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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.
Northern Corn Leaf Blight,
Corn Borer, Several caterpillar species, and Corn Root Worm
Corn Borer + Broad caterpillar control
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
Triple sweet, Synergistic
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.
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.
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
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.
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.”
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.