Soybean and corn disease update

decrease font size  Resize text   increase font size       Printer-friendly version of this article Printer-friendly version of this article

Bacterial diseases in soybean and corn fields got a head start this growing season due to the wet spring and hail events occurring throughout South Dakota.

"The wet spring and also a few hail events have created conducive environment for bacterial diseases to develop in soybean and corn fields," said Emmanuel Byamukama, SDSU Extension Plant Pathology Specialist.

Several soybean fields inspected throughout the state had bacterial blight. Byamukama explained that bacterial blight is characterized by small water-soaked spots on the lower leaves. These spots later turn yellow then brown to black in the center, with a yellowish-green halo around the spots. The brown spots may coalesce into blotches that may tear and fall out after windy weather, giving the leaves a ragged appearance.

Cool (less than 80° F), wet weather favors the spread of the disease. Dry weather halts the spread of the disease up the plant.

"The bacteria survive on residue, therefore crop rotation and tillage may help reduce the severity of this disease," Byamukama said.

Goss's wilt and blight

Goss's wilt and blight were found in two counties: Faulk and Brown. This disease is caused by the bacteria, Clavibacter michiganesnsis subsp. nebraskensis. The pathogen causes two types of symptoms: systemic wilt of the entire plant and leaf blight.

The leaf blight symptom is the most encountered and is characterized by the dark spots that resemble freckles. The leaf blight lesions are large and longitudinal and can resemble other corn disease lesions like northern leaf blight. The presence of water soaked lesions and freckles are distinct symptoms for Goss's wilt.

"When the bacteria infects the vascular system, it blocks water-conducting tubes leading to wilting of the entire plant," Byamukama said.

The bacteria overwinter on infested corn residue on soil surface and enter the plants through wounds created by hail, sand blasting, high winds and wounds created by insect feeding. Goss's wilt can be managed by selecting corn hybrids that are tolerant to this disease. If the field has history of Goss's wilt, selection of resistant/tolerant cultivars is the first step.

"Because the Goss's wilt pathogen survives on residue, tillage and crop rotation will reduce the inoculum. Fields at high risk are corn following corn and no-till/minimum till fields," he said. "Some weeds like foxtail, shattercane, and barnyard grass are hosts of the bacteria; therefore, early weed control is important to eliminate further sources of inoculum."

Some products are being marketed for Goss's wilt control; however, Byamukama said there is insufficient data in the region on the efficacies of these products.  

Holcus spot

Holcus spot, another bacterial disease was seen in one corn field in Brown County, the same field also had Goss's wilt. Holcus spot is caused by a different bacteria, Psedomonus syringae pv. sringae. Holcus spot is a rare disease and even when it occurs, seldom will it cause yield loss. Byamukama explained that the pathogen also survives on residues and is favored by rainy and windy weather early in the season.

Common smut and rust

Common smut on corn leaves was seen in a few fields that had hail damage in the northeast counties. The fungal pathogen infects young, actively growing parts usually through wounds and forms galls. The fungus survives on crop debris or soil and can remain viable for several years. If the spores land on the silk, the fungus will infect the developing kernels resulting in galls on ears.

"Most corn hybrids have good resistance to common smut, however, corn on corn, no-till, and hail damage conditions may increase the risk for common smut infection on leaves," Byamukama said.

Another disease beginning to develop on corn is common rust. Several fields scouted had trace levels of this rust developing.

"This disease rarely develops to high levels to cause yield loss because most hybrids have good tolerance to this pathogen. The common rust pathogen does not survive in South Dakota; the spores are blown in from the southern states in spring. . Therefore residue management or crop rotation will not affect common rust or any other rust disease, for that matter", he said

If growers plan to apply fungicide, Byamukama said a general note on fungicide application on corn is that several research reports show that increase in yield from fungicide application happens when disease severity on flag leaf at R5 is greater than 5 percent. He encourages growers to review a publication published by Iowa State University, at see:

"Most of the corn scouted across the state looked very clean with no disease developing. Corn following corn or corn on no-till may have an elevated risk for significant disease to develop, depending upon the cultivar planted and weather conditions," he said. "Applying a fungicide at tasseling in this case may be beneficial."  

The corn plant pathology working group published a list of fungicides that are effective for several fungal pathogens on corn. This table can be found here:

Byamukama said fungicide application should be done when all corn has fully tasseled to avoid arrested ear syndrome, a physiological disorder that is caused by nonionic surfactant (NIS) fungicide additives when applied before tasseling. To learn more about this visit, 

Prev 1 2 Next All

Buyers Guide

Doyle Equipment Manufacturing Co.
Doyle Equipment Manufacturing prides themselves as being “The King of the Rotary’s” with their Direct Drive Rotary Blend Systems. With numerous setup possibilities and sizes, ranging from a  more...
A.J. Sackett Sons & Company
Sackett Blend Towers feature the H.I.M, High Intensity Mixer, the next generation of blending and coating technology which supports Precision Fertilizer Blending®. Its unique design allows  more...
R&R Manufacturing Inc.
The R&R Minuteman Blend System is the original proven performer. Fast, precise blending with a compact foot print. Significantly lower horsepower requirement. Low inload height with large  more...
Junge Control Inc.
Junge Control Inc. creates state-of-the-art product blending and measuring solutions that allow you to totally maximize operating efficiency with amazing accuracy and repeatability, superior  more...
Yargus Manufacturing
The flagship blending system for the Layco product line is the fully automated Layco DW System™. The advanced technology of the Layco DW (Declining Weight) system results in a blending  more...
Yargus Manufacturing
The LAYCOTE™ Automated Coating System provides a new level of coating accuracy for a stand-alone coating system or for coating (impregnating) in an automated blending system. The unique  more...
John Deere
The DN345 Drawn Dry Spreader can carry more than 12 tons of fertilizer and 17.5 tons of lime. Designed to operate at field speeds up to 20 MPH with full loads and the G4 spreader uniformly  more...
Force Unlimited
The Pro-Force is a multi-purpose spreader with a wider apron and steeper sides. Our Pro-Force has the most aggressive 30” spinner on the market, and is capable of spreading higher rates of  more...
BBI Spreaders
MagnaSpread 2 & MagnaSpread 3 — With BBI’s patented multi-bin technology, these spreaders operate multiple hoppers guided by independent, variable-rate technology. These models are built on  more...

Comments (0) Leave a comment 

e-Mail (required)


characters left


YOUR BEST HARVEST IS NOW WITHIN REACH J&M introduces their patented line of X-tended Reach grain carts, featuring a frontfolding single ... Read More

View all Products in this segment

View All Buyers Guides

Feedback Form
Feedback Form