Lethal yellowing

the palm suddenly drops most or all of its nuts at once, and they fall at every size — tiny green buttons, half-grown, and near-ripe all on the ground together. Look at a fallen nut's stem end: you often see a brown, water-soaked rot ring where it broke off. A healthy palm never sheds all ages of nut at the same time.

(the young flower branches just coming out of their sheath). On a sick palm these turn black and dead at the tips, as if scorched by fire, and they set no fruit. Blackened new flowers together with the nutfall is the strongest early clue.

The oldest, lowest fronds go golden-yellow first, then the yellow climbs upward toward the crown, leaf by leaf. Yellowed fronds turn brown, dry out, droop and hang down against the trunk like a dead skirt.

The topmost spear leaf dies, the whole cluster of fronds falls away, and you are left with a bare grey trunk standing like a telephone pole. From first nutfall to a dead palm is usually only 3 to 6 months.

Plain potassium or nutrient hunger also yellows old fronds, but it does not cause all-ages nutfall or blackened new flowers, and the yellowing is often speckled or orange-spotted rather than an even golden sheet climbing upward. Drought or salt stress wilts and browns fronds but, again, no sudden nutfall of every size and no blackened flower spikes. Normal ageing yellows only the one or two lowest fronds and stops there. It is the combination — nutfall of all sizes + black dead new flowers + yellowing that climbs up — that means lethal yellowing, not any one sign alone.

watch your mature, nut-bearing and flowering palms — the older palms in their bearing years are the ones this disease strikes and kills. Walk your grove to check them at least once a week, and step up to twice a week if a neighbouring farm or nearby wild palm has shown the disease, because the planthopper flies the germ across from there.

don't just look at the palms along the path. Walk a big "W" pattern across the whole grove so you pass the four corners and the middle, and make about 8 to 10 stops, checking the nearest few palms at each stop — you want eyes on every block, not only the edge.

(1) the ground under the crown for freshly fallen nuts of mixed sizes; (2) the newest flower spikes for black, dead tips; (3) the lowest fronds for the first golden yellowing; (4) the spear and crown for any collapse. Use the same three-part signature every time — nutfall, black flowers, climbing yellow.

This disease has no cure and spreads fast by insect, so the threshold is not a percentage — it is a single palm. The moment even 1 palm shows premature nutfall or fronds yellowing from the bottom up, flag that palm, mark it, and report it to your plant-health / extension service immediately. Do not wait to see if more appear.

and keep checking the palms around it every few days — the neighbours of a sick palm are the most likely to fall next.

There is no medicine that cures an infected palm, so the sick palm's real job now is to stop being a source of germ for the rest. As soon as a palm is confirmed, cut it down and burn it — this is called roguing. Doing this early, while only one or two palms are affected, removes the reservoir the insect feeds on and is the single most useful thing you can do to protect the grove. Do not leave a dying palm standing.

An insecticide for vector control (sprayed to knock down the planthopper) gives only partial, temporary protection — it does not cure any palm and cannot be relied on alone; it is the weakest of your options for good reason. If a technician advises it during an outbreak, treat it as a short-term way to slow the insect while you rogue and replant, not a solution.

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, drinking water, children and animals, and avoid spraying flowering plants where bees are working. Wash yourself and your clothes afterwards, and respect the pre-harvest interval (the number of days the product says you must wait between spraying and eating or selling the nuts). Rotate to a different chemical group each time rather than using the same product over and over, so the insect does not build up resistance (stop being killed by it).

When palm after palm keeps falling in a block even after you remove the sick ones, stop pouring effort into the standing crop: clear the affected block, burn the debris, and replant the whole area with resistant dwarf or hybrid coconut sourced from a clean area — and keep the grove floor mowed to starve the insect. A fresh, resistant stand is worth far more than nursing palms that will die anyway.