Moringa root and collar rot

a young tree that suddenly wilts, yellows and droops even though the soil around it is still wet or muddy. This is the tell-tale sign. A merely thirsty tree perks up when you water it; a root-rotted tree keeps wilting no matter how wet the ground is, because its roots have rotted and can no longer drink. Whole seedlings and young trees flag, brown off from the tips down, and can collapse within a few days.

scrape the bark at ground level with your thumbnail. Healthy wood underneath is firm and creamy-green; rotted wood is soft, brown to black, water-soaked and often sour-smelling. You may find a dark, sunken, cracked patch (a canker) ringing the base, sometimes weeping a gummy ooze, and later tiny black pin-head specks — the fungus's fruiting bodies — peppering the dead bark.

lift a wilting plant and look at the taproot. In root rot the fleshy taproot is brown, soft and rotten, its outer skin sloughing off in your hand, instead of firm, pale and carrot-like. The rot runs up from the root into the collar, and the tree sits loose in the ground and rocks or pulls out easily. This is the disease the crop guide calls Diplodia root rot.

with: frost — which browns and kills the leaves and shoots after a cold, clear, still night but leaves the root firm and white; drought — where the soil is dry and the plant revives after a good watering (root rot never does); or termites — a chewed, hollowed base with mud tunnels crusted up the stem, not a soft wet brown rot. The one sign that always points to root rot is a plant wilting while its feet are wet, with a soft brown collar.

while the trees are young and getting established (the establishment and early-growth stages — roughly the first few months after planting), because the soft young taproot rots most easily. Step up your checks after every heavy rain, flood or heavy watering, and right through any warm, wet spell, since warm ground that stays soggy is exactly what sets this rot off.

go straight to the low spots and the heavy, slow-draining patches where water pools after rain — that is where trees rot first. Check the trees on flat, wet ground before the ones on mounds, ridges or slopes.

look for any plant wilting, yellowing or dying while the soil around it is still wet or muddy. At each suspicious tree, scrape the bark at the base to look for the soft brown collar rot, and give the stem a gentle push — a rotted root lets the tree rock in the ground or lift out easily.

the threshold is the very first tree you find wilting-and-dying while its soil is wet, with a soft brown base — 1 such tree is enough to act. One is not bad luck: it means that patch is waterlogging and the rot will take its neighbours next. Don't wait to 'see how many' — pull that tree and fix the drainage straight away.

the moment you find a rotted tree, dig it out with as much of its rotten root as you can and destroy it — burn it or bury it deep, well away from the field. Never leave it lying, and never put it on the compost. Then stop watering that patch, open a channel to drain it, and let the soil dry out. Where you can get it, water a Trichoderma biofungicide (a friendly soil fungus sold as a powder or liquid) into the soil around the surviving trees — it settles on the roots and crowds out the rot fungus, and it is safe for you, your animals, your soil and the leaves you eat.

if trees keep rotting in a valuable planting even after you have improved the drainage, you can drench the soil around the collar with a systemic benzimidazole fungicide (the chemical group that includes carbendazim and thiophanate-methyl). Know its limit plainly: a drench can slow the rot in roots not yet killed but cannot bring a rotted tree back to life, and it will never beat wet soil — it only buys a little time while you fix the real problem, the drainage.

mix and apply with your skin, eyes, nose and mouth covered; keep the product off the leaves and pods you will eat, out of drinking water, ponds and rivers, and away from children, animals and bees. Respect the pre-harvest interval — the number of days the label says you must wait between treating and picking leaves or pods. Wash yourself and your clothes afterwards, and never tip leftover drench near a well, stream or pond.

benzimidazoles are a group this fungus can quickly get used to if you lean on them — so do not drench again and again with the same product. Treat only when you truly must, rotate to a different fungicide group if you treat more than once, and keep drainage, mounding and Trichoderma as the real backbone of your control, not the chemical.

when trees keep dying in the same wet patch however you treat them, the soil there is the problem, not the individual tree. Stop replanting moringa into that spot; put the next trees on high mounds or ridges, or on better-drained land altogether, and rest the sick patch under a different, non-woody crop for a season or two so the fungus in the soil starves down. Chasing the rot with sprays on waterlogged ground will only cost you more trees.