Okra
Bhendi Yellow Vein Mosaic Virus
BYVMV
Virus
In a Nutshell
- This viral disease of Okra may cause significant yield losses.
- It occurs at all crop stages and is transmitted by whiteflies (Bemisia tabaci).
- Occurrence of yellow veins and mosaic patterns on the leaves.
- Fruit yield may be reduced to a maximum of 96% if the crop is infected in an early stage.
Can also be found in
Okra
Symptoms
The disease is characterized by different degrees of chlorosis and yellowing of veins and veinlets, as well as mosaic-like alternating green and yellow patches, smaller leaves, fewer and smaller fruits, and stunted plant growth. Initially, infected leaves show only yellowing of veins but the entire leaf turns yellow during later stages. When the plants get infected during 20 days after germination, they remain stunted. If the young leaves get infected during the early season, they become completely yellow, brown and then dry up. Plants that are infected after flowering are characterized by upper leaves and flowering parts showing vein clearing symptoms. They will still produce some fruits but these become yellow and hard. Plants that were growing healthy and fruiting normal until late season will then get few small shoots at the basal portion of the stem.
Recommendations
Organic Control
Restrict the vector by spraying 5% neem seed kernel extract, or ginger, garlic, and chili extracts. Cut pieces of cactus, or milk bush, immerse in water (enough for the pieces to float), allow it to ferment for 15 days. Filter and spray on affected plants. Apply neem and mustard oil, Rhizobacteria, Crozophera oil followed by Palmarosa oil. A mixture of oil (0.5%) and (0.5%) washing soap is also reported to help.
Chemical Control
The virus cannot be completely controlled by chemical means. Hence, it is advisable to always consider an integrated approach with preventive measures together with biological treatments, if available. Early application of insecticides to the soil against certain white fly groups and diseases seem to be the most effective method. White flies quickly develop resistance to all pesticides, so a rotation of different formulation is recommendable. Two sprays of Acetamiprid 20SP (40g a.i/ha) has been proven effective in reducing the incidence of the mosaic virus and subsequently increases the yield of Okra. Imidacloprid 17.8% SL applied twice and one seed treatment (Imidacloprid @ 5 gm/kg of seed) can significantly reduce the pest population up to 90.2%.
What caused it?
The damage is caused by the begomovirus, which is transmitted through whiteflies. The viruses do not replicate in their vector but are moved readily from plant to plant by the adult whitefly by various means. The female whiteflies are more efficient than the males in transmitting the virus. This viral disease infects during all the stages of growth, however, the most susceptible stage is from 35 to 50 days. Whitefly population and severity of the virus are largely influenced by temperatures, humidity, and minimum temperature of 20-30°C. The second most important transmitter is Okra leafhopper (Amrasca devastans).
Preventive Measures
- Grow resistant varieties like Parbhani Kranti (Arka Abhay, Varsha, Uphar) and Arka Anamika.
- Maintain proper crop spacing.
- Plant Maize or Marigold as a border crop to trap the vector insect.
- Avoid summer season planting as this is the peak season of whiteflies.
- Avoid sowing susceptible varieties during the summer season, when the whitefly activity is high.
- Place yellow sticky traps (12/acre) above the plant height to monitor and catch vector insects.
- Destroy weeds and other wild hosts, especially Croton sparsiflora and Ageralium spp., whenever possible.
- Remove the affected plants from the field and burn them.
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