Recently, a perplexing ailment struck the paddy crop resulting in the “dwarfing” of plants in Punjab and Haryana. The enigma has been unraveled by science, identifying the cause as ‘Southern Rice Black-Streaked Dwarf Virus’ (SRBSDV) – first observed in Southern China in 2001.
Interpreting Paddy Dwarfing
Rice dwarf disease is characterised by the stunting of the plant and the presence of white chlorotic specks on the foliage. Essentially, the affected plants exhibit a reduction in height from half to one-third of a regular plant’s size. Plants with this condition have shallow roots and can be easily uprooted. This trait was witnessed in practically all varieties cultivated in local farmers’ fields.
Stunting was noted to range between 10% to 25%, although in exceptional cases it rose above 40%. The incidence was especially noticeable in early sown paddy crops, regardless of the variety.
The Role of SRBSDV
The Southern rice black-streaked dwarf virus (SRBSDV) is a non-enveloped, icosahedral virus composed of 10 double-stranded Ribonucleic Acid RNA segments. It belongs to the Fijivirus family (Reoviridae) and represents a distinct species. An icosahedral virus is characterized by identical subunits forming equilateral triangles that are symmetrically arranged.
This virus is conveyed by the white-backed plant hopper (WBPH) in a persistent circulative and propagative manner. Besides infecting rice, the SRBSDV also affects different weed species. Nymphs of WBPH transmit the virus more efficiently compared to adults. Long-distance transmission can occur due to WBPH migration propelled by typhoons and powerful convection winds.
Preventive Measures to Consider
As there’s currently no corrective solution for this viral disease, farmers are advised to regularly check the crop presence of WBPH. A few plants should be mildly tilted and tapped at the base 2 to 3 times weekly. If WBPH nymphs or adults are seen on water, insecticides can be applied towards the base of the plants.
Farmers are also advised to adhere to the transplanting dates provided by Punjab Agricultural University (PAU), as instances of stunting were recorded to be higher in early planted crops. This practice will not only aid managing the viral disease but also conserve water.
UPSC Examination Question from Previous Year (2018)
Question: Which among the following spread plant diseases?
Options:
(a) Birds, Rain
(b) Rain, Wind blowing
(c) Birds, Dust blowing, Wind blowing
(d) Birds, Dust blowing, Rain, Wind blowing
Answer: (d)
Explanation: Severe epidemics of plant diseases often result from wind and dust blowing which transmit pathogens. Thus, options 2 and 4 are correct. Raindrops can also spread foliar diseases from leaf to leaf, shoot to shoot, and between closely spaced crops, making option 3 also correct. Birds play a small role in disease transmission in plants mainly through seed dispersal. So, option 1 is also correct. Hence, the answer is (d).
