include flea beetle, cutworm, army- corn back to corn, then one of the three seed treatment. Another disease
GeoffreyTrainer,
worm, slugs, corn rootworm and rootworm technologies should be used. favored by wet weather, Rhizoctonia is
aGronomisT,
European corn borer. Flea beetles will Fields also should be scouted at this characterized by reddish-brown areas
seedConsulTanTs, inC.
feed on newly emerged corn plants time for European corn borer. The first on the main stem and upper root at the
causing “windowpane” feeding on the generation appears in late May through soil line. Phytophthora continues to be
leaves. The corn flea beetle is a vector mid-July (V6—VT) depending on the our main pathogen, attacking soybean
U
AG
PD
R
A
O
T
N
E
OMY
of Stewart’s wilt and is normally a growing season. Damage appears as plants in poorly drained soils. Control
problem after a mild winter. Ohio State leaf feeding (shot holes or window measures include commercially applied
University data suggests that southern pane feeding). When feeding appears, seed treatments at the highest labeled
By April 13, only extremely isolated
Ohio may see a low or moderate threat, pull the whorl and gently un-roll the rate and planting soybean genetics
corn planting has taken place across the
while northern Ohio should not be leaves. If damage reaches threshold with gene resistance. Anne Dorrance,
state. If the weather cooperates and
affected. Slugs can damage seeds and levels, rescue treatment is available. An OSU plant pathologist, also recom-
farmers are able to get their crops
seedlings and have the potential to alternative to insecticides is to plant mends rotating varieties with different
planted in a timely manner, the months
delay plant development by defolia- hybrids with the Bt (Bacillus Rps genes to overcome shift in phy-
of May and June can be some of the
tion. Cutworms can be present through thuringiensis) gene for complete con- tophthora populations.
less stressful and problematic times of
V8, so producers should continue to trol of first and second generation Post-emergent herbicide perform-
the year.
scout fields for leaf feeding, irregular European corn borer. If you are yet to ance in corn and soybeans should be
With good emergence and weed
holes, notched plants, cut plants, wilted finish corn planting, seriously consider monitored closely this year. Weed size
control, these months can be easier to
plants or dead plants. Insecticide treat- the use of Bt hybrids. After May 20, it needs to be checked before herbicide
deal with compared to later on in the
ments are available and genetic protec- is imperative that growers switch corn application. The proper rate for the size
growing season. If a producer doesn’t
tion is available with Herculex Insect genetics to a European corn borer of weeds might need to be adjusted.
achieve good emergence and adequate
Protection technology. Armyworms, an resistant version. Second brood Glyphosate, for example, needs to be
stands, there are several factors that
occasional problem, feed through V12, European corn borer is attracted to late- used at the recommended labeled rate
could contribute to these problems.
leaving damaged, ragged leaves to planted corn and may cause significant for the largest size of weed present in
Corn insects, which could affect
complete defoliation. Insecticide treat- yield loss. the field. Crop growth stage should be
seedling emergence and stands,
ments are available. If producers are able to get into the closely monitored before herbicide
include seed corn maggot, white
If you are planting corn following fields toward the end of April or first of application. Proper spray adjuvant
grubs and wireworm. All these insects
corn or are located where the western May, much of the corn planted during should be used in post-emergence
will attack the seed and/or the newly
corn rootworm variant is present, you that time should be approaching V6. applications to get adequate control of
germinated seedling. These early sea-
should be scouting. Rootworm larvae And, while the growing point is still at weeds and lessen the risk of crop
son insects tend to be problematic in
begin feeding about the time fireflies the soil surface, the corn plant should injury. Increased rates of herbicides (i.e.
fields with cover crops, sod or grass
(lightning bugs) appear and may feed have accumulated approximately 475 glyphosate) may be warranted to con-
weeds. Control of these insects can be
until July. Root lodging, also known as growing degree days if planted around trol some tougher weeds.
obtained with a seed-applied insecti-
“goosenecking,” is a symptom of root- that time. Ear size initiations start at In driving by many fields in the past
cide (Cruiser or Poncho) or by a soil-
worm feeding, but the roots should be approximately V8 and end about a couple of years, producers seem to be
applied insecticide.
examined for positive identification. If month later. Corn stands should be waiting longer to make their herbicide
Late May and early June insects
you are in the variant area or plant evaluated before V6, especially if corn applications in corn and soybeans. In
is to be side dressed. If adequate stands waiting, they are limiting their yield
are achieved in early planting and the potential. As a rule of thumb, I suggest
field has a good history of high yield to growers that weeds should get no
potential, then side-dressed nitrogen taller than a pop-can before spraying.
would probably pay for itself. First off, these weeds are competing
Evaluating plant stands, matching with the crops being grown for nutri-
nitrogen rates to hybrid and final ents, moisture and sunlight. Secondly,
stands may prove to be beneficial if a the smaller the weeds are the easier it
producer takes the time to walk their is to control them. Third, when these
fields. If all things come together, nitro- weeds are allowed to grow and com-
gen can be the limiting factor in yield pete with crops, yield potential can be
potential. There is a chart in the “Corn, greatly reduced. Fourth, if weeds are
Soybean, Wheat, and Alfalfa Field not completely killed by herbicide
DAVE’S VOLUME
Guide” from OSU Extension on page 53 applications they produce seed, and
that estimates nitrogen loss by source, that gets added to the weed seed bank
time of application, etc. Through V6, to battle in years to come.
DISCOUNTS
the corn plant takes up about 5% of its Research done at Ohio State and
nitrogen needs, but uses an additional Purdue University has shown that
55% in the next 40 days (V18). Nitrogen yield losses can be as high as 50% with
rates should be adjusted as to popula- season-long interference of giant rag-
Creosote Post -
tion and hybrid yield potential. There weed. Delaying post- glyphosate appli-
could be potential to boost yields with cations in soybeans (from 9-inch to 12-
New LOwER Prices
additional nitrogen! inch weeds) has shown to reduce soy-
Early season soybean insects include bean yields as much as 10%. In univer-
seedcorn maggots, wireworm, slugs sity trials, the use of a pre-herbicide
and bean leaf beetle in Ohio. Seedcorn has shown to increase yields 4 to 9
maggots, wireworms and slugs will bushels compared to post glyphosate
attack the seed and/or the newly ger- only! Corn yield losses have been docu-
New Campfire Grills -
minated seedling. These early season mented by university by as much as
insects tend to be problematic in fields 44% yield loss from season long inter-
Easily converts to firepit
with cover crops, sod or grass weeds. ference with lambsquarters and 40%
Bean leaf beetle feeding occurs on in soybeans.
emerged seedlings through pod fill, so These are just a few of the potential
this is one pest that needs to be moni- problems that Ohio growers could be
800-220-2377 • 740-796-6531
tored throughout the growing season. faced with in the next couple of
5385 Edgemoor Rd. • Adamsville, OH 43802
Early season soybean diseases months. As with every year, crops
include pythium, phytopthora and rhi- should be closely monitored and scout-
www.daileyfence.com
zoctonia. At this time, newly emerging ed, and if a problem is noticed, you
soybeans may still be susceptible to should contact your agronomist, seeds-
COME SEE US NOw!
pythium, which could have been easily man or county Extension educator to
controlled with a commercially applied have it diagnosed.
16Crops • Ohio’s Country Journal • May 2009
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