Foliar Corn Diseases Ramping Up in Some States


Foliar ailments are constructing in some cornfields and plant pathologists are particularly cautious of southern corn rust, above, which is fast-moving and unusually widespread in the Corn Belt this month. (Photo courtesy Bob Kemerait, UGA)

Nathan Kleczewski needs all of the soiled corn leaves you may ship him.

It’s peak season for the University of Illinois Extension plant pathologist, who has been tromping by means of cornfields in Illinois, attempting to find ailments. They have been comparatively straightforward to search out, he famous, a positive signal that farmers needs to be checking their fields.

Southern corn rust is of explicit concern this 12 months, because the illness surfaced early in southern states and has been noticed in the Great Plains and Midwest in loads of time to do financial harm. Kleczewski can also be seeing a smattering of tar spot in corn to this point this summer season.

“If you see something like tar spot or southern corn rust, contact me by Twitter, email or phone call,” he urged Illinois growers. “That way we can confirm it, document it and put it on the map to alert other people.”

And look ahead to the previous summer season standbys — grey leaf spot and northern corn leaf blight — that are beginning to floor extra continuously, particularly in well-watered spots, Kleczewski mentioned.

Bacterial ailments equivalent to bacterial leaf streak and Goss’s Wilt are surfacing in Nebraska, added University of Nebraska Extension plant pathologist Tamra Jackson-Ziems. Remember that these ailments, which can favor fields with plant wounds from hail harm, can’t be handled by fungicides.


Southern scientists sounded the alarm on the early arrival of southern corn rust in the primary week of June. (See more here). By mid-July, it had swept up into japanese Kansas and southeast Nebraska. Now it’s been confirmed in northern Illinois and north-central Missouri, as effectively. Monitor its unfold here.

“The big concern about southern rust is it is an aggressive fungus,” defined Jackson-Ziems. “It can reproduce quickly and it’s airborne.”

Frequent scouting is necessary, particularly when situations are perfect for its unfold — particularly, sizzling with a contact of moisture, Kleczewski mentioned. “It doesn’t need a whole lot of moisture once it’s established in a field,” he warned. “Usually the amount of dew that forms when nighttime temperatures go down is enough for the spores to germinate and infect.”

The spores are simply carried by winds and storm fronts, and plenty of corn hybrids developed for the Midwest and Great Plains are prone to the illness.

“Given this combination — it can move fast, conditions are ideal and we don’t have much resistance out there — people need to be looking,” Kleczewski mentioned.

For assist scouting for southern corn rust, which could be simply confused with widespread rust, see this guide.

When sending samples, bear in mind first to contact the plant diagnostic clinic for directions, as many soil and disease-testing laboratories are dealing with new procedures for accepting samples due to the pandemic, Jackson-Ziems added.


Northern corn leaf blight is displaying up continuously in Nebraska fields, which has shocked some folks, for the reason that illness is understood to favor cooler, moist situations, and the state, like a lot of the Corn Belt, has trended sizzling and dry not too long ago, Jackson-Ziems mentioned.

“But nighttime temperatures have been pretty cool, which has helped the disease continue to spread,” she defined.

Gray leaf spot, which is completely comfortable in the warmer situations, can also be changing into a typical sight on corn leaves, each Kleczewski and Jackson-Ziems added.

Both ailments have been lurking the decrease cover of a cornfield Kleczewski was scouting in northwest Illinois, as he talked to DTN. Growers who not too long ago noticed rainfalls and storm fronts transfer by means of needs to be particularly alert for them, he mentioned.

DTN’s Crop Disease Risk maps reveals {that a} dozen states, stretching from western Nebraska to Ohio and from Kentucky up by means of central Minnesota, have situations that put them at excessive danger for northern corn leaf blight and grey leaf spot proper now. In the following week, the high-risk areas for the unfold of each ailments will seemingly retreat northward, in keeping with the maps.

See extra on scouting and figuring out northern corn leaf blight and gray leaf spot.


The tell-tale black spots of tar spot in corn are surfacing at low ranges in a number of Midwest states this summer season. Jackson-Ziems is looking out for the illness in Nebraska, because it has steadily expanded its vary westward in previous years.

Remember that in contrast to hen or insect droppings, the small black tar spot lesions is not going to scrape off, mentioned Kleczewski, who has examined many a poop-specked corn leaf in his looking.

See extra on the illness’s identification and administration here.

The violent storms and hail that swept throughout elements of the Corn Belt final week have left many growers with shredded corn leaves and the next danger of ailments that hunt down plant wounds to enter a plant, equivalent to bacterial leaf streak and Goss’s Wilt.

See extra on these ailments here and here.

But bear in mind fungicides is not going to reduce or deal with these ailments, and fungal ailments they do deal with don’t essentially worsen after hail harm, each plant pathologists mentioned. See extra from Kleczewski on the subject here.

Source: Emily Unglesbee, DTN