Grain Weevil

Print page
Grain Weevil - Stored Product Pest - Bayer
Classification
Scientific name: Sitophilus granarius
Family: Curculionidae

Description
There are 3 different species:
  • Sitophilus granaries (Grain Weevil)
  • Sitophilus oryzae (Rice weevil)
  • Sitophilus zeamais (Maize Weevil) 

Each of these species varies considerably in size but has a distinctive elongated snout which is adapted to the size of its preferred grain. Typically, they reach 2-4mm in length and have a long cylindrical body which is dark brown or nearly black in colour.

Grain weevils are encountered in all temperate and warm-temperate climates. They are widely distributed around Europe. Both adults and larvae are cold-hardy.
Rice and Maize weevils are widely distributed in tropical and sub-tropical areas and will be carried to temperate areas on imported commodities.
The maize weevil breeds on maize in the field but the Rice weevil only breeds in stored grain. Both insects will not normally overwinter in unheated premises or grain stored at normal temperatures.

Behaviour
Grain weevils do not fly but instead, infestations often occur after being imported in grain and cereal products, also from the fabric of vehicles used to transport grain or buildings to store it.
The female will lay a single egg inside the grain, where larva and pupa stages will occur, once developed, the weevil bores its way out leaving a hole in the grain.

The Grain weevil can only breed in grain with moisture content of more than 9.5% and at temperature within the range 13-35C.

Risks
Grain weevils are primary grain pests, infesting undamaged grain and attacking other hard cereal products such as macaroni and spaghetti. Weevil-damaged grain is readily recognised by the presence of large holes which are the exit holes of the emerging adults.

Both the adults and the larvae feed on the grain causing holes and also contamination with their excretions. Grain quality and marketability is reduced.

Other Problems

Grain Beetle - Stored Product Pest - Bayer

Grain Beetle

One of the most common pests affecting stored grain...

Read more
Portuguese Black Millipede - Bayer - Pest Management

Millipede

The Black Portuguese Millipede is an invasive pest species...

Read more
Hide and Larder Beetle - Bayer

Hide and Larder Beetle

Typically associated with materials with high protein...

Read more
book lice can damage food sources

Booklice

Detailed information on the pest including classification,...

Read more
Flea - Bayer Pest Control

Flea

Adult fleas live exclusively as parasites of warm blooded...

Read more
Carpet Beetle - Bayer Pest Control

Carpet Beetle

Including varied Carpet beetle, Furniture Carpet beetle,...

Read more
midge - biting flies

Midge - Biting flies

Midges (or "biting flies") are a group of insects that...

Read more

Rust Red Flour Beetle

The Rust-Red Flour Beetle resides in the smallest of...

Read more
Tropical Warehouse Moth - Bayer

Tropical Warehouse Moth

Commonly also referred to as the Almond moth or Dried...

Read more
Lesser Mealworm - Stored Product Pest - Bayer

Lesser Mealworm

This pest favours humidity and warmth and is most prevalent...

Read more

Silverfish

Silverfish are nocturnal and secretive insects that are...

Read more
Case-making-clothes-moth

Case-Making Clothes Moth

They are typically 7–8 mm in length when the wings are...

Read more

Lesser Grain Borer

In Australia and India, it is a serious pest of grains....

Read more
Spider - Bayer - Pest Control

Spider

Most spiders are harmless and play an important role in...

Read more
Flour Beetle - Stored Product Pest - Bayer

Flour Beetle

The Flour Beetle resides in the smallest of crevices, and...

Read more
Tick

Ticks

There are over 850 species of tick. They are all...

Read more

Other Insects

Siverfish, Black Portuguese millipede, Banana Flower...

Read more