I have had a few calls from some reps and growers who have been amazed and delighted and some who have been frustrated and frazzled this week. But I’m in it with you, believe me. Soybean aphids seem to be very active right now, developing winged generations and have been moving from one field to another for the last two to three weeks. I have had sites that were approaching 200 or more and then the very next week there were barely 20 per plant with a lot more natural enemies present too. In part this drop is due to the natural enemies that are moving in to make the kill. But a stronger influence could be the cooler temps we are starting to experience at night and the desire of the aphids to keep finding later planted fields to finish off in before heading to buckthorn. We tend to still see aphids active in fields until at least the second week of September but this year is a bit of a guessing game. On one hand, the soybean growth stages are behind and have quite a few more weeks to go before maturity, on the other, the temps are starting to make it feel like fall already.
Either way, it does mean that it really pays off for you to at least hold off a couple days before spraying at threshold just to make sure that the aphids are truly there to stay. If you are lucky like some, they may decide to leave and the ones that are left can easily be taken care of by the natural enemies.
Patience is key when it comes to these aphids.