Pest prospects for new crop season

ANKENY, Iowa — Looking back on the challenges and successes of the previous growing season can be used to gauge what lies ahead in 2023.

Mark Storr, BASF senior technical service representative, covers central Iowa from Minnesota to Missouri and reflected what he saw in his territory last year and what to look out for going forward.

“Every year is a little different and certainly the environment plays into that. Insect pressure in 2022 was not severe, but there’s always a presence of things like Japanese beetles. We worry about armyworm in the spring in no-till and cover crops. Black cutworms seem to be a little more prevalent in 2023, which like one out of every seven years we need to be concerned with that,” Storr said.

“We had the usual suspects that show up every year, soybean aphids, for example. There hasn’t been a lot of aphid pressure in the dry years we’ve had, and we’ll see if that changes in 2023.

“It’s a dynamic situation with the dry weather we’ve had. We may see a greater grasshopper population in 2023 because they had some pretty good conditions for reproduction last year.”

Corn rootworm is another pest of concern, particularly due to the loss of some effectiveness offered by the Bt trait.

“Mother Nature has allowed the rootworm to become resistant to the Bt, and so we’re seeing a resurgence of that in some areas,” Storr noted.

“We generally think of it being more prevalent in corn-on-corn fields because the western corn rootworm overwinters and is a pest in continuous cornfields, but a lot of Iowa is rotated areas or corn and soybeans.

“So, we have to worry about northern corn rootworm beetles, as well. They go through extended diapause and the eggs stay dormant and don’t hatch in the soybean year and then wait until the following year when the field is back in corn.”

Tar Spot

As if there wasn’t enough to look out for in fields, tar spot has also made its presence known, first appearing in Illinois and Indiana in 2015 and has since spread across the Corn Belt.

The disease robs yield by reducing the photosynthetic capacity of leaves and causing rapid, premature leaf senescence.

“Tar spot is the big question that all growers and retailers are concerned about. It’s a very devastating diseased. It’s been here in Iowa for several years and is becoming a permanent resident because we know that fungal organism overwinters on corn residue and we certainly have plenty of that here,” Storr said.

“The overwintering structure survives and the lifecycle starts all over again this season and when the environment is right, we see potential for infection in this year’s corn crop.”

There hasn’t been any notable major yield losses the last few years in Storr’s area from tar spot because it infected the corn plants late in the growing season.

“But as the inoculant continues to build, and that’s where I think we’re at in today’s game, the thing that worries us the most is we’ve had this disease for several years now. The inoculant continues to grow in size, so there are more spores available to land on a susceptible corn plant the next year,” he said.

“So, as we move into the 2023 growing season, that will be something we’ll have to monitor very closely.”

Spore monitoring locations have been set up throughout the Midwest by university plant pathologists to measure when the spores are being formed in the environment. The information can then be utilized to determine fungicide application timing.

Products

“If we have a little more moisture this year earlier in the growing season, we may see infections occur earlier than what we’ve experienced in the past,” Storr noted.

“So, this is where we really need to put a plan in place to protect that corn stand with a fungicide like Veltyma or Headline AMP from BASF to prevent that disease from attacking your corn.

“Veltyma and Headline AMP are class-leading fungicides for controlling tar spot. I think you’ll see a lot of use this year regardless of whether or not we have tar spot infections.

“For a product like Veltyma, we can apply it a little bit earlier in the growing season and typically we’re talking about a week or so before tasseling to be getting into that good window for protection of your corn.

“We used to wait and start making applications around tassel stage which is still where the predominant applications will be made. But with Veltyma, we can apply a little earlier and take advantage of the effectiveness of that fungicide and protect our plants throughout the reproductive stage and give us the best yield benefit.”

Early Plans

Storr was asked what farmers need to be watching for in their fields through this early stage of the growing season.

“Late May is the time to take stock of the pre-herbicide effectiveness and develop a plan to deal with escapes or second flushes with a post program,” he said.

“Know the weed species you have and select the most effective products for those species. Post-herbicide applications are most effective when weeds are small, generally under 3 to 4 inches in height.

“I always recommend using a nozzle that will reduce drift, but still give good coverage. Apply with at least 15 gallons per acre of water to help with the coverage and utilized the proper additives like (ammonium sulfate), (non-ionic surfactants) or crop oils as specified on the herbicide label.

“It is also a great idea to add a residual herbicide like Outlook or Zidua to the post tank mix to extend residual control of weeds like waterhemp.”