3 Tomato diseases and their management

Transcript

Welcome to the third talk of this week i.e Important diseases of tomato and their management. In the previous talk we talked about the important diseases of pigeon pea and their management. The tomato is also affected by a variety of pathogens causing different types of diseases and the most important ones are Damping off, Late blight, Septoria leaf spot, Bacterial Wilt, Leaf curl and Tomato spotted wilt. These are some of the most important diseases of tomato that occur globally and cause severe loss to the crop.

Let us start with Damping off of tomato. It is caused by a number of pathogens including Pythium and Rhizoctonia species. The pathogen mostly attacked the young seedlings and the seedlings within a very short time their stem gets affected and they topple down. It is mostly a nursery disease where it is very commonly observed in most of the tomato growing areas. The pathogen is Soil, Seed and Water borne. So it is important to look into this aspect of their survival so that we can have a proper management of this particular disease. There are important Cultural and Chemical methods that needs to be considered for management of this particular disease. The Cultural practices include – Burning of the trash on the surface then, Providing better drainage, Forming raised beds and Thin sowing. These are very very useful and economical method of suppression of the disease. Since this disease is favored by highly moist nurseries so raised bed is one of the aspect that needs to be considered thoroughly along with good drainage. The chemical methods that include seed treatment with 3gram Thiram or 4gram Trichoderma viride formulation along with 6 gram Metalaxyl per kg of seed is recommended for management of this particular disease. We can also drench the soil with 1% Bordeaux mixture or Captan at a rate of 2gram/ liter or even we can go for application of Metalaxyl at eight to ten days intervals until the ceilings are ready for transplanting. Once the seedlings grow into a definite size the pathogen infection starts lowering down. So early protection is very important for this pathogen to manage the seedlings from these particular disease.

The next important pathogen is the Phytophthora infestans which cause Late blight in tomato. Just like potato Late blight here also you can see their blighted leaves and these are distinct from a far distance and the pathogen also infect the fruits and that is how it becomes more severe. The pathogen survives as Oospores in soil and as Mycelium in the fruits. So important IPM Practices include Cultural practice, Application of fungicides, Use of resistant cultivars and Bio Control agents. So Cultural practices which include Weed free potato or tomato fields because if the field is either cultivated earlier by potato or tomato the disease may Harbor in the same field. The tomato should be grown on high ridges that also helps in reducing the pathogen in devastation. Mulching between rows is another practice which needs to be done for suppression of or lowering down disease severity from in the field. Application of fungicide include Ridomil, Blitox. These fungicides has proven to be given very effective control over the pathogen. There is no immune cultivars of tomato either reported from different under growing varieties but, there are partial resistant sources are available and that needs to be utilized if available locally. Biological control includes Seed treatment and foliar application of certain Biocontrol agents like Bacillus cereus, Pseudomonas fluorescens and they are reported to have good control over this particular disease.

The next important pathogen is Ralstonia solanacearum, it is a bacterial pathogen and which cause bacterial wilt in tomato. The field can be seen blighted or the wilted plant can be seen from a distance where the initially the plant remain wilted but held a green in color later on they become completely brown and wilted. The pathogen survives through wounds soil and other implements that are used in agricultural practices and it is also soil borne in nature and that is why these things needs to be taken care of while going for management of this particular pathogen. IPM practices include Cultural and Use of resistant varieties and no chemical has proved effective in management of this particular bacterial pathogen so it is not recommended any chemical for management of this disease. Cultural practices include because the pathogen is a persistent in soil for a longer period of time, it is very difficult to control and that is why Crop rotation is single-handedly taking care of this pathogen and it needs to be done alternatively with Cruciferous vegetables as it is a wide host ranged pathogens Ralstonia solanacearum, it infects more than one solanaceous crop plants. So that is why crop rotation with Cruciferous vegetables help us in education of the initial inoculum of this particular bacterial pathogen for the next seasons. There is no commercial resistant varieties are available so far as well and that is why the challenge is managed this pathogen successfully we have to depend on the most likely on the Cultural practices which include Crop rotation.

Then the next important pathogen is Leaf curl of tomato. It is caused by a tomato leaf curl virus. The disease is very easy to detect under field conditions as the leaf rolls upward and inward and the slowly all the leaves from the particular plant may get affected and they me get curled. The pathogen is a virus and that is why it is mostly it is survived in the infected plants and therefore the IPM practices include Cultural, Use of resistant varieties and Chemical. And Cultural practices include there should be roughing out and destruction of the infected plants. So this is the most important cultural practice whenever we see a infected plant it should be roughed out and it should be destroyed within no short time. The use of resistant varieties is another method of managing this disease. Resistant varieties are reported in many cases and therefore we must adopt resistant varieties for management of this leaf curl virus. Some of the chemicals are used basically to manage the vector and this includes Dimethoate and Carbofuran along with Phorate granules, they are applied as soil application and they are helpful in reducing the vector for management of this particular disease.

The next important tomato disease is Tomato Spotted wilt disease. It is again caused by another pathogen which is virus that is tomato spotted wilt virus. Here you can see that the tomato plants are getting affected it is dry and it is brown developed of the spores along with the leaves. Finally, the plants get blighted then wilt it at the end of the season. The pathogen survives mostly in the collateral hosts along with the infected plants. So management of the collateral host is very very important in this context. The IPM practices include Cultural and Chemical methods. The Cultural methods again include roughing up of the infected plants along with their destruction and then removal of collateral host is very important. Chemical control includes control of the Thrips which are the vectors of this particular virus and application of insecticides can help in reduction of the Thrip population so that we can have a good control over the virus. Carbofuran granules in the nursery and in the main field ten days after transportation gives good protection. So vector management is the only way of chemical method to may reduce the disease severity along with cultural methods like roughing out of infected and volunteer plants as well as their destruction under field condition. So these are some of the most important tomato diseases that are reported globally to have affected by these pathogens and the most damages are caused in tomato by these pathogens and we need to take care of these pathogens for a successful production of tomato under field condition.

Thank you.