Phyllody

is at flowering: the flowers on a plant look wrong. Instead of normal blooms that become pods, the flower parts turn into tiny green leaves — little leafy tufts sitting where a flower should be. This flower-turned-to-leaf is the tell-tale sign (the disease is named for it).

, the whole plant changes shape. It throws out too many thin shoots and side-branches bunched together, so the top looks like a small green broom or a bird's nest — this bushy tangle is called a witches'-broom. The gaps between leaves get short and crowded, and the plant often looks stiff and upright.

On sesame the seed capsules stay small, green and empty; on groundnut and chickpea the pods are few, shrivelled or hold no good seed. A plant may look green and alive but give you nothing to harvest.

with drought or poor soil, which make the whole field small and pale evenly — phyllody hits scattered single plants while their neighbours flower normally. It is also not the same as an insect eating the plant: there are no holes, no chewing, no caterpillars — the flowers are simply the wrong shape and colour.

start walking your field from the time plants are growing strong and putting on branches (the development stage) and keep going right through flowering and mid-season — this is when the leafhoppers are active and when the twisted flowers first show. Look most closely in warm spells, which the leafhoppers love.

cross the field in a big "W" shape so you cover all four corners and the middle, not just the edge by the path. Make about 10 stops, and at each stop look closely at a small group of plants.

look at the flowers and pod-heads for green leafy tufts instead of blooms, and look at the top of the plant for bunched broom-like shoots. While you bend down, watch the leaves and stems for leafhoppers — small green or brown wedge-shaped insects, shorter than a grain of rice, that hop or run sideways when you disturb them.

phyllody spreads fast and has no cure, so the threshold is low — as soon as you find even the first plant with leaf-like flowers or that broom-like bushy growth, act the same day: pull that plant out and start knocking back the leafhoppers before they carry the germ further.

keep your seed clean — save seed only from healthy, well-podded plants or buy from a trusted source. Clear the weeds in and around the field before and during the season, because leafhoppers shelter and breed on them and weeds can hide the germ. Where you can, sow early so the crop is past its tender flowering stage before leafhopper numbers build up in the warm months; late-sown crops get hit hardest.

walk the field often and pull out every diseased plant the moment you spot it — roots and all. Carry it right out of the field and burn it or bury it deep; do not leave it on the edge or throw it on the compost, because it stays a source of infection for the leafhoppers. Removing sick plants early is the single most important thing you can do to protect the healthy ones.

if a tolerant or resistant variety of your crop is offered by an extension officer or trusted seed seller, choose it — it will not stop phyllody completely but it stands up to the disease better than an ordinary variety.

spraying an insecticide kills the leafhoppers that carry the germ, so it slows the spread, but it cannot heal a plant that is already infected. Use it only when leafhoppers are many and the disease is appearing. Safety: cover your skin, eyes, nose and mouth, spray in the cool of morning or evening with the wind at your back (never into your face), and keep the spray away from food, drinking water, children and bees. Wait the number of days written on the label before you harvest (this waiting time is the pre-harvest interval), and wash yourself and your clothes afterwards. To stop the leafhoppers getting used to one poison, rotate to a different type of insecticide each time rather than using the same one over and over.

keep roguing hard and stay on top of the leafhoppers and weeds — but if diseased plants are appearing across much of the field and few flowers are setting pods, accept that there is no cure for the plants already infected. Cut your losses: harvest whatever healthy pods remain, clear and destroy all crop residue after harvest so the germ has nowhere to overwinter, and next season rotate to a different, non-host crop on that land and start again with clean seed and early sowing.