Cocoa swollen shoot virus

When a tree pushes out a flush (a burst of soft, newly-opened young leaves), look closely along the veins. Healthy young cocoa flush is red all over and then hardens to an even green. With swollen shoot you instead see bright red or pink banding that follows the veins — red running as stripes ALONG the leaf veins, not spread over the whole leaf. This vein pattern is the surest early sign.

As the leaves harden and the disease builds, the red fades to yellow flecking and a fern-like mottle that follows the veins, together with pale, see-through veins (called vein-clearing) that stays even on older, hardened leaves. Over months the tree yellows, sheds leaves, and its branches die back from the tips.

Look for swellings (galls) on the green shoots, stems and even the roots — a shoot or twig that bulges out fat in one spot instead of staying an even thickness along its length.

Infected trees carry small, rounded, smooth, mottled pods — almost ball-shaped instead of the normal long, ridged cocoa pod — with few, small beans inside.

On the shoot tips, leaf joints, and the cushions (the knobbly spots on the trunk and branches where flowers and pods form), look for tiny soft insects coated in white, cottony, mealy wax, usually with ants running up and down the trunk tending them. These mealybugs are the vector — the insect that carries the virus from tree to tree.

(a) normal red flush — new cocoa leaves are naturally red, then green up evenly; swollen shoot red is a stripe along the veins that turns into a yellow vein-mottle and never fully greens up. (b) Hunger yellowing (nutrient shortage) — that yellows the leaf between the veins and shows up evenly across many trees on poor soil; swollen shoot yellowing follows the veins and radiates out from a patch of sick trees. (c) Drought or capsid (mirid) bug dieback — dieback on its own, with NO red vein-banding and NO shoot swellings, and not spreading as a widening patch, is not swollen shoot.

check hardest when the trees push a new flush of soft young leaves — that is when the red vein-banding shows up clearest. Keep it up right through the season, from the young developing trees into the mid and late season, because the sick patch keeps widening month by month.

walk the whole plot in a big "W" so you cross the middle and all four corners, not just the row by the path. Pay special attention to the edges next to any old, abandoned or neighbouring cocoa — that is where the virus usually creeps in from.

stop at trees as you go (at least 10 stops across the plot) and at each one check three things — the young flush for red vein-banding, the shoots and stems for swellings, and the pods for the small round mottled shape. Then check the shoot tips and trunk cushions for the white mealybugs and the ants tending them.

Tie a ribbon on or paint any suspect tree. Because felling a tree is final, get it confirmed (by a survey or extension team where one exists) before you cut — but do not sit and wait for months while it spreads.

There is no safe number to live with: even ONE confirmed infected tree is too many. As soon as a tree is confirmed, act — cut it out plus a ring of the touching neighbour trees around it, because those contacts are almost certainly already infected but not yet showing it. And if you find white, ant-tended mealybug colonies building up on the pods and shoot tips, act on those too.

Plant only certified virus-free (tested-clean) seedlings from a trusted nursery, and never take seed, budwood or suckers from a sick or unknown tree — grafts and planting material carry the virus. Where they exist, plant tolerant varieties that suffer less. Keep a barrier between your cocoa and any old, abandoned or infected cocoa nearby — a real gap or a band of non-host plants (plants the virus and its mealybugs cannot live on) — so the carrier cannot cross. This cultural line is the mainstay of control.

The virus lives inside the wood and sap, so there is no spray that can cure an infected tree, and this disease has no chemical control listed — do not waste money on one. The only thing an insecticide could do is knock back the mealybug carriers, and even that is better done by managing the ants and natural enemies above. IF you ever do reach for any insecticide against mealybugs: cover your skin, eyes, nose and mouth, spray in the cool of the day with the wind at your back, keep it well off food, water, children and bees, wash yourself and your clothes afterwards, respect the label's pre-harvest interval (the wait between spraying and picking pods), and rotate to a different chemical group each time so the pest cannot build up resistance. It still never replaces cutting out the infected trees.

If the sick patch keeps growing after you rogue, it usually means infected trees nearby (a neighbour's plot, or abandoned cocoa) keep feeding the virus back in, or you did not take the full ring of contacts. Widen the cut — take a bigger ring, or a cordon right around the whole outbreak — and get your neighbours to rogue on their side the same season (it must be done area-wide, together, or the virus walks straight back in). When a block is too far gone and most trees are sick and dying, stop nursing single trees: cut your losses — clear the whole block, leave it fallow or under a non-host crop for a season to starve out the mealybugs, then replant the entire area at once with certified virus-free, tolerant stock. Clean, all-together replanting beats patching a dying block.