Crop Report – September 14, 2022

No Fungicide Check

Tar Spot and Fungicide Application Timings!

Although tar spot was detected in Ontario in the first week of July the past two years, 2022 is much different than 2021 and shows the importance of environmental conditions for disease development. Remember, this holds true for any disease! The big difference was the dry conditions early and shortened leaf wetness periods which delayed tar spot establishment until later (post-tassel). Areas along the north shore of Lake Erie (Essex through Haldimand-Norfolk) are seeing tar spot at higher levels compared to other areas. 

OMAFRA and UG Ridgetown Campus results in 2021 supported U.S. data that fungicides applied between tasseling (VT) and silking (R1) provided optimum control of tar spot. Fortunately, the optimum application timing for effective tar spot fungicides is the same for other common leaf diseases like northern corn leaf blight and especially Gibberella ear rot (DON). 

This year there have been a lot of questions around fungicide application timing for fields at risk of late season tar spot infection. In OMAFRA tar spot trials in Rodney, ON with Dr. Dave Hooker (UGRC) there are definite differences in tar spot control as expected since fungicide efficacy is largely dependent on fungicide selection and application timing. The images below illustrate some of the differences to date. The pre-tassel applications (7 to 12 leaf) did not reduce visual symptoms of tar spot compared to non-sprayed check (Figure 1) and plants are prematurely shut down which is expected since product wouldn’t be available when needed (Figure 22). The VT/R1 application again provided good control for those fungicides which have demonstrated good tar spot control, but some late tar spot is present (Figure 3). Similarly, later applications at R3 (milk) and R4 (dough) either alone or as a second application have shown good control (Figure 4).  

Figure 1. No fungicide check
Figure 1. No fungicide check
Figure 2. Pre-tassel fungicide application
Figure 2. Pre-tassel fungicide application
Figure 3. VT/R1 fungicide application
Figure 3. VT/R1 fungicide application
Figure 4. VT/R1 + 3 weeks later (R3)
Figure 4. VT/R1 + 3 weeks later (R3)

Will these observations between VT/R1 and later applications result in significant yield differences and will the “Return on Investment (ROI)” cover a late or second fungicide application? We cannot wait till these and other tar spot trials are harvested so we can answer these questions and more! Stayed tuned for updated fungicide performance information!!

Fall is BEST Time to Sample for SCN!

Soybean harvest has begun and for many growers, managing soybean cyst nematode means planting SCN resistance varieties BUT effective SCN management does not end when you have selected your soybean varieties! It is imperative to not only know your SCN population levels in each of your fields but what is happening to those levels over time and it begins with SCN soil testing!

The fall is a perfect time to sample harvested soybean fields or those which will be planted to soybeans in 2022. A fall sample takes into account any significant SCN population changes that have occurred during the growing season. If it’s the first-time sampling a field, the results provide you a baseline for future comparison. If you already have a baseline, the SCN test provides critical information.

If your SCN levels are decreasing, this could indicate your management program is working. If your is SCN levels are rising, this is a big red flag that the problem is getting worse and could get out of hand, costing you significantly in lost yield, dollars and sleep! If you do not know what is happening to your SCN population levels in your fields over time, your efforts may be wasted. One of the most important decisions a producer can make concerning this devastating pest is to take a SCN soil test.

For more information, visit the SCN Coalition website at or OMAFRA Agronomy Guide Publication 811 at

Ontario Nematode Survey Request for Samples!

OMAFRA specialists Albert Tenuta (Field Crop Pathologist) and Katie Goldenhar (Horticultural Crop Pathologist) are coordinating a nematode survey, targeting field crop and horticultural crop fields across the province. Nematodes present a significant and ongoing threat to plant health in Ontario and can result in significant economic and production losses. The primary objective of this 2-year CAP funded project is to update provincial nematode distribution maps as well as establish baseline data, for six different nematode species including soybean cyst nematode, root lesion or other nematode species. These results will support the enhancement of current nematode Best Management Practices for field and horticultural crop farmers, helping to improve the economic and sustainability of crop production in Ontario. Participating in the nematode survey is FREE, easy and soil samples can be collected specifically for nematode testing such as SCN or alternatively, soil samples collected for soil fertility can be split, with subsamples submitted for nematode testing. If you would like more information on the Nematode Survey, please contact Albert Tenuta ( or Katie Goldenhar (

Ontario Diagnostic Day Videos Now Available!

It was great getting back together in-person on July 20th and 21st, 2022 at the UG Ridgetown Campus for the Ontario Crop Diagnostic Days which combined the Southwest (Ridgetown), Elora and Eastern Ontario (Winchester) Crop Diagnostic Days into one hybrid provincial event! Thanks to all those who attended and our sponsors! As promised the 8 in-field session recordings have begun to be rolled out at Those CCA’s unable to attend in person will be able to register for the virtual event to receive their CEU credits (

Weather DataSeptember 4 – 10, 2022

LocationYearHighest Temp (°C)Lowest Temp (°C)Rain (mm)Rain (mm) April 1stGDD 0C April 1stGDD 5C April 1stCHU May 1st
10 YR Avg. (2011-20)26.313.320.7496286920563252
10 YR Avg. (2011-20)25.611.624.6452270418963030
10 YR Avg. (2011-20)25.111.428.4471267718743006
10 YR Avg. (2011-20)
10 YR Avg. (2011-20)23.99.331.4467242216312691
Mount Forest202227.18.80.8374246017032706
10 YR Avg. (2011-20)23.79.533.0481240916262708
10 YR Avg. (2011-20)
10 YR Avg. (2011-20)24.88.722.3460257717872871
10 YR Avg. (2011-20)
10 YR Avg. (2011-20)22.67.318.8444225215222561
Thunder Bay202226.80.820.5477202513242214
10 YR Avg. (2011-20)21.74.816.8404201812992227
Fort Frances202226.72.30.9576210714082366
10 YR Avg. (2011-20)22.25.415.2406214414082379
Report compiled by OMAFRA using Environment Canada data. Data quality is verified but accuracy is not guaranteed. Report supplied for general information purposes only. An expanded report is available at