Staggered germinations and insect impact on canola
By Paul Breust, Projects Coordinator SFS
Southern Farming Systems is comparing crop performance in retained stubble as part of the GRDC funded project “Maintaining profitable farming systems in retained stubble”.
We presented an article three weeks ago on the emerging dangers of dry sowing. This trial was sown to canola on April 12 at Streatham in South-West Victoria.Following the break on the May 10 we have since seen more canola establish in both treatments. Local advisers have reported widespread staggered emergence in canola this year resulting from the dry start to sowing.
To refresh the trial details, we are evaluating disc compared to tine sowing, into retained stubblecompared to burnt, with urea added at sowing. The Initial results showed the disc seeder had lower establishment than the tine seeder in both the burnt and stubble retained treatments.
On April 28, sixteen days after sowing, the disc seeder in stubble had 1 plant/m2and in the burnt area had 3 plants/m2. On May 19, five weeks after sowing, the disc seeder in stubble had 12plants/m2 emerge and the burnt area had 20 plants/m2. The tine in stubble had not changed between the two dates while the tine in burnt areas had increased slightly.
Urea was applied at sowing to half of each plot to test the impact this had on establishment, growth and yields. Applying 60kg/ha of urea with the seed in the retained stubble and burnt sections had very little effect on establishment for the disc. This surprised us as it is commonly thought that urea with seed at dry sowing will reduce disc emergence. However in the tine plots adding urea at sowing dropped establishment by 6 plants/m2 in both stubble and burn sections. This was despite the urea being placed under the seed to minimise impact.
To examine the impact of post sowing baiting, Mesurol at 2.5kg/ha, and Metarex at 8kg/ha were appliedin three 10m wide bands across the trial site. The reduction in plant numbers was very noticeable in the unbaited areas in the stubble retained plots. In the disc plus stubble plots, establishment dropped from 12 plants/m2 to 2 plants/m2. In the disc plus burn withno bait, emergence was reduced by 5 plants/m2. The tine plus stubble emergence with bait was 6 plants/m2 higher whilst in the burn plus bait there were 4 plants/m2 more plants than no bait.
We placed tiles in each treatmentstrip immediately after sowingto allow us to count slugs, millipedes and earwigs. No slugs have been found to date. Millipedes were present in high numbers and the seedlings suffered serious damage. The whole site had an insecticide applied on May 12. It was sprayed at night to maximise efficacy. Counts after spraying indicate reasonable control but there are still low levels of millipedes alive.Numbers are similar to those present on the April 28 and will need to be watched to manage any spikes in populations that may damage late emerging seedlings.
The work thus far has highlighted the many challenges with establishing canola in the Western district of Victoria and we will update growers regularly on any further developments. Millipedes and Earwigs can cause serious damage to emerging canola and there is little or no information on threshold levels, integrated pest management (IPM) methods and efficacy of a range of control measures. Growers traditionally use Cosmos coated seed or apply insecticides either pre or post sowing. By retaining stubble,pest damage can be significantly worse compared to burning, as stubble provides an excellent habitat for survival.
Follow progress on the SFS web site or Stubble Project Wordpress Site