4 Groundnut diseases and their management

Transcript

Hello, welcome to the fourth talk of this week i.e important diseases of Groundnut and their management. In the last class we talked about important diseases of potato and their management and today we are going to talk about important diseases of groundnut and their management. There are some important disease of groundnut and the most important of them all are:

• Early and late leaf spot which are also known as (Tikka) diseases.
• Collar or Stem rot of groundnut
• Rust
• Anthracnose

These are some of the important Groundnut diseases and we need to understand its mode of survival and how to manage them. Leaf spot diseases include two diseases one is early leaf spot. It is caused by (Cercospora arachidicola) and Late leaf spot it is caused by (Phaeoisariopsis personatum). Both the disease develop slightly different symptom and they are easy to detect in a way that in the Early leaf spot the colour of the spots are light brown and they are normally surrounded by a yellow halo around the brown zone. Whereas, the Late leaf spot the colour of the spots are metallic black and they are not surrounded by yellow halo at the initial stage. So, both the diseases are easy to detect in the early stages of their development.

The pathogens survive in soil and they are also air-borne in nature so, IPM practices include Cultural, Use of resistant varieties as well as Chemical methods. Cultural practices include – since disease is triggered by deficiency of mangnesium in the soil, so proper magnesium management in soil is very important. Then we should also destroy the plant debris from the previous crops which harbor the pathogen. Crop-rotation with non host and deep plowing of the previous crop residues are also helpful. Weed hosts should be removed where ever it is applicable. Then there are some resistant varieties available and one should go for use of this resistant varieties where disease is a problem. Chemical spray includes carbendazim, mancozeb and chlorothalonil. All these chemical has given good effective control over the disease. Foliar application of aqueous Neem leaf extract at 2 weeks interval 3 times starting from 4 weeks after planting. This is another natural way of managing the disease with the natural products.

The next important disease is Stem rot of groundnut which is caused by (Sclerotium rolfsii).The pathogen is soil born in nature so cultural practices here again it becomes very important to manage the pathogen.

So IPM Practices include Cultural, Use of Resistant varieties, Chemical management and Biological management. Cultural practices include destruction of plant debris from previous crop because it harbor’s the initial inoculum. So destruction of the crop debris from previous crop has proved very important. Crop rotation with non host particularly with cereals because this is a pathogen which is polyphasique in nature and it has more than 500 host range. So that is why it is advisable that crop rotation should be done with non host like cereal crops where the pathogen is not a problem. Along with deep summer plowing help to reduce the initial inoculum of the pathogen.

Flooding the field for two weeks is again recommended and this helps us to decompose the Sclerotia that are present on the field. Solar heat treatment of the soil is also important and it as proved effective through raising the soil temperature and at high temperature the Sclerotia gets destroyed. Although, there is no resistant variety available or recommended for this particular pathogen then we must go for any resistance sources which are even partially effective.

Chemical management include seed treatment with thiram and Carbendazim. This has been recommended but Cultural practices has proved to be better than the chemical management.

Biological management include seed treatment with Trichoderma viride, Trichoderma harizanum at the rate of 4g/kg seed and soil applicatiion of Trichoderma viride and Trichoderma harizanum at the rate of 25 to 62 kg/hec is preferred with organic amendments in the form of castor cake, neem cake or mustard cake at the rate of 500kg/ha.

So biological control along with organic amendment has become a very very important tool in management of this particular pathogen Sclerotium rolfsii.

The next disease is Rust and it is caused by (Puccinia arachidis). The disease is mostly air[1]borne. So its IPM practices include Cultural, Use of resistant cultivars and Chemical management. Cultural practices include destruction of volunteer wheat plants. This is very important because this is the volunteer wheat plants, wheat plants harbor the pathogen and they provide inoculum for the fresh crop. Here again a community effort is required to tackle this particular problem. So, resistant cultivars where ever it is available according suitability to local conditions they should be adopted and they should be used for growing. Chemical management include spraying of chlorothalonil and mancozeb alongwith Hexaconazole or propiconazole. This all prove effective in reducing the disease severity. Foliar application of aqueous neem leaf extract at the rate of 2-5% is useful and economic for the control of rust. So here again we have a natural product in the form of ne extract and it should be used for management of the pathogen. The next disease is Anthracnose of groundnut and it s caused by two different species Colletotrichum dematium i Colletotrichum caps. The seed and soil are the main source of the survival of pathogen whereas the air-borne nature is also observed in the particular pathogen. The IPM practices include Cultural, Use of resistant varieties and Chemical management. So cultural control measure include use of disease free seeds. Being seed borne in nature this is the most important criteria to avoid disease development. Debris of disease crop should be collected and burnt and because these are the prior source for soil inoculum. So these are the important cultural practices that needs to be handled with utmost care. Resistant variety are available under different climatic conditions so we should go for utilization of these resistant sources. Chemical management include seed treatment with copper Oxychloride or Mancozeb or even we can use Carbendazim and which all are proved effective in controlling the anthracnose disease of groundnut. So we could see that these are major pathogens of groundnut and they all causes severe lose to the crop every year annually in a worldwide and we have seen that what are the cultural methods that are need to be adopted for management of this disease along with the effective fungicide that are recommended for management of this different pathogens.

Thank You.