The cabbage stem weevil (Ceutorhynchus pallidactylus) and rape stem weevil (Ceutorhynchus napi) are two closely related species that cause significant damage to canola crops in Europe.
The rape stem weevil primarily affects canola, while the cabbage stem weevil affects canola, Indian mustard, radish, white mustard, sea kale and field penny cress.
The larvae of both species feed inside the stems of canola plants and cause significant yield losses, with losses of over 30% reported overseas.
Cabbage stem weevil and rape stem weevil are small (<4 mm) dark greyish coloured beetles that are covered in white hairs and feed on brassicas.
Larvae live inside the stems of the host plant and are white coloured with yellowish heads. The larvae are up to 8 mm long and 0.5 mm wide.
Larvae feeding inside the stems of infected plants cause the plant to show a loss of vigour, stem distortion, leaf loss, delayed flowering and lodging. Close inspection of the stems may reveal very small exit holes caused by the larvae leaving the host plant to pupate underground.
Adults could be confused with other small weevils, such as the endemic spotted vegetable weevil and the small lucerne weevil, however, the larvae of these species do not affect canola stems. Similarly lodging can occur for various reasons. Any larvae found within lodged stems should be investigated further.
Look for the small, grey coloured adult beetles, which begin laying eggs during the stem elongation stage.
It is also important to investigate the cause of lost vigour, split or distorted stems, leaf loss, delayed flowering or lodging. Affected stems should be inspected for signs of pin sized exit holes or split to look for larvae.
Adults are capable of flight allowing localised spread. It is also possible that they could be accidentally spread on vehicles or machinery.
Cabbage stem weevil and rape stem weevil are only known to occur in Europe.
You can protect your farm from cabbage stem weevil and rape stem weevil by checking your property frequently for the presence of new pests and by closely examining the cause of any lodging in canola crops. Make sure you are familiar with the symptoms of common pests so you can tell if you see something different.
If you see anything unusual, call the Exotic Plant Pest Hotline on 1800 084 881.
You can protect your farm from cabbage stem weevil and rape stem weevil by checking your property frequently for the presence of new pests and by closely examining the cause of any lodging in canola crops. Make sure you are familiar with the symptoms of common pests so you can tell if you see something different.
If you see anything unusual, call the Exotic Plant Pest Hotline on 1800 084 881.
