- Bruchids are small (most range from 1.5 to 4.5 millimetres long), globular, triangular or teardrop-shaped beetles.
- The beetles are usually dull coloured, with markings on the wing covers (elytra), which do not typically cover the entire abdomen.
- Bruchids feed on a range of seeds, particularly pulses harvested for their dried grain, such as mungbeans, chickpeas and faba beans.
- Some bruchids are host-specific while others are polyphagous (subsist on a wide range of pulses).
- Adults are active and can readily fly, while larvae feed inside individual seeds, where their presence can go unnoticed as symptoms of infestation are not obvious until harvest.
- Adults lay eggs on seedpods. The larvae hatch and bore directly into the seedpod to feed inside the developing seeds, causing reduced seed quality, germination and yields.
- Larvae pupate inside the seed and infestations could potentially spread as infested seed is moved.
- The most obvious sign of bruchid infestation is the presence of round exit holes in the sides of pulse grain. The small adult beetles may also be seen around the infected grain and/or in the paddock.
Bruchids, such as the Mexican bean weevil, cause damage to pulses that make crops unattractive to the human food market, which is growing.
PHOTO: Frank Peairs, Colorado State University, www.bugwood.org
Protecting stored pulses against insect pests such as species of bruchid beetles can help growers gain access to higher-value export markets for human consumption.
Bruchids are little-known pests that leave holes in stored pulse grains – the kind of damage that is likely to result in a crop being rejected by export markets, which were worth an estimated $1.3 billion to Australian pulse producers in 2014-15.
Australia has several native bruchid species, which most commonly affect pulses in more humid environments. However, Mary Raynes, from Pulse Australia, says this situation could easily change as insects have a tendency to evolve and adapt to broader climate ranges.
“It might be just a matter of time before these pests are able to spread to southern-Australian production regions if they are not monitored and controlled,” she says
There are currently no exotic bruchid threats in Australia, a situation the grains industry would like to maintain, particularly given its reputation for high-quality, blemish and insect-free lentils, chickpeas, field peas, mungbeans and faba beans.
“Exotic bruchid species such as Bruchus emarginatus and Zabrotes subfasciatus would make it even more challenging to produce high-quality disease and insect-free food for overseas markets,” Ms Raynes says. “Australia’s grain growers don’t need the extra difficulties that these exotic pests would pose in what is already a competitive market.”
Border biosecurity plays a vital role in preventing bruchid damage, but good on-farm biosecurity is key. Clean pulse production and grain-storage hygiene are essential.
Bruchids can occur in-crop, feeding on the pollen and nectar of some pulse flowers. However, their damage is more obvious in stored grain and growers should monitor their grain stores, ensure that they know how to identify bruchids and what their damage looks like (see fact box below).
Growers are advised to immediately report any insects that they do not recognise to state government authorities or the Exotic Plant Pest Hotline (1800 084 881).
Storing pulse grains in sealable silos is the best way to maintain seed coat colour and to protect grain quality against potential downgrades.
Ms Raynes says that not all silos are sealable to Australian standards. Improving on-farm and commercial storages to ensure they are gas-tight allows growers and grain handlers to achieve total control when treating insect infestations in stored pulses. More information on grain storage is available at the Stored Grain website.
Ms Raynes believes that the benefits and extensive uses of pulses are now being realised. For example, the area planted to faba beans globally is increasing, with emerging markets in Poland, Lithuania and Ukraine. There are also improved market opportunities for premium pulses for human consumption through use in canning, snack foods, protein bars, protein chips and noodles.
Plant Health Australia
Stored Grain Information Hub
Exotic Plant Pest Hotline, 1800 084 881
Stored Grain Pests Identification: The Back Pocket Guide
Grain storage is about food and safety
Pest identification in Grassroots Agronomy classes