Greenhouse tomatoes are suffering from virus diseases this year.

The four most common virus diseases affecting tomatoes are:

• Tomato Mosaic Virus (TMV)
• Cucumber Mosaic Virus (CMV)
• Tomato Spotted Wilt Virus (TSWV)
• Pepino Mosaic (PM)

Symptoms on leaves:

• light green or yellowish mosaic patches - caused by TMV or CMV
• poorly formed leaf blades, with prominent midribs, resembling ferns - CMV
• leaves have long, brown streaks which shrivel - TMV
• young leaves curl downwards, turn bronze, & plant stops growing - TSWV
• leaves have a bubbly, mosaic surface, and plant growth is stunted - PM

Symptoms on fruit:

• fruit does not set (TMV)
• bronzy, patch at the stalk end of the fruit (TMV)
• streaky, raised brown spots with bronzing (TMV)
• uneven ripening with paler mottled areas (TSWV)
• marbled pattern with areas of lighter skin (PM)

Spread of viruses

Viruses have to be transferred to the plant by something . The gardener, an insect, or the tools actually pick up the virus from another diseased plant and carry it to the new host.

• TMV is very infectious and is easily spread by the gardener’s fingers, clothes or tools
• CMV is spread by aphids
• TSWV is spread by thrips

Control of tomato viruses

• hygiene - wash hands in soapy water to remove the virus & stop spreading it as the plants are handled.
• handle infected plants last
• sterilise tools
• do not touch plants after cigarette smoking
• increase the temperature of the greenhouse to above 25C - TMV & CMV symptoms will be reduced
• remove & destroy crop debris at the end of the season
• grow virus resistant strains of tomato

Older plants infected with TMV may produce normal fruits.