Southeastern U.S. Vegetable Crop Handbook - 2023 - 106

Minimum Tillage. No-tillage is the most commonly used minimum
tillage practice with sweet corn. No-till planters currently
in use with row crop production will plant sweet corn seed with
minimal modifications. Type of winter cover crop residue can
affect sweet corn seed depth. Inspect seed placement and adjust
for correct depth. Early spring planting with no-tillage in sweet
corn may delay growth and days to harvest. Planting after soils
warm in the spring will improve vigor. Use of small grain cover
residue may require additional nitrogen (20 to 30 lbs N/acre in
addition to the normal recommendation) if cover crop is fairly
mature when killed. No additional nitrogen above recommendations
is required if a legume cover crop (hairy vetch, winter
peas, or crimson clover) is used as residue.
SPECIAL NOTES FOR PEST MANAGEMENT
(listed as " Corn, Sweet " in the Pest Management section)
INSECT MANAGEMENT
Corn Earworm (CEW): CEW initiates egg laying when the
plants begin to silk and ends when the silks wilt. Eggs are laid
singly on the fresh silks. Begin to control CEW when 10% of the
ears are silked. Repeat sprays at three to five day intervals until
90% of the silks have wilted. Control is more difficult late in the
season. Direct sprays toward the middle third of the plant. Corn
hybrids having a long, tight-fitting shuck appear to suffer less
damage than those with loose shucks.
Another management tactic for CEW and European corn
borer (ECB) control is the use of BT sweet corn. These hybrids
produce their own natural insecticide for control of these pests.
However, under high pressure, supplemental sprays may be
needed to achieve damage-free ears. Minimum acreage and resistance
management practices are required with BTs sweet corn.
Some markets may not accept these hybrids.
Corn Flea Beetle: Flea beetles transmit a bacterial wilt disease,
known as Stewart's Wilt, and these beetles are numerous after
mild winters. Treat susceptible varieties at spike stage when 6
or more beetles per 100 plants can be found. Repeat every 3 to 5
days as needed. Note: Soil-applied insecticides may be ineffective
during the first week of plant growth if soil temperatures
are cool. Foliar applications of an insecticide may be necessary
during this period.
European Corn Borer (ECB): Thorough spray coverage in
whorls and on plants is essential. Many insecticides are highly
toxic to bees. Granular formulations, if applied over the whorl,
are generally more effective than liquid formulations for ECB
control.
Sap Beetle (SB): Loose-husked varieties tend to be more susceptible
to sap beetle attack. Ears damaged by other insects
attract SB. Begin sampling at pollen shed and treat when 5%
of the ears have adults and/or eggs. Note: Insecticides used for
worm control at silk may not control SB infestations.
Fall Armyworm (FAW): Direct granules over the plants so that
they fall into leaf whorls when FAW first appear and repeat application,
if necessary. For foliar spray applications, high-spray
gallonage (50 to 75 gallons per acre) is necessary for effective
FAW control.
INSECT MANAGEMENT DECISION-MAKING
Whorl/Tassel Infestation: In general, insect larval feeding (ECB
and FAW) during the whorl stage of sweet corn development
has a greater impact on early planted, short-season varieties. For
ECB on early plantings, apply first spray or granular application
when 15% of the plants show fresh feeding signs. Additional
applications may be necessary if infestation remains above 15%.
An early tassel treatment is usually more effective than a whorl
treatment because larvae are more exposed to the chemicals.
The impact of infestation on mid-and late-season plantings
depends on the stage of the plants when the infestation occurs.
Treat for FAW during the early whorl stage when more than
15% of the plants are infested. During mid- to late-whorl stages,
treatment for both FAW and ECB may be necessary if more than
30% of the plants are infested. Treat fields in early tassel stage
if more than 15% of the emerging tassels are infested with ECB,
FAW, or young corn earworm (CEW) larvae.
Ear Infestation: Direct sampling for CEW, FAW, and ECB
during silking is not practical because of the low thresholds for
ear damage. Begin treatment when 10% of the ears show silk.
If CEW populations are heavy, it may be necessary to begin
treatments when the very first silks appear. Silk sprays should
continue on a schedule based on area blacklight and pheromone
trap counts, geographical location, and time of year. Early in the
season, silk sprays may be required on a 3- to 6-day schedule.
When CEW populations are heavy, it may be necessary to treat
on a 1-to 3-day schedule. Applications during low populations
can end up to 5 days before last harvest. During heavy populations
and high temperatures, treatments will need to be made according
to the legal " days to harvest " of the chemical.
For best control during heavy populations, maximize the
gallonage of water per acre, use a wetting agent, and make applications
with a high pressure sprayer (200+ psi) with drop nozzles
directed at the silks.
HARVESTING AND STORAGE
See Table 14 for postharvest information.
106
2023 Vegetable Crop Handbook for Southeastern United States
Southeastern U.S. Vegetable Crop Handbook - 2023

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