Guardians of the crop: How earwigs protect corn from the Asian corn borer

Earwigs are characterized by their distinctive forceps-like structures at the end of their abdomen called cerci. (Signe Allerslev/Pixabay)


The Asian corn borer, scientifically known as Ostrinia furnacalis, is a notorious pest that wreaks havoc on corn crops, causing substantial yield losses. Farmers around the world are constantly seeking effective strategies to combat its infestations. One such solution involves an insect known as the earwig. As we confront the challenges of pest infestations, the earwig emerges as a valuable asset in the field of natural pest control.

The life cycle of the Asian corn borer

The Asian corn borer’s damage on corn plants begins approximately 20 to 25 days after planting. During this crucial period, adult Asian corn borer moths lay their eggs, often beneath the leaves or occasionally on the upper leaf surfaces near the midrib. These eggs are quick to hatch, emerging as larvae within three days.

Asian corn borers are voracious feeders that leave pinhead-sized holes on the leaves in their initial hours after hatching. As they grow, they molt and increase in size, inflicting larger holes comparable to the size of a match head on the leaves. Eventually, Asian corn borer larvae escalate their damage, boring into the leaves to create holes resembling gunshot wounds.

As corn plants mature and develop tassels, the Asian corn borer larvae will ascend the plant, targeting the tassels, which they infest. The tassels and clusters of flowers eventually succumb to the damage done by the larvae, causing them to break, further compromising the crop.

Asian corn borer larvae pose their most formidable threat as they penetrate the corn stalks, devouring their way through the plant’s vital parts. This invasion disrupts the transport of nutrients, inevitably leading to the breaking of the stalk. Once inside the stalk, they prove exceptionally difficult to control, causing irreparable damage.

Th earwig, a natural predator of Asian corn borer

The earwig (Euborellia annulate) is an insect that exhibits elongated and flattened bodies, with a shiny black hue. Their 10-14 mm length is emphasized by their distinctive forceps-like structures called cerci, extending from the abdomen.

The predatory earwig’s forceps aren’t just for show. These remarkable structures serve multiple purposes, including the capturing of prey. Earwigs feed on a variety of soft-bodied insects, including leafhoppers, aphids, cutworms, and even Asian corn borer’s eggs, larvae, and pupae. They primarily conduct their hunting activities during the night, often gathering in damp areas such as stalks and beneath leaves.

Studies conducted by PCARRD have shown the potent impact of releasing earwigs to counter Asian corn borer infestations. Field evaluations involving the introduction of earwigs have led to astonishing results. Corn yield has surged by up to 40%, accompanied by a noteworthy 8% reduction in production costs for open-pollinated varieties and 10% for green corn.

The prospects of maintaining a sustainable population of earwigs in the fields are promising. Earwigs can disperse up to three to six meters away from their release points, ensuring that their presence extends across the corn crop.

The Regional Crop Protection Center of the Department of Agriculture has taken a proactive approach by actively engaging in the mass production of these biocontrol agents. Interested individuals can access these agents at their regional offices.

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