Generally speaking, late-planted crops are subject to more insect problems during the growing season. With rains and flooding keeping Mid-South farmers out of the field, scouting should be more intense this year.
“That’s one reason we plant milo and corn so early — corn borers, sorghum midge, and others,” says Gus Lorenz, Arkansas Extension entomologist. “The later you plant and harvest cotton, the more the crop is subject to late-season pests like bollworms, budworms and fall armyworms.”
However, none of that is written in stone. “Of course, pest problems depend on what happens with environmental conditions after planting. Yes, we’re set up for harder growing and harvesting seasons. There’s nothing definite about what will, or won’t, show up. But it’s fair to say this later planting is setting us up for more insect trouble.”
Sometimes the unexpected happens. After last year’s Easter freeze, cotton was planted later in much of north Arkansas. Those fields largely “avoided some of the problems cotton in southeast Arkansas had with bollworms and plant bugs coming out of corn into the cotton. Maybe something similar will happen again.”
Lorenz is now seeing high aphid populations in Arkansas wheat unaffected by flooding. “Generally, we don’t treat for bird cherry-oat aphid — the predominant aphid in the wheat currently. The aphids are showing up most in the earliest-planted, most lush wheat.”
There are some green bugs, as well. “At 18 to 20 inches high, the threshold for those is 300 per linear foot. We haven’t found a field that needs treatment yet.
“But there are some extremely high populations of bird cherry-oat aphids. Last year, a study in Mississippi showed that where those were running 200 per stem, an insecticide application increased yield about 20 bushels. We’re currently trying to reproduce that study in fields around Arkansas.”
Arkansas recently received a Section 18 designation for Dupont’s Dermacor, a seed treatment Lorenz believes will be a strong replacement for Icon.
“The EPA took Icon away a couple of years ago. From one year of tests, Dermacor looks to have all the efficacy of Icon — maybe even a bit better.”
This year, acreage for the product is limited to between 18,000 and 20,000. However that will still give researchers a good look at it.
“I’m very curious how well it’ll perform on rice pests like grape colaspis, our number one pest. It also has good activity on rice water weevil — and there’s no doubt about how well it does on the weevils.”
Dermacor has outstanding residual qualities. It is rather expensive, however, particularly for growers using high seeding rates.
“Here’s the thing, though: this product — just like Icon in the past — will allow growers to cut back on seeding rates. That’s because Dermacor will protect the seed and help them jump out of the ground, lessening the need to plant such a high seeding rate.”
The seed treatment makes use of a “unique chemistry. It’s the only product in its class and there are no issues with any resistance. It’s also what the EPA terms as a ‘green’ product. It has virtually no problems with off-target insects or organisms. It has low mammalian toxicity, so it has a nice profile.”
With soybean seed so difficult to find, Lorenz suggests growers “seriously consider a seed treatment. That’s especially true for fields with a history of rootworm, wireworms or grape colaspis problems. Our studies indicate you can expect a yield increase of 3 to 6 bushels with an insecticide seed treatments.”