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Wheat
Insects
Weed Management
Field Updates/Resources
Bob Klein, Extension crops specialist at North Platte, reported that in areas where the rains had been spotty or nonexistent, wheat quality and yields were deteriorating rapidly. Plant leaves were browning and drought damage was becoming apparent in much of the dryland wheat as it reached a critical growth stage for determining yield. Yields are likely to drop to 30 bu/a and as low as 5 bu/a on some of the fields scouted this week, Klein said.
A month ago the wheat never looked better, said Drew Lyon, Extension dryland crops specialist in the Panhandle. Stands were thick and lush and growers were optimistic for an excellent year. Now with limited to no soil moisture available, assessments are much more cautious, he said, adding that frost damage was also becoming more apparent in the stressed crop. In the Panhandle, "we're at a precipice," Lyon said. It could go either way for the crop, depending on whether we get rain, he said. Areas in the Republican River Valley and near McCook have received rain and the wheat crop is looking good.
According to the USDA Nebraska Agricultural Statistics Service: Wheat condition declined slightly last week and rated 1% very poor, 10% poor, 30% fair, 45% good, and 14% excellent, above last year and the five-year average. Wheat fields were 69% headed statewide, ahead of last year at 63% but the same as average.
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Usually the adult weevils are associated with the delay in green up of the second cutting; however, this year the larvae are still present (small, yellow to green legless worms with white stripes down the back, about 1/8 to 1/4 inch long) and feeding on new growth after the first cutting. The larvae will be smaller in the northern counties, while in the southern counties there may be a mixture of larvae, cocoons, and adults.
Management
If you haven't cut your alfalfa yet, do so and remove it from the field as soon as possible. Often the cutting will kill enough larvae to eliminate the need for an insecticide treatment (Table 1). Also, most insecticides have a preharvest interval of seven days or more and most growers want to harvest alfalfa now rather than wait. (Mustang Max has the shortest preharvest interval: three days.)
To decide whether an insecticide treatment is necessary, first determine if the regrowth has been held back enough to justify an application (Table 2). Generally, with the rain we have had, anything not greening up four to six days after regrowth probably has a problem. Then determine the percentage of larvae, cocoons, and adults present. If two to three larvae per crown are found and the alfalfa is not greening up, an insecticide is necessary.
If there are no cocoons, spray as soon as possible. Spraying will not greatly affect the weevils in the cocoon stage until they emerge and become active. The pupae stage in the cocoon lasts 7 to 14 days. Adults will feed for a week or so after emerging, so this also may affect regrowth. Spraying now will enable the new growth to get a "jump" on any late emerging adults. Because of the lack of vegetation in the newly harvested fields, rates of registered insecticides in the low range should do the job. However, to get better residual activity, use rates in the mid to upper end of the label.
Some salesmen are suggesting a "combo" of two products with different modes of action. For example, Lorsban (an organophosphate) withWarrior (a pyrethroid). While the rates of both may be lower in the combo, the price of the two combined may be higher than when using a medium range rate of a single product. With the products listed in Table 1, there is no reason to mix them as a "combo", unless other harmful insects are present. All of the suggested insecticides will control other alfalfa pests, as well.
Stubble treatment calculation
After cutting and removing the hay, examine the stubble in several areas for evidence of continued feeding. Sift through the litter where the windrows were, checking in and around crowns for larvae, pupae, and adult weevils. Table 2 provides a calculation for determining if an insecticide treatment of the stubble would be necessary if regrowth will be delayed by alfalfa weevils. It calculates the number of days of complete defoliation that can be tolerated before an insecticide treatment will be economically warranted. The number of days will vary, depending on the cost of treatment, hay value and whether the hay is cut at first bloom or on a 28-day harvest schedule.
Keith Jarvi
Extension IPM Specialist
Northeast REC
Another factor in the treatment decision is the so called "threshold level" for treatment. It's not
like counting the number of insect eggs on a corn leaf at a certain growth stage. With wheat rusts
it isn't that clear cut. The objective of treating wheat is to reduce infection of the flag leaf and
head to maximize the grain filling period.
If the rust severity on the flag leaf is already greater than 20% before treatment, much of the
benefit of treatment will have already been lost because that 20% will probably become 40-50%
in a few days regardless of treatment. If the flag leaf has 10% or less rust severity at the time of
treatment, the fungicide will probably hold rust severities to an acceptable level. The decision to
treat has to be made early before the disease has had a chance to build up on the upper part of the
plant.
In making a decision, consider the following criteria for treatment:Treatment window for wheat rust
closing for most of the state
The window for applying a fungicide to wheat for protection against stripe rust and other foliar
diseases has passed for much of the state with the exception of some areas in the far west. Wheat
cannot be treated with a foliar fungicide beyond growth stage 10.53 on the Feekes scale which
corresponds to flowering. A lot of the wheat that I examined this week is 1/2 to 3/4 berry which
is well beyond flowering. Any wheat that is just now in the flowering stage (yellow anthers
protruding from the florets) could still be treated; however, you'll need to decide now since the
treatment window will pass quickly.
John Watkins
Extension Plant Pathologist
Controlling weeds in alfalfa after first cutting
Typically there is a 5- to 10-day window after the first cutting for weed control. Once you take the first cutting, you dramatically change the crop canopy for the field. Weeds that germinate after the crop can now get the sunlight they so desire for growth and, now that these weeds are more visible, you can target them with your spray boom. If you wait much past the 10-day window, you may run the risk of having increased crop canopy, taller weeds and problems with the 30-day pre-harvest interval with such herbicides as Butyrac or Pursuit.
Several herbicides can be used to control these weed species on established stands (one year or more) after dormancy. Butyrac (2,4-DB) is a growth regulator that is converted to 2,4-D within the plant through an enzymatic process not found in alfalfa plants. Butyrac has fair activity on many annual broadleaf weeds at 1-3 qt/A. The effect of Butyrac on mature mustards will be very limited. Butyrac should not be used when temperatures are expected to fall below 50oF for three days after application.
Poast at 1.5-2 pt/A, Poast Plus at 1.5 to 3 pt/A and Select at 6-8 oz/A will have good activity on most annual grasses but will not control broadleaves. Growers should be aware of the 14-15 day preharvest interval with these products. In addition be sure to use the additives suggested on the herbicide label. Pursuit can be used at 1-2 oz/A with good activity on sunflower, kochia, and pigweeds. Raptor can be used at 4-6 oz for control of waterhemp (not ALS-resistant), nightshade, yellow foxtail, kochia, and pigweed. Select will provide excellent control of downy brome at 6-8 oz/A.
In fields where this control will not be effective enough, growers will need to wait until fall, after dormancy. Once the alfalfa stand has gone dormant, winter annuals can be more easily controlled with treatments such as Roundup Ultra, Lexone/Sencor, Velpar, Zorial, Gramoxone Extra, and or Karmex. The best advice for producers at this time is to assess the quality of the stand and weed growth stage, control what weed species they can this late in the season and throughout the summer, and regain control of winter annuals once the stand has gone dormant in the fall.
Brady Kappler
Extension Educator - Weed Science
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Research at the University of Nebraska has shown that each crop has a CPWC and that the length of this period can be influenced by cropping practices, such as row spacing in soybean.
Timing of weed removal as affected by soybean row spacing
The critical time of weed removal is when weed control needs to begin in order to prevent yield losses. Studies were conducted in 1999 at Mead and in 2000 and 2001 at Mead and Concord to study how this period was affected by row spacing. Predominant weed species at both locations and years were velvetleaf, common waterhemp and green foxtail, with densities of 70-100 plants per square yard.
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This data implies that reducing row spacing delays the timing of weed control and increases the tolerance of soybean to weed presence. The mechanism of soybean tolerance needs to be determined yet, although we believe it is related to the effects of crop shading. The speculation is that even though weeds are present in narrow row soybeans, they are not growing as vigorously and are not as competitive against the crop, due to crop shading. Furthermore, from a practical standpoint, these results indicate that a reduction in soybean row spacing increases soybean tolerance to weeds, likely leading to less intensive weed management programs.
Cost of delaying weed control
The commonly asked question among producers is "how much is it going to cost me if I delay weed control." Possible reasons for delayed weed control may include weather constraints such as wind and rainfall and time constraints due to large acreage to spray. In order to answer the above question the yield loss data from the above studies were pooled among years-locations and graphed against the crop growth stage at the time of weed removal in corn and soybean (Figure 1).
The 2% yield loss for every leaf stage of delay after the critical stage of weed control was determined as the cost of delaying weed control in soybean. For example, the time to control weeds in 7.5-inch rows of soybean is the V3 stage (third trifoliate-Table 1). If weed control is delayed to the V4 (fourth trifoliate), it will cost a producer about 2% in yield losses due to prolonged competition from weeds. The same is true if weed control is delayed past the recommended critical time in other soybean row spacings. This recommendation is applicable up to the R3 stage in soybean (beginning pod). If weed control is delayed further than these indicated stages, yield losses will be much higher than suggested.
In terms of actual economic losses in soybean, it will be about $5 per acre for every soybean leaf stage of delay, assuming a price of $5 per bushel and a yield goal of 40 bushels.
Weed size
Weed size at the time of weed control is another concern. If the weeds emerge four to five days before the crop or they are taller than the crop, they will shade the crop. In this case control should be initiated four to five days (one to two leaves) prior to the beginning of the critical period of weed control. If the weeds emerge 5-10 days after the crop, they will not shade the crop. In this case control can be initiated 5-10 days (two to three leaves) after the critical period begins.
The size of weed species will affect herbicide use rates too, especially the rates of Roundup or any generic glyphosate in Roundup-Ready soybeans. It is well known that Roundup has much better activity on grassy rather than broadleaf species. The 16-24 oz rates should provide control of most common annual grassy species (foxtails, barnyardgrass, field sandbur, woolly cupgrass, and panicums) that are 3-8 inches tall. The same rates should control annual broadleaves (velvetleaf, lambsquarters, pigweeds, mustards) less than 6 inches tall. For taller grasses and broadleaf species a full rate (32 oz) will be required. Higher rates of Roundup (40-60 oz) will be needed to control species such as ivy-leaf morning-glory, sweet clover, field bindweed, Venice mellow and various smartweed species (lady's thumb, Pennsylvania smartweed, wild buckwheat, etc).
Timing weed control in herbicide tolerant crops
Roundup-Ready soybeans are widely used in Nebraska. The concept of critical period of weed control is an important part of integrated weed management in answering the fundamental questions as to if and when to apply postemergence herbicide.
A generally sound strategy in Roundup-Ready soybeans will be to apply Roundup tank-mixed with a residual herbicide at the beginning of the critical period, which will provide adequate weed control throughout the period. In order to select appropriate herbicide mixtures for the weed spectrum at your farm, consult the herbicide efficacy tables from the Guide for Weed Management in Nebraska (NU Extension Publication, EC-130).
Stevan Knezevic
Extension Weeds Specialist
Haskell Ag Lab
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Following is a schedule of topics and speakers:
These adverse effects often lower rental rates or sale prices of infested grassland. On many sites
complete coverage by eastern redcedar can be expected, resulting in total loss of production.
Control measures should be initiated as soon as possible to improve effectiveness and reduce
total costs. In most cases, a single control measure won't provide long-term management;
however, an integrated management approach combining manual, mechanical, cultural,
biological and chemical control methods will work.
Manual control involves pulling or digging trees. It can be very effective for small areas and is
most efficient on trees up to 2 feet.
Mechanical control methods include cutting or mowing trees at the soil surface or below the
lowest branches. Short trees can be mowed off as part of the regular cutting and haying process.
Red cedar trees cut low should not regrow. If the goal is to just reduce the overall number of trees
and reduce further spreading to better manage the wildlife habitat), cut only female trees (those
producing berry-like fruits).
Biological weed control involves the use of natural enemies to reduce weed populations to
economically acceptable levels. Goats are known browsers and can be effective bio-control
agents for trees up to 3 feet tall. Seventy-five percent of their diet consists of non-grassy species,
so they don't compete with cattle for grass. They also can help control many noxious weeds,
especially leafy spurge.
Prescribed burning is an inexpensive and effective method of controlling smaller trees; however,
its effectiveness declines as tree size increases. Adequate fine fuel (usually last year's dead grass)
is necessary for satisfactory results. Safety also is a concern with prescribed burning.
Chemical control should be viewed as just another tool in the integrated control tool box.
Herbicides can be used for both individual tree spraying and broadcast application.
Individual tree treatments
Several herbicides are suggested for individual tree treatments in spring or fall, including Tordon
22K, Velpar-L and Spike 20P. Tordon 22K can be used as a spot gun application of soil around
the tree before rainfall. Rainfall will aid chemical uptake. The recommended rate is about 1 cc
(ml) per foot of tree height. Cost of Tordon 22K is about $85 per gallon. It would cost about $65
per acre plus labor ($15 /hour) to spray 1,500 two-foot trees.
Velpar-L also can be used through a spot gun in spring at the rate of 4 cc's (ml) per inch of tree
diameter. Cost of Velpar is about $65 per gallon. Spike 20P is another alternative but can only
be used in non-crop areas as a total vegetation control at the rate of 0.5 oz per every inch of stem
diameter. Spike 20P costs about $9 per pound.
Treatment trials
We also have conducted a preliminary study of individual tree treatments at two locations
(Center and St. James) in northeastern Nebraska. Excellent tree control (more than 90%) was
achieved with Plenum at 1.5% volume per volume (v/v), Grazon P+D at 2.0% (v/v) and Tordon
22K at 1.0% v/v (Table 1). All other treatments provided poor control (less than 50%). Grass
injury in the form of temporary yellowing and burning of top growth was evident among all
treatments, especially Tordon 22K (Table 1). Cost of Grazon P+D and Tordon 22 K was
$11-$16 per acre (Table 1). Plenum and Garlon are experimental and not available for purchase.
Application tips
Here are a few practical hints:
Broadcast treatments
In general the taller the trees, the poorer the control. Excellent control (more than 90%) of up to
1-foot trees was achieved with Plenum (5 pts), Grazon P+D (6 pts and 8pts) and Tordon 22K (2
pts) at both locations (Table 2). The same treatments, however, provided poor control (less than
50%) of trees taller than 2 feet. Plenum at 4 and 5 pts per acre provided good to excellent
control of up to 2-foot tall trees. All other treatments provided poor control (less than 50%)
regardless of the tree height (Table 2). Physical removal provided the best control (100%),
however it was the most expensive method.
Cost of Grazon P+D and Tordon 22 K ranged from $21-$26 per acre. Plenum and Garlon are
experimental products and can not be purchased. Cost of physically removing a tree was about
$120 per acre, assuming that 8 hours of work was needed to cut 1,500 trees, 2 feet tall, per one
acre and an hourly labor cost of $15. For illustration purposes, 1,500 trees per acre is equivalent
to one tree per three square yards. Grass injury in the form of temporary yellowing and burning
of top growth was evident among all treatments.
Standing dead trees
A commonly asked question is: What should you do with the trees that died as the result of
herbicide application. This is especially true for taller trees over 4 feet. Cut the trees at ground
level. The stumps won't regrow, but they can puncture tires. Standing dead trees will reduce the
aesthetic value of the land, however there are several benefits of leaving dead trees for several
years:
Registration begins at 7:30 a.m. with the clinic starting at 8 a.m.
The clinic is designed to help participants stay informed about today's constantly changing world
of crop production while providing information to help them improve crop profitability. Speakers
from the NU faculty and agricultural industry bring an unbiased approach and hands-on
opportunities for learning. Participants also will view field research and learn how findings may
be implemented on their farms.
Last year's participants estimated they received an average of $3.89 per acre in added profits, due
to information from the program. Those just out of school, well-seasoned producers and crop
production professionals will benefit from this clinic and be able to use information from it daily.
Early diagnostic clinic registration is $115 until July 3. After that, registration is $165.
Approximately nine Certified Crop Advisor credits are expected to be available in soil and water
(3), soil fertility (3), and pest management (3).
This is one of three clinics to be offered in summer 2003. An end of season clinic August 20 will
include field crop diseases, late season insects, fall nutrient management, and implications of fall
tillage. An introductory precision farming clinic will be held September 3. Watch CropWatch
for more details on these programs or check the ARDC Web site at
http://ardc.unl.edu/training.htm.
NU Cooperative Extension, a division of the Institute of Agriculture and Natural Resources, is
sponsoring the clinic. To register, call (402) 624-8000 or (800)529-8030, via fax at (402)
624-8010, via e-mail at cdunbar2@unl.edu, or write to NU ARDC, CMDC Programs, 1071
County Road G, Ithaca, Neb. 68033.
Registrants signing up for the e-mail list will save $10 on the registration fee.
Keith Glewen
Learn to diagnose field problems for troubleshooting calls and how to use symptom distribution
as an indicator; learn how agronomic cultural practices impact crop growth; and how to
differentiate disease, herbicide, and insect problems in the field.
Speakers: Dale Flowerday, Agronomist; Loren Giesler, NU Plant Pathologist; Brady Kappler
and Jennifer Chaky, NU Extension Educators; Alex Martin, NU Extension Weed Specialist; John
Watkins, NU Plant Pathologist; and Bob Wright, NU Extension Entomologist.
Irrigation Scheduling
Learn irrigation strategies using ET and soil moisture data; crop growth stage and deficit
irrigation scheduling strategies; and the pros and cons of soil moisture monitoring equipment and
how it works.
Speaker: Steve Melvin, NU Extension Educator.
Manure /Nutrient Management
Learn how to determine agronomic rates for land application of manure for corn and soybean
production; potential nitrogen losses from unincorporated surface application of manure; and
in-season soil and plant testing for nitrogen. Also includes an introduction to record keeping
requirements for Comprehensive Nutrient Management Plans.
Speaker: Charles Shapiro, NU Extension Soils Scientist
Soil Moisture Conservation
Understand the importance of soil moisture conservation by reducing tillage trips; crop residue in
soil moisture conservation; and the role of crop residue and no tillage in developing soil structure.
Speaker: Paul Jasa, NU Extension Engineer.
Soil Yield Potential and Problem Soils
Learn about soil structure, organic matter, water conservation, and nutrient availability;
differences between high pH and calcareous soils, managing high and low pH soils; sampling
analysis; managing alkali spots and correcting saline and/or sodic soils; and learn how
compaction affects root growth and nutrient uptake.
Speaker: Charles Wortmann, NU Extension Agronomy Nutrient Management Specialist, and
Dale Flowerday, Agronomist.
Rootworms and the Root Rating System
Observe the effectiveness of transgenic hybrids and insecticide control methods and learn how to
dig roots and scout for rootworm larvae.
Speaker: Tom Hunt, NU Extension Entomologist
Seed Treatments and Corn Rootworm Control
Guidelines for seed treatment fungicides and the diseases they control; demonstrations of
insecticide seed treatments on soybean; zone of activity -- how long and where activity occurs;
learn if insecticide seed treatments affect fungal diseases and how to manage bean leaf beetle and
bean pod mottle virus.
Speakers: Loren Giesler, NU Plant Pathologist; Tom Hunt, NU Extension Entomologist; and
Amy Ziems, Plant Pathology Graduate Research Assistant.
We received the following samples between May 20 and June 3:
Alfalfa - spring black stem and leaf spot (Hamilton County);
Bob Wright, Extension Entomologist at the South Central Ag Laboratory: European corn borer moth flight has begun in south central Nebraska. Light traps are operated by UNL faculty at Aurora and Clay Center, with more locations to be added later. Updated light trap reports can be found through the UNL Department of Entomology Web site at http://entomology.unl.edu/fldcrops/index.htm.
I received a sample of millipedes and crane fly larvae from a seedling corn field. In one case the crop consultant thought the millipedes were injuring germinating seed and causing stand loss. Millipedes normally feed on decaying organic matter but have been reported to damage crops occasionally. Emerged plants are unlikely to be damaged. The recent cool wet weather encouraged millipede activity at the soil surface. Crane fly larvae are sometimes mistaken for cutworm larvae, but they feed only on decaying organic matter in the soil. They can be distinguished from cutworms by the lack of legs and lack of a well-developed head.
John Wilson, Extension Educator in Burt County: Corn and soybean planting (and replanting) was basically completed over the past weekend. Last Friday (May 30) we received enough heat GDDs from our first peak flight that we are in the window when we would anticipate seeing black cutworm feeding damage this week. I recorded four significant flights between April 30 and May 5 this year so, with them being that close together, I’d expect damage from all of these to run together. We will accumulate enough GDDs today for the last of the flights.
Paul Hay, Extension Educator in Gage County: Planting is largely completed. Corn, soybeans and milo look good. Leaf stripe is attacking wheat fields and will likely decrease yields by at least 10%. We also have a lot of loose smut, 3-4% of heads will have no yield. Chinch bugs are being reported rather frequently. They will pose a problem later for milo and corn growers.
Ralph Kulm, Extension Educator in Holt and Boyd counties: The rains have missed this area, allowing for planting to be completed and a lot of alfalfa and small grain to be harvested for hay. The problem is that we’re running out of moisture and soon could be back in drought trouble. The winter wheat is losing its lush look also with rust starting to show up in some fields. Hopefully we will receive moisture this week.
Whether to "unscrew" embedded ticks by twisting clockwise or
counterclockwise has long been a subject for argument and debate. But
both are bits of folklore that increase the odds for problems.
Research has found the safest way to remove the little bloodsuckers
is to grip them as close to their head as possible – preferably using
tweezers or forceps at your skin level. Then gently and relentlessly
pull straight away from your skin. Ticks will usually relax their
hold within just a few seconds.
Kansas State University Press ReleaseAg Lab to host wheat field day
June 19 at Sidney
The University of Nebraska High Plains Ag Lab near Sidney will host its
annual Wheat Field Day June 19. The gathering is free and open to the public. Lunch will be
provided by local agribusinesses.
The NU High Plains Ag Lab will host its Summer Crop Field Day on August 12.Controlling redcedar in pastures
requires integrated, multi-pronged approach
Eastern redcedar (Juniperus virginiana L.) is one of
13 juniper species native to the United States. It is the most widespread tree-sized conifer and is
native to every state east of the 100th meridian. Throughout this vast range, eastern redcedar
grows on many soils and under varying climatic conditions. On grasslands eastern redcedar can
be a serious problem because it competes very effectively with pasture species for light and
nutrients, reducing forage production. Heavy tree infestations also will interfere with livestock
handling.
Trees that are 4-8 feet tall do not have
much red heartwood tissue so they will naturally deteriorate in 3-6 years.
Stevan Knezevic
Extension Weeds Specialist
NU Crop Management Clinic:
Agribusiness professionals and crop producers will learn from taking a close-up look at
field conditions, research and cropping practices at a July 10 NU Crop Management Clinic. The
training will be held at the NU Agricultural Research and Development Center near Mead.
timely, unbiased information to help you improve profits
Extension EducatorCrop Management Clinic: Program topics and speakers
Herbicide, Disease, Insect Diagnostics and Agronomic Challenge PlotsField updates
Jennifer Chaky, Extension Educator in the UNL Plant Diagnostics Laboratory: Field crops have been a little slow coming into the clinic, so I am reporting on the last two weeks in this issue.
Corn - environmental effects on corn emergence (coleoptile growing down) (York County); pythium seedling disease (Holt County);
Wheat - stripe rust (Hall and Nance counties), septoria leaf blotch (Hall County).Tips for removing ticks
No matter what you learned from grandpa or your
camp counselor, petroleum jelly and irritants don't help remove
ticks. Neither do lit cigarettes or other heat sources.
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