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Aspergillus flavus Link, 1809 (with A. parasiticus in groundnut)
Aspergillus flavus is a common soil mould that infects maize ears and groundnut pods, especially in hot, dry seasons and in insect-damaged or poorly stored produce. Its main danger is not the visible mould but aflatoxin, a poison that causes liver cancer, stunting in children and, at high doses, fatal acute poisoning; it also harms livestock. Grain can be heavily contaminated without obvious mould, so prevention from field to store is essential.
Aspergillus ear rot and aflatoxin is caused by Aspergillus flavus Link, 1809 (with A. parasiticus in groundnut), a fungus (mould, an ascomycete) (order Eurotiales, family Aspergillaceae).
Present worldwide in warm soils. Aflatoxin contamination is most serious in hot, drought-prone and humid tropical regions - sub-Saharan Africa, South and Southeast Asia, Latin America - and in the southern United States in drought years.
| Region | Status |
|---|---|
| Sub-Saharan Africa | Widespread; a major food-safety problem |
| South and Southeast Asia | Widespread in maize, groundnut and spices |
| Americas | Present; outbreaks in drought years |
| Other regions | Present; imported products regulated |
The mould forms olive-green to yellow-green powdery spore masses. Strains differ: many produce aflatoxins B1 and B2 (A. parasiticus also G1 and G2), while some strains produce none (atoxigenic strains). Aflatoxin is detected only by laboratory or rapid test kits, not by eye.
| Crop stage | What you see |
|---|---|
| Silking and grain fill (maize) | Usually no visible signs; infection enters through silks and insect damage. |
| Maturity and harvest | Olive-green powdery mould on and between kernels, often at the ear tip or around insect damage; bright greenish-yellow fluorescence of kernels under ultraviolet light may indicate infection. |
| Storage | Mould growth, heating and caking in damp grain or groundnuts; contamination can rise rapidly in storage without visible mould. |
The fungus lives on soil and crop residues and produces airborne spores that reach maize silks and groundnut pods. Infection increases sharply when crops suffer heat and drought during grain or pod filling and when insects damage kernels or pods. After harvest, slow drying and humid storage allow further growth and toxin production.
| Stage | Duration | Notes |
|---|---|---|
| Survival | In soil and residues | Sclerotia and mycelium. |
| Spore dispersal | Hot, dry periods | Air and insects. |
| Infection of silks, kernels and pods | Grain or pod filling | Drought and insect damage increase it. |
| Growth and toxin production | Field and storage | When grain moisture stays high. |
Field infection is favoured by high temperatures (about 30-35 °C) and drought stress; in storage, toxin production is high at about 25-35 °C when grain moisture is above about 13-14%.
Continuous where conditions allow.
Heat and drought during grain or pod filling, insect damage (ear borers, weevils, termites), late harvest, rain at harvest, slow drying, damp storage and damaged grain.
There is no field threshold; the relevant limits are legal maximum levels for aflatoxin in food and feed, set by Codex Alimentarius and national regulators (for example 15 micrograms per kilogram of total aflatoxins for groundnuts for further processing in the Codex standard). Lots above the limit are rejected or diverted.
Thresholds are local. They depend on crop price, control cost, variety and natural-enemy activity, so use the figure your local extension service publishes where one exists.
Aflatoxins cause liver cancer and acute poisoning in people (outbreaks in East Africa have killed many people), are linked to stunting in children, reduce livestock growth, and lead to rejected exports and lower prices.
Control works best as a sequence: prevent, monitor, then act only when a threshold or a risk forecast says so, using the least disruptive option that works.
Fungicides do not prevent aflatoxin effectively; control focuses on agronomy, insect control, drying, storage and biocontrol. What is registered differs by country and changes over time; follow the label and your local plant-protection and food-safety authorities.
Maize and groundnut are the most important; also cottonseed, tree nuts (pistachio, almond, Brazil nut), chillies and spices, rice and sorghum in storage, and dried fruit.
How to grow the crop well is the first line of defence. Laisha's free grow guides cover each crop from sowing to harvest:
Written by Laisha from the sources above, in its own words. This page is general reference, not a prescription: confirm identification locally and follow the label and your plant-protection authority.