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2 Pigeonpea diseases and their management


Welcome to the next topic that is diseases of pigeon pea and their management. Pigeon pea is affected by a large number of pathogens and cause significant yield by each of them and the most significant ones were the Wilt of pigeon pea, Sterility Mosaic Phytophthora blight, Alternaria blight, and root rot these are the major diseases of pigeon pea that cause severe loss to this particular crop.

First, let us see the Wilt of pigeon pea. It is caused by a soil borne pathogen known as Fusarium udum. The symptoms of the disease is very easy to identify where the whole plant starts wilting at the initial stage and it becomes completely dry after some time. So infected plants are easily visible from a distance because of the wilt symptoms. The pathogens survive in the soil and survive for a longer period of time. So IPM practices are very important or essential to manage this particular pathogen. The practices include cultural use of resistant varieties as well as biological, as chemicals has not proved effective against his particular pathogen. So cultural practices include three or four years of crop rotation with non host crops or we can also use a mixed cropping system by taking Jowar and Arhar as a cropping model for management of this particular Fusarium wilt disease which must also collect and burn the plant trashes that are left after harvesting. This also help us to reduce the inoculum load because the infected plants Harbor the pathogen inoculum so their collection and burning help us to reduce the initial inoculum in the next season. Resistant varieties are reported from different places and we must go for utilization of these resistant plants which give good control over this particular pathogen. Again biological control has also proved effective. Being a Soil borne pathogen. It is biological control has a good effect on the pathogen and that is why they should be delivered as seed treatment with Trichoderma viride with the rate of 4 gram/kg at a cfu at 106 cfu per gram. So this is a good way of managing the pathogen in soil as it reduces the inoculum in the soil for the next season.

Next important disease of pigeon pea is Sterility mosaic. It is caused by a virus known as sterility mosaic virus. The symptoms appear as mosaic development that is yellow and white mosaic areas on the leaf and this is easy to diagnose by looking into the mosaic symptom on the leaves. The pathogens survive in infected plants and IPM practices includes Cultural, Use of resistant varieties and Chemical methods. So cultural practices the most important ones include destruction of the source of sterility mosaic inoculum on perennial and ratooned pigeon pea. Since it is a virus so the virus survive on this perennial and ratoon pigeon pea plants so, they should be uprooted and they should be thoroughly destroyed. Uprooting of infected plants at an early stage of disease development and destruction them helped us to reduce the source of inoculum. So this is the best practice that is recommended for management of this particular disease. There are some Resistant varieties reported and one should go for adoption of this resistant varieties wherever it is available. Other chemical control includes mostly and a spray application of 0.1% Metasystox because this help us in reducing the vector population in the field. Other acaricides such as Kelthane, Tedion which are also used to kill the insects or ants that carried a pathogen. So these are the most effective control measures that are used for management of the sterility mosaic virus in Pigeonpea.

The next important pathogen is Phytophthora blight it is caused by Phytophthora drechsleri variety cajani. The pathogen here starts developing partially on the plant as some of the branches starts wilting at the very beginning. The whole plant gets wilted in a later stage and we can see that the infected stems are becoming browning and they are drying up at the bottom where the pathogen is having a development. So pathogen survive in soil and infected plants so, management of the pathogen becomes very important as it survives in soil and infected plants. The IPM practices that includes Cultural, Use of Resistant varieties and Chemical methods for its successful management. Cultural methods include good drainage in the field and the plants should be protected from stem injury because these are the two conditions that favor the pathogen development in the host. So a good drainage system in the field along with avoidance of stem injury may lead to less establishment of the pathogen on the field. Ridge sowing of pigeon pea gives very good control. So the ridges uplift the height of the plants and the pathogen in the trenches may not reach the stem because of the height and mulching on the trenches are also recommended because it helps in rain splash dispersal of the pathogen from the trenches to the ridges. Then there are certain resistant varieties reported for this particular pathogen so use of resistant varieties should be adopted and the chemicals that has been proven effective against this pathogen is Ridomil MZ which is a combination of Metalayxl and mancozeb. So this should be applied for management of the pathogens under field conditions.

The next important disease is Alternaria leaf spot and it is caused by Alternaria alternata. The pathogens developed as brown spot and within the spot there are concentric rings that are developed within the region. The pathogen survived in seed, soil and debris. So management of the pathogen through managing this soil debris and seeds are helpful. So IPM practices mostly include Cultural and Chemical methods. We must select a field away from a perennial pigeon pea as the pathogen survives on those perennial pigeon pea plants. So the site selection is very important for this particular pathogens the inoculum may reach to the fresh crop from this perennial plants. We should also select seeds from healthy crops because the pathogen is also seed borne so by adopting these practices we can reduce the chance of development of this disease on in a fresh crop. Chemicals include Maneb at the rate of 3 gram/ litre which has proved to be very very effective and mancozeb at the rate of 1 kg per hectare is also recommended for management of the particular disease. There is no resistant cultivar recommended for this particular disease so far so there is mostly the chemical and cultural method that are used for successful management of this particular pathogen.

The next important pathogen is Rhizoctonia bataticola. It causes Root rot in pigeon pea. The pigeon pea plants when they are uprooted their roots can be seen to be half dry rotting and this is a common indication that the plants are affected by the root rot pathogen Rhizoctonia bataticola and the whole plants get wilted thereafter. The pathogen is a soil borne pathogen and it survives mostly in the soil in the form of sclerotia.

So the IPM practices include Cultural, Chemical and Biological. Cultural practices includes early sowing or early maturing cultivars which help escaping the dry root rot pathogen. Crop rotation with non-host also reduces the population of sclerotia that are present in the soil and deep ploughing followed by removal of infected debris has proven effective in reducing the multiplication rate of this sclerotium under the field condition.

Again Tillage and Residue management has proved effective in lowering down the severity of the root rot maintaining good soil moisture is another aspect that needs attention throughout the crop growing season. Chemical methods include seed treatment with Carbondazim, Thiophanate and Vitavax which are helpful in reduction of dry root rot in Pigeonpea. Significantly, Carbondazim, Etaconazole are also effective in management of this particular pathogen. Biological methods include application of antagonists such as Trichoderma viridi, Pseudomonas fluorescens and Bacillus subtilis. They all improve lowering down the inoculum level of the soil and thereby we can have successful management of this pathogen through lowering down the initial inoculum. So these are some of the important pathogens of pigeon pea that causes these particular diseases and we need to have a very very focused attention for management of these particular diseases to have a good control over these diseases.

Thank you.



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