Divisi
Rhizome scale
Aspidiella hartii · Insect
Photo: Friday musa · CC BY-SA 4.0
Rhizome scale (Aspidiella hartii) is a hard-bodied armoured scale insect that infests the rhizomes of ginger and turmeric — the fat underground stems you dig up to eat and sell. Hidden under a circular grey cap about the size of a pinhead, it sucks sap from the rhizome, and colonies build up thickly around the buds until the rhizome shrivels and dries. It attacks both in the field near the soil surface and, above all, in dry storage, where numbers explode. Because it rides silently on infested seed rhizomes and multiplies in store, it carries over from one season to the next on the very stock you keep for planting.
Grey Smith · CC BY 4.0 
Mike Bowie · CC BY 4.0
Why it matters
Rhizome scale attacks the very part you grow the crop for — the ginger or turmeric rhizome itself (the fat underground stem you dig up to eat and sell). The tiny insects hide under a hard grey cap and suck the sap until the rhizome shrivels, dries and loses weight, so a heavy attack can cost you up to 40% — nearly half — of your crop's weight and value. Worst of all, it rides unseen on your seed rhizomes and multiplies in dry storage, so once it is in your planting stock it comes back season after season and is very hard to shake off. The armour cap also shields the insect from sprays, which is why starting with clean seed matters more than any chemical.
When to act
circular greyish scales visible on rhizomes at harvest or in storage
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 rhizome scale field guide
- Identify it
- Scout for it
- Control it
14 field-guide sections in the app
The full guide to rhizome scale — every symptom to check, how and when to walk your field looking for it, and the controls that actually work, ranked. Built into your crop plan, so you are told to look before it costs you a harvest.
Crops it affects
Frequently asked questions
How do I identify rhizome scale?
The damage first: when you lift ginger or turmeric, look hard at the rhizome — the fat underground "hand" you dig up to eat and sell. An attacked rhizome is crusted with tiny circular grey scales, thickest around the buds and eyes (the growing points). Badly hit rhizomes turn light, wrinkled and shrivelled, feel dry and papery in the hand, lose weight, and seed rhizomes kept in the store fail to sprout.
When should I take action against rhizome scale?
circular greyish scales visible on rhizomes at harvest or in storage
How do I control rhizome scale?
Prevent it — start clean (your most important step): the scale travels on seed rhizomes, so plant only clean, plump, scale-free rhizomes and reject any with grey crusts around the buds. Clean seed does more to protect you than any spray, because the armour cap makes the insect hard to kill once it is already there.
Which crops does rhizome scale affect?
Among the crops covered here: Ginger, Turmeric.
Catch it before it costs you a harvest
Divisi builds scouting into your crop plan — it tells you when to walk your field, what to look for at that stage, and what to do when you find it. Free for farmers, works offline.
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