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Cassava green mite
Mononychellus tanajoa · Mite
Photo: David Monniaux · CC BY-SA 3.0
Cassava green mite (Mononychellus tanajoa) is a spider mite so small it looks like green dust, and cassava is its only host. It gathers on the underside of the youngest top leaves and in the growing tips, sucking the sap and leaving a fine yellow-green speckling. It builds up in the hot, dry season and in long droughts, then collapses when the rains return. Brought to Africa from South America, it is now found right across the cassava belt — but a tiny predatory mite, introduced to hunt it, keeps it in check in many areas.
EdwinAlden.1995 · CC BY-SA 4.0 
Abike25 · CC BY 4.0
Why it matters
A bad dry-season attack can cost you up to half your root harvest — the mites feed on the growing tips, so the plant stops pushing out new leaves and the roots below the ground stay small. The mites are almost too small to see and hide under the youngest top leaves and deep in the shoot tips, so by the time the tips look burnt and stand up bare like a candlestick, much of the damage is already done. There is no quick spray that fixes this well — once the mite is established you are managing it, not curing it — so the real win is preventing the build-up and letting its natural enemy do the work.
When to act
Green speckling and stunting on young top leaves during the dry season; treat when growing tips are heavily colonised.
This guidance is general, compiled from published agronomic references including FAO and CABI. Thresholds and timing shift with your crop, your variety and the season.
In much of the region a spray is simply called mushonga — medicine. But a chemical group you cannot name is one you cannot rotate, and a product you did not write down has no pre-harvest interval you can observe. Mushonga, and other farming words →
The full Cassava green mite field guide
Identify it
The damage first
look at the youngest leaves at the very top of the plant. Fine yellow-green speckles appear first — as if someone flicked pale dust across the leaf — then those top leaves turn mottled, twisted and small. In a bad, long dry spell the growing tips die back and the plant is left with a bare, stalky top — a 'candlestick' look — and it stops growing taller.
The mite itself
it is tiny — a green-yellow speck smaller than a pinhead, like fine green dust or a single grain of sand, so it hides against the green leaf. You will need a hand lens (magnifying glass), or hold the leaf up to the light. Look on the underside of the youngest top leaves and inside the shoot tips, and check in the hot, dry months — the mite loves dry heat and vanishes when steady rains come.
Don't confuse it with cassava mosaic disease
mosaic makes a yellow-and-green patchy mosaic over the whole leaf, including the older lower leaves, is there from early on, and is spread by whitefly — you will find no mites underneath. Green-mite speckling is a fine, even stippling on the youngest top leaves only, with the tiny green mites on the underside.
Don't confuse it with mealybug or red spider mites, either
cassava mealybug leaves white, cottony tufts you can see with the naked eye on the tips and bunches them up; red spider mites attack the older, lower leaves, turning them bronze with fine webbing. Cassava green mite is green specks — no cotton, no webs — on the young top leaves.
Scout for it
When to look
start checking once the plant is actively growing and bushing out (the development and mid-season months) and a dry spell sets in. The mite builds up fastest in hot, rain-free weather, so step up your checks during any long dry stretch and ease off once steady rains return.
How to walk the field
every week or two, walk a big 'W' across the field so you cover all four corners and the middle — not just the edge by the path. Stop at about 5 points, and at each stop check the tops of 10 plants (around 50 plants in all).
What to check at each plant
turn over the youngest top leaves and look into the shoot tip. Use your hand lens to spot the tiny green mites, or hold the leaf to the light and look for the fine speckling. Fresh, spreading speckle on new leaves means a live, growing attack — not old damage.
When to act
if the young top leaves of about 3 in every 10 plants show fresh green-yellow speckling — or you find shoot tips heavily covered in mites and starting to shrivel — the mite is established and it is time to act. A few specks on one or two plants is not yet a reason to panic; just keep watching.
Control it
Prevent it — start clean and plant early:
take your cuttings only from healthy, mite-free plants, and never carry cuttings from an infested field into a clean one — that is how the mite travels. Plant early, at the start of the rains, so the crop is strong and well-established before the dry season arrives and the mite builds up. Keep plants vigorous — good spacing, weeded, not drought-starved — because a strong plant shrugs off far more mite feeding than a stressed one.
Grow a tolerant variety
where the green mite is a regular problem, plant a cassava variety bred to resist or tolerate it — ask your extension officer or a trusted seed source which released varieties are recommended for your area. A tolerant variety is the cheapest long-term protection and never washes off or wears out.
Let its natural enemy do the work — the predatory mite:
a tiny predatory mite (Typhlodromalus aripo) was introduced across Africa's cassava belt and lives right in the cassava tips, eating green-mite eggs and young. It gives lasting, area-wide control for free. Protect it: do not spray broad poisons that would kill it, and if your area does not have it yet, ask your extension service or a research station (such as IITA) about getting tip cuttings from a field where the predator is already established to spread it to yours.
Don't reach for a sprayer
there is no good, affordable spray for cassava green mite on a smallholding — the mites hide under the top leaves and deep in the tips where spray never reaches, cassava stays in the ground for many months, and general pesticides just kill the helpful predatory mite and make the next outbreak worse. If you ever spray anything on cassava for another reason, protect yourself: cover your skin, eyes, nose and mouth, spray in the cool of the day with the wind at your back, keep it off food, water, children and bees, respect the pre-harvest interval (the wait between spraying and harvest printed on the label), and wash well afterwards.
If it keeps spreading
pull out and destroy (rogue) the worst 'candlestick' plants so they stop feeding the mite, and make sure the predatory mite is present in your field. When the rains come, the mite collapses on its own and the plant pushes fresh, healthy tips again — so a dry-season attack is rarely the end. If a field is hit hard year after year, cut your losses for next season: switch to a tolerant variety and plant early with clean cuttings, which breaks the cycle far better than ever chasing the mite with sprays.
Catch Cassava green mite before it costs you the harvest
This guide is the general answer. Divisi works out yours — the week to scout your own field for Cassava green mite, and what to do the day you find it.
Crops it affects
Plan the crops it attacks
All planting calendars, country by country
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Frequently asked questions
How do I identify Cassava green mite?
The damage first. look at the youngest leaves at the very top of the plant. Fine yellow-green speckles appear first — as if someone flicked pale dust across the leaf — then those top leaves turn mottled, twisted and small. In a bad, long dry spell the growing tips die back and the plant is left with a bare, stalky top — a 'candlestick' look — and it stops growing taller.
When should I take action against Cassava green mite?
Green speckling and stunting on young top leaves during the dry season; treat when growing tips are heavily colonised.
How do I control Cassava green mite?
Prevent it — start clean and plant early:. take your cuttings only from healthy, mite-free plants, and never carry cuttings from an infested field into a clean one — that is how the mite travels. Plant early, at the start of the rains, so the crop is strong and well-established before the dry season arrives and the mite builds up. Keep plants vigorous — good spacing, weeded, not drought-starved — because a strong plant shrugs off far more mite feeding than a stressed one.
Which crops are attacked by Cassava green mite?
Among the crops covered here: Cassava.