Glossary of diseases and resistance codes
Seed companies state resistances with standard codes (ISF). Here is what they mean, in plain words.
| Code | Meaning |
|---|---|
HR / IR | High / intermediate resistance, ISF standard |
TYLCV | Tomato yellow leaf curl virus (whiteflies) |
Rs / BW | Bacterial wilt (Ralstonia) |
Mi / Ma / Mj / N | Root-knot nematodes |
Fol / Fom / Foc | Fusarium wilt (tomato / melon / cabbage) |
TMV / ToMV / Tm | Tobacco / tomato mosaic virus |
CMV | Cucumber mosaic virus |
ZYMV | Zucchini yellow mosaic virus |
TSWV | Tomato spotted wilt virus (thrips) |
PVMV / PVY | Pepper veinal mottle / potato virus Y |
Px / Lt / Si / Gc | Powdery mildew |
Pc / Pi / DM | Downy mildew / late blight |
Va / Vd / V | Verticillium wilt |
PRSV | Papaya ringspot virus |
The diseases
TYLCV
Tomato yellow leaf curl virus, spread by whiteflies. Yellow, curled leaves, stunted plants, few fruits. Severe in the hot season.
Bacterial wilt
Soil-borne bacterium (Ralstonia, code Rs or BW): the plant suddenly wilts in the heat of the day and dies. Common in the rainy season on tomato, eggplant and pepper.
Root-knot nematodes
Tiny soil worms (Meloidogyne, codes Mi, Ma, Mj, N) that form galls on roots. Weak plants, especially in warm sandy soils.
CMV
Cucumber mosaic virus, spread by aphids: mosaic, deformed leaves and fruits.
ZYMV
Zucchini yellow mosaic virus, spread by aphids: deformed fruits on squash, melon, cucumber, watermelon.
TSWV
Tomato spotted wilt virus, spread by thrips: bronze spots, mottled fruits on tomato and pepper.
TMV/ToMV mosaic
Tobacco and tomato mosaic viruses (codes TMV, ToMV, Tm), spread by contact and tools.
PVMV / PVY
Pepper veinal mottle virus and potato virus Y, spread by aphids.
Fusarium wilt
Soil fungus (Fusarium, codes Fol, Fom, Foc) that blocks the vessels: yellowing then wilting.
Powdery mildew
Fungus forming a white powder on leaves (codes Px, Lt, Si, Gc). Common in the dry season.
Downy mildew / late blight
Disease with brown spots and down under the leaves (codes Pc, Pi, DM), favoured by humidity.
PRSV
Papaya ringspot virus, spread by aphids: ring spots on fruits, loss of vigour.
Verticillium wilt
Soil fungus (Verticillium, codes Va, Vd, V): progressive wilting, mostly in cooler areas.