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Corn & Soybean News April
2008, Volume 8, Issue 1
Cooperating
Departments: Agricultural Economics, Biosystems and Agricultural Engineering,
Entomology, Plant and Soil Sciences, Plant Pathology Editor:
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1. Are Seed Treatments Enough
Control on Corn? Ric
Bessin, Extension Entomologist Well
over 90% of field corn seed may have one of several seed treatments
pre-applied. The most common
treatments are those that are applied at concentrations to control
‘secondary’ pests of corn, including wireworms, white grub, seedcorn maggot,
flea beetles, and seedcorn beetle. Personally,
I don’t like the term ‘secondary’ pest because when these pests are at high
levels and occur in a field on a regular basis, they are actually primary
pests. We
have two leading seed treatment active ingredients in corn, clothianidin and
thiamethoxan. They are combined with fungicides and sold as Poncho and
Cruiser and ordered on the seed. Both
of these are in the same chemical class and have the same mode of
action. Both are systemic and are
rapidly absorbed by the seed as it imbibes water during germination and later
through the roots. Once inside the seedling they move throughout the plant
providing insect protection above and below ground. While these seed
treatments are similar in many ways there are also some subtle differences
that can affect performance. The
differences that I’m aware of include substantial differences in solubility
in water and some difference in the spectrum of insects that they manage.
Each of these come in two loading rates on the seed, a 0.25 mg active
ingredient per kernel and a 1.25 mg active ingredient per kernel. The higher rate is primarily intended for
the corn rootworm market, and the lower rate for secondary pests. Research at UK and other
universities has shown that these seed treatments are able to prevent stand
loss and can help to maintain more uniform vigor during early growth stages
in fields where secondary soil insect pests are present. Now
the question I ask is, are these seed treatments providing the level of
control that we need? That is a
difficult question to answer as it depends on the level of particular pests
in a given field. In the vast majority
of fields, the secondary pest rate is sufficient to control light to moderate
levels of soil insect (excluding corn rootworm). However, there are certain fields where
secondary pests are found at very high levels and the secondary rates are not
providing enough control. Our research
has shown that moving to higher rates of these seed treatments when there is
a history of high levels of secondary pests improved control as measured by
improved stands. In a few problematic
fields, growers have also combined seed treatments with low rates of soil
applied insecticides with some success. These
seed treatments are usually found on Bt corn, CB or RW, or on stacked
hybrids. So these hybrids could have
protection from corn borers (European and southwestern), corn rootworms, fall
armyworm, black cutworm, and those pests listed at secondary pests. Can
we walk away from these fields and let the seed treatments and biotech traits
manage all of the insect pests for us?
These have been excellent tools in Kentucky, but I don’t think we
should forget about insect pests during the season. First, while corn prices remain strong,
input prices have increased dramatically as well. It would be a huge mistake to let an insect
pest get out of control. The other
reason is that we can see insect pest levels on some occasions that can
overwhelm control tactics. So my
recommendation would be to use seed treatments and biotech traits as needed
based on field history, planting dates, and other factors that may predispose
fields to higher risk, but do not discontinue to regularly monitor fields for
performance and insect pests. With
high investments and possibly higher returns on corn, it would be too
expensive to make a mistake by letting a pest problem get out of control. The future of seed treatments looks quite promising with additional active ingredients to control other pests such as nematodes or even to relive stress and improve vigor in certain situations.
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· If a seed insecticide treatment is used, it will be sufficient for
most fields. · New traits and new chemistry do not replace the need for scouting and
targeting pests. |
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2.
Seed-Treatment Fungicides in Corn Paul Vincelli, Extension
Plant Pathologist Pythium species are fungal-like organisms commonly found in
agricultural soils. They are the
primary cause of seed rot and seedling damping off in corn in Kentucky, and
they are typically most active in cool, wet soils. The wet spring of 2008
could favor Pythium species. The
increased use of conservation tillage also increases pressure from Pythium
seed and seedling diseases, since residue-protected soil does not dry out as
quickly as plowed soil. The importance
of effective fungicidal treatment of corn seed has increased because of these
two trends. A recent study (1) by
plant pathologists at The Ohio State University closely examined the Pythium
organisms associated with seed and seedling problems in corn and soybean in
Ohio. This article focuses on their
findings for corn, which are summarized as follows: 1.
The most common species isolated from
diseased corn seeds and seedlings were Pythium
sylvaticum and Pythium dissotocum. Less common were Pythium torulosum, Pythium
irregulare and Pythium inflatum. One interesting find was that Pythium ultimum, the organism that
typically has been regarded far and away as the Number 1 Pythium in corn, was
infrequent in their surveys. Perhaps
changes in cultural practices account for this shift; perhaps something else
is at work; but either way, it is interesting how P. ultimum is so far down the list now. 2.
Of the five most common Pythiums found
in diseased corn seeds and seedlings, none were highly aggressive on
corn. Two were moderately aggressive: P. sylvaticum and P. irregulare. These two
species were relatively sensitive to the seed-treatment fungicides mefenoxam
and captan but insensitive to the QoI fungicides azoxystrobin and
trifloxystrobin. 3.
P.
dissotocum, P. torulosum, and P. inflatum were slightly aggressive on corn seeds and
seedlings. Based on their results,
less than complete control of P.
dissotocum and P. inflatum
would be provided by mefenoxam, trifloxystrobin, or captan. P.
torulosum would be difficult to control completely with mefenoxam or
captan. 4.
Pythium
graminicola was isolated less commonly than the
five listed above, but it was aggressive on corn and insensitive to both
mefenoxam and trifloxystrobin. Significance These results suggest
that a diversity of Pythium
organisms are responsible for seed and seedling disease in corn under current
production practices. Significantly,
these Pythiums are not all controlled by a single fungicide used for seed
treatment. Because of this diversity,
improving drainage and planting when soil temperatures exceed 50°F remain
important cultural practices for minimizing seed and seedling diseases in
corn. For fields and farms with a
history of seed-establishment problems in cool, wet soils, consider using a
mixture of seed-treatment fungicides to assure the best chance of success in
stand establishment. 1.
Broders, K. D., Lipps, P. E., Paul, P. A., and Dorrance, A. E. 2007.
Characterization of Pythium spp. associated with corn and soybean seed
and seedling disease in Ohio. Plant Dis. 91:727-735.
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· Different seed fungicides target different Pythium species. · For fields with a history of seedling disease, a combination of
fungicides might be needed. |
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3. Preplant
Applications of N, P & K Lloyd
Murdock and Greg Schwab, Extension Soil Specialists The
prices of fertilizer inputs have increased greatly the last couple of
years. Fortunately, the prices of
commodities have also. With both price
increases, the fertilizer recommendations remain the same. However, efficiency of fertilizer use, to
maintain high yields, becomes a primary objective at this point. Below
are a few basic points that might help with this. 1.
Rethink your program. If you have not changed your fertilizer program in the
last several years and are relying on post management practices, that seemed
to work during previous times, now is the time to rethink what you are
doing. It could pay handsomely for
you. 2.
Soil Test More Often – Soil testing at least every second year will help you
know what level of nutrients you have in the soil and better refine your
fertilizer needs. 3.
Operate in the Medium
Soil Test Range for P and K (as per U.K.,
AGR-1 guide) – A soil test of P of 35 to 45 lbs/ac and K of 200 to 250 lbs/ac
using Mehlich III extractant means you have enough of these nutrients in the
soil to grow a crop this year.
Maintenance rates of P2O5 and K2O are
all that is needed. When you are above
the medium soil test range, you can stop adding fertilizer until you get down
into this range. If you are below the
medium soil test range, the only way to conserve of fertilizer additions is
with the use of row fertilizers 4.
Row Fertilizers – When you are in the low range of P or K soil test, the
fertilizer can be banded beside the row and improve the efficiency of
use. Fertilizer rates can be reduced
by 1/3 to ½ of that recommended for broadcast treatments. 5.
Maintain a Proper pH – The best pH for most crops is between 6.2 and 7. When in this range, fertilizers are used
more efficiently. Phosphorus can be as
much as 20-25% more available in this pH range as opposed to a pH in the 5’s. 6.
Manures are an
excellent source of fertilizers and
are usually much cheaper than commercial fertilizers. Good distribution and nutrient testing are
the keys to the use of manures as fertilizers. They will usually build P levels and
maintain K levels when used. The N
availability is somewhat unpredictable but good estimates can be made for the
conditions under which the manure was used. 7.
K fertilizer timing is important on crops when the vegetation is the
harvested crop such as silage, hay or straw.
The plant will take up more K than is needed for production if it is
available for uptake. This is called luxury
consumption. If vegetation is going to be removed, then K fertilizer should
be applied before each crop. For example, if wheat straw is to be harvested,
then K fertilizer should be applied before wheat and again before double crop
soybeans. If growing alfalfa, K should
be applied after the 1st harvest and again after the 3rd
harvest. 8.
Nitrogen rates for grain cannot be changed with the present
economics. However, sidedressing some
of the N on poorly or somewhat poorly drained soils will improve nitrogen
efficiency and rates can be reduced by 35 lbs of N per acre from preplant
recommendations.
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· More frequent soil tests are justified. · Adjust your program according to these tests. |
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4. Soybean
Seed Quality Chad Lee, Extension
Agronomist As many of you already
know, soybean seed quality is questionable this year. Some soybean seed is
being sold with standard germination below 80%. This is not an ideal
situation and most companies would prefer to not sell seed with this low of a
germination percentage. However, the tight supply demands that the seed be
sold. Cindy Finneseth in
Regulatory Services has an excellent summary in their last newsletter: http://www.rs.uky.edu/other/newsletters/2008_1stQ.pdf The combination of
poor seed quality and tight supplies means that getting the first planting of
soybeans established is critical. Jim Herbek and I have
been recommending lower seeding rates. Maximum soybean yield is often
accomplished with a final stand of 100,000 plants per acre in full season
soybeans. Please look at the
seed tag for the standard germination and make adjustments to your seeding
rates as necessary. If standard germination was 80%, then a minimal seeding
rate of 125,000 seeds per acre would be needed to get a final stand of
100,000 plants per acre. If standard germination was 70%, then a seeding rate
of 143,000 seeds per acre is needed. Poor seed quality and
cool wet conditions at the time of planting are a terrible mix. Under these
conditions, plant stand is often reduced even with good quality seed.
Planting in these conditions should be avoided, but if you must, then you may
need to increase seeding rates by another 20 to 30,000 seeds per acre. With the poor soybean
seed quality, we anticipate many questions about re-planting soybeans. We
have seen very little, if any yield loss at populations near 75,000 plants
per acre in 15-inch rows for full season soybeans. We may be hesitant to
recommend a re-plant until populations drop below 50,000 plants per acre. In a highly scientific
study (my opinion), soybeans at the unifoliate or first trifoliolate stage
will look terrible at stands less than 150,000 plants per acre. So, it is
very possible that you will look at a field of soybeans and be convinced that
it needs replanting. Please, take a stand count to see what the numbers
actually are. See AGR-188 for
guidelines on determining soybean stands. http://www.ca.uky.edu/agc/pubs/agr/agr188/agr188.pdf The soybean seed
quality may be poor, but we still have full potential to get maximum yield. |
· Soybean seed quality is poor this year. · Adjust your drills and planters to the standard germination on the
seed tag. |
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5. Corn and
Soybean Budgets, 2008 Greg Halich, Extension
Ag Economist Updated corn and
soybean budgets are now available for the 2008 planting season. One major modification from previous budgets
is that the user has the option of estimating machinery related costs (fuel,
labor, repairs, depreciation, and overhead) based on the publication “Custom
Machinery Rates Applicable to Kentucky (2008)” (http://www.uky.edu/Ag/AgEcon/pubs/ext_aec/2008-01.pdf). Rates for all major
crop operations are calculated from published rates in five nearby states
after adjusting for changes in fuel price, labor rates, and machinery costs
from the time of the respective survey’s.
These custom rates are used in the budgets to approximate the costs of
crop operations necessary for no-till corn, conventional tillage corn, and
no-till soybean production. The user can modify
these machinery-related costs with options for adjusting the fuel price,
labor rates (hired and operator), and grain trucking distances. The user can also adjust the final rates up
or down by a specified percentage. For
instance, a grain farmer in an area with relatively small fields might
increase rates by 15% due to smaller equipment size and less efficient field
operations. Alternatively, a very
large grain farmer in western Kentucky working with more efficient equipment
may decrease rates by 10% to approximate machinery-related costs. The user also has the
option of estimating these machinery-related costs using the traditional
budgeting method. For operators with
detailed records, this may be the best approach. 2008 Budget Example
and Major Assumptions Used (per acre): ·
150 bushel corn yield and 48 bushel soybean yield. ·
Elevator prices of $4.75 for corn and $11.00 for soybeans. ·
$20 direct government payment. ·
Custom machinery rates used to approximate all
machinery-related costs including trucking.
These result in a total cost (fuel, repairs, labor, depreciation, and
overhead) of $89 for no-till corn, $109 for conventional-tillage corn, and
$64 for no-till soybeans. ·
Seed cost $54 corn and $35 soybeans. ·
Herbicide cost $30 no-till corn, $22 conventional corn,
$20 no-till soybeans. ·
60 lbs P and K for corn and 40 lbs P and K for soybeans at
$0.70 and $0.50 per unit for P and K respectively. ·
Drying costs $30 for corn (3 pts removed per bushel and
$2.50/gallon LP). ·
$25 crop insurance premium. ·
$175 cash rent. ·
8% operating interest. Using the assumptions
in this example, net returns above variable costs and all specified costs are
$204 and $159 for no-till corn, $201 and $147 for conventional tillage corn,
and $187 and $151 for no-till soybeans.
These budgets can be
found at http://www.uky.edu/Ag/AgEcon/pubs/ext_other/2008CornSoybeanBudgets.xls and should also be available at your county
cooperative extension office.
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· Updated budgets are now available. · You can adjust the budget for your own operation depending on the
detail of your records. |
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6. Corn
Planting Date, It may not be too Late Chad Lee, Plant and
Soil Sciences | |||||
