Insect Damage

Insect damage is assessed visually on a representative sample drawn from the lot: an inspector examines individual kernels for exit holes, internal tunnelling visible on cutting or breaking a kernel, surface gouging, or other feeding marks characteristic of storage insects. The share of kernels showing this damage is reported as the grading figure. It is a manual, visual method — no instrument counts damage automatically, and the result depends on the sample drawn being genuinely representative of the lot.

Because the assessment looks at physical evidence left behind rather than at the insects themselves, it necessarily lags behind, and can diverge sharply from, the actual pest status of the lot at the moment of inspection.

The reverse failure is more consequential: an early or hidden infestation can produce almost no visible damage. Internal feeders such as weevils and the lesser grain borer lay eggs inside or bore into the kernel and complete larval development entirely within it, emerging only once they reach adulthood. A lot can therefore be heavily infested internally — with substantial numbers of insects developing inside apparently sound kernels — while a visual inspection finds very little damage to report, because the insects have not yet emerged.

Because visible damage lags behind an active infestation, stored-grain monitoring often adds temperature probes at fixed points through the bulk. Insect feeding and respiration generate heat, so a rising temperature reading near a probe can be an early warning of activity before it produces visible kernel damage.

This is a surveillance proxy, not a direct measurement of insect numbers or damage. A probe only senses heat that reaches its location, and a stable or normal temperature reading is not evidence that a lot is free of insects — activity in a pocket of the bulk away from the sensors can go undetected. Probe readings and grain-probe sampling, which determines what a drawn sample actually contains, work together with visual inspection rather than substituting for it.

Where an active infestation is confirmed, control measures — fumigation, aeration, sanitation, or other interventions — are governed by product labels, national pesticide and food-safety regulation, and qualified pest-control operators. This entry does not describe fumigant doses or treatment procedures; those are set out in the applicable product label and regulatory framework and must be applied by suitably qualified personnel.