Pigeon pea is an important pulse crop and has major role in food and nutritional security because it is a rich source of protein, minerals and vitamins.
The cultivated area and production of pigeonpea have recorded a steady positive growth in the past 50 years, but the mean national productivity has remained unchanged at around 700 kg/ha.
To increase its productivity, breeders are trying to develop suitable varieties with subjective spread, growth, duration, disease and pest resistance under varied agro-climatic growing conditions.
Diseases are a continual problem and control measures must be planned for developing sustained production. Each condition that affects plant growth also affects the disease causing organism and the effectiveness of any control measure.
In general, conditions that favour rapid, lush plant growth also favor disease development. No single control method is effective in every disease situation.
Often a complex of disease interactions defies simple explanations or solutions. Thus to overcome these constraints Integrated disease management (IDM) has been developed for pigeonpea diseases.
“Integrated disease management (IDM) involves reducing losses due to diseases to tolerable levels, allowing agriculture to remain productive and profitable while minimizing health and environmental risks. IDM contributes to long-term sustainability by combining the judicious use of management tools”.
Integrated disease management for pigeonpea diseases includes the following management strategies.
Several cultural practices like field sanitation, soil solarisation through summer ploughing or using polythene sheets, green manuring reduces the wilt inoculums.
- Deep summer ploughing and removal of stubbles reduces the Fusarium population build up.
- Ridge planting (60 cm spacing) of pigeon pea has been advocated for successful cultivation of pigeon pea in North Eastern Plain Zone (UP, Bihar, Jharkhand, and West Bengal) for ensuring better crop stand minimizing the incidence of Phytophthora. Yield increase have been 17-20% in ridge planting over flat bed plantings.
- Intercropping pigeon pea with sorghum is a well demonstrated technology against wilt in Maharashtra.
- Rotation of pigeon pea with sorghum, tobacco or castor every three years is recommended for wilt control.
- Green manuring with Crotolaria juncea decreases incidence of wilt. Soil amendment with neem or castor oil cake is also useful.
- Solarization should be done by covering the soil with transparent polythene sheeting (100 μm thick) for 6-8 weeks during summer (Apri l/May), helps in control of wilt.
- Application of press mud 10 tone/ha after solarization the field with 25μ clear polyethylene film for a month reduced the wilt.
Large number of rhizobacteria and fungi have been used as biocontrol agents. Some of these bacteria, especially fluorescent pseudomonads and Bacillus spp. have considerable potential for the biocontrol of plant pathogens.
These rhizobacteria generally improve plant growth by colonizing the root system and pre-empting the establishment of, or suppressing deleterious rhizosphere microorganisms. The selection of effective strains of particular bacteria is of prime importance for the biocontrol of plant pathogens.
Isolation of bacteria from pathogen suppressive soils may increase the chances of finding effective strains and to get effective strains the isolation of bacteria should be made from the same environment in which they will be used. The ability to colonize roots and resistance against antibiotics are the other parameters to screen for effective strains, like any other soil-borne diseases, the wilt disease of pigeonpea is difficult to control.
Some pesticides and chemicals have been recommended for the management of the disease, but none have been proven to give the desired success in controlling the disease. Pesticides are reported to cause adverse effects on treated soil ecosystem because of their non biodegradable nature and also because they induce resistance in pathogens .
Biological pesticides have the potential to replace or augment conventional plant disease management which makes use of synthetic pesticides. Several studies have demonstrated reduced incidence of diseases in different crops after supplementing the soils with fungal or bacterial antagonists and are as follows.
- The population of F. udum was found to be markedly reduced when the antagonists, Trichoderma (Gliocladium) virens were applied at the rate of 3% (w/w), in the soil.
- Seed dressing with Trichoderma harzianum and T.viride @ 4g/kg seed followed by soil application of 250g/Q FYM) reduces wilt, root rot and anthracnose.
- Seed treatment with metalaxyl @ 3g/kg of seeds in Phytophthora blight prone areas is beneficial.
- Seed treatment Thiram or Captan + Carbendazim (2:1) @ 3g/kg seed reduces wilt and root rot.
- Spraying of Metasystox and Dimethoate @ 0.1% for control of mite the vector of Sterility Mosaic Disease is recommended.
- Seed treatment with the mixture of iprodione 25% + carbendazim 25% (1:1by vol.) at 2 g a.i. kg-1 seed) and Spraying of Mancozeb @ 1kg/ha reduces Alternaria blight.
- Dust captan @ 3 g/ kg of seed. Additionally, spray Bordeaux mixture 5:5:50 or a copper fungicide at 1 kg in 250 litres of water as soon as the anthracnose symptoms appear.
- Spray Chlorothalonil @ 3 g/ litre of water or mancozeb @ 3g/litre of water reduces botrytis grey mold.
Host plant resistance
Host plant resistance is the best option for management of pigeonpea diseases. List of resistant varieties of pigeonpea is:
|Fusarium wilt||AL 1, BDN 2, Birsa Arhar1, DL 82, H 7 6 - 1 1 , H 76-44, H 7 6 - 5 1 , H 76-65, ICP 8863 (Maruti), ICP 9145, ICPL 267, Mukta,|
|Sterility mosaic||Prabhat, Sharda, TT 5, T T 6 Bageshwari, Bahar, DA 1 1 , DA 13, ICPL 86, ICPL 146,ICPL 87051, MA 165, MA166, PDA 2, PDA10, Rampur Rahar|
|Phytophthora blight||Hy 4, ICPL 150, ICPL 288, ICPL 304, KPBR 80-1-4, KPBR 80-2-1 (Field resistant)|
|Cercospora leaf spot||UC 796/1,UC 2113/1, UC 2515/2,UC 2568/1|
|Powdery mildew||ICP 9150, ICP 9177|
|Alternariablight||DA 2, MA 1 2 8 - 1, MA128-2, 20-105 (West Bengal)|
|Dry root rot||ICPLs 86005, 86020,87105, 91028|
|Bacterial leaf spot and Stem canker||ICPs 12807, 12848, 12849,12937, 13051,13116,13148|
|Phoma stem canker||AL 133, AL 136, ICPL 148, ICPL 84018|
|Rust||Blanco, Todo Tempo No.17|
|Phyllody||BDN 5, ICPL 83057, MRG 66|
|Halo blight||GW 3, ICPL 362|
|Phyllosticta leaf spot||EMC, ICPL 1 6 1 , ICPL 269, ICPL 335, Pusa 33,Pusa 85|
|Root-knotDirty root||ICP 11289, ICP 11299, A G S 522, Basant, GAUT 82-75, GAUT 83-23, G A U T 84-22, ICP 12744, PDM1|
Disease resistance has proved useful in controlling many diseases of edible legumes but much more remains to be done in development of multiple disease and pest-resistant cultivars of this crop.
More emphasis should be given to host plant resistance as costs of other control measures that depend heavily on the use of fossil fuel energy and other scarce resources rise.
This method of control requires that researchers have access to a large, variable source of germplasm of different food legumes to use in their breeding programs, along with the availability of recent tools and techniques.
Dr. Smita Puri
Scientist Plant Pathology
Regional Agricultural Research Station, JNKVV, Sagar- 470002 (M.P.)