Okra yellow vein mosaic virus

the fine little veins on the youngest leaves at the top of the plant turn yellow, making a net or spider-web of yellow lines on a still-green leaf. This is the clearest early sign — look at the new growth, not the old bottom leaves.

the yellow widens out from the veins until the whole leaf looks bright yellow all over, sometimes almost white. The plant stays small and stunted while healthy neighbours grow tall.

infected plants make pale yellow-green, small, hard and twisted pods instead of long green tender ones. These pods are unmarketable — that is the money you lose.

for the culprit: tiny white flies about the size of a pin-head that jump up in a little cloud when you shake the plant. They cluster on the underside of young leaves.

with plain hunger (nitrogen shortage), which yellows the whole old leaf evenly from the bottom up with the veins staying green — the opposite of this disease, where the veins yellow first on the young top leaves. Also not to be confused with leaf-eating damage: this virus makes no holes, it only changes colour and shape.

start the day your okra comes up and keep checking hard through the seedling, young-plant and mid-season stages — this is when the plant is most vulnerable and when catching it early saves the crop. Warm weather (about 25–35°C) makes whitefly breed fast, so look more often in the heat.

twice a week, walk a big "W" shape across the field so you cross all four corners and the middle — not just the row next to the path where you always look.

along the W. At each stop pick a plant and check the youngest top leaves for the yellow vein-net, and turn 2–3 leaves over to look for the tiny white flies underneath.

(any bright-yellow board smeared with grease or old oil) just above the crop — whiteflies fly to yellow and stick. A trap filling up with tiny white flies is your early warning that vector numbers are rising.

as soon as you find even 1 plant in 10 with the yellow vein-net, or you see whitefly numbers climbing on leaves or traps, act the same day. There is no "wait and see" — the virus has no cure, so every infected plant left standing is a source that infects the rest.

remember, no spray can cure an infected plant — chemicals only reduce the whitefly that spread it. If whitefly pressure is high, use a systemic insecticide ("systemic" means it is taken up inside the plant sap, so the fly is poisoned when it feeds — unlike a "contact" spray that only kills flies it lands on). A seed treatment at planting plus targeted early sprays works best while plants are young.

cover your skin, eyes, nose and mouth; spray in the cool of early morning or evening with the wind at your back so it blows away from you; keep it off food crops, drinking water, children and bees; respect the pre-harvest interval (the number of days the label tells you to wait between spraying and picking pods to eat or sell); and wash your body and clothes afterwards. Rotate — change to a different chemical group each time so the whitefly does not build up resistance and stop dying.

step up roguing to a daily walk, tighten whitefly control, and clear every mallow weed and old okra plant nearby — the source is almost always an infected plant or weed close by. When most of the field is already infected and stunted early, cut your losses: pull the crop out, clean the ground completely, rest it from okra, and next season start fresh with a resistant variety and early, all-at-once planting so the crop grows past its tender stage before whitefly numbers build.