Biology, Ecology, Symptoms and Management of Okra Vein Clearing Yellow Mosaic Virus.

1. Welcome

2. Biology, Ecology, Symptoms and Management Okra
Vein Clearing Yellow Mosaic Virus
Mrinmoy Kumar Roy Tanu
Reg. No. 14-05816
Level: MS, Semester: II
Department of Plant Pathology
Sher-e-Bangla AgriculturalUniversity
Dhaka, Bangladesh January 1, 2020

3. Introduction
Okra (Abelmoschus esculentus (L) Moench), is widely grown all over tropical, subtropical and
warm temperature regions of the world. It is a popular crop in Bangladesh due to its ease of
cultivation and adaptability to varying moisture conditions. It is called lady’s finger in England,
Gumbo in the USA and Okra in Bangladesh. Okra appears to have originated in South Africa or
Asia. The cultivated okra containing chromosome number 2n=130 is an amphidiploid
vegetable of Abelmoschus tuberculatus (2n=58) and an unknown species with chromosome
number 2n= 72.
The crop is prone to damage by various diseases caused by various insects, fungi, nematodes
and viruses. But its cultivation is seriously threatened by attack of one most important Yellow
Vein Mosaic Virus (YVMV) by affecting different parts of plant which causes heavy losses not
only in respect to the fruit yield but fruit quality and occurred at all crop growth stages.

4. What are Mosaic Viruses ?
This virus infects more than 150 types of plants, including many fruits, vegetables,
and flowers. It is characterized by leaves mottled with yellow, white, and light and
dark green spots or streaks. Some of the most commonly infected plants include
okra, tomatoes, squashes, cauliflower, and cucumbers.

5. Vector of Yellow Vein Mosaic Virus
The YVMV is neither sap transmissible nor seed transmissible. It is mainly transmitted
through most important sucking pest, white fly during feeding. Under experimental
conditions, it has also been transmitted by grafting. Okra leaf hopper (Empoasca
devastans) is the 2nd most important to transmit this disease. Rail weed (Croton
sparsiflora), and goat weed (Ageratum sp.) are the important wild hosts of this virus.

6. Symptoms of Yellow Vein Mosaic Virus
 Yellowing of the entire network of veins in the leaf blade is the characteristic
symptom.
 In severe infections the younger leaves turn yellow, become reduced in size and the
plant is highly stunted.
 The veins of the leaves will be cleared by the virus and inter venal area becomes
completely yellow or white.
 In a field, most of the plants may be diseased and the infection may start at any stage
of plant growth.
 Infection restricts flowering and fruits, if formed, may be smaller and harder.
 The affected plants produce fruits with yellow or white colour and they are not fit for
marketing.
 The virus is spread by whitefly.

7. Symptoms Continued…
Infected leaf
Yellow vein mosaic disease on mature
plant
Yellow vein mosaic
disease on young seedling

8. Triggering of Yellow Vein Mosaic Virus
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).

9. Environment Impact on Occurrence of YVMV And
Vector in Okra
During rainy season, the temperature and relative humidity might have been high enough to
support disease development. Following this, in late rainy season, a fall in temperature might
lead to a decline in vector population that could reflect in a reduced expression of disease.
The infection becomes susceptible to YVMV when the crop is sown in month of July.
The whitefly population dynamics was monitored throughout the seasons and it was
observed that it was remarkably low during February to 1st fortnight of April and reached its
peak in the month of August. It was found that the disease incidence increased with the
increase in lower temperature and whitefly population decreased with increase in the relative
humidity. The bright sunshine hours revealed significantly positive association and
minimum temperature revealed significantly negative correlation with YVMV disease
incidence.

10. Biological 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.

11. 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 whitefly groups and diseases seem to be the most effective method.
Whiteflies 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%.

12. Preventive Measures
 Grow resistant varieties.
 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.

13. Okra yellow vein mosaic disease is one of the most devastating disease causes by
the begomovirus in Bangladesh. The weather condition in Bangladesh is more
congenial to the vector whitefly survival throughout of the region i.e. the warm and
humid condition. Another issue is that whitefly is polyphagous in nature resultantly
survive on other crop.
Further, it cannot be control by only insecticide. Development of host resistance to
viruses is the one of the important strategy against the okra yellow vein mosaic
disease which is most economical and environment- friendly process for reducing
the yield potential of okra.
Conclusion

14. Thank You