Bruce MacKellar

MSU Field Crops Pest Management Educator

[Bruce MacKellar @BruceMacKellar]

@IowaWeeds My condolences. It has been everywhere in southwest michigan for a long time. Gives springtime a sometimes pretty purple hue however...

[Bruce MacKellar @BruceMacKellar]

@MartinChilvers1 @MikaelaBreunig @MI_Corn @USWBSI @MSUSoilFert @MLSakalidis @TheTrailLab @MSU_PSM @CANRatMSU @MSUAgBio Congrats Mikaela!

[Bruce MacKellar @BruceMacKellar]

@MIbluedoc I have seen quite a few too mark.

[Bruce MacKellar @BruceMacKellar]

Time to determine stalk strength to prioritize harvest order in your tar spot impacted corn fields in southwest Michigan.

[Bruce MacKellar @BruceMacKellar]

Keep an eye out for stalk decline in corn fields with tar spot lesions. Starting to be able to find stalks where you can pinch a segment and topple the plants over. Not all fields are impacted the same.

[Bruce MacKellar @BruceMacKellar]

@stevekoeman Rainfall Monday brought some needed relief from drought stress across much of southwest Michigan. Corn at (R2) is likely to be vulnerable to tar spot until R 5.5, most likely September 15. Dry weather helps to reduce the threat, but Aug. dew get worse. Scout fields regularly.

[Bruce MacKellar @BruceMacKellar]

Rainfall this morning brought relief from drought stress near Decatur Mi. With heavy rains expected tonight, fields like this June 1st planted corn (R2) are likely to be vulnerabe to tar spot until R5.5, most likely September 15. Scout fields regularly. #tar spot.

[Bruce MacKellar @BruceMacKellar]

Legacy of tar spot in 2019. This small strip was missed with clethodim earlier in the summer in a field heavily impacted by tar spot last fall in Van Buren County. Stalk strength was greatly compromised in the field, resulting in heavy
volunteer corn. #tarspot @MSUEFieldCrops

[Bruce MacKellar @BruceMacKellar]

Legacy of tar spot in 2019. Small strip not treated with clethodim this early summer in heavily impacted field last fall in Van Buren County. #tarspot #@MSUEFieldCrops

[Bruce MacKellar @BruceMacKellar]

Tar spot moving up the canopy fast on some irrigated fields in Southwest Michigan. Some evidence that spores infected the upper leaves first, denoting aerial spread. Well above the 1-2 lesions per upper leaf threshold. Zoom in on the picture to see in better detail. #TarSpot

[Bruce MacKellar @BruceMacKellar]

The Fungicide Efficacy for Control of Corn Diseases Table is an excellent resource for fungicide options for controlling corn leaf disease. The bulletin, CPN-2011-W, is produced by the Corn Disease Working Group. https://t.co/TCv1n2vulr

[Bruce MacKellar @BruceMacKellar]

Tar spot moving up the canopy fast on some irrigated fields in Southwest Michigan. Some evidence that spores infected the upper leaves first, denoting aerial spread. Well above the 1-2 lesions per upper leaf threshold. Zoom in on the picture to see in better detail. #TarSpot

[Bruce MacKellar @BruceMacKellar]

Western Bean Cutworm moths still flying in southwest Michigan. Early egg masses have hatched and larvae are heading up the plant. Threshold for treatment is when a cumulative 5% of the plants have egg masses. See Difonzo's Fast Fonz Facts-July 24, 2020. https://t.co/53MLLOBBYl

[Bruce MacKellar @BruceMacKellar]

It is time to begin to check corn fields for tar spot in southwest Michigan in earnest once again. The cooler weather and recent rainfall have set the stage for potential development of the disease. Fields in the Decatur area do have tar spot lesions on the lower leaf canopy.

[Bruce MacKellar @BruceMacKellar]

MSU Field Crops Pathologist Marty Chilver's Tar Spot Fungicide Field Day will be held August 18, 2019 from 2:00 - 5:00 PM at 6270 116th Ave., Fennville, MI 49408

[Bruce MacKellar @BruceMacKellar]

Big increase in the number of dry-land corn fields showing visible signs of decline from tar spot in southwest Michigan this week. This likely will hurt yield potential for many later planted fields, many of which have not reached R5 (Dent).

[Bruce MacKellar @BruceMacKellar]

@PKaatz Have Fun!

[Bruce MacKellar @BruceMacKellar]

MSU Extension Tar Spot Fungicide Trial Field Day -- Wednesday, September 18, 2019
2:00 - 5:00 PM

6270 116th Ave. Fennville, MI 49408
Host: Dr. Martin Chilvers, MSU Field Crops Entomologist
There is no cost for this program. For more info, click:

https://t.co/DkxAXfz6Mv

[Bruce MacKellar @BruceMacKellar]

Tar spot is on the increase across west Michigan, especially on irrigated fields. Until yesterday, I had not seen tar spot symptoms on more than 1-2 plants per 100 consecutive while scouting. This field (NE of Holland) had multiple lesions on many plants in some areas.

[Bruce MacKellar @BruceMacKellar]

@ClintonReports @USDA That is the best thing I have seen yet. I might consider this if we get another rain.