon can be practiced. A second spray may be given, if necessary, during the mid-monsoon period.

Chemical fertilizers and plant protection chemicals should not be used along with bio control agents.


Tolerance limit of biofertilizers

In case of Rhizobium, Azotobacter, Azospirillium and Phosphate Solubilizing Bacteria, the total viable count shall not be less than 1 x 107 CFU per g of carrier material in the form of powder or granules or 5 x 107 CFU per ml in case of liquid formulations during the entire period of shelf life.

In case of Mycorrhizal Biofertilizers, the viable propagules shall not be less than 80 per g.