Mosaic Virus
Act nowVirus · spreads to other plants · also called tobacco mosaic, cucumber mosaic, tomato mosaic
Mosaic viruses distort growth rather than spotting it, and the mottling has no defined edges — it is a blend rather than a lesion. There is no cure, and infected plants are a source of infection for the rest of the garden, mostly carried by aphids or on hands and tools.
What it looks like
A patchwork of light and dark green across the leaf, giving a mottled or marbled look with no clear spot edges. New leaves come out narrow, puckered, strap-like or fern-like. Fruit is small, mottled and often fails to set.
How to confirm it
- Light and dark green mottling with soft, blurred boundaries.
- New growth distorted, narrowed or puckered.
- Plant stunted with poor fruit set.
- No spots, fuzz, powder or insects to account for it.
What to do
- 1Remove and bin the plant. This is unwelcome advice and it is the right advice.
- 2Wash hands and tools thoroughly afterwards. Tobacco mosaic in particular survives on surfaces and on tobacco products.
- 3Control aphids, which move most of these viruses between plants.
What it gets confused with
One observation settles each of these.
Drift distorts growth too, but affects several unrelated plants at once and usually shows a directional pattern across the garden.
Chlorosis makes a clean green vein network on yellow. Mosaic makes irregular green-on-green blotching.
Preventing it next time
- Buy resistant varieties — the T code on tomato labels covers tobacco mosaic.
- Do not handle plants after handling tobacco.
- Keep aphid populations down and remove weed hosts nearby.
Plants affected
Check these two things first
- Push a finger into the soil, two knuckles deep. Wet soil plus a wilting plant means too much water, not too little — and it is the commonest reason a plant is dying. Dry soil plus crisp leaves means the opposite. The leaves look nearly identical either way, so the soil is what tells you.
- Turn a damaged leaf over. Half of all diagnoses live on the underside: fuzz means downy mildew, fine webbing means spider mites, clusters of insects mean aphids. Nothing on the top of a leaf is as informative.
Most garden problems are cosmetic and resolve without treatment. Reach for a spray last, not first.