Diseases & Disorders

All Diseases & Disorders Content

Left Mosquito specimen with dark coloration. Right: Mosquito specimen with white band on its proboscis.

Mosquitos to Watch for in South Dakota

After many areas in South Dakota experienced heavy rainfalls, mosquitos are now a major issue. Learn which species are most common throughout the state and which carry the highest risk for West Nile Virus.

A green corn leaf with yellow to brown spots throughout.

Corn Disease Update: September 2, 2025

As of September 2, 2025, a number of corn diseases have been reported and confirmed throughout South Dakota. View our latest findings as we approach the fall harvest season.

Coneflower with Aster yellows disease.

Aster Yellows Phytoplasma

Aster yellows is a phytoplasmal disease carried and introduced by aster leafhopper. It is known to infect over 80 different plant families, as the aster leafhopper has extremely broad feeding habits.

Corn leaf samples with Southern Rust and Tar Spot.

Corn Diseases in South Dakota Update

Several South Dakota counties have confirmed positive cases of Southern Rust and Tar Spot this growing season. See our latest recommendations for dealing with these diseases before they become a problem.

Green wheat leaves with yellow streaks throughout.

Wheat Streak Mosaic Virus Complex: Breaking the Green Bridge

As wheat harvest proceeds, it won’t be long until winter wheat planting is underway in South Dakota. To effectively reduce wheat streak mosaic virus, it is important to manage the green bridge effect to slow spread of disease in newly emerging wheat fields.

Wheat plants infected with wheat streak mosaic virus.

Volunteer Wheat and Kochia Management With Herbicides Will Likely Require Two Passes

Wheat curl mites, which carry wheat streak mosaic virus, use volunteer wheat and grass weeds as secondary hosts to infest recently planted winter wheat crops. Therefore, effective management of these plants before winter wheat planting is critical.

Instructor leading a proctored exam in an agriculture classroom.

South Dakota Commercial Pesticide Applicator Certification Testing

New commercial pesticide applicators and those that have allowed their licenses to lapse must pass commercial pesticide applicator exams to receive certification. Learn about some some helpful resources, contacts, and tips to help you be successful in your certification testing.

Three chokecherry trees exhibiting various x-disease symptoms on their foliage.

X-Disease in Chokecherries

X-disease is the name given to a set of diseases caused by a strain of the bacteria “Candidatus Phytoplasma pruni” that primarily affects stone fruits. Infected plants will typically display yellowing or reddening of their leaves by mid summer.

Green Canada thistle with whitened leaves at the top. Various green plants throughout.

White Thistle Disease: Biological management at work

White thistle disease can be seen among many Canada thistle plants throughout South Dakota this growing season. Plants infected with the disease exhibit significant reductions in both growth and seed head compared with non-infected plants.

Husband and wife preparing a healthy meal.

Chronic Disease

Chronic diseases and their consequences can often be prevented or managed effectively through medical management, behavioral change efforts, and sustained patient support.