T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Weevil (Pea weevil) Bruchus pisorum

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Suborder: Polyphaga
Infraorder: Cucujiformia
Superfamily: Chrysomeloidea
Family: Chrysomelidae
Subfamily: Bruchinae
Genus: Bruchus
Species: B. pisorum
Binominail name: Bruchus pisorum
Common name: Pea weevil

Pea weevil (Bruchus pisorum) is a small flying insect pest whose entire lifecycle is dependent on the pea species (Pisum sativum). It is a major insect pest of Pisum sativum worldwide. 

A Bruchus pisorum infestation in imported seed was not detected by the Ministry for Primary Industries inspectors. Bruchus pisorum were found on March 30 at a Masterton seed processing plant inside a bin of seeds that had been harvested from Wairarapa eight growers. All pea production in Wairarapa was halted from August 1, 2016.

Bruchus pisorum is a small weevil (4–4.5 mm long) globular in shape with long legs. They are a brownish-grey in colour and flecked with white. The wing casings (elytra) do not reach the end of the abdomen, leaving the last abdominal terga exposed. The last abdominal terga have white markings and are covered with setae (stiff hairs).
The larvae of the Bruchus pisorum are grub-like, crescent shaped, white to cream in colour and about 6mm long when mature. The larvae have a brown head capsule and mouthparts, their legs are reduced.
Females lay a dozen yellow eggs on the outside of young pea pods. The larvae hatch and burrow through to the seed pod wall and into the seed, creating a small, dark entry hole, about 0.2 mm in diameter. The larvae initially feed near the surface of the seed and then move into the centre of the seed to feed more extensively. Infested peas are 'heated' by the development of the larva. The fully-grown larva prepares an exit hole. It eats its way out towards the seed surface and chews a circular hole, about 3-5 mm in diameter, partly through the seed coat. A dark, circular window can be seen on the pea. The larva pupates behind this window. They can spread by flying between flowering crops, they are also spread through the movement of infected pea seed, pea straw or machinery.

Click ling below for MPI’s fact sheet.
http://www.hortnz.co.nz/assets/Uploads/Pea-weevil-fact-sheet-20.5.2016.pdf

  

The weevils head.


Diagram of  Bruchus pisorum life cycle