Native cockroaches in crops

Two recent reports of native cockroaches damaging canola are unusual, but can be related to retained stubble and possibly a warm autumn.

Where have they been reported?

Within the past fortnight, reports of cockroaches possibly feeding on canola cotyledons have been received from near Normanville (Victoria’s Northern Country) and Hopetoun (Victorian Mallee).

In both cases the cotyledons had either been chewed or completed nipped off, leaving only a stem. There was no direct evidence that the cockroaches caused this damage, but in the Hopetoun crop, they were quite abundant and there were no other pests found.

In Normanville, vegetable beetles were also present and probably contributed to the damage.

Both locations had stubble coverage close to the drill rows that is likely to have been a major factor in their presence.

About native cockroaches

More than 500 species of cockroaches have been recognised in Australia, over 90% of which are endemic. They are extremely diverse in behaviour and occupy just about every type of habitat.

The identity of the pest species apparently causing the damage to canola is unknown.

In Queensland, wingless (native) cockroaches (Calolampra spp.) are recognised pests of seedling field crops. Cockroaches are probably less common in south-eastern Australia as they prefer warmer conditions.

In cropping environments within south-eastern Australia, native cockroaches have not previously been reported as a pest. The majority of species are detritivores that prefer to break down dead organic matter.

However, increasing stubble loads within newly seeded paddocks provide the moist, dark and sheltered habitat that these insects prefer, and damage to the emerging seedlings is possibly opportunistic.

Our advice

The damage caused by cockroaches this year may be a reflection of the warmer than average autumn. As such, cockroaches are unlikely to become a major pest in crops even within high stubble loads.

Control is unlikely to be warranted.

Management of stubble is the key to reducing feeding damage. Insecticide treated seed may also reduce damage to emerging crop seedlings.


Sources of field reports of cockroaches

Bronwyn Hunt – Grower, Merriwa Pastoral Company (Victoria’s Northern Country)

John Stuchbery – Agronomist, AGRIvision Consultants (Victorian Mallee)

Cover image: Photo by John Stuchbery

What is Pestfacts south-eastern?

PestFacts south-eastern keeps growers and advisers informed about invertebrate pests and beneficials in broadacre crops and pastures during the winter-cropping season in Victoria and southern New South Wales.


Never miss a beat. Get articles, advice and more straight in your inbox.

Since 2019 PestFacts south-eastern has been running through IPMforGrains: Best Practice Insect Pest Management, a project delivered by the National Pest Information Network (Cesar Australia, DPIRD, QDAF, NSW DPI, and SARDI). This project aims to provide grain growers and advisors with information on invertebrate grain pest occurrence and equip industry with the knowledge needed to implement integrated pest management practices. This initiative is a GRDC investment and includes in-kind contributions from all project partner organisations.

The online PestFacts south-eastern collection also includes a selection of articles published between 2015 – 2018 when the service was run through a previous GRDC investment, The National Pest Information Service.

PestFacts south-eastern is supported by