Arkansas Fruit, Vegetable and Nut Update

2021 County Agent Sweet Corn Demonstration Results

by Aaron Cato, Amanda McWhirt, and Hank Chaney - November 5, 2021

A wrap-up of the 2021 Corn Earworm Resistant Sweet Corn Cultivar Demonstration carried out by Arkansas Horticulture Specialists and County Agents.

In 2021 the county agent horticulture demonstration shifted from tomatoes, as had been trialed the last few years, to sweet corn. This change was the result of a multitude of questions we were getting from both growers and county agents centered around corn earworm management in sweet corn. In 2021 we trialed four cultivars of sweet corn that had varying degrees of corn earworm (CEW) resistance to determine how well they grew in the state, as well as whether consumers found the taste acceptable. The ultimate goal was to build confidence in recommending new CEW resistant cultivars such as Pursuit.

The table below (Table 1) outlines the 4 cultivars we grew in the demonstration and the expected resistances based on the genes present in each cultivar. The orange indicates conventional varieties with no GM traits and the red indicates that corn earworm (CEW) control is no longer expected due to resistance to GM traits.

Table 1: Resistant Traits of each Sweet Corn Cultivar used in the 2021 Demonstration.

Cultivar	Disease Resistance Traits	GM Genes	GM Resistance (Insects Suppressed)
Obsession I	Northern Corn Leaf Blight, Common Rust, Stewart’s Wilt	NONE	NONE
Serendipity F1	Southern Corn Leaf Blight	NONE	NONE
Obsession II Performance Series	Northern Corn Leaf Blight, Common Rust, Stewart’s Wilt	Cry1A.105 + Cry2Ab2 + Cry3Bb1 + Roundup Resistant	Corn Borer, Several caterpillar species, and Corn Root Worm (CEW NOT Suppressed)
Pursuit F1 (Attribute II)	-----------------	Cry1Ab + Vip3A + Roundup and Liberty Resistance	Corn Borer + Broad caterpillar control (Suppresses CEW)

The table below (Table 2) exhibits important growth habits of each cultivar. The main choice of these cultivars was based off of GM traits and expected CEW resistance, but we were also sure to choose cultivars with similar sweetness types so they could planted at similar times.

Table 2: Growth Habits and Sweetness Type of Sweet Corn Cultivars Grown in the 2021 Demonstration.

Cultivar	Sweetness Type	Kernel Type	Notes
Obsession I	Sh2	bicolor	79 days, 8’’ ears
Serendipity F1	Triple sweet, Synergistic SE-Sh2	bicolor	82 days, 7-8” ears
Obsession II Performance Series	Sh2	bicolor	80-82 days, 8-8.5’’ ears
Pursuit F1 (Attribute II)	Triple sweet, Synergistic SE-Sh2	bicolor	82-82 days, 7.9’’ ear

We sent out enough seed to each agent to plant around 48 row feet of each variety. Agents were supplied with a standard fertility plan and relied on hand weeding. Agents were also asked to instruct growers to not use any insecticides for CEW control, which allowed us to see how much suppression was truly provided by the plant itself.

Cultivars with the same sweetness types (Sh2 or Triple Sweet) were planted together, with either a 14 day or 500 ft. of planting buffer between the cultivars with the other sweetness types. This combination of cultivars allowed for each planting to have one known CEW susceptible/conventional cultivar vs. one cultivar with GM resistance to CEW (Obsession I vs. Obsession II and Pursuit vs. Serendipity). We expected to see a larger difference in CEW suppression in the latter pairing based on reports of waning efficacy in Obsession II vs. excellent suppression with Pursuit.

We asked county agents to report their results in two ways. First, agents posted progress of the demonstration on social media using the hashtag #uaexHORT. Below are some of the social media posts made by agents that really helped to showcase this work and get the community interested. Second, agents reported on growth characteristics of the sweet corn cultivars, how much damage they observed from CEW, and taste characteristics.

Social media posts made by two county agents that illustrated progress and results at their sweet corn demonstrations in 2021.

Results

Plant Characteristics

The table below (Table 3) shows the average of the measured plant characteristics across the counties that participated in the demonstration*. Combining these values, along with comments from county agents, indicates that these cultivars produced similar sized ears. This is important because our known CEW resistant variety in Pursuit looks to be growing at an acceptable size and yield in Arkansas. Days to harvest was similar, with our two later planted cultivars (Serendipity and Pursuit) taking less time to maturity than the earlier planting date cultivars (Obsession I and Obsession II).

Table 3: Average Ear Size, Corn earworm (CEW) Damage, and other Characteristics of Four Cultivars Demonstrated by County Agents across Arkansas.

Cultivar	Ear Length (Inches)	Rows of Kernels	CEW Damage (% Damaged Ears)	Flavor Rank (1-4)	Days to Harvest	Brix
Obsession I	7.68	16	48	2.7	72	17.25
Obsession II	7.75	16	29	2.1	72	17.25
Serendipity	7.72	14	53	2	62	21
Pursuit	7.69	14	1	2.3	62	20

Corn Earworm (CEW) Damage

We expected to see a lot of damage from CEW across the state and we were not let down, as we observed at least some level of ear feeding in every county that participated. We did have a good bit of variance from county-to-county in regard to how much damage we saw in our conventional cultivars, but the trend seemed to stay the same. In many counties, our conventional cultivars (Obsession I and Serendipity) sustained CEW feeding damage to 100% of ears. When averaged across all counties we saw 48% and 53% of ears damaged respectively.

Obsession II contains a genetic modification that confers resistance to corn earworm, but many states report that CEW are now resistant to this genetic modification. Across all counties we saw an average of 29% of ears damaged by CEW, and even observed 100% damaged ears in multiple counties. This is only a 19% reduction in ear feeding when compared to the conventional Obsession I cultivar.

Pursuit is also genetically modified but with different genes than Obsession II, so we expected to still see 100% CEW damage suppression. Across all counties, only one demonstration observed any CEW damage at all on just 1 ear. This means that 100% suppression should still be expected when using this variety without any insecticides.

Different corn cultivars exhibiting different levels of corn earworm (CEW) feeding. Photos by Lesley Smith, Kibler Vegetable Station.

Taste

Along with how well these cultivars grow and can avoid CEW damage, it’s important to have the customer wanting to come back. We asked each county to rank these cultivars from their favorite to least, which we then averaged and presented along with the growth characteristics above. Serendipity was ranked the lowest (best), followed closely by Obsession II and Pursuit, and a bit more distantly by Obsession I. The interesting aspect is that each cultivar listed here, with the exception of Obsession I, received multiple #1 votes. However, there were some differences in opinion especially regarding the CEW resistant Pursuit cultivar. Pope County rated Pursuit as #1 although it wasn’t the sweetness, which this quote from Phil Sims illustrates; “Based on this survey, Pursuit was given a 4.75 even though the Brix test was only 14. Apparently participants not only want a good tasting ear of corn but also a tender ear.” This is in staunch comparison to one of Allison Howell’s taste testers in Clay County which had this to say about Pursuit; “Yuck, not good. Doesn’t taste like sweet corn.”

Conclusions

This demonstration exhibited new sweet corn cultivar options to grow across the state through a comparison with known standards, such as Obsession II. Pursuit is one of the new options in the Attribute II series that we expected to have excellent CEW resistance. This resistance paired with a good showing in growth and taste compared to our known standards creates great opportunity for agents to recommend these types of cultivars. This is especially true when you consider that a cultivar resistant to CEW generally requires NO foliar insecticides, whereas our recommendation on all other cultivars is spraying every 2-3 days.

Thanks to all the county agents and collaborators who participated in providing feedback in the 2021 Sweet Corn Demonstration. Although sweet corn seems simple to grow, I believe we collectively were reminded that we have to plant it at the most erratic time of the year (for weather) and that basically every animal under the sun is trying to get to the cobs before we before we can pick them.

Name	County
Bryce Baldridge	Lawrence
Rachel Bearden	Hot Spring
Kurt Beaty	Jefferson
Grant Beckwith	Arkansas-Stuttgart
Ray Benson	Mississippi
Ethan Brown	Mississippi
Terrell Davis	Pike
Randy Forst	Pulaski
Dave Freeze	Greene
Herb Ginn	Crawford
Brett Gordon	Woodruff
Cindy Ham	Clark
Darrin Henderson	Madison
Samantha Horn	Howard
Phil Horton	Arkansas
Allison Howell	Clay
Jerri Lephiew	Columbia
Matthew Mann	Lonoke
Brad McGinley	Grant
Michelle Mobley	Cleburne
Ryan Neal	Benton
Nicole Nichols	Saline
Shawn Payne	Phillips
Krista Quinn	Faulkner
Shaun Rhoades	Scott
Kimberly Rowe	Hempstead
Sherri Sanders	White
Jennifer Sansom	Little River
Amy Simpson	Clark
Phillip Sims	Pope
Becky Sterner	Polk
Jesse Taylor	Franklin
Branon Thiesse	Craighead
Cory Tyler	Fulton
Adam Willis	Newton
Kibler Vegetable Station
Hope Research and Extension Center