To spray or not to spray

Although our growing conditions are often a lot different it’s still a good idea to keep an eye on what’s happening south of the border – if only as an early warning of what might happen here. Take soybean aphids for example. Yes, they’ve started to show up across much of the province last week, but not in particularly huge numbers. OMAFRA issued a heads-up in last week’s Crop-Pest newsletter but a couple of agronomists that I spoke to this week didn’t seem too concerned - yet.
It’s a different story on the other side of Lake Erie. Ohio State University entomologists found the critters on early planted beans – as many as 100 per plant. That’s well below the threshold established for later infestations but experts readily admit they have no idea what the spray trigger should be when the plants are still small.
So, should you go in and spray this early – just to be safe? It’s a tough call. There’s no guarantee you’ll get a yield benefit. In fact, some will tell you that in a year with lots of moisture the impact of aphids, even on smaller plants, is not nearly as big a deal. If it had been hot and dry all along, the risk would be much greater. And, according to people like OMAFRA’s Tracey Baute, the last thing you want to do is knock back the beneficial insects that may be able to keep the aphids at acceptable levels and save you a lot of money on insecticides. Once they’re gone and the aphids start to build up again – and boy can they do it quickly when the weather turns warm - you’re on your own.
But she’d like to know if you do happen to find aphids on about half of the bean plants in your scouting pattern. She’s doing some trials on early season aphid pressure and your information could help everyone in the future. She’s at 519-674-1696.
One thing on which everyone seems to agree: this is a good year to have Cruiser-treated beans. The seed treatment protects beans against several insect pests but, when the aphids come out early, there’s the extra bonus of not having to make that spray decision for the first 60 days at least.