Bug problems can strike when you least expect them. About 35 years ago, we had “woolly bear caterpillars” invade our farm, causing us to spray most of our acres. I had never heard of that insect prior to them showing up in massive numbers in our crops. Since then we’ve had grasshoppers, painted lady butterfly larvae, stinkbugs, black cutworms, soybean aphids, spider mites, bean leaf beetles, and I’m probably missing a few others, too. All these bugs appeared seemingly out of nowhere, and within a few days of us spotting them, we were spraying.
Our number one piece of advice is always, “Scout your fields often”, because you never know what new or old insect may show up, and when exactly you will need to spray. Below is a list of some mid to late-season insects to watch out for this summer and how to get them under control.
Before I go through this big list of insects, let me also say that economic thresholds have almost never been so low. The economic threshold is the amount of insects you must have in your field to breakeven from an insecticide treatment. This varies based on potential yield loss, the price of the crop per bushel, and your total cost of application. If you are already out spraying something else like a herbicide or fungicide, your cost could be as low as $2 per acre, since many pyrethroids are that cheap. On the other hand, if let’s say you need to use an expensive miticide for $10 and you have to call in a plane for another $10, $20 in total means more yield would be needed to offset the expense.
Corn – Western bean cutworm late season, corn leaf aphids on the tassel, grasshoppers at any point, adult corn rootworm beetles clipping silks, European corn borer for the rest of the summer, spider mites (not an insect but a definite threat, especially if they are damaging the ear leaf).
Soybeans – Gall midge larvae (on your end rows look for holes in the lower portion of the stalk the rest of this summer), soybean aphids (don’t believe the 250 thresholds, I can promise you it doesn’t take that many aphids to hurt your yield), bean leaf beetles (look for a black triangle on the back right behind the head), painted lady butterflies and their larvae at any time, adult corn rootworm beetles (control them as soon as you seed them and you will have fewer rootworm issues in your corn next year), stinkbugs & spider mites at any time, Dectes stem borer, thrips, whiteflies, leafhoppers, and many others!
Wheat – aphids, grasshoppers, mites, wheat stem sawfly, armyworms, Hessian fly, cereal leaf beetles
INSECTICIDES
Since Lorsban is now off the market for corn, soybeans, and wheat, you may be wondering about alternatives. Here are your best options. All of these are labeled in corn, soybeans, and wheat except Brigade, which is only for corn and soybeans.
1) Second-generation pyrethroids including Mustang Maxx, Silencer, Warrior, and Asana. These are great on most insects but have no activity on spider mites.
2) Brigade (Capture/bifenthrin) – 3rd generation pyrethroid. Brigade has more residual and slightly better control on most insects than the second-generation products. Plus, it gets spider mites. That’s also why at a minimum it costs about double what the other pyrethroids do, and it’s not labeled in wheat.
3) Dimethoate. This insecticide is in the same chemical family as Lorsban, organophosphate. It also costs similar money at around $7 per acre. The differences, though, are that Dimethoate is not as effective on most insects, and it doesn’t have the “gas” effect that a lot of people liked about Lorsban. When spraying Lorsban, it would move around a little bit inside the crop canopy, which helped the control. Dimethoate does have activity on spider mites, soybean aphids, grasshoppers, and many other common pests, so it is certainly a good option as a rotation partner for the pyrethroids. Acephate is also in the same chemical family (Group 1B), but it doesn’t kill spider mites and it costs a little more than Dimethoate, running in the $8 to $11 range for the low and high rates.
4) Group 1A – Carbamate – Lannate – $6 to $12/acre – has broad-spectrum activity on worm species, aphids, beetles, thrips, and suppression on stinkbugs
5) Group 4C – Transform –$6 to $8/acre – best on aphids, has suppression of stinkbugs and is easy on most beneficial insects
6) Group 28 – Prevathon – $6 to $16/acre – best on worm species including Dectes stem borer
7) Group 4D – Sivanto Prime – $17 to $33/acre – has activity on aphids, leafhoppers, and whiteflies
8) Group 5 – Radiant – $14 to $40/acre or Blackhawk – $9 to $27/acre – best on worm species but has grasshopper suppression
Despite losing Lorsban there are still many good insecticides. Just be sure to keep scouting your fields on a regular basis, spray if necessary, and don’t forget the economic threshold for this year is lower than almost ever for any harmful insect or mite in your fields.