By Tracey Baute, OMAFRA Field Crops Entomologist
Some fields are starting to see soybean aphids colonize in the last few weeks. This is their typical behaviour and of no concern until soybeans reach the R stages, specifically R1 to R5.
Plants need to have at least 250 aphids per plant across 80% of the field and see that population increasing over time before a spray is warranted.
Yield is impacted once aphids reach 660 per plant so there is some time to assess whether natural enemies are sufficient to keep the population from rising. We have had many fields in the past see aphid numbers rise to 300 and even 400 aphids per plant one week and drop down to below 250 the next, thanks to the help of the beneficials. That is why it is important to not spray too early as the insecticide knocks back the beneficial population far longer and allows the aphids to rebound in their absence.
To help you make that spray decision, we have a new version of the Aphid Advisor app available for download. This app uses both aphid and natural enemy numbers entered, as well as expected population growth rates, to indicate whether there are enough natural enemies to keep aphid populations below action thresholds or if an insecticide application may be needed.
The new version has an aphid pressure estimator showing varying levels of aphids per leaf to help speed up some of the work in determining if your populations are even close to worrying about or are already way above what natural enemies can help control. If it is in the grey area or maybe there are enough natural enemies, then the app takes you through the more detailed scouting process to come to a decision of whether to “Spray”, “Wait” or “Do not Spray”.
We have also added photos of the various soybean R stages to help ensure you are in the correct stages that the action threshold works for. And finally, regional results based on other users results will be displayed on the app and the website, showing you if other fields nearby have also required spraying or not.
The app is free and available for both Android and Apple devices at: www.aphidapp.com.
Thank you to our sponsors for covering the costs of revising the Apple version and creating the new Android version. And a big thanks to AgNition for their hard work and patience in revising the app.