Rutherglen bug in canola stubble – potential to damage establishing summer crops.

Melina Miles   November 12, 2013   Comments Off on Rutherglen bug in canola stubble – potential to damage establishing summer crops.
Canola stems with adult and nymphs clustered on the base after harvest.

Multiple stems with adult and nymphs clustered on base post harvest.

Rutherglen bug (RGB) are best known for the damage they can cause in sunflower and sorghum during grainfill, but they can also damage and even kill seedlings when present in large numbers.

In 2012 RGB damaged establishing spring crops in areas of southern and northern NSW.

This spring, in some crops there are large numbers of RGB in the canola stubble post-harvest.

As the canola stalks start to dry out and no longer provide a source of food, the RGB start moving out of the canla stubble and into neighbouring fields, or onto emerging seedlings planted directly into the stubble.

All summer crops are susceptible to direct feeding damage from RGB, including grains (sorghum, soybeans, sunflower) as well as cotton. Damage to seedlings in neighbouring fields tends to be along the crop margin closest to the canola stubble.

Symptoms of RGB feeding on a cotton seedling.

Wilting as a result of RGB damage to petioles of a cotton seedling.

Symptoms of RGB damage to canola include wilting, browning of leaves and terminals and the death of small seedlings.

Managing RGB moving from canola stubble

If large numbers of RGB move into the establishing crop, insecticide seed dressings will not prevent damage to seedlings, as each RGB must feed to get a dose of the insecticide, and in doing so contribute to the plant damage.

Some of the tactics suggested to minimise crop loss caused by RGB moving from canola stubble into neighbouring crops are:

i) plough a deep furrow or cultivate the ground between the susceptible crop and the canola stubble,
ii) apply an insecticide bare earth barrier treatment
iii) fill channels, tail drains or head ditches with water to form a barrier

Flightless nymphs are most commonly move from the stubble to the seedling crop, which is why tactics that form a barrier to ground movement are effective. The winged adults appear to disperse more widely from the stubble, rather than moving into nearby crops.

Planting into RGB-infested canola stubble
Planting into canola stubble where there are RGB nymphs is high risk as the nymphs can easily move from stubble to seedlings as they emerge. RGB infestations in canola stubble is patchy, so damage and seedling loss will  occur in patches across the field where the RGB densities are high.

If damage to seedling and seedling loss is severe, it may be necessary to control the RGB by treating the field. High water rates and good coverage will be needed to control the nymphs sheltering on the stubble and trash.

Watch a short video on  Rutherglen bug in canola stubble on the Beatsheet YouTube Channel.