4 Crucifer diseases and their management
Transcript
Hello! Today we are going to talk about important diseases of some cruciferous plants. In the last talk we talked about the important diseases of tomato and today we are going to talk about the cruciferous diseases which is not crop specific rather same pathogen may have an impact on different cruciferous plants. So the most important diseases are Black Rot, Black Leg, Club Root, Alternatia Leaf Spot and White Rust. These are the most important pathogens or diseases that leads to severe losses in cruciferous plants. The first one is Black rot which is caused by a bacterium Xanthomonas campestris pv. campestris.
So this is a pathogen which can be identified by development of a symptom a v-shaped symptom and it progresses from the margin towards the downward and towards the center and later on this yellow v-shaped region turn brown in color under severe condition and it can slowly migrate to the central stem portion and it can cause rotting in the stem region as well. So this is an important disease of many cruciferous plants and the pathogens survive in seed or infested crop residue in soil. So this is how we have to tackle this pathogen by managing this inoculum at these levels. So the IPM practices include Cultural and Chemical once. Cultural practices include use of disease free seed which is considered to be the most important because it is seed and soil borne so disease free seed help us in reducing the inoculum or it is establishment of the pathogen in new fields. Clean sheet along with disinfested containers and planting material they all combine to help us to manage this pathogen in the field condition. Planting should be done where soil drain is good. This is another criteria that needs to be paid attention because a good soil drainage will help us in lesser establishment of the pathogen on the new host. Another important practice is Fall Tillage which basically helps us in composing the infested residue. So Fall Tillage is considered useful because it helped us to bury the infested crop debris and at the same time the bacteria will be buried deep into the soil and they will be destroyed because of this practice. We can also go for crop rotation out of crucifer crops for at least 3 years. So this also helped us in bringing down the inoculum level to a great extent in the field. Chemical sprays includes fixed copper which have bactericides properties and although there is not much success but at least by application of this particular fixed copper bactericides may help reduce the spread of the bacteria from one plant to another.
The next important disease is Black leg which is caused by Phoma Lingum. From the name itself we can see that the bottom or the stem portion is affected and they become black in color and that is why the name of the disease is known as black leg. The disease can also be seen on foliages and the symptom appears here is a light color center followed by a dark margin.
The pathogens survive in soil and crop debris and these are the two important areas that needs to be targeted for management of this particular pathogen. So the IPM practices include Cultural, use of Resistant varieties as well as use of chemicals. Use of disease free seeds and transplants this is a very important criteria because the plants survive on either crop debris or in soil. A four year crop rotation without cruciferous plants will help us in reducing the disease severity in the next or fresh crop.
Similarly, Fall ploughing can reduce the over-wintering pathogen population as they get buried deep into the soil and we should also avoid poorly drained fields or rather we should have a good drainage facility of the soil under field condition. We can also go for resistant varieties which are available in certain areas and we should adopt locally recommended resistant varieties for successful management of the pathogen. Chemicals include Rovral which is a highly recommended chemical for Black Leg infection and thereby we can reduce the disease development on pathogen after application of this particular chemical.
The next important disease is Club root of cruciferous plants that is caused by Plasmadiophora brassicae. Here you can see that the bottom or the root of the cruciferous plants become tumorized and they form club shaped tumors and this is a very difficult pathogen to manage and that is why its establishment in the new field should be avoided by taking care. The pathogen basically survive in soil and for a long period of time. So the IPM practices that include cultural along with it chemicals. So cultural practices as I mentioned earlier must include prevention of its establishment in the new field. So we should take care of this particular aspect so that a new field should not be infestation with Plasmodiophora brassicae.
That is why we should go for growing disease-free transplants this is a very very healthy practice and a seven year crop rotation without cruciferous plants is recommended for eliminating this pathogen from field. We can also go for adjustment of field soil acidity to a range of pH 7.2 to 7.5 because in acidic conditions favored pathogen so we can raise the pH to a level of 7.2 to 7.5 which have a suppressive effect on the pathogen. Control of seedbed plantings may be maintained by growing plants in well-drained and uninfected area. So this is another important practice that needs to be adopted where seed bed should be well-drained and it should be in an uninfected area. So these cultural practices help us in reducing the pathogen development on the host or its establishment on a new field. The chemicals include Terrachlor in transplant water that reduces the incidence and severity of the disease. So this is an effective chemical that is recommended for this particular pathogen once it is applied then it is having a good control over the pathogen.
The next disease is Alternaria Leaf Spot of cruciferous. It is caused by at least two alternaria species – Alternaria brassicae and Alternaria Bracy sekolah. So and the pathogen disease can be easily diagnosed with brown spots that are having concentric circles within it. So this is a very very easy way of diagnosing the disease by looking into the concentric rings on the infected spots. The pathogens survived in infected seed, transplants and infested crop residue. So this management of these seeds, transplants and crop residue will help us in lowering the disease severity under field conditions. There are different IPM practices recommended among them Cultural, Chemical and use of resistant varieties are the most widely adopted. Cultural practices include disease-free plant material which is the foremost and prior most important method of adopting for management of the disease. Avoiding field with a history of disease for at least three to four years that is crop rotation for at least three to four years is essential for management of this particular Alternaria Leaf Spot disease. Some of the chemicals are effective which includes Mancozeb, Benomyl and they give good control over the pathogen for under field condition. Some of the resistant varieties are partially available although the complete resistance is not available currently especially for crop like mustards. So we have to go for partially resistant sources for management of this disease. So we can integrate these different tactics for management of the disease under field condition despite having no or highly resistant cultivars for some cruciferous plants.
The next one is White rust of cruciferous. It is caused by Albugo candida and the pathogen developed just like development of rust pustules, but the color of the pustules are white in nature. So looking at this white pustules one can very easily identify the disease under field conditions. The pathogen survive in soil mostly in the form of oospores and therefore the IPM practices includes Cultural, Chemical and Use of resistant varieties. Cultural practices help us in reducing the pathogen population in field through crop rotation without cruciferous crops for at least 3 to 4 years. So this is again a very healthy practice rotating crops without cruciferous plants for at least three to four years which helped us in reducing the inoculum of the pathogen. Fall ploughing is another important practice that helped us to bury the inoculum into deep into the soil and thereby loss of its viability in the long run. A good weed control measure is also recommended because the pathogen can be harbored by some of the related weed species and that is why its control of weed in the field is very important. Chemical application include application of Metalaxyxl along with mancozeb which gives good control over the pathogen. Some of the resistant varieties are partially resistant to this particular pathogen so they should be adopted although there is no highly resistant varieties reported in some cruciferous plants including mustard at the moment. So these are some of the important management criteria that needs to be taken care of while managing the white trust pathogen and we have seen how this different diseases cause loss in cruciferous plants. They are difficult to control because we don’t have proper resistant sources against most of these pathogens. So cultural practices along with the available chemicals they are the sole basis of management of these particular diseases that cause severe losses in some of the cruciferous plants.
Thank you.
