Weather is a major factor that decides whether or not growers are going to be facing an insect and disease problem. And with the widely varied and climate altering conditions around the county, ag retailers will have their hands full helping their grower-customers decide the right tools to deal with a variety of infestations.

What to Expect

“It’s been a very light winter this year, above average temperatures,” David Reif, Northern Sales Agronomist for Vive Crop Protection, told CropLife Editor Eric Sfiligoj at 2024 Commodity Classic in March. “That tends to lead to higher insect pressure.”

Given those conditions, Reif expects to see a pair of pests.

“In soybeans, soybean cysts are always a problem,” he says. “Corn rootworm could be very problematic this year in corn.”

BASF’s Kurt Maertens, Technical Service Representative, also agrees. “It could be interesting due to the generally mild Midwest winter that happened.”

It’s not just insects influenced by the weather.

The concern for disease is also concerning says BASF’s Kim Tutor, Technical Marketing Manager.

“Coming out of a relatively hot and dry season in 2023, a lot of growers in the U.S. may not have disease top of mind,” she says. “However, we know that fungal inoculum are present in the soil and are simply awaiting the right environmental conditions to rear their ugly heads. We can’t always predict what kind of stress a crop will experience, but we do know stress is constant. That’s why it’s imperative to start having conversations with retailers now about implementing a planned, preventative fungicide application.”

It’s difficult to generalize pest pressure since so much of it is a result of weather and weather is so variable from region to region.

“Every year is a little different. Weather conditions dictate so much of what happens in localized areas,” says Gail Stratman, Regional Technical Service Manager for FMC Corp. “In general, we see a few pest issues that have been on the increase in the last few years. Corn rootworm (CRW) has been a larger issue the last two to four years. Some of that can be due to CRW adapting to the CRW traits, but also drier weather conditions and the economics of corn-on-corn rotations have favored survival, allowing corn rootworm to increase.”

Soybean crops are facing their own challenges.

“In soybeans, I hear more growers talking about stinkbug populations on the increase and asking questions about managing them than in the past,” Stratman continues. “Dry conditions also usually favor more alfalfa weevil populations, but we’ll have to see how the rest of the winter progresses and how the alfalfa weevil populations overwintered this year. It’s been wet in some areas, and dry in others, so it could be something growers just need to keep an eye on.”

Brian Bishop, U.S. Crop Protection Marketing Leader, Corteva, expects to see different infestations on soy in the Southeast.

“For insect pressure, it really depends on your location, but we expect to see continued difficulties with soybean loopers in the Southeast and aphids in the Midwest/Corn Belt, in particular,” Bishop says.

“The insect prevalence will also heavily depend on the weather we see,” he continues. “2023 was a droughty year across much of the Corn Belt. Pests like spider mites and grasshoppers tend to thrive in hot, dry conditions, leading to increased predation on corn and soybeans – although soybeans tend to suffer more in these circumstances.”

The disease side of the equation is also expected to see the effects of recent weather.

“For disease pressure, we expect tar spot in corn and white mold in soybeans to pose the biggest challenges for growers in the Corn Belt states,” Bishop says. “Again, this is heavily dependent on your location and weather conditions, but both these diseases have been moving rapidly to new areas over the last few seasons – and both can spread very quickly to rob yield once an infection starts. Farmers reported tar spot in several states across the Corn Belt in 2023 season, including Iowa, Illinois, Indiana, Kansas, Missouri, and Nebraska.”

FMC’s Stratman agrees that tar spot is a major concern for growers. “As far as diseases go, tar spot in corn continues to be the hot topic,” he says. “We continue to see it spread to new areas as inoculum builds and allows for economically damaging infestations to occur. Areas of Missouri, northeast Kansas, as well as eastern Nebraska and western Iowa saw some areas with heavy tar spot infestations. Other areas in the eastern Corn Belt saw lesser issues in 2023, but it’s still present.”

The Retailer’s Role

There is good news. Pesticide providers offer numerous solutions growers can take advantage of. And perhaps just as important is an informed “second opinion” from their local retailer.

“Ag retailers can provide a lot of guidance for growers to help them in areas where they can get the maximum return on investment,” Stratman says. “There are lot of product choices that growers have to spend their money on each year. Many of those products can’t ever see much return or claims are unproven. Helping growers invest their dollars on inputs that have a consistent, positive yield response or return on investment will be key to grower profitability in 2024. Looking at company data, talking with manufacturing representatives and agronomists to help position products on the right acres is key. In 2024, having the right advice from your retailer is going to be very important to grower’s bottom line.”

For growers looking for deeper insight into how the products work, they can also have discussions with the product manufacturer.

“In order to hedge your bets and feel confident in protecting your investment, we encourage growers to start having conversations now about preventative, planned BASF Performance-Driven fungicide applications,” says BASF’s Tutor. “Our performance-driven fungicides, like Veltyma and Revytek, provide consistent performance. Not only do they provide unparalleled disease control, but they also promote optimized growth efficiency, and environmental stress mitigation. All of these factors support consistent performance, helping growers protect their yield and their return-on-investment year in and year out.”

Deciding what pests might show up is a mix of experience, science, and art. And the consequences of getting it wrong can be devastating.

“To have yield loss from a pathogen you will need to have both the host plant, the pathogen, and then of course the right environmental conditions present,” says Syngenta. “This is very difficult to predict if all three variables will be there throughout the growing season. For some pathogens, epidemiological models have been developed to help farmers spray at the right time, but for many pathogens this is still not available. Growers must then rely upon scouting and personal experience in the decision-making process since susceptibility of various varieties and hybrids also play a role on disease levels.”

For similar reasons treating disease is also challenging.

“Being able to understand and predict the disease pressure you may anticipate and then ensure you’ve got the right tools to combat them,” says Dr. Tyler Harp, Fungicide Technical Manager, Syngenta. “Most crop protection inputs do just that, they protect the crop, and in order to do that they must be applied preventatively, or at least at the on-set of the pest. Luckily for corn and soybean growers, Syngenta plant health fungicides protect from both biotic (diseases) and abiotic stress (like heat or drought). As a result, when using these products, you are preserving yield and protect the crop regardless of the upcoming weather conditions.”

Growers have plenty to keep track of. Researching the efficacy of products doesn’t need to be one of them.

“Ag retailers can help growers manage by keeping them informed of new tools and technologies to help overcome these challenges,” Corteva’s Bishop says. “Ag retailers also play an important role in reminding farmers of those traditional best practices, like regular scouting, and helping them implement newer best practices on their acres. Some of those may include Integrated Pest Management programs, as well as diverse disease management programs that include multiple modes of action and, potentially, multiple passes to prevent fungicide resistance.”

The 2024 Growing Season

Despite the variety of pests that might make an appearance this season, FMC’s Stratman doesn’t expect infestations to increase.

“Populations of insects and disease incidence are pretty much in line with what we’ve seen the last two to three years.” he says. “If we happen to get a significant shift in weather across a wider geography, that may alter where and what pests may dominate the discussion in 2024. The warmer than normal winter may get our insect and disease cycles started earlier this year if it continues through spring or soil conditions warm more quickly due to the lack of frost/frozen soils.

“Many insect hatch cycles are determined by reaching a minimum GGD (growing degree day) accumulation,” Stratman continues. “If we start the spring earlier, it could mean insects like alfalfa weevil and corn rootworm could emerge earlier in the season. A wetter, maybe cooler pattern would likely favor more disease outbreaks across a wider area, with fewer insect issues. That doesn’t mean we can’t still have insect issues, but it can change the level of severity we see from different pest problems. It will still depend on what happens in March, April, and May as we can see populations build in a hurry early in the spring and be a challenge the remainder of the season.”

Some initially dry areas faced different pest pressure.

“With the widespread prevalence of drought and severely dry conditions last season, tar spot took some farmers by surprise,” Corteva’s Bishop says. “This is because the disease typically prefers cooler, more humid and dewy weather.

“However, tar spot is fast-moving and highly adaptable. So, certain areas started the season dry and, when moisture moved in later, any present disease spores were able to take off and grow quickly with the change in conditions. This is good information to have for planning 2024 knowing that one, if you’ve seen tar spot in the past, you’re likely to see it again and, two, you’ll want to be consistently scouting for this disease and watching weather conditions closely.”

“The last several years we’ve had average winters, which for the Midwest means freezing soils, deep frosts, and some snow cover,’ BASF’S Maertens says. “It’s been typical. This year, we’ve had about two weeks of hard winter, but didn’t have ground freeze due to the snow cover. This year’s been extremely mild and extremely dry. We’re looking at an earlier start to the spring and that could also mean earlier than normal emergence of insect pests.

“It takes heat for different insects to hatch, so with an earlier spring, everything could potentially be moved up,” Maertens continues. “We’ve seen increasing corn rootworm pressure year after year, especially in Iowa and Minnesota. We’re seeing a lot of that pressure move further south and east into east/central Iowa and northwest Illinois.”

Challenges

“Trying to predict what kind of stress your crops will encounter every year is incredibly difficult,” BASF’s Tutor says. “There’s the old adage: ‘The only two things in life that are certain are death and taxes,’ but I think we should add a third to the list – stress. We never know what kind of stress our crops will experience – heat, drought, wind, hail … but we do know stress is constant. Taking that ‘wait and see approach’ can often be really detrimental, especially for folks combatting tar spot. Fungal pathogens can infect a plant, robbing it of yield potential, days and sometimes even weeks before lesions can be detected with the naked eye. It can be upwards of three weeks before you may even know you have tar spot and begin detecting lesions. And unfortunately, in some instances, that ‘wait and see approach’ is really costly, as a lot of damage is already done.”

Corteva’s Bishop also decries the “wait and see” attitude growers sometimes adopt.

“Growers face numerous challenges each season, from fluctuating markets to extreme weather to changing regulations, they have so many decisions to make year in and year out,” he says. “Growers know for a fact they have a top list of inputs they need to buy each year, including seed, fertilizer, and herbicides; however, many still prefer to take a ‘wait and see’ approach to solutions like fungicides and insecticides. Understandably, growers don’t want to spend additional money if they don’t have to.

“The problem is ‘waiting and seeing’ is no longer the best approach as insect and disease pressures evolve,” Bishop continues. “Proactive control measures are becoming increasingly essential – and the challenge that comes with this shift is that the insect and disease pressures will continue to change. So, growers, along with the rest of the agriculture industry, need to keep moving to keep up.”

“The most challenging crop diseases are typically those that multiply fast including those with different spore structures and survival mechanisms,” says Syngenta’s Harp. “Some pathogens can be pathogenic on multiple crops and even on some weeds, which means the pathogen inoculum will always be present in the area.”

On the pest side corn rootworm posts a particular challenge.

“CRW is a challenge because a grower must decide at the time of planting whether or not to deploy a soil-applied insecticide,” Syngenta’s Meck says. “These decisions are largely based on field history, seed traits packages, and trends of adult beetle catches. There is not a good way to ‘scout’ for insect pressure at the time that the application decision must be made.

“Examples of other insects that are difficult to forecast are diamondback moth, which is found in brassica crops, and thrips in multiple crops,” Meck continues. “Diamondback moth has developed resistance to a number of different chemistries over the years which make it even more challenging to control. Thrips can be difficult to control just based on where they tend to live on a plant. They can live in really tight spaces on the crop that make it difficult to deliver an effective spray application. Just like the diamondback moth, there are some thrips populations that have developed resistance to certain classes of chemistry which limits the options available and makes them more difficult to control.”

A Deeper Dive into Weather Effects

BASF’s Tutor explains conditions over the past few years have influence pest pressure on corn and soybean crops:

Disease Outlook: Tar Spot in Corn

“In corn, the disease that is most top of mind for growers is tar spot,” Tutor says. “It’s a relatively new disease and has proven to be truly detrimental. Some areas have seen 50-plus bushels per acre yield losses. Tar spot is particularly problematic due to its long latent period – the time between initial pathogen infection and reproduction. During that time, pathogens infect the plant, produce toxins, and reduce photosynthetic capability – all before a lesion can be detected with the naked eye. Every disease has a latent period with some longer than others. Tar Spot has one of the longest latent periods – it’s upwards of three weeks! That’s three weeks that the disease is inside that corn plant, robbing it of water and nutrients, reducing photosynthetic capability, and ultimately, reducing yield. A lot of disease infections start from the bottom of the plant and work their way upwards (from soil inoculum). But tar spot is an ascomycete, also known as a ‘spore-shooter.’ So those reproductive structures actually burst open, launching tar spot spores up and out.”

“For a large portion of the U.S., especially the Midwest, the majority of the 2023 growing season was hot and dry,” she says. “However, we did see some later season rains in various geographies starting in June and July. As such, corn started to see later-season infestations of tar spot, GLS, and rust. Another interesting fact to note is that despite the overall hot and dry season that was 2023, we noticed that tar spot continued to spread. Tar spot was first identified in the U.S. in 2015 and has now spread to 19 states. The ipmPIPE Tar Spot map now shows expansion of the disease as far west as central Nebraska and northeast Kansas.”

The corn rootworm seems to be particularly troublesome and appears to be showing resistance to some treatments, she says.

Disease Outlook: Additional Concerns

“Other diseases that are problematic in corn include Grey Leaf Spot, Northern Corn Leaf Blight, Southern Corn Leaf Blight and Rust,” Tutor says. “Rust spores are windblown and come up from the Gulf of Mexico. As such, southern geographies are typically impacted first, before the disease makes its way to the Midwest.”

Pest Outlook: Corn Rootworm

“We’re growing a lot of corn on corn – we always have – and so the corn rootworm are adapting to management strategies,” Tutor says. “In western corn rootworm, we’re seeing resistance to Bt rootworm traits. Northern corn rootworm is adapting to our rotation away from corn, which is what we call the extended diapause variant. When the females lay eggs in corn, they don’t hatch for two years; if you’re on a corn soy rotation you won’t see those hatch until you plant corn again, which defeats the purpose of rotation – one of our key tools against resistance. Corn rootworm larvae eat the roots of the corn plants. If the pressure’s high enough, they can potentially eat most of the roots. With no roots, there’s limited water nutrient uptake, along with less to anchor the plants, which all has a negative impact on yield potential. As adults emerge, they can clip silks which affects pollination.”

Disease Outlook: Soybeans

“For soybeans, the 2023 disease pressure really just depended on where you were, geographically speaking,” Tutor says. “Again, the Midwest didn’t see much disease pressure, but shifting over to Tennessee (TN) and Kentucky (KY), it was a moderate disease pressure year for soybeans. Lots of folks experienced moderate Septoria brown spot and Frogeye leaf spot (FLS) pressure. Cercospora blight came in later in TN and KY. As you move further South into Arkansas and Mississippi (MS Delta region), soybean growers had a dry June, followed by a wet July. Growers in that geography did see moderate Cercospora blight and tar spot, and some Frogeye leaf spot pressure.

“Soybean disease has been documented to have an average economic loss of $45 per acre and reduce yields by 11%, or more,” Tutor continues. “FELS is top of mind for a lot of soybean growers. In the last several years this disease has developed resistance to Group 1 and 11 fungicides, becoming troublesome for a lot of folks to manage. Cercospora leaf blight is another disease that’s becoming more prevalent. This disease is actually seed-borne and has a really long latent period ― approximately 109 days after planting. As such, symptomology often doesn’t present itself until the plants become stressed. In addition to negative seed quality impacts like purple seed stain, Cercospora leaf blight also results in soybean leaf defoliation. Soybean leaves are like little photoreceptors, constantly absorbing sunlight to promote photosynthesis and drive yield. When those leaves drop prematurely, photosynthetic capability and yield potential is reduced.”