Bacterial blight is a serious disease that affects pomegranate cultivation in India, which is caused by the bacterium Xanthomonas axonopodis pv. punicae. The disease can cause significant damage to pomegranate trees, leading to reduced yield (in some cases up to 90%) and poor fruit quality. This, in turn, can affect the marketing value of the fruits and lead to significant economic losses for farmers. Thus, effective disease management strategies are crucial for controlling bacterial blight in pomegranate and maintaining productivity.
What causes Bacterial Blight Disease in Pomegranate?
Bacterial blight disease is more severe during fruiting stage. The bacterium can survive on infected plant debris, in soil, and in plant tissue, and can be transmitted through various means as given below.
- The bacterium can be spread from infected plant tissues to healthy tissues through splashing rain or irrigation water.
- Natural openings and wounds can act as a source for bacteria entry.
- Contaminated pruning tools, equipment and movement of workers may spread the disease over short distance.
- Infected planting material such as seedlings or cuttings can serve as a means of introducing the bacterium to new areas.
- Certain insects, such as thrips, blister beetles and whiteflies, can transmit the bacterium from infected to healthy plants while feeding.
- Environmental factors such as high humidity (> 50%) and temperature (25 – 35°C) along with intermittent rainfall and cloudy weather can create favorable conditions for the growth and spread of the bacterium.
- Small, circular, water-soaked spots appear on the leaves, which later turn brown and necrotic. The spots may coalesce and form larger lesions.
- In severe cases, the infected leaves may turn yellow and fall off the plant, leading to defoliation.
- Infected twigs turn brown or black and may wilt, causing dieback of the affected branches.
- Small, dark, sunken spots appear on the fruit surface, which can enlarge, cover the whole fruit surface and cause the fruit to crack or split open.
- The bacteria can cause the formation of gum-like exudates on the surface of infected tissues.
- Infected fruits may show internal discolouration due to rotting.
- Use disease-free planting material.
- Use disinfectant pruning tools and equipment.
- Remove and destroy infected plant parts.
- Avoid overhead irrigation to reduce the spread of the disease.
- Ensure proper spacing between plants to promote good air circulation.
- After harvesting during Dec – Feb, prune the secondary and tertiary branches with infection.
- Apply the recommended dosage of fertilizers and incorporate well-decomposed farmyard manure and vermicompost along with it to enhance the resistance of plants against diseases. Application of manures and fertilizers during the rest period is also important.
- Apply Biocontrol agents such as Pseudomonas fluorescens (10 ml/lit water) or Bacillus sp (250 ml + 10 kg FYM/Compost) and Trichoderma sp (1 – 2 kg + 100 kg FYM) as a prophylactic measure.
- Give a spray of 40% Tulsi extract followed by neem oil spray.
- The extracts of garlic bulb, meswak stem, and patchouli leaves at a concentration of 30% can be sprayed.
- Spray Geolife Geomycin Bio Bactericide at 0.5 – 1 gm/lit water or Terra BactoKill.at 3 ml/lit of water.
Chemical (Prophylactic Measure):
- To reduce the severity of the disease, apply a 1% Bordeaux mixture by spraying prior to pruning.
- Smear application of copper-based fungicides onto the surface of the plant parts susceptible to infection, such as the basal trunk, branches and twigs, before the onset of disease symptoms helps to control the disease.
- For this, following pruning, apply Streptocyclin or Streptomycin sulphate (0.2 gm/lit water) or Bactinash (0.5 gm/lit water) + Copper oxy chloride (2 gm/lit water) to the basal trunk of susceptible plants to decrease the occurrence of the disease.
(Note: Always prepare Bordeaux mixture fresh and use on the same day)
Management of Bacterial Blight in Pomegranate:
In order to effectively manage bacterial blight in pomegranate, it is recommended to implement an integrated approach that combines preventive measures with other methods, as relying solely on chemical control is ineffective.
The below mentioned chemicals can be used alone or in combinations.
|Blue Copper Fungicide or Blitox Fungicide||Copper Oxychloride 50% WP
|2 gm/lit water|
|Dhanuka Kasu B Fungicide||Kasugamacyin 3% SL||2 – 3 ml/lit water|
|Borogold Fungicide||Combination of Nano Silver Particles & Peroxy Acid||1.5 gm/lit water|
|Crystocycline Bactericide Antibiotic||Streptomycin sulphate 90% + Tetracylin hydrocloride 10% SP||0.2 gm/lit water|
|Kocide Fungicide||Copper Hydroxide 53.8% DF||2 gm/lit water|
(Note: After application of bactericide, spray General liquid micronutrient (2.5 ml/lit of water). It helps in effective management of the disease and also increases plant’s resistance against the disease. Also, check the product’s label to know the right time of application)