Feature image courtesy of croplife.com

Each planting season there always seems to be those unexpected market challenges that pop up seemingly overnight. From once-in-a-decade storms that flood certain areas to once-in-a-generation pandemics to sudden supply chain issues, agriculture has had to deal with lots of uncertainty each year. But when it comes to the areas of insects and diseases, things pretty much stay the same from season to season: Always a challenge, no matter what else might be going on.

As many market insiders point out, crop diseases are unusually persistent. They can overwinter in infected crop residue, allowing inoculum to build up from year to year in fields. Disease spores are spread by rain splash and air currents to leaves of crop plants, where primary infections are produced. Secondary spread occurs from plant to plant and field to field as spores are carried long distances by the wind. Infections generally begin on lower leaves and then progress up the plant.

Because these diseases overwinter in corn debris, production practices, such as tillage and crop rotation, can reduce the amount of surface corn residue and decrease the amount of primary inoculum. In severe cases of disease infestation, multiple years of crop rotation away from corn may be necessary.

To manage diseases that can overwinter in fields, ag retailers and their grower-customers should make management plans for their next planting season as early as possible. “We can do a number of things to manage these diseases in 2022,” says Mary Gumz, Agronomy Manager at Pioneer. “Number one, pick the right hybrid. The right hybrid will have tolerance to the disease as well as overall foliar disease health. Number two, start planning for fungicide use. Weather will favor these diseases, so have a plan in place before pressure gets too severe.”

Matthew Wiggins, Technical Service Manager for FMC Corp., agrees. “What I always tell folks is, let’s develop a plan and let’s try to stick to it as we go throughout the year,” says Wiggins. “Be timely in your thinking and be timely as far as scouting.”

Tar Spot Emergence

This is certainly good advice given what the agricultural industry saw in the way of crop diseases during the 2021 planting season. In particular, the emergence of tar spot in corn was a major issue for many parts of the country. A relatively new foliar disease, tar spot infested substantial portions of the eastern Corn Belt last year, with many ag retailers and their grower-customers taken by surprise.

Caused by the fungus Phyllachora maydis and named for the small, tar spot was first detected in Northern Illinois and Central Indiana during 2015 and has steadily increased each year since, expanding to surrounding states. By 2021, it had reached Kentucky, with Ohio expected to possibly see an outbreak in 2022, according to university experts.

During 2021, extremely rainy conditions across much of the central U.S. were favorable for the disease to spread more aggressively than in the past because it thrives in humidity, specifically in areas where leaves are consistently wet. The wind patterns of the season also have contributed to the outbreak, as the disease is spread by black spores that hatch and blow more spores into the air.

It can take anywhere from 14 to 40 days after infection for symptoms to appear, with key visual indicators being browning leaves and raised black, circular fungal structures, which appear as specks of tar splattered onto the leaf surface. Unlike other diseases that produce similar black specks, those resulting from tar spot do not rub off. These visual symptoms usually begin on lower leaves and rapidly move up the infected plant, appearing on both healthy and dead plant tissue. When the disease hits newer plants it shuts down their vital functions, ruining their ability to fill out corn ear kernels, ultimately reducing weight and yield. It also is more likely to result in faster plant death if contracted in early growth stages and has the potential to increase risk for other agronomic issues such as stalk lodging.

“While physiologically mature plants are much less likely to see the adverse effects of tar spot, developing plants are extremely at risk, and an infestation can mean great loss for growers who are not equipped with the right tools to combat the disease,” says Craig Mackey, NK Agronomist at Syngenta. “Given the circumstances with tar spot this year, growers need to keep this in mind as they make their hybrid decisions going into next year’s planting season.”

For soybeans, Soybean Cyst Nematode (SCN) is present in nearly all soybean geographies and is the leading cause of soybean yield loss in North America. In a 2020 study conducted by The SCN Coalition, soybean growers reported they perceive SCN reduces yield by 5.1 bushels per acre. According to Jeremiah Mullock, Soybean Seed Treatment Manager for BASF, there are an estimated 60 million soybean acres in the U.S. that are impacted by SCN or other nematodes.

But BASF has a potential solution, he adds. “ILEVO seed treatment delivers direct mortality across all stages of nematode life cycle to prevent development and provides increased yield potentials by protection from nematode feeding and limits the impact of reproduction,” says Mullock. “And keep in mind that overlap between SDS (Sud-den Death Syndrome) and SCN is estimated to be extremely high, with at least 80% of SDS acres also impacted by SCN in the U.S. On top of that, SDS symptoms can be more severe under SCN pressure. While nematode damage increases in hot, dry conditions, SDS thrives in cool, wet conditions. ILEVO seed treatment protects against both, no matter the weather conditions.”

Help to Combat Insects Coming

During 2021, insect infestations were quite prominent for agriculture. The fall armyworm invasion of 2021 caused late-season issues in many areas. Furthermore, the resurgence of corn rootworm in the Midwest in the past couple of years is expected to continue challenging growers.

But help for these and other pests is on the way. In early March, Bayer announced the commercial registrations from the EPA for the traits that will enable the commercialization of its newest corn product, VT4PRO with RNAi Technology, in the U.S. VT4PRO Technology will mark the first product that combines three modes of built-in action in Trecepta Technology, an aboveground pest package for corn that controls insects such as corn earworm and Western bean cutworm, along with an RNAi-based mode of action, to help manage corn rootworm.

“We’re excited about the potential of this product and believe it will provide tremendous value for farmers, helping provide added protection against some of the toughest corn pests,” says Scott Stein, North America Corn Product Management Lead for the company. “Bayer plans to conduct large scale field testing of VT4PRO Technology during the 2022 and 2023 growing seasons, with the potential to launch commercial volumes as early as 2024, pending state registrations.”