Alison Robertson
Dr. Alison Robertson is a professor of plant pathology and microbiology. She provides extension education on the diagnosis and management of corn and soybean diseases. Her research interests include Pythium seedling disease of corn and soybean and Goss's wilt. Dr. Robertson received her bachelor's degree in plant pathology in 1991 from the University of Kwazulu-Natal, Pietermaritzburg, and came to the United States in 1999 to pursue a doctoral degree in plant pathology at Clemson University. She started working at Iowa State University in May 2004.
Subscribe to RSS FeedBacterial leaf streak (BLS) is particularly prevalent across Iowa this growing season. This past week I received numerous emails and texts with photos. I’m not overly surprised we are seeing BLS because we...
As corn approaches tasseling, I hear more and more rumblings about fungicide application. The good to abundant moisture we have had this growing season, has resulted in some itchy trigger fingers. In addition, the early reports of tar spot haven’t helped with the itch. Do we need to scratch...
The torrential rains that northern Iowa experienced last week may have favored several diseases of corn including crazy top, Physoderma brown spot and node rot, Goss’s wilt and bacterial stalk rot. While there are no in-season management practices for these diseases, correct diagnosis can help...
I have had several calls and emails about corn turning black – particularly the husks and leaf tissues. Walking in these fields turn a white shirt black quickly, and not surprisingly, combining this blackened corn can be very dirty.
The corn is black because the tissues are being...
Harvest is approaching too quickly this fall. Between the dry summer and the spurts of hot weather in August and early September, crop standability is degrading quickly. This blog will go over some potential reasons for standability issues and ways to assess and prioritize fields for harvest....
Well, I’ll be darned! Yesterday I tweeted the only disease being seen in Iowa corn was common smut on leaves. Thanks to an overzealous crop scout from a seed company, we can confirm that tar spot was observed in central Iowa (Poweshiek, Tama, Marshall, Jasper, Story and Polk counties) yesterday...
It’s a great time of year! The weather is finally warming up enough to wear shorts and green stripes are finally occurring across the landscape as corn (and beans) emerge. USDA reports 85%...
Corn foliar fungicide trials were done at six locations in Iowa in 2022: ISU Northwest Research and Demonstration Farm (NWRF), Sutherland; Northeast Research and Demonstration Farm (NERF), Nashua; Northern Research and Demonstration Farm (NRF), Kanawha; Southwest Research and Demonstration Farm...
It’s hard to believe another growing season has come and is almost gone. 2022 has had its share of challenges: a wet start, drought, corn root worm, soybean gall midge, pigweed, and (my favorite) tar spot. And now, as we approach harvest, we face final challenges like ear and crown rot.
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I continue to receive tar spot reports from across Iowa. Given the moisture we have had the past couple of weeks and the growth stage of the crop, this is not surprising. Tar spot development is favored by leaf moisture. As the growing season...
In pathology, we joke that to control a disease, just put a research plot out, and you’re guaranteed no disease. A couple of days ago I blogged about tar spot, hoping for a similar effect. Alas,...
Are you using the Tarspotter app this year? If you are, you may have noticed that the forecast for tarspot is high for Iowa. In addition, The Cruz Lab in Indiana tweeted they had found tar...
Brrrrrrrrr. Is summer ever going to come? It’s cold. It’s wet. Planting progress is behind and everyone is starting to get antsy. When we finally get our seed in the ground, as Emily Unglesbee so eloquently wrote, “...
As the 2021 growing season comes to a close, what should you be thinking about in terms of corn disease and how that might impact your harvest plans?
If you listen carefully, you can hear corn tassels rattling in the breeze, and occasionally the hum of a crop sprayer.
This growing season started off exceptionally dry, apart from southeast Iowa. The moisture that arrived in July and hung around for a couple of weeks was welcomed by...
Despite the cooler conditions and precipitation (in some parts of Iowa) last week, the U.S. Drought Monitor categorizes most of Iowa in moderate to severe drought. As we approach tasseling, more and more questions around fungicides are being asked.
All diseases managed by...
With cool weather conditions potentially causing delays in cover crop termination, what options are available? Cereal rye ahead of soybean is not nearly as problematic. While planting green may not be advised for beginning cover crop users, more experienced cover crop users have...
As more producers integrate cover crops into their operation, there has been increased interest in planting corn into a green or living cover crop, such as cereal rye, and terminating the cover crop after planting.
To help provide some insight into how “planting green” might affect corn...
Occasionally, corn planted after a cereal rye cover crop may have reduced yields. Proposed reasons for this yield decline include allelopathy, seedling disease, nitrogen immobilization and poor planter performance. In our lab, we are interested in understanding how seedling disease and...
The 2020 derecho left large amounts of downed corn as it swept across Iowa. Farmers faced the challenge of determining the best way to deal with this corn, which in some cases is being left in the field. Most of these fields will be planted to soybean in 2021, which brings up an interesting...
The challenges of this growing season continued this month when a storm front brought more than 3 inches of rain to much of the state. While the rainfall was welcome for pastures and cover crops, it added to the challenges in corn fields, especially those suffering from drought and the derecho....
Wind and storm damaged soybean have been reported across Iowa, creating yet another stress for farmers this growing season. Certain fungicide products are marketed as being capable of reducing stress in crops, so should they be sprayed on soybean this late in the season?
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Hailstones damaged corn and soybean in multiple locations across Iowa on July 11, 2020. Fungicide use after hail injury is sometimes suggested as a way to benefit damaged plants. In order to help determine if fungicide use after hail is beneficial, Iowa State University undertook multiple years...
Over the weekend there have been several reports of bacterial leaf streak (BLS) of corn in eastern Iowa. The infections also appear to be quite severe (Figure 1).
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Earlier this week I was out in corn fields "helping" my lab crew collect disease data. The corn was not looking great but hopefully it has perked up with the past few days of sun and warmth. I know I have!
I noticed in my corn-on-corn fields anthracnose leaf blight on the lower leaves of...