After very little effort on our part, we were able to find soybean aphids on soybeans in the Arva Ontario area. Only 5-10% of the plants had 1-15 aphids per plant on average but we found them in every field that was within the VC, almost V1 stage. Similar reports are coming in from Eastern Ontario. Ohio just reported to us that they have found a site with 30 to 40 aphids per plant on several plants in the field.
Ontario experienced early infestations around this date in 2007 but in that year there were only isolated fields within the Arva area and the weather changed to hot dry conditions shortly after and became less favourable for aphid development. So far this month’s weather has been ideal for the aphids to keep multiplying.
Scouting soybeans this week is advised. Particularly those fields that are not treated with Cruiser. Do not rely on planting date to determine which fields should be scouted first. Early planting date this year does not necessessarily indicate first fields to emerge. And the Arva fields are not necessarily the most advanced soybeans in the province. Fields that are at least within the VC stage or bigger should be scouted first. Focus on the newly emerging trifoliates. Aphids are tough to see at this stage, as they are still green from feeding on buckthorn all this time (not their typical Mountain Dew colour) and hide in amongst the leaf hairs. Ants crawling along the plants is a good sign that aphids are nearby.
So far in the fields that we scouted, there have been no beneficials on the plants to take down the aphid populations. Hopefully they will be responding soon but again scouting is encouraged to ensure that the aphid populations do not get out of hand in the absense of their natural enemies.
If you find fields with more than 10 aphids per plant on more than 50% of the plants assessed, please contact me as we are hoping to conduct some field trials for aphid control on these early stage soybeans.