Pea weevil

Bruchus pisorum (pea weevil) adults are subglobose, compact beetles, 6–7 mm long, with relatively long legs. The elytra are shortened and do not reach the abdominal apex, leaving the posterior tergites exposed. The terminal abdominal tergite carries a distinct pattern of black and white setae. Along the inner ventral margin of each metafemur, a single denticle is present. Larvae are white, soft‑bodied, and virtually apodous.

A bruchine primary pest of stored legumes, this internal feeder attacks peas in storage. Adults and larvae are endophagous, consuming the cotyledons within each seed. Infested peas show minute oviposition/entry punctures, and mature adults leave circular emergence holes about 2.5 mm in diameter. Feeding hollows out the kernel until only the testa (seed coat) remains, producing light, perforated, non‑viable seeds. Consequences include severe dry‑matter and test‑weight loss, high levels of fines and powder (frass), and contamination with frass, cast exuviae, and cadavers. Lots are visually downgraded by the characteristic round holes, with seed germination essentially destroyed. Perforations increase moisture ingress, favor mold development and off‑odors, and can lead to caking and spoilage. Under heavy infestation, entire pea stocks may be reduced practically to dust.

Key signs of the pea weevil (Bruchus pisorum (L.)) in stored pea grain are unmistakable seed perforations. Infested seeds exhibit clean, circular entry or emergence holes formed by endophagous larvae that feed within the cotyledons and by adults that later exit. Internally, cotyledons are tunneled, with smooth-walled feeding galleries and compact, powdery frass; split seeds often appear partially or completely hollowed. Batches may show lightweight, shrivelled kernels, reduced germination, and occasional live or dead bruchid adults among the grain. Together, these features confirm a bruchid infestation in storage.

Pea weevil, Bruchus pisorum, reproduces via an endophagous cycle. Females oviposit on pea pods. After eclosion, the neonate larva bores through the pod wall and penetrates a developing seed, where it feeds and completes larval development. Pupation occurs in situ within the same seed, typically in a chamber sculpted in the cotyledons. The adult (imago) then emerges by drilling a clean, round exit hole through the seed testa. This concealed development leads to hidden infestation and undermines grain integrity during storage.

Prefers flowering pea fields in temperate spring. Adults colonize canopies and oviposit on green pods; larvae are seed endophages. Volunteer pea stands and split peas amplify pressure. It cannot reinfest dry, cool stores—storage is an unfavorable habitat.

Bean weevil (Acanthoscelides obtectus); Chinese bruchid, also called the adzuki bean weevil (Callosobruchus chinensis).