Integrated pest management
Harvest results 2011
We have recently harvested the first season’s crop in this trial, after a year starting dry and becoming progressively wetter. In early winter, pests such as redlegged earth mites and lucerne flea were present and were effectively controlled in the Conventional plots by the two broad spectrum insecticide applications, whereas in the Strategic plots there were some pests present however the seed treatment meant they did not significantly limit seedling vigour. Plant densities were assessed at various dates after emergence, with Control plots having the lowest plant numbers, then Conventional, while the Strategic plots had the highest numbers at each sampling date (Figure 1).
Figure 1. Average numbers of canola plants per square metre in plots at 7, 14, 28 and 42 days after crop emergence. Error bars indicate standard error of the mean. Different letters above bars indicate significantly different means at each sampling date
(at the P < 0.05 level, Tukey’s-b post hoc test).
Typical ‘spring pests’ (e.g. aphids, diamondback moth, native budworm) appear to have been kept relatively low this season, likely due in part to the high spring rainfall. At no stage did any pests reach a level at which spraying was warranted, and consequently no insecticides were applied to any plots during spring. Beneficial insects on the other hand were relatively high during spring, particularly in the Control and Strategic plots which had no broad-spectrum insecticide applications. For example, aphid parasitic wasps averaged 4–7 per six sweeps across all treatments on the 10th of November.
Yields were variable, with the Conventional plots (1.79 t/ha) averaging the highest overall, followed closely by the Strategic plots (1.70 t/ha), and the Controls were the lowest (1.67 t/ha). Unfortunately, the high amount of rainfall in December is likely to have affected the yield in all plots as harvesting was delayed for several weeks beyond the optimum date and some canola was lost on the ground. Although the Controls had the lowest yield, the difference between the Control plots and the other treatments was less than expected. This is largely because spring rainfall meant canola in these plots was able to recover from early season damage, and consequently the true effect of the strategic approach was not measured.
The Conventional treatment sprays cost $11/ha and the Strategic treatment had a total cost of $1.35/ha, indicating conventional practice may not be the most economical approach for pest management. However, the cost of monitoring and the time taken to identify invertebrates are important considerations, and these factors will be incorporated into the 2011 trial. These components of IPM are likely to be an ongoing challenge in broad-acre cropping, particularly for larger farms, and need to be investigated thoroughly.
 |  |  |
| Stuart McColl | Thunderstorm approaching the trial site, 6th October 2010 | Harvesting the canola plots, 21st December 2010 |
Charlton IPM trial update
The IPM trial at Charlton is now underway after the canola was sown into a dry site on the 11th of May. The trial site at Charlton was selected because it had not been cropped for many years prior to this, and also had minimal insecticide history in recent years. This trial forms part of national GRDC funded project involving a total of five replicate trials across southern Australia The components of each trial are kept as consistent as possible with the overall aim of increasing our understanding of pest and beneficial invertebrate dynamics in grain cropping systems.
 |  |  |
| Sowing the trial 11/5/10 | Spraying a bare-earth insecticide on conventional plots 2/6/10 | Control plot @ 76 days after emergence 17/8/10 |
A variety of methods are being used to assess the trial, and these include:
- Vacuum– to collect small invertebrates from plants and the soil surface
- Pitfall traps– to capture all ground dwelling invertebrates
- Soil cores – to collect species found below the soil surface
- Sweep-netting– used in spring to collect insects from the crop canopy
- Plant damage scores– to assess the extent and type of feeding by invertebrates
- Plant density– to compare numbers of plants per square metre across treatments
These methods have been used regularly from pre-sowing onwards and findings have been used to guide insecticide decisions for the IPM plots. The table below summarises the insecticide applications so far, with treatments in conventional plots guided by local farmer practice. Note that the IPM plots were sown with treated seed and based on our routine monitoring, we have determined that no additional insecticide applications have been warranted to date.
|
| Insecticide – seed treatment | Insecticide – bare-earth (PSPE) | Insecticide – post-emergent |
| Control plots | None | None | None |
| Conventional plots | None | Alpha-cypermethrin@ 100 ml/ha, 2/6/10 | Omethoate @ 100 ml/ha, 30/6/10 |
| IPM plots | Imidacloprid | Not required | Not required |
 |  |  |
| IPM plot @ 76 days after emergence 17/8/10 | Conventional plot @ 76 days after emergence 17/8/10 | Researcher, Samantha Strano (CESAR Consultants) inspecting plants for signs of pest damage |
In terms of plant scores, the conventional plots and IPM plots have had less ‘chewing’ and ‘sucking’ damage than the untreated control plots. The IPM plots have also had the highest average number of plants per square metre which is a very promising results given these plots have had a lower insecticide input than the conventional plots.
As we move into spring we expect to see a different suite of pests which may include caterpillars, increased numbers of aphids and possibly locusts once hatching begins. Monitoring of plots will continue and be used to guide insecticide applications in the IPM plots, whereas insecticides used in conventional plots will continue to mirror local practice as far as possible.
Project background
With support from GRDC, BCG and CESAR Consultants are undertaking a two year Integrated Pest Management (IPM) trial at Charlton to determine whether IPM is the best option for farmers managing pests in the region. IPM is a shift away from the conventional practice of applying broad-spectrum insecticides to infested crops. As the name suggests, it is a pest management strategy which takes a number of factors into account to control damage caused by insects, mites and other invertebrates. IPM principles involve a sound understanding of pest biology, natural enemies of pests (beneficials) and host crop phenology to allow rational use of a variety of control tactics. The strategy also considers economics, the impact on people, the community and the environment.
The trial will compare three pest management strategies: a no input approach (control), a conventional pest management approach (based principally on the application of broad-spectrum insecticides) and an IPM approach. The aim of the trial is to give farmers a better understanding of the different pest management tools and which work best in certain circumstances. It hoped that this knowledge may reduce farmers’ reliance on broad-spectrum insecticides to fight pests. Several potential problems arise with the use of broad-spectrum insecticides; they can be harmful to the environment, present human health risks, and, with increasing application costs, are becoming more expensive. Also, thresholds to identify whether pest populations warrant spraying are unknown and therefore insecticides may be applied without economical benefit.
The preventative use of broad-spectrum chemicals also increases the probability of resistance and secondary pest outbreaks. Where severe widespread resistance has occurred in industries such as cotton and horticulture, growers have been forced to adopt IPM as production is no longer economical using conventional approaches that are largely reliant on broad-spectrum insecticides.
A workshop will be held for farmers and advisors on Wednesday 18 August at BCG to further explain the principles of IPM and disseminate current results.
For more information contact the BCG office on (03) 5492 2787 or Cesar Consultants on (03) 9329 8817.
This work is part of a national IPM GRDC funded project.
 |  |  |
| Stuart McColl from CESAR consultants at the IPM site at Charlton | Locust found at Charlton site | Adult hover fly |
 |  |  |
| Adult ladybird beetle | Lucerne flee | Redlegged earth mites |