Context: 

Cucumber Mosaic Virus (CMV) and  Tomato Mosaic Virus (ToMV) have impacted crops in Karnataka and Maharashtra respectively.

About CMV and ToMV:

• The two plant pathogens have similar names and cause similar damage to crops, but they belong to different viral families, and spread differently. 
• Both viruses can cause almost 100 per cent crop loss unless properly treated on time.
• ToMV 
  1. It belongs to the Virgaviridae family and is closely related to the tobacco mosaic virus (TMV). 
  2. ToMV hosts include tomato, tobacco, peppers, and certain ornamental plants.
• CMV:
  1. It was identified in cucumber in 1934, which gave the virus its name.
  2. CMV has a much larger host pool that includes cucumber, melon, eggplant, tomato, carrot, lettuce, celery, cucurbits (members of the gourd family, including squash, pumpkin, zucchini, some gourds, etc.), and some ornamentals. 

How do these two viruses spread?

• ToMV: 
  1. It spreads mainly through infected seeds, saplings, agricultural tools and often, through the hands of nursery workers who have failed to sanitise themselves properly before entering the fields. 
  2. It would require only a few infected saplings for the virus to take over an entire field in a matter of days.
• CMV:
  1. It is spread by aphids, which are sap-sucking insects. 
  2. Conditions of high temperature followed by intermittent rain, which allow aphids to multiply, are conducive to the spread of CMV.
  3. CMV too can spread through human touch, but the chances of that are extremely low.

Ways to Control the Virus Spread:

• Follow biosafety standards in nurseries, and compulsory seed treatment.
• Checking the trays of seedlings  before planting, and discarding any visible infected material.
• Clearing the field of weeds and plant material before fresh planting.
• Spraying quick acting insecticides or mineral oils on the plants to kill the aphids.

News Source: Indian Express