Basing which diseases to watch in 2025 on what happened in 2024 is far from foolproof. Any of the three key factors — susceptible host, favorable environment and pest inoculum — can change dramatically from year to year. However, what happened last year can provide a place to start for this year.

Recently, Ethan Harmon and Peng Tian with the University of Missouri Plant Diagnostic Clinic released the clinic’s 2024 Annual Report for Field Crops. Here is a peek at what diseases are on the rise in corn, soybeans and wheat:

Corn diseases

Just over 1 in 4 field crop samples submitted in 2024 were corn plants.

Corn stunt. More samples were positive for this new disease than any other disease. “This was the first time it was confirmed in Missouri, and we didn’t expect it,” reports Mandy Bish, MU Extension plant pathologist. The first sample, confirmed in mid-August, came from southwest Missouri.

Corn leafhopper transmits this bacterial infection. It is not believed to overwinter in Missouri, but Extension staff are monitoring it. Suggested cultural control practices include crop rotation, early planting and control of volunteer corn plants, Bish says.

Tar spot. This disease ranked second in samples and was confirmed in over two dozen counties in Missouri. Based on ipmPIPE mapping, a national program, it was confirmed in a handful of southern Missouri counties for the first time.

Related:What is bugging Missouri crops most this year?

Bish says tar spot showed up earlier than normal in ’24. While inoculum overwinters, there is no guarantee what will happen in ’25. She advises growers to scout and stay alert.

Southern rust. Tian identified four samples of southern rust and two samples of common rust. National ipmPIPE maps indicate southern rust was confirmed in a handful of counties in Missouri. This inoculum must ride up into the Midwest from the South each season, Bish explains.

Soybean diseases

More soybean samples were submitted for disease diagnosis than any other crop.

Phytophthora rots. This category includes crown rot, root rot and stem rot if caused by phytophthora. Wet, compacted soils give phytophthora species a foothold, Bish notes. Symptoms can be confused with other diseases. Rhizoctonia forms a sunken, reddish lesion near the soil line, while phytophthora root rots do not.

Consider fungicide treatments for phytophthora rots, especially if there is a field history of seedling blights.

Charcoal rot. This disease pushed phytophthora for the most samples of all soybean diseases, Tian says. It’s usually associated with dry weather. Surprisingly, only a small number of plants with spider mites, also associated with dry weather, were submitted.

Related:Scout 2024’s corn diseases this year

Symptoms can be confused with rhizoctonia, but lesions are not as sunken, and black specks appear just below the epidermis of root and lower stem tissue. Cultural practices that lessen stress help reduce incidence.

Sudden death syndrome, pythium, and pod and stem blight. These three diseases tied for third place in sample numbers. SDS infects plants early, but symptoms show up later, Bish says. Symptoms are sometimes worse if there is heavy soybean cyst nematode pressure.

Pythium often causes seedling blight. Pod and stem blight appears most often when it is warm and wet while pods mature. Harvesting sooner rather than later helps.

Notable. Other soybean diseases where Tian saw numerous samples in ’24 included cercospora or purple seed stain, soybean vein necrosis, brown stem rot, brown spot and red crown rot. Red crown rot can be confused with SDS, except dead leaflets tend to remain attached.

While it is an insect, Tian notes that Dectes stem borer was found in a sizable number of plants.

Not so notable. Some diseases that are often problems weren’t as numerous in ’24, Tian says. They include, with number of samples submitted: frogeye leaf spot, 1; fusarium seed rot and root rot, 2; rhizoctonia, 2; sclerotinia (white mold), 2; and downy mildew, 1.

Related:Want to preserve corn yield by more than 50%?

Wheat diseases

The clinic, in cooperation with the Missouri Field Crop Plant Pathology Program, offered free testing of wheat samples for viruses in 2023 and 2024. Number of samples submitted shot up from 10 in ’22 to 47 in ’24, Tian reports.

Wheat streak mosaic virus. Over half of all wheat samples exhibited wheat streak mosaic virus. Symptoms generally include stunting and yellowish streaks on leaves. In severe instances, yield losses can occur, Bish says. The disease is transmitted by insects, such as the wheat curl mite.

Cultural controls begin before planting with removal of grassy weeds and volunteer wheat that could harbor insects. Some varieties have more resistance than others, Bish says.

Barley yellow dwarf. This virus, along with cereal dwarf viruses, is transmitted by aphids. Consider seed insecticides if aphid numbers are high before planting.

Fungal diseases. Fungal diseases appearing in Missouri wheat in ’24 included stem rust, leaf rust, stripe rust, fusarium head blight, and stagonospora leaf and glume blotch. Wet conditions in the spring favor these diseases.

“Many wheat varieties have resistance ratings to fungal diseases,” Bish says. “The combination of resistant wheat with timely fungicide applications has been quite effective in reducing some of our most problematic diseases such as fusarium head blight.”