Diagnosing rutherglen bug

Sap-sucking insects that can damage crops and pastures that emerge in warm conditions. Often associated with mintweed after summer rain. Adults can contaminate canola at harvest.

What to look for

Insect Adult

Adult bugs are greyish-brown with dark markings. They are narrow bodied, 3 to 4 millimetres long with wings that are folded flat when the bug is at rest.
Immature bugs are dark red and more swollen in shape than the adults.

Plant

Withered seedlings caused by adults and nymphs sucking on leaves and stems.
Damage is most common on very early sown crops after summer rains have allowed bugs to multiply on summer weeds.
Canola is not damaged after it has developed leaves.

Where did it come from?

Rutherglen bug is a common native insect that breeds in a wide range of weed and crop hosts.
Eggs are deposited on the soil, on grass blades and on the flower heads of weeds.
These eggs hatch into nymphs, which grow through five moults until they become adults. The length of the life cycle from egg to adult is about four weeks.
Rutherglen bugs survive winter as adults and breeding commences in early spring. Large numbers do not usually develop until early summer.

Management strategies

Control summer and autumn weeds prior to seeding, particularly when there is a green bridge over summer and an early break.
Insecticide spray is usually economic if seedlings are withered and rain is not expected.
Several days of continuous rain usually stops an epidemic.

Economic and financial considerations

To assist in assessing the economic risk and financial costs associated with various treatment strategies go to MyEconomicTool [1]

There may be other economic and financial implications that need to be considered when choosing a management option. These may include:

Pre-crop [2]

Understand the potential yield losses associated with RGB feeding damage.
Assess the costs and benefits of taking preventative action.

In-crop [2]

Compare the costs, benefits and risk of each management option against doing nothing.
Consider risk and associated costs or savings of no treatment or delaying treatment.
Consider further costs associated with re-infestation.
Ignore all previous treatment costs in assessing current management options.

Post-crop [2]

Include a resistance management strategy into your spray program.

View these economic considerations in more detail. [2]

How can it be monitored?

Check all young crops, especially those in paddocks that contained summer weeds.