1 Chickpea diseases and their management

Transcript

Welcome to the fourth week of the course. In this week we will be talking about vegetable diseases along with cruciferous diseases and their management practices. So first of all we’ll be talking about Chickpea diseases and their field crops. Chickpea diseases are affected by Wilt, Dry root rot, Ascochyta blight, Blight grey mold and Sclerotinia blight. These diseases are considered to be most important for chickpea diseases. First, we will take up the example of Wilt of chickpea that is caused by a fungus Fusarium oxysporum former specialist ciceris. The disease is very easy to diagnose where you can see that plants get wilted and if you just see the root and stems portion of the plant just split open and then you will see that there is browning in the vascular tissues of the plant. This indicates that that the pathogen is nothing but Fusarium oxysporum. The pathogen is soil borne in nature and that is why IPM practices will include Cultural, Chemical, Use of resistant cultivars as well as Biological. Cultural measures includes Crop rotation which is considered to be the most important cultural practice because this is a soil borne pathogen and it needs a crop rotation for at least three to four years for minimizing the crop loss in the subsequent years. Late sowing should be avoided because it favors the disease condition. Deep planting around 10 centimeter deep in light soil is important for minimizing the crop loss by this particular disease. Chemical controls will include seed treatment with carbendezim at a rate of 2.5gram/ kg of seed or we can combine Carboxin with Thiram 1:2 ratio at the rate of 3 gram/kg of seed is proved again very effective in management of this particular pathogen. There are certain Resistant varieties recommended for this particular pathogen and one should go for adoption of resistant varieties for chickpea cultivation. Biological control has some effect on lowering the initial inoculum from the soil which include application of antagonists such as Trichoderma harzianum and Trichoderma viride. They are able to suppress the initial inoculum in the soil.

The next disease is Dry root rot and it is caused by another sclerotial fungal pathogen Rhizoctonia bataticola. The pathogens survive in soil and it is very easy to diagnose that you can see here the roots are drying up and this disease is seen in warm and dry conditions when the soil is having less moisture in the field. So the IPM practices includes Cultural, Chemical and Biological as there is no resistance source identified to the resistant against these disease in chickpea so far. So early sowing and early maturing chickpea cultivars can be used for escaping the dry root rot disease in chickpea. One can also go for crop rotation with non host and because it reduces the population of scleratia in the soil followed by deep plowing and removal of infected debris which basically help in lowering the multiplication of the scleratia that are survived in the soil. Tillage and residue management can also reduce the disease severity of die root rot in subsequent seasons. Maintain good soil moisture throughout the crop growth because it is observed that maintaining good soil moisture adequately at different growth stage of the crop help us to lower down the inoculum level in the soil. Some of the chemicals has proved effective in managing this particular pathogen which includes seed treatment with Carbendazim and Thiophanate methyl along with vitavax. This has been shown reduction in Dry root rot development in the field condition. Then Carbendazim Etaconazole can be also used as seed treatment along with soil drenching. So these are the effective chemicals has been reported in management of this particular disease under field condition. Biological control agents has also proved to be effective in managing this disease. Biocontrol agents include Trichoderma viride, Pseudomonas fluorescens, Bacillus subtilis. They can be used either alone or they can also be combined and applied to the field where dry root rot is prevailing and thereby we can reduce the disease severity by the Dry root rot pathogen.

Next is Ascochyta blight, it is caused by Ascochyta rabiei. The field is distinctly observed from a distance where blighted regions are visible in fields where disease is very severe. When examined the plants individually you can see that blighted leaves and blighted pods have dotted the fungal contents on the leaf surface as well as under pods and these characteristic symptoms are easy to identify the plant pathogen. The pathogens survive in seed, soil and plant debris. So adequate care should be taken to remove the initial inoculum from these sources. So IPM practices includes Cultural, Use of resistant varieties as well as Chemical methods. Cultural methods are adopted to remove the initial inoculum from seed, soil and plant debris and that is why one should go for use of planting only healthy seed. That is the foremost requirement for management of this particular pathogen. It should be followed by at least three year of crop rotation which will help in minimizing the initial load from the infected field. Plant varieties which are either resistant or tolerant has been identified in some areas and appropriate varieties should be selected for growing of the crop. Some of the chemicals are also important for management of this particular pathogen which includes Thiram and Carbendazim which can be used at the rate of 2.5 gram/kg of seed. So these chemicals when we apply on seed are helpful in managing the pathogen development and these same chemicals may also be used particularly Carbendazim for foliar spray for management of the pathogen.

Next is Botrytis grey mold and it is caused by another fungus known as Botrytis cineria. The symptoms of the pathogen can be disease can be easily observed under field condition where the fungal growth can be seen on the infected pods and new leaves and even on the stems where grey color of mycelial growth are visible and if the disease becomes severe then the infection which starts from the tip of the plants mostly progress towards downward and it is very clearly it can be detected under field condition by looking at the brown mycelial growth on different parts of the above-ground parts. The pathogens survived mostly in infected seed, infected crop debris, as sclerotia in the soil or on alternate host. So these are the primary source where the pathogens survive and this source needs to be taken care of for reducing the initial inoculum.

So the IPM practices that include Cultural and Chemical should be adopted for management of this pathogen. We should go for planting of the crop late at least first fortnight of November for avoiding the pathogen. The disease can be prevented by using disease-free seed and applying of fungicide as seed dressing. So these are the other two recommended practice that use of clean or disease-free seed and seed treatment with fungicides help in reduce the disease severity. Other cultural management practices that includes lower seeding rates and wider row spacing this help us to modify the canopy of the chickpea crop and this modified canopy help in suppressing the disease development in chickpea under field conditions. Crops when we use less seed per area then the crop canopy will be more open and dry out quicker following the moist condition and this condition is not favorable for the pathogen to develop and that is why we can have a good control over the pathogen by adopting such practices. So chemical spray with carbendazim has proved effective and it should be used at a rate of 0.2% for management of the Botrytis grey mold.

The next one is Sclerotinia blight. It is caused by another fungus that is Sclerotinia sclerotiorum where all above ground part is affected by the crop and by the pathogen and we can see that the pathogen develop white cottony growth on different parts where it infects. There later on the pathogen developed dark black colored sclerotia which are visible on the surface of the plant stem or on infected parts. So this is again very easy to diagnose under field conditions by looking at the pathogen on the plant surface. The pathogens survive in soil, infected plant parts or debris for a longer period of time and that is why cultural management of this practice is proved to be the most effective one. Other then IPM practices include along with Cultural, Use of resistant varieties and Use of certain effective chemicals. So cultural practices include the disease plants should be allowed to stand in the field but should be destroyed and burning. So destruction of crop of standing infected plants along with debris is the most important and highly recommended practice for the suppression of the plant disease. Deep summer ploughing help in burrowing the sclerotia that are produced on plant debris. So this is another practice that help us to decompose the inoculum in the form of sclerotia by deep slumber ploughing. Again use of healthy seeds free from sclerotia, this is also important if we take clean seed healthy seed without infestation of sclerotia we can have a good control over this pathogen. Some of the varieties are reported to be resistant and this reported resistant varieties should be used for management of this particular pathogen. The chemicals that are effective in management of the pathogen include Brassical and Captan and they can be used at the rate of 10 kg/hectare for successful management of this particular pathogen. So with this we have seen some of the most important pathogens of chickpea and we have also come across the control measures that can be adopted by adopting them successfully we can reduce the loss caused by this particular pathogens and we can have a successful chickpea growth for the season.

Thank you.