Guava wilt

on an otherwise healthy grown tree, the leaves on one branch or one side suddenly turn pale yellow and wilt — they hang limp as if the tree is thirsty, even when the soil is wet. Watering does not bring them back.

the wilting jumps branch to branch through the canopy. Leaves dry to brown and drop early, twigs die back from the tip, and any fruit stays small and hard. Over weeks to a couple of seasons the whole tree browns off and dies, often still holding its dead leaves.

slice into a wilting branch or dig and cut a root. A healthy guava is creamy-white inside; an infected one shows brown or dark streaks in the wood just under the bark. That brown staining in the water-pipes is the surest sign it is wilt and not just drought.

with plain drought or waterlogging (whole tree droops evenly and perks up after rain or watering — wilt starts one-sided and never recovers), with sunburn or nutrient shortage (yellowing is even across the tree, no brown wood inside), or with termite or borer damage (you see tunnels, holes and sawdust, not clean brown streaks in the wood).

guava wilt shows up on established, bearing trees — through the main fruiting and later part of the season (mid- and late-season), and especially in warm weather (about 24–32°C) on heavy, poorly drained or waterlogged ground after rain. That is when to walk the orchard with your eyes open.

every week or two, walk a large "W" across the whole orchard so you pass through all four corners and the middle, not just the trees by the path or gate. Low, wet patches deserve an extra look.

look up into the canopy for any branch or side that is yellowing, wilting or losing leaves while the rest is green. Stop at every tree that looks off.

on a suspect tree, cut into a wilting branch (and a root if you can reach one) and look for the brown streaking inside the wood. Brown streaks confirm wilt.

this disease has no safe level to tolerate. Even ONE established tree with sudden one-sided yellowing, wilting and dieback — confirmed by brown wood inside — means the disease is in your orchard and you must act at once. Mark every affected tree with paint or a tied rag so you can find them again and watch the trees next to them closely.

Start every new tree with clean, disease-free nursery stock on well-drained land, never in low, waterlogged spots. Do not plant guava again where guava has just died of wilt, and avoid moving soil, water or tools from a sick area to a clean one.

Where you can get them, plant tolerant rootstocks or resistant selections — graft your good fruiting variety onto a rootstock that resists the fungus. This is one of the most effective steps you can take because it protects the tree from the inside.

The fungus gets in through wounds, so avoid injuring roots when you hoe, plough or dig near trees, keep water from standing around the trunk, and improve drainage on heavy ground with ridging or channels.

The fungus rides on blades and soil. Disinfect pruning saws and hoes (wipe with a strong bleach or spirits solution) between trees, and always work on healthy trees first and suspect trees last so you don't carry it around.

Trichoderma is a helpful fungus that fights the wilt fungus in the soil. Work Trichoderma-based soil treatment plus plenty of compost or well-rotted manure into the root zone of your healthy trees and around new plantings to build up defenders in the soil. It cannot cure a tree that is already dying, so use it to protect — best applied early, before symptoms, and repeated. When handling any soil treatment, cover your nose and mouth, wear gloves, keep it off food and away from children, and wash your hands and clothes after.

Because the fungus lives inside the wood and deep in the soil, there is no fungicide that will save an infected tree — do not waste money or risk your health chasing one. Your defence is prevention, resistant stock and sanitation, not a chemical rescue.

As soon as a tree is confirmed dying of wilt, uproot it with as many of its roots as you can and burn it on the spot, so the fungus does not feed on the dead roots and spread. Do not replant guava in that hole. If tree after tree keeps dying despite this, stop growing guava on that land for several years and rotate to a non-host crop, or move new guava to fresh, well-drained ground — chasing a dying orchard only spreads the disease further.