Gummy Stem Blight or Blackrot [GSB] on Cucurbit Crops! How To Manage?
Gummy Stem Blight [GSB] has become one of the important and deadly disease of cucurbit crops. This disease is infecting cucumber, ridge gourd, bottle gourd, watermelon, muskmelon crops. Under favourable conditions for disease development, gummy stem blight [GSB] can infect at stage of the plant growth and crop stages. GSB can infect seedlings to fruit stage.
Why the name gummy stem blight [GSB]?
The plants of the infected crop show the symptoms of oozing out the gummy substance from the stems, sometimes from the growing the branches with splitting. The infected plants show different symptoms may be based on the intensity of infection. Gummy stem blight is so deadly that it can spread very fast and can cause significant crop damage and loss.
What causes Gummy Stem Blight?
The fungus Didymella bryoniae is the culprit and causal organism of Gummy stem blight disease. This fungus Didymella bryoniae have ability to survive on seeds, weeds and the debris of previous crops which would be infected. More importantly the fungus is more active and aggressive in moist and cooler weather conditions.
How to identify the disease? Symptoms!
- Gummy stem blight is visible only on the over ground plant parts of cucurbits like leaves, petioles, vines, stems, peduncles, fruits and even seeds and tendrils
- Water-soaked leaf spots start as initial symptoms and many times very nearer to the margins where margins show chlorosis.
- Infections on the young seedlings is observed as light to dark brown spots on the seed cotyledons.
- The brown spots start to grow, coalesce and may lead to leaf blighting.
- GSB infected plants’ creepers may split, the growth of that creeper branch is slower, the leaves turn yellow, the flowers and peaches will ne malformed. There may be brown coloured liquid ooze out at the place of split. The ooze out may not be present sometimes.
- Complete wilting or damping off of the plant is observed and gummy liquid oozing out is noticed at the stem of the wilted plant.
- The fruits in the infected plants may show fruit cracking and ooze out of brown gum.
- The fruits also show the typical symptom on fruits rotting with black colour and this is called as black rot.
Note: Many times, Gummy stem blight (GSB) is confused with anthracnose while comparing with symptoms. Anthracnose leaf spots are usually smaller than the GSB spots and are round where anthracnose spots are distinctly angular. The anthracnose infected plants will not show blighting and gummy liquid oozing out.
IMPORTANT STRATEGIES FOR MANAGING GUMMY STEM BLIGHT (GSB) / BLACK ROT OF CUCURBIT CROPS.
1. Care @ Seed stage:
Seed is one of the sources of gummy stem blight disease occurrence. During selection and sowing of the seeds is more important. Selection of good quality seeds from reputed seed producers may be the better option and can reduce the occurrence of the disease. Seed treatment may be required for non-pre-treated seeds to avoid the infections of GSB.
2. Care @ transplant Stage:
Gummy stem blight disease is also infecting the cucurbits at seedling stage and symptoms may be evident, selecting the good quality disease free seedlings to transplant will help in reducing occurring and spread of the disease. Seedlings have to be inspected to the possible signs and symptoms of the disease and can take care to avoid the occurrence and the spread of the disease. Selecting and transplanting even healthy-looking plants form the infected lot or nursery may have chances of disease occurrence at the later crop stages.
3. Care @ Crop residues
Crop residues of the previous cucurbit crop may carry the gummy stem blight disease infections which can be spread to present of future crop. If the previous cucurbit was infected one than the chances of developing disease this season is for sure. Hence the discarding of the debris properly is much important to keep a break to the disease. The debris may be burnt to avoid further multiplication, spread and development.
4. Care @ land preparation
Weeds are another primary source of disease. The weeds may be members of the same cucurbit family and they may carry disease. Care need to be taken to remove the weeds and make the plot free from gummy stem blight disease.
6. Care @ crop selection
Growing continuously the cucurbit crops from same family or crops which primary hosts of gummy stem blight disease have to be stopped to stop the disease spread and development. Crop rotation with non-hosts and different crops of different families have to grown to stop and eradicate the gummy stem blight in the plot. Minimum of two and half to three years rotation is required to nullify the stem blight disease infection in the field.
6. Care @ crop stage
Regular checking or scouting for the disease sign and symptoms will definitely help detect early, prevent the spread and cure the disease sooner avoiding major crop loss. One can plan for the management measures like sprays and other things.
a. Spraying biological and biopesticides.
Trichoderma viridae, Bacillus subtilis, Pseudomonas fluorescens are some of the biological agents which may be sprayed to manage the GSB disease. Some of the biopesticides that may be used to manage the disease are as follows
Multiplex Nisarga or Biocure - F OR Alderm OR Trimax 10 gm if powder and 2 mL if liquid in 1 liter of water spray.
b. Spraying of chemical fungicides
The final method the managing the gummy stem blight disease in cucurbits is use or application of fungicides as foliar sprays. It is better to use the fungicides in preventive manner so that the crop damages or loss may be reduced for larger extent. There are lot of chemical fungicides both systemic and contact in nature which may be used to control the gummy stem blight on cucurbit crops.
Tata Ergon 0.75 - 1 mL/L OR Merivon 0.35 mL/L OR Custodia 1 mL/LOR FolioGold 2 mL/L OR Luna Experience and for more fungicides click here
K SANJEEVA REDDY
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Disclaimer: The performance of the product (s) is subject to usage as per manufacturer guidelines. Read enclosed leaflet of the product(s) carefully before use. The use of this product(s)/ information is at the discretion of user.
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