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.

Alison Robertson photo
September 14, 2021 7:14 AM

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?

Plant Diseases
July 21, 2021 4:37 PM

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...

Plant Diseases
June 29, 2021 2:12 PM

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...

Plant Diseases
April 16, 2021 11:07 AM

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...

Crop Production
April 6, 2021 8:30 AM

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...

Plant Diseases
April 2, 2021 2:02 PM

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...

Crop Production
October 23, 2020 12:45 PM

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...

Plant Diseases
September 18, 2020 11:06 AM

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....

Crop Production, Plant Diseases
August 17, 2020 7:34 AM

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?  


Plant Diseases
July 14, 2020 8:38 AM

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...

Crop Production, Plant Diseases
June 22, 2020 3:27 PM

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).


Plant Diseases
June 4, 2020 9:52 AM

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...

Plant Diseases
October 11, 2019 7:16 AM

Tar spot is the latest new disease of corn to be observed in the U.S. The disease was first observed in Indiana in 2015. In 2016, it was found in eastern Iowa, Illinois, Michigan, Wisconsin and Florida. Last growing season, the disease caused significant damage to corn in northern Illinois,...

Plant Diseases
September 23, 2019 5:59 PM

As corn fields start to reach maturity across the state of Iowa, we need to start thinking about stalk and ear rots, particularly in terms of scheduling harvest and grain storage. Read on for more details on stalk rots and ear rots and how to scout for them.  

Stalk rots...

Plant Diseases
August 9, 2019 3:57 PM

This past week there have been numerous new reports of tar spot within the Midwest, including Iowa (Figure 1). For updates maps, please visit


Plant Diseases
July 22, 2019 9:05 AM

Corn is starting to tassel and beans are flowering so no wonder everyone is asking about fungicides.  We’ve tried to address some of the questions regarding whether to spray or not in this...

Pesticide Education, Plant Diseases
June 23, 2019 5:44 AM

In 2018, tar spot was detected in 12 counties in eastern Iowa. The disease was observed late in the growing season, at did not cause a lot of damage. In Wisconsin, Illinois, Michigan and Indiana, however,...

Plant Diseases
June 5, 2019 4:25 PM

#plant19 has been a year to remember, and not necessarily in a good way. A couple of days ago we talked about anthracnose leaf blight on corn. Although we...

Plant Diseases
June 5, 2019 8:10 AM

With some planting progress still stalled, many of you are probably finding ways to pass the time, possibly scrolling through Twitter. Adding to some of the anxiety, you’re probably seeing photos of diseased seedling corn, by the name of Anthracnose leaf blight. While last week’s...

Plant Diseases
April 29, 2019 1:04 PM

Now that we’re within the time frames for planting to achieve optimal yields for corn and soybean, producers might be getting antsy with the cold, damp weather, and weighing the risks of a potential cold front that can cause damage to germinating seeds or seedlings.

For those that have...

Crop Production, Plant Diseases
June 8, 2018 9:41 AM

Widespread hail occurred in Iowa on 6 June 2018, causing damage to many acres of corn and soybean plants. At this time, most of the corn is in the V6 to V8 growth stages, while soybeans are at the V1 to V3 growth stages. Some areas of the state also received hail injury earlier this season....

Crop Production, Plant Diseases
October 6, 2017 8:44 AM

Over the past couple of weeks we’ve been doing stalk rot assessments at several of the ISU Research Farms including the Southeast Research and Demonstration Farm, the McNay Research Farm, and the Ames Farm. While the plants seemed to be standing well, minus where the raccoons had fun in one of...

Plant Diseases
September 18, 2017 2:30 PM

To help farmers and agronomists identify, scout, and manage corn diseases a new Corn Diseases booklet, published by Iowa State University Extension and Outreach, is now available to crop producers and industry professionals. The up-...

Plant Diseases
July 10, 2017 1:45 PM

Bacterial leaf streak is a new disease of corn that was confirmed in the U.S. last year - as if we don't have enough spots to diagnose on corn!  And, as you might expect, a lot of spots and streaks on corn can be misdiagnosed for bacterial leaf streak.

Over the winter, corn pathologists...

Plant Diseases
May 15, 2017 7:24 AM

Cooler and wetter conditions can effect corn germination and emergence, but they can also provide a favorable environment for seedling diseases.

One research study being conducted by ISU is taking a closer look at seedling diseases in corn. The goals of the...

Plant Diseases