Volume
11, Issue 1
March 14, 2003
Volume
11, Issue 1
March 14, 2003
The Weekly
Schedule Begins –
This newsletter is designed
to provide subscribers with the latest information on disease and insect
problems, weed control information, crop progress reports, and other timely
topics related to agronomic and vegetable crop production in
302-856-7303
or at wootten@udel.edu .
Has the Winter
Weather Affected Insect Populations? -
Entomologists are often asked
if extremely cold or mild winter weather has an impact on insect populations in
the spring. Most would agree that there is no one answer
to this question. Although mild weather conditions enable some overwintering
insects to survive, winter weather has little or no impact on other species.
If you look at the major
insects that attack field and vegetable crops, some general principles can
apply ---
(a)
Overwintering
Stage: Insects that overwinter in
the soil in the egg stage are generally not affected by cold winter
temperature. The best example is the corn rootworm. In comparison, insects that
overwinter in the adult stage, especially beetles can be more affected by cold
winter temperatures. However, the heavy snow cover can negate these affects
because it offers some degree of insulating protection.
(b)
Overwintering
Location: Insects that overwinter
deep in the soil -- like grubs and wireworms -- are generally not affected by
the cold winter temperatures. Spring conditions including early planting
followed by cool, wet weather can favor damage from these pests.
(c)
Natural
Protection: The European corn
borer (ECB), which overwinters as a full grown larva, has an antifreeze type
material in its body that protects them from cold winter weather. Vacillating
temperatures (from very cold to very warm) in the winter can have a greater
impact on reducing overwintering ECB populations.
(d)
Migratory
Species: Obviously, winter
conditions in our area have no affect on migratory species like the potato
leafhopper, cabbage looper and beet armyworm.
So, predicting the potential
for infestations based on winter weather conditions is often not very accurate.
It has been the experience of most entomologists that spring weather conditions
have the greatest impact on insect populations and determine if an insect will
become a pest problem. The only way to know if you have a problem is to
understand which cropping systems favor certain pests and plan to scout fields
on a routine basis in-season.
Fruit
Fruit Insects
-
Peaches.
A Section 18 Emergency Use
request was again submitted to EPA in February for the use of Provado on stone
fruit to control aphids that vector the Plum Pox Virus. There is also a
possibility that the full Section 3 federal registration may come through
before this use season. We will let you know as soon as we get a response from
EPA.
Vegetables
Vegetable Insects
-
Seed Corn Maggot (SCM).
With the recent cool, wet
weather, SCM management should be considered in most spring planted vegetables
including cabbage, peas, snap beans, spinach and sweet corn.
The only
available control options are a seed applied Lorsban SL treatment (must be done
by a commercial treater) or a hopper box treatment of diazinon 50W. Gaucho is no longer labeled on snap beans for seed
corn maggot control. In recent years, diazinon 50W has provided good SCM
control. It should be applied at a rate of ˝ oz per bushel of seed and graphite
added to prevent bridging in the planter.
As of November 2002, this is the only diazinon formulation registered
for use on peas and snap beans. We will have this label until July of 2004,
but it is in jeopardy of being lost. We will need to hear from growers and
processors interested in maintaining this registration. Documentation
and information regarding the importance of this material for your operations
will be needed. Please contact
302-831-1303
for more information.
Spinach.
The only available option is
a broadcast application of 3 qts/A of diazinon applied right before planting
and immediately incorporated 2-3 inches deep. Diazinon should not be incorporated
too deeply and the ground should only be worked once after application.
Sweet Corn.
In addition to hopper box
treatments, a number of seed applied treatments including Lorsban SL, Gaucho
and Cruiser are available for sweet corn. Soil insecticides including Force,
Lorsban, Fortress, Furadan and Counter are also labeled for SCM control in
sweet corn. Under heavy pressure, a soil
insecticide and a seed treatment may both be needed. Furadan and Counter are the
only two soil insecticides that will also provide flea beetle control. Gaucho
and Cruiser will also provide flea beetle control.
Sandea Herbicide Receives Federal Label for Several Vegetable Crops – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu
In December, EPA granted a
federal registration for Sandea, a broadleaf weed herbicide for use on
cucumbers, cantaloupes, pumpkins, tomatoes, winter squash, and asparagus as
post-plant preemergence or post-emergence treatments. It is also labeled for use in the row middles
for peppers and summer squash.
Sandea provides excellent
control of yellow and purple nutsedge, as well as many other broadleaf
weeds. Pre-emergence applications
require 0.5 to 1.0 ounce per acre.
Post-emergence applications should be applied at the 2-5 leaf stage, with
the 3 leaf stage being ideal. Rates for
post-emergence applications are 0.5 to 0.66 ounce per acre with a non-ionic
surfactant. Irrigation should be delayed
until 2 to 3 days after application and cultivation until 7 to 10 days after
application. Both applications should be
applied in a minimum of 15 gallons of water per acre.
Sandea does not control
grasses. Therefore, herbicides that
control grasses should be used as part of the weed control program. The selection of the grass herbicide will
vary with the crop.
Please read the label
carefully before purchasing and using Sandea.
More details about Sandea on a crop by crop basis will be published in
future Weekly Crop Updates.
Pictsweet Frozen Foods Changes Plans – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu
In early March, Pictsweet
Frozen Foods chose not to exercise its option on land south of
While these plans have been
dropped, the company is committed to contracting and receiving 3,000 acres of
lima beans this year and in the foreseeable future. Pictsweet is contracting with growers for
delivery of raw product in
While the news is
disappointing in light of the company’s original plans, Pictsweet’s interest in
procuring lima beans from
Vegetable Diseases
-
Stewart’s
Wilt of Sweet Corn.
For control of Stewart's wilt, which is vectored by
the corn flea beetle, it is important to control the flea beetle. Plant resistant
varieties and control the beetles early. The following index predicts
conditions favorable for overwintering flea beetle populations not the
abundance of the bacteria. The prediction has its limitations including the
influence of snow cover on survival, but indicates that flea beetles should be
reduced compared to most seasons. The question always becomes how much bacteria
is available for them to spread. It’s interesting to note how cold this period
was compared to previous seasons, in case you had not noticed.
Winter Temperature Index For Predicting Stewart’s
Wilt in
Average
monthly temperatures in oF at
|
|
2002-03 |
2001- 02 |
2000-01 |
1999-00 |
1998-99 |
1997-98 |
1996-97 |
1995-96 |
1994-95 |
|
December |
36.7 |
43.2 |
31.2 |
40.3 |
41.3 |
39.3 |
42.0 |
33.5 |
43.0 |
|
January |
28.9 |
40.0 |
33.8 |
33.9 |
39.5 |
42.6 |
35.0 |
33.5 |
39.0 |
|
February |
33.8 |
39.9 |
38.8 |
39.7 |
38.7 |
40.6 |
41.5 |
34.7 |
33.8 |
|
INDEX |
99.4 |
123.1 |
103.8 |
113.9 |
119.5 |
122.5 |
118.5 |
101.7 |
115.8 |
Average
monthly temperatures in oF at
|
|
2002-03 |
2001- 02 |
2000-01 |
1999-00 |
1998-99 |
1997-98 |
1996-97 |
1995-96 |
1994-95 |
|
December |
33.5 |
43.3 |
31.1 |
39.1 |
41.0 |
38.4 |
40.9 |
32.1 |
41.8 |
|
January |
27.1 |
39.6 |
31.5 |
32.6 |
34.8 |
40.9 |
33.2 |
30.9 |
37.6 |
|
February |
29.5 |
40.1 |
38.4 |
37.8 |
38.0 |
40.6 |
40.3 |
34.7 |
31.7 |
|
INDEX |
90.1 |
123.0 |
101.0 |
109.5 |
113.8 |
119.9 |
114.2 |
97.7 |
111.1 |
Severity Index: <90, usually absent; 90-100, intermediate; >100, usually severe.
Vegetable Diseases
-
Fungicide Update.
There have been some new
fungicide additions for 2003 that will be welcome additions for control of
troublesome plant diseases. Specific use information can be found in the 2003
Commercial Vegetable Production Recommendations E.B. 137.
Field Crop Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Alfalfa.
Although alfalfa weevil
populations have been high the past 2 seasons, winter weather conditions may
help to reduce some of the overwintering adult and egg populations. However,
heavy snow cover can negate this affect since it produces an insulating effect.
So, you should begin sampling fields for early feeding signs by the last week
in March. Look for small larvae feeding in the tips of plants producing a
round, pinhole type of feeding. Once you detect tip feeding, a full field
sample should be taken. You will want to avoid treating fields too early since
it may result in multiple applications. In general, no treatment should be
needed before you observe 50 percent of the tips with feeding damage.
Field Corn.
New Registration – On
As you make plans to plant
field corn, understanding the factors that favor soil insect pests can be used when
making a treatment decision and selecting the best treatment option:
Seed Corn Maggot (SCM).
This insect overwinters in
the pupal stage and becomes active at temperatures as low as 40 degrees F.
Although we have not observed any egg laying activity, we know that cool wet
conditions at planting, the use of manure and/or plowing under of green cover
crops close to planting all favor maggot problems. Since the recent weather
trend has been cool and wet, most early planted conventional corn and all no-till
plantings will be susceptible to seed corn maggot attack. In addition to
granular and liquid soil insecticides, seed treatments can provide effective
control. Hopper-box treatments containing diazinon or permethrin as well as
seed commercially treated with imidacloprid (Gaucho or Prescribe) or
thiamethoxam (Cruiser) will provide seed corn maggot protection. In fields with
the potential for heavy pressure (i.e. manure has been used, or a spring cover
crop is plowed under), a soil insecticide plus a seed treatment may be needed.
Wireworms (WW).
High soil organic matter, sod
covers, and heavy grass weed pressure the previous season all favor wireworm
populations. Fields having a combination of high organic matter and heavy grass
weed pressure are the most susceptible to damage. Wireworm larvae spend
multiple years in the larval stage and the larvae move up and down in the soil
profile following moisture gradients. Therefore, good control is often
difficult to achieve. Seed treatments containing diazinon/lindane or permethrin
will only control larvae feeding on the seed. The Gaucho label states seed
protection only and the Cruiser label states early season seedling protection.
Soil insecticides including Regent, Force, Fortress, Lorsban, Counter, and Warrior
are labeled for wireworm control. All materials must be placed in-furrow to get
effective control. The Mustang MAX in-furrow label for field corn only has
cutworm control on the label and Baythroid does not have an in-furrow label. Remember,
the use of Capture or Empower (both formulations of bifenthrin) is prohibited
on field corn grown in coastal counties.
White Grubs.
In general, grubs are favored
by a number of factors including planting into double crop soybean stubble, old
sod, hay, pasture or set-aside acreage. The most
accurate way to measure the potential for a grub problem is to sample fields
for grubs before planting, but it should be done before a field is tilled. The
most accurate results will be obtained when the soil temperatures at 6-inches
deep are at least 45 degrees F. At each site, sample one square foot of soil
dug six inches deep. One to two samples should be taken for every 10 acres with
no less than 10 samples per field. A treatment is recommended if you find 1-2
grubs per foot in heavy soils or 0.5 – 1 grubs per foot in sandy soils. Soil
insecticides need to be placed in-furrow to get effective grub control. Under
high population pressure, the most consistent grub control has occurred with
Counter or Force. Remember, both materials need to be placed in-furrow for grub
control and they need rainfall to be activated. In terms of seed treatments,
Gaucho and the low rate of Cruiser will only provide early season seedling
protection.
Black Cutworm.
This insect is favored by
late planting, broadleaf weed growth (especially chickweed) present before
planting, poorly drained field conditions and reduced tillage. Rescue
treatments can be applied for this soil insect if you are able to scout fields
twice a week once leaf feeding is detected. If you are unable to scout and you
have conditions favoring cutworms, a pyrethroid tank mixed with a herbicide and
applied close to planting has provided effective control. The granular
insecticides Force and Lorsban are labeled for cutworm control, but must be
applied as a T-band to be effective. The new BT insect protection trait,
Herculex, has also provided good control of cutworms. However, fields should
still be scouted especially if pressure is high or large worms are present at
the time of planting. In some cases, a rescue treatment may still be needed.
Wheat.
Although we continue to find
spotty distribution of Barley Yellow Dwarf Virus (BYDV) in the state, aphid
management can play an important role in reducing losses from BYDV. It still
appears that the most important time to control aphids and help reduce problems
from BYDV is the first 30 to 60 days after plant emergence. Although many fields are small and it is
possible to have virus vectored in the spring, if you see BYDV in wheat this
spring it was likely vectored late last fall and early winter. Information from
The aphid still causing the
greatest amount of damage in recent years has been the greenbug. This aphid can
be easily identified by the green stripe down the center of the body. Although
this aphid can vector barley yellow dwarf, the main damage occurs when it
injects a toxin into the plants. Feeding damage initially appears as small
reddish pinspots which lead to yellowing of leaves that eventually turn brown
and die. Although this aphid causes the greatest damage from mid to late fall,
it was still causing damage in early January and can be present throughout the
winter and into the spring. So, be sure to check fields at least once in March
to early April for overwintered populations. Dimethoate, Lannate, Malathion,
Penncap and Warrior can be used for greenbug control in wheat. The following greenbug thresholds are used in
other areas of the country and can be used as a general guideline in our area:
|
|
Plant Height |
Time of
Year |
|
20-50 |
4-6 " |
Fall - late Winter |
|
200 |
7 - 10 " |
mid-March |
|
300 |
18-20 " |
mid-April |
|
800 |
30 + " |
mid-May |
Precautions for
Herbicide Use with Nitrogen Applications to Small Grains -
It is common to add
herbicides when nitrogen is applied to small grains and small grain-legume
mixtures. These precautions are from
manufacturer’s label:
Harmony Extra or Harmony GT-
slurry in water first and may result in temporary crop yellowing. If liquid nitrogen is less than 50 percent of
the spray mix, then include a surfactant.
For 2,4-D it varies with the formulation. The ester formulation can be mixed directly
with nitrogen, but labels recommend good agitation. Amine formulation of 2,4-D
should be mixed with 3 to 5 parts of water before adding it to the nitrogen
solution. Buctril label cautions about potential
leaf burn when mixed with liquid fertilizer, but leaves emerging after
application are not affected. For MCPA,
it varies some with the manufacturer.
The ester formulation should not be applied with liquid nitrogen. The amine formulation varies, ranging from no
mention of liquid nitrogen to application is allowed.
Small Grain Weed
Control -
It is time to consider your
weed control for the small grain crop.
Fields that were no-tilled or chickweed emerged shortly after planting
in the fall are fields to check first for spring treatment. If you have wild garlic or Canada thistle,
the time of application should be delayed since you need to spray these weeds
when they have fully emerged. Coverage
is important for these species. If weed
pressure from winter annuals is great, it may not be possible to get control of
the winter annuals and perennials with one application. In that case, two applications maybe
required. You can mix your Harmony Extra
with nitrogen. If spraying Harmony Extra
with nitrogen be sure to pre-mix it in water
first. If using nitrogen as your
carrier, no need for a surfactant unless wild garlic is over 8 inches
tall. Applying Harmony Extra in nitrogen
diluted with water, use a non-ionic surfactant at ˝ to 1 pint/100 gallons of
solution. If applying it in water use
non-ionic surfactant at 1 qt/100 gallons.
Have you considered
resistance management with your small grains?
Most of the small grains get treated only with Harmony Extra, which
contains two ALS-inhibiting herbicides (some types of herbicides as Pursuit,
Accent, Classic, etc). And many weeds
have developed resistance to herbicides that have this mode of action. Consider how often a field is planted to
small grains and how often it gets treated with Harmony Extra. If this rotation is short, 3 years or less,
consider tankmixing another herbicide with Harmony Extra to minimize the risk
of developing herbicide resistant weeds.
Finally, the following are
the timing limitations for small grain herbicides. The timing restrictions are based on crop
safety.
2,4-D - up to jointing stage (pre-jointing)
Banvel/Clarity
- up to jointing stage (pre-jointing)
Buctril - up
to boot stage
Harmony Extra
- up to flag stage (pre-flag leaf)
Control of Horseweed (or Marestail) in No-Till
Soybeans When It’s Small -
The presence of
glyphosate-resistant horseweed has made no-till soybean burndown programs more
challenging. This species is not a
problem in tilled fields (because it emerges before the tillage is completed,
so tillage kills it) or in corn (because atrazine is pretty effective on it). Rather the problem has only been showing up
in no-till soybean fields where glyphosate alone has been used for burndown
control prior to planting. The presence
of glyphosate-resistant horseweed is so wide-spread and it moves so easily with
the wind, you have to assume that the horseweed plants in your field are
resistant and not rely on glyphosate to control them.
What to use?? Paraquat sometimes will not effectively
control all the plants and it often requires two applications for excellent
control. There is concern about
excessive use of ALS-inhibiting herbicides such as Amplify, FirstRate, Canopy,
or Canopy XL that could lead to additional resistance. That leaves 2,4-D. The pint rate of 2,4-D
ester is only marginal on horseweed (particularly when the plants are 4 inches
or taller). A quart rate of 2,4-D ester is needed to consistently control this
species. A quart rate requires a period
of 30 days from time of application until soybeans can be planted. So this treatment should be made as early as
possible due to controlling small weeds and allowing the time interval prior to
planting. Additional flush of weeds is
possible with this early application, so an application of paraquat at planting
may be necessary if significant number of weeds emerge.
If you cannot treat your
no-till soybean fields until 30 days or less before planting, use a pint rate
of 2,4-D plus paraquat (this must be applied at least 7 days prior to
planting). (Paraquat is the active
ingredient in Gramoxone Max and formulations are available). If 2,4-D is not a
viable option for a variety of reasons or spraying less than 7 days before
planting, use sequential applications of paraquat made 3 to 5 days apart.
New Weed Control Guides For Corn and Soybeans
Available - Free -
Available from your county
extension office are two weed management guides for assistance in weed control
in corn and soybeans. The first half of
each guide deals with soil-applied herbicides and the second half is for
postemergence herbicides. These guides
have pre-mixes and what is in the pre-mix, expanded weed control tables,
information on application timing, comments for each
of the herbicides, and much more.
Contact your county extension office for these free guides.
Grain Marketing Highlights - Carl German, Extension Crops
Marketing Specialist; clgerman@udel.edu
Key
Supply/Demand Numbers in USDA's March Report
Ending
Stocks for the '02/'03 MarketingYear
Ending Stocks for
Ending stocks for
Ending stocks for
Soybean exports increased 20 million bushels from last
month, now estimated at 960 million bushels. This is on the high side of
pre-report trade expectations.
Corn exports placed at 1.750 billion bushels are
estimated to be 75 million bushels less than last month, and below pre-report
trade guesses of 1.775-1.8 billion bushels.
Wheat exports place at 875 million bushels are 25
million bushels less than last month and within trade expectations.
Southern
Hemisphere
Argentine soybean production was indicated at a new
record 35 mmt, 1.5 mmt more than last month's estimate and above pre-report
trade estimates of 34-34.5 mmt.
Brazil Soybean Production at 51 mmt is unchanged from
last month's record level forecast.
General
Comments
Today's report contains few surprises to commodity
traders with the exception of the larger than expected drop in
Market
Strategy
The only new crop sales opportunity presented at this
time is in new crop corn. The CBT Dec '03 corn futures price currently at $2.39
per bushel is expected to soften from current levels.
Some market observers are anticipating some winter
crop damage to the mid-western wheat crop, although the extent of damage is not
likely to be known until harvest.
Dry weather concerns in parts of the
Dry February's do not automatically equate to reduced
crops. Therefore, commodity traders are currently bidding the impact of trend
line yields and world supply/demand into '03 new crop futures prices.
Assessing Small Grain Stands This Spring - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu
After the ice, snow, and
rain-fed ponds disappear from small grain fields this spring, growers and
consultants will be left with the problem of assessing the extent of damage to
these fields. The easiest portion of the
task will be calculating the proportion of a field that died as a result of ice
sheeting or long-term emersion under water (see Photo 1). Ice sheeting and ponding can rapidly eliminate
stands in affected areas. Visual
estimates of the proportion of the field affected can give you a working
estimate for calculating acres needing fertilization, although actual
measurement of the affected areas is best.
Using GPS and GIS to plot maps and estimate acreage will be the most
accurate method. If you need assistance
in calculating area of various shapes, please contact the author.
Photo 1. Ice formation in fields can lead to carbon
dioxide toxicity in most plants especially in areas where a porous underlayer
of snow does not exist (Photo by R. Taylor).
A more difficult question
will be how to evaluate for water damage from water logged conditions where the
plants have not died. It’s been my
experience that recovery of small grains in areas water logged for a period of
time is very slow and grades outward from the lowest spot. Often as much as a half to two thirds of the
badly affected area will show only minimal recovery even with additional fertilizer. The outer quarter to a third although delayed
often shows significant recovery and growth.
The problem in many water logged areas is that the root systems are
severely damaged and the wet conditions mean that the soil is much slower to
warm up than surrounding drier areas.
The saturated conditions often result in denitrification and inhibit
(low soil oxygen levels as well as colder temperatures) mineralization of
nitrogen (N) from the soil organic matter pool.
Applied nitrate in these areas can be rapidly lost because of localized
areas of anaerobic conditions and thus denitrification. An ammonium source for N will help those
plants still alive recover better.
For water logged areas, again
estimate the area of the field affected and figure that no more than about half
will recover adequately to have a fair to average yield potential. If the areas are large enough to be able to
adjust your N application pattern, then limit the amount and type of N applied
to these areas. Otherwise because of the
high cost of N this year, you may want to recalculate your yield potential and
decide how much N the lowered yield potential for the field will justify.
A third question concerns the
problem with damage from geese feeding on the small grains. If the damage relates to stand loss because
the geese are pulling the small plants out of the ground and either eating them
or leaving them to wither on the soil surface, an evaluation via stand counts
after the geese have left will provide a reasonable estimate of yield potential
for the field. This also assumes that
the geese do not feed past about mid-March.
Take stand counts on either a foot of row basis or on a plants/ft2
basis from 20 to 30 areas in the field and take an average. If stand counts are 30 or more plants/ft2
(15 per foot of row on 6 inch rows or 18 to 19 per foot of row on 7 or 7.5 inch
rows) or 70 or more tillers/ft2 (a tiller has 3 leaves emerged) at
spring green-up time, yield potential will be maximized for the growing
conditions expected in the spring. At
counts of 15 to 20 plants/ft2, yield
potential is reduced by about 10 to 15 percent.
If counts are 10 to 15 plants/ft2,
If geese are grazing the
wheat, the timing of when the geese leave the field will be critical in
determining yield potential. In the
Considerations for Rutted Fields - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu
Beginning
with a 7-inch rain in early September last fall, rainfall was significantly
above average across much of
What
occurs when ruts are made in a field?
Under saturated conditions, there may be less compaction than you might
expect since the soil may flow rather than compact. In Photo 1 you can see how the side ridges
show the flow of soil during saturated conditions. In these situations, there may be less deep
compaction, but sidewall compaction is still likely. For unsaturated soil conditions (Photo 2), flow is minimal so the pressure results in both surface and side-wall, plus deep compaction. Photo 3 shows one of the problems experienced
this spring when high rainfall and snow amounts result in significant ponding
in the fall ruts.
Photo 1. Fall compaction under saturated soil
conditions leading to some soil flow and moderate deep soil compaction (Photo
by R. Taylor).
Photo 2. Fall compaction under unsaturated soil
conditions leading to significant surface, side-wall, and deep compaction (Photo
by R. Taylor).
Photo 3. Heavy winter snow and rain can lead to
significant ponding problems in fall ruts (Photo by R. Taylor).
There are fall options
available that need not be considered here except for mention of planting
cereal rye to help reduce compaction effects.
What should be done about
ruts this spring? There are three
potential situations that can arise, a dry spring, wet spring, and normal
spring (however you would define the term normal or average).
In a dry spring, as soon as
the ruts dry out they should be evaluated to determine the extent and severity
of compaction. As a handy tool, a simple
wire flag can be used to assess the extent and possibly severity of the
compaction. Although it is unlikely this
spring will be dry enough for deep tillage to be effective if the soil does dry
out completely, deep ripping can be used to help alleviate severe
compaction. Straight-type ripping
coulters have been shown to be the most effective tool for shattering deep
compacted layers. Much more likely is
that the soil will remain too wet for effective soil shattering during deep ripping. Ripping will
need to be postponed until this fall when dry soil conditions are more likely
and ripping is generally more effective.
To remove ruts, chisel plow or disk to smooth the ruts and prepare a
seedbed. A dry spring can help make
planting on time possible.
If the spring is wet,
evaluation of ruts for compaction severity will be delayed, but should take
place as soon as possible. Determine if
compaction occurred along the sidewalls or whether you will have to contend
with deep compaction. Delay tillage
until ruts dry out and then either disk or chisel plow to smooth out the ruts
and prepare the seedbed all in one pass.
Plant as soon as the soil is ready but expect to be delayed past the
normal planting time. If compaction in
the rutted areas was severe, plan to deep rip in the fall when the soil is dry.
Time your tillage this spring
for when the soil in the ruts dries out enough to support tillage equipment. Again, the best options are chisel plowing
and disking. However, if you are set up to handle in-row ripping during the
planting process and compaction occurred when the ruts formed, this practice
may help improve yield this coming growing season. You will likely have to consider using deep
ripping in the fall to completely eliminate the compaction problems from the
ruts.
If the field was no-tilled,
you can limit the area tilled to the damaged areas and till them as early in
the spring as possible. Emerging weeds
should be controlled with herbicide at planting time. The damaged areas will again need ripping in
the fall and then the areas can be reestablished in a no-till system.
I
want to acknowledge and thank several soil scientists who helped in preparation
of this article. They include Dr. Bruce
Vasilas,
Dr. Jeremy Singer and Dr. Tom Kaspar from the
USDA-ARS National Soil Tilth Laboratory in
Managing
Wheat After a Late Wet Fall Planting Season - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu;
After an extremely dry summer last year, the fall
turned off wet and cold. While August
was warmer than average with 2.25 inches below normal rainfall, Sept. was 5
inches of rainfall above average, Oct. almost 3 inches above average, Nov. 2
inches above average and Dec. about average.
Daily high temperatures averaged 2, 4, and 2˚ F. below the 20 year
average for the period Oct. thru Dec., respectively. This meant that many small grain fields were
planted late, planted in wet soil, and made little growth in the fall. The heavy snow fall this winter and periods
of ice sheeting have also taken a toll on small grain stands and vigor.
First, fields should be evaluated for the proportion
of the field that has maintained a stand that should produce harvestable yield
this spring (refer to the article on assessing small grain stands this spring
included in this Weekly Crop Update issue).
Yield potential should also be estimated for those fields that did not
tiller at all last fall. The combination
of percentage stand and yield potential can be used to estimate nitrogen need
of the crop.
In the past, we often found that many small grain
stands could produce maximum economic yields with only 60 to 80 lbs N/A applied
in one application either early at spring green-up or later (if well tillered)
at early jointing. Due to high N prices,
variable stands, cold-wet soils, and the likelihood of an abbreviated growing
season (at least between now and jointing), growers and consultants should
consider limiting N rates to about 60 lb N/A on wheat and 40 to 50 lb N/A on
barley. Exceptions are for those fields
that were planted early and have come through the winter with minimal
damage. In other studies and experiences
we’ve had, wheat that emerged very late in the fall or early spring and had few
if any tillers visible at green-up time produced yields in the 40 to 60 bu/A
range. A nitrogen rate of 60 lb/A applied as early as feasible should be enough to reach the
expected yield potential for these fields.
Keep in mind that with very low tiller counts, early N application will
be critical to encourage tillering especially after the excess of fall
rainfall.
If wet soil conditions are expected to significantly
delay spring N application, it might be worth considering at least a minimal
amount be applied by air. As long as the
weather stays cool, urea with 46 percent nitrogen will be a good choice even
though some N will be loss because of urease activity causing release of urea
as ammonia. If the urea can be applied
before a rain event or irrigation event, the N will be carried into the soil
and transformed into ammonium and then nitrate as the soil warms. Wheat does have a preference for the ammonium
form of N, so uptake of N from urea should begin quickly. This procedure will also protect one from
additional denitrification losses in wet areas of the field. Since denitrification can occur in a matter
of hours to a few days, calculate your nitrogen rate for very wet fields using
only the urea and ammonium nitrogen proportion in your fertilizer. A 30 percent UAN solution weighs 10.83
lbs/gal and has 3.249 lbs N/gal and of this 0.80 lbs/gal will be N as nitrate
so figure that the 30 percent UAN will give you 2.45 lbs N/gal. Also note that the denitrification loss will
only occur in very wet areas where the soil is anaerobic for a period of time
and this often does not involve the entire field.
For fields that were not as severely impacted by last
fall’s weather or the winter weather this year, information available from
studies conducted at Virginia Tech may be useful in planning nitrogen (N) applications
this spring. With wheat in many fields
still in the very early tillering stage or not yet to the point of tillering,
growers should use their fertilization practices to boost the tillering
potential of wheat. When fields are
fairly uniform, maximum yield potential in wheat requires a stand count of 30
or more plants/ft2 (15 per foot of row on 6 inch rows or 18 to 19
per foot of row on 7 or 7.5 inch rows) or 70 or more tillers/ft2 (a
tiller has 3 leaves emerged) at spring green-up time. For stands this good, use your regular
fertilizer program, but split the N with 1/3 to 1/2 of the total N at green-up
and the remainder at Feeke’s growth stage five.
Early season N tends to stimulate more vegetative growth, taller plants,
and more potential for lodging. Growth
stage five (initiation of jointing) N improves yield and protein content of the
grain. For stands with counts well below
30/ft2 and tiller counts of 50 to 70 tillers/ft2
or less, early N at green-up will help stimulate further tillering and maintain
current tillers.
Although split applications can improve yield
potential, early spring weather conditions warrant applying most, if not all,
the N to small grains as soon as possible.
For no-till wheat, data from several sources indicate
that an extra 20 lb N/A (applied at green-up) will be needed. Apply a larger
proportion of total N at green-up if splitting N applications. Why?
Conditions in early spring are more unfavorable for growth with no-till
compared to reduced or conventional till wheat.
The extra N improves the plant’s growth and vigor.
You may obtain copies of the
Pest Management Recommendations for Field Crops 2003 from the Research &
Education Center by mail, cost is $15.00 (includes shipping and handling), or
purchase a copy for $13.00 by stopping by the Research & Education Center
in Georgetown. Please use the enclosed
form and make checks payable to “
Crop Profiles For
Delaware - Susan Whitney, Extension
Specialist, Pesticides, Urban Entomology, swhitney@udel.edu
We are also
writing Pest Management Strategic Plans that address pest management needs and
priorities for individual commodities. EPA has said that they will use these plans
when making regulatory decisions on pesticides affected by the Food Quality
Protection Act. The draft plan for lima beans will soon be in Grower/ Processor
review. Next year we plan on preparing a plan for spinach. Contact Susan
Whitney (swhitney@udel.edu) if you have
questions about Crop Profiles or Pest Management Strategic Plans.
UPCOMING
MEETINGS:
Profiting From A Few Acres –
Growing for Market in
An introduction to growing for and selling at Farmer’s Markets or
your own “Farm Stand”
Dates:
Time:
Location: Univ. of DE Paradee Center, Kent Co.
Ext. Office, Rt. 113,
Registration: Phone
(302) 730-4000 to register
For more information, contact:
The Basics of Greenhouse
Production as a Business or
An Introductory Course for those Considering a
Green house Business
Introductory Session:
Monday, March 24, University of
Greenhouse
Tour:
Saturday, March 29,
Additional Sessions will be scheduled according to participant interests.
Pre-registration is required.
To register contact
Weeks of March 1 to
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Rainfall: |
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0.33 inches: March 2 0.37 inches: March 5 0.49 inches: March 6 |
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Air Temperature: |
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Highs Ranged from 65° F on March
5 to 36° F on March 7 & 11. |
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Lows Ranged from 38°F on March
2 & 5 to 18° F on March 4. |
|
Soil Temperature: |
|
40°F average for the week. |
|
(Soil temperature taken at
a 2 inch depth, under sod) |
Web Address for the U of D
Compiled and Edited
By:
Extension Associate -
Vegetable Crops
Cooperative
Extension Education in Agriculture and Home Economics, University of Delaware,
Delaware State University and the United States Department of Agriculture
cooperating, Robin Morgan, Director. Distributed in furtherance of the Acts of Congress of May 8 and
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