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Crop Production & Management
Corn Production
Wheat Production
Sunflower Production
Weed Management
Insect Management
Field Updates
AgNews
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The Nebraska Agricultural Statistics Service estimated Sunday (May 8) that 74% of the state’s corn and 15% of the state’s soybean crop had been planted, with about 10% of the corn having emerged. That compares to an average emergence by this date of 19% for corn. NASS estimated that at least 75% of the state’s wheat had jointed, slightly ahead of average at 59%.
With rains of 5-10 inches over a 24-hour period, some fields in the Hall County area were completely submerged. Historically fields here have drained in one to two days and plants may recover well if they don’t receive another downpour, reported Jim Hruskoci, Extension Educator in Hall County. Saturated fields may take longer though.
Darrel Siekman, Extension Educator in Merrick County, said they received 6-10 inches of rain in about a 6-hour period Wednesday night. "Water was everywhere -- in buildings and homes and over roads. Hail has damaged wheat and oats, causing losses of 10-40%. About 10-30% of the corn is damaged from hail and water. Time will only tell the real damage because corn was not emerged to just emerged or from spike to the 4-5 leaf stage. Some soybeans were up and received about 10% damage. The ridge tilled crops had the soil washed away from them so the hail in places did more damage." "According the National Weather Bureau, this storm was a record setter," Siekman said, "dropping the most rain ever recorded for a 24-hour period for this area. The 75-80 mph winds didn't help either. We are still hoping to dry out."
Other areas of south central Nebraska, including an area in Adams County, also sustained hail damage although it’s too early to fully assess the extent of crop injury.
Assessing flood damage
How much rain is too much and how long is too long when fields are flooded? The following
information on assessing flood damage is reprinted from a longer June 27, 2003 CropWatch. article:
Duration, temperature of flood waters dictate extent of crop damage.
The severity of damage from flooding and ponding will depend on the plant growth stage, depth of
flooding, length of time an area was flooded and the temperature of the flood water. Depth of
flooding refers not only to the water visible above ground, but also to the level of moisture in the
soil profile.
In some situations, producers may want to dig ditches to help drain a field more quickly. Before
doing so, check with the Natural Resource Conservation Service (NRCS) to ensure that you will
not be committing a wetlands violation. Even after the surface flood water has receded, the soil
may remain saturated for some time.
The length of time a field is flooded also affects the rate of plant survival. Peter Thomison,
Extension Corn Specialist at Ohio State University, notes that corn usually can survive two to
four days of ponding, depending on the temperature. If the air temperature is over 77oF, plants may not survive longer than 24 hours.
Early spring flooding is a lot less harmful than late spring flooding when the flood waters are apt
to be warm. The temperature of the flood water is important for two reasons:
Note: CropWatch will include further stories on post-storm damage management options in future issues. You also may want to read Wet Conditions Cause Multiple Problems, an Iowa State University article published as part of the 1998 Decisions for Crop Producers.
Assessing hail damage
Hail storms are likely to occur throughout the rest of the summer. If you’re looking for information on assessing hail damage to corn, soybean or sorghum, please check out the following University of Nebraska - Lincoln NebGuides, which are available from your local Cooperative Extension office or online at the addresses provided.
Freeze damage update
Ten days after much of Nebraska sustained several nights of freezing temperatures, it appears the
damage to the state’s winter wheat crop may not have been as deadly as first feared. While wheat leaves show some damage. wheat heads generally appear to have escaped serious yield-limiting injury. The state’s sugarbeet crop, however, did not fare as well. About half of the contracted sugar beet acres in
Nebraska will need to be replanted.
This week USDA’s Nebraska Agricultural Statistics Service reported that wheat
conditions rated 1% very poor, 4% poor, 34% fair, 48% good, and 13% excellent. Fields
were 75% jointed, behind last year at 78% but ahead of the average at 59%. Alfalfa
conditions continued to decline due to the impact of the freezing temperatures and
rated 7% very poor, 12% poor, 37% fair, 37% good, and 7% excellent.
Reports from Extension specialists and educators surveying fields in west central and western
Nebraska provide some insight into how crops have fared.
Drew Lyon, Extension Dryland Crops Specialist at the Panhandle REC in Scottsbluff: Late
last week I surveyed winter wheat fields in Box Butte County, which had some of the coldest
recorded temperatures (13oF) May 2. I saw symptoms of cold damage -- burnt leaf tips, purple
culms and leaves, and a few split stems -- but few signs that the heads were injured. This means
that the wheat here has probably escaped serious injury and the loss of significant grain yield
despite the very cold temperatures.
University agronomists in the Panhandle are speculating that the cold weather prior to the very
cold temperatures probably hardened the wheat and made it more resistant to the freeze than may
have otherwise been the case. Although the area had had many warm days this spring, night
temperatures were still consistently in the upper 20s and low 30s up to the cold front. It appears
that, luckily, much of the Panhandle wheat just hadn't lost its cold tolerance yet. While there will
be some widely scattered frost injury in the Panhandle, the moisture probably did far more good
than the cold did harm.
Kent Been, Extension Educator in Red Willow County in west central Nebraska: In several
field surveys conducted this week (May 9-12) we saw some freeze damage to wheat, some
burning of upper leaves, and some damage to the bottom portion of the stem that killed the stem,
but we didn’t find any damage to the wheat head. The damage to the lower portion of the stem is
particularly concerning because the rest of the tiller is still green but will dry out if water can’t
move up through the plant when we have warmer days and will lay down and not produce.
Fields that were planted early and those that were thin were hit harder by the freeze. We also
saw some drought stress. We have not seen significant moisture in the last six weeks. We did
see some stunting of alfalfa, but it seems to be coming out of it.
Bob Klein, Extension cropping systems specialist at the West Central REC: Most of the
winter wheat in the west central area didn’t have major freeze damage and should recover,
although individual fields may have severe injury. While we found leaves that were frosted and
burned back, on splitting the stems the head and awns appeared to be light green, which is normal. In a few cases the
awns were white, which indicates potential injury. We won’t be able to determine the full extent
of injury until we can see kernel development.
The potential for damage was greatest in low field areas, thin stands and where earlier varieties
were planted. The microclimate under the crop canopy can really effect the extent of damage. A
healthy, dense stand with a good canopy will help moderate temperature fluctuations better while
thin stands will cool off more quickly.
In the west central area, lack of soil moisture is creating greater problems than recent weather.
Effects of drought were visible in some fields surveyed as the area enters the sixth year of
drought.
Where individual fields sustained severe injury, options are limited due to the lack of soil
moisture for replanting or planting another crop. In these cases, it may be best to graze the crop if cattle are available or let the crop
grow to maturity and provide protection from erosion. If producers are considering planting a
field to a different crop, they should carefully consider the previously applied herbicides and any replanting restrictions.
Corn emergence and growth in this area is generally delayed due to the colder than normal
temperatures in early May. What has emerged looks pretty good.
Even if flooding doesn't kill plants outright, it may have a long-term negative impact on crop
performance and the potential for disease development. Thomison notes, "Excess moisture
during the early vegetative stages retards corn root development and can kill the deepest roots.
As a result, plants may be subject to greater injury during a dry summer because root systems are
not sufficiently developed to access available subsoil water."
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First, there have been several reports of “yellow wheat” that appears to be wheat streak mosaic, plus the Russian wheat aphid is widespread and some economic infestations have been observed. (See page 100 for additional issues facing wheat in western Nebraska.)
With this spring’s intermittent warm weather, wheat streak mosaic virus is developing in a number of winter wheat fields in the Panhandle, including in northern Cheyenne County and southeast Cheyenne County east into Duel and southern Garden counties. Last June several hail storms passed through these areas, resulting in pre-harvest volunteer wheat that served as oversummering sites for the wheat curl mite and wheat streak mosaic virus. In the fall, the mites transmitted the virus to the current winter wheat crop. The virus increases in plants through the fall, but the plants often remain symptomless until it warms up in the spring. This warm weather – especially days of more than 80oF – enables the virus to replicate in the plant and create the severe symptoms common to wheat streak mosaic.
Symptoms may not be dramatic early in the spring; plants may just look slightly yellow and appear unthrifty. These symptoms may resemble cool temperature stress, low fertility or some other cereal disease. With warm spring temperatures, often the plants will outgrow these symptoms, especially if adequate moisture is present. However, if wheat streak is present, the plants will continue to decline with the warm weather. The yellowing of the plants gets considerably more severe, and the plants may begin to spraddle (grow more horizontal to the ground rather than vertical). Wheat streak infected leaves show a yellow mosaic pattern of parallel discontinuous streaks. These mosaic symptoms are best seen on the youngest leaf. Older leaves take on more extensive yellowing. Another obvious symptom is the tight curling of the edge of the leaf that is caused by wheat curl mite feeding. These tight curls are indicative of mite presence and ultimately virus infection.
Plants infected with wheat streak will not recover in the spring and likely will only get worse as temperatures become consistently warmer. Mild infections in fields may show an obvious effect at the edge closest to the mite source, but severe infections will extend across the field. In areas where extensive pre-harvest volunteer wheat was present in the fall, the source of mites may be difficult to identify since it may be from further away than the neighboring field.
Fields severely infected with wheat streak can have very low yield potential but the fields cannot be released for insurance until the symptoms develop into the obvious stages. In severely infected fields, management options include grazing the wheat or planting the field to a summer crop. However, by the time the wheat has been released for insurance the wheat will have used most of the soil moisture that would support a summer crop. The final impact of wheat streak on yield will be determined by the seriousness of the infection and the weather conditions through the rest of the season.
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Gary L. Hein
Panhandle REC, Scottsbluff
Powdery mildew is currently active in many wheat fields in southeast Nebraska and this week leaf rust was identified in south central Nebraska. Stripe rust and leaf rust have been reported to be developing rapidly in Kansas and Oklahoma. These diseases are most damaging when severity on the upper leaves reaches a high level by mid-June. This causes early loss of these leaves, which shortens the grain filling period and results in reduced yields and lower test weights.
Statewide, foliar diseases reduce yields about 1%, but in the last four years stripe rust has reduced yields on susceptible varieties as much as 30%. When May and June temperatures are moderate and precipitation is at or above normal, these diseases, particularly stripe rust, pose an even greater threat.
Overcast humid weather promotes the development of powdery mildew which is already on the middle leaves and will continue to move upward onto the flag-1 leaf if current weather conditions prevail. If temperatures remain moderate, however, and key rains occur during grain fill, wheat may still produce acceptable yields, despite moderate disease pressure. Certain products such as Stratego, Tilt, and Quilt have to be applied at flag leaf emergence (Feekes 8 stage) to comply with the labels. Other products such as Headline and Quadris can be applied up to late head emergence (Feekes 10.5).
Treatment criteria
How likely are you to have significant damage from foliar diseases? Intensively managed irrigated wheat is at greatest risk because the moisture necessary for infection is often supplied by the irrigation. The greatest risk for having a tan spot or Septoria leaf blotch problem is drilling wheat into or next to standing wheat stubble.
Monitoring the rust situation in the southern Great Plains and the local powdery mildew and leaf spot situation beginning in early May and continuing into late May or early June gives a good indication of the potential for foliar diseases to become a significant production factor in an individual field. Use the following criteria when determining whether to treat:
Variety planted: What is the variety’s level of resistance to rust diseases? Varieties that are moderately resistant or resistant to stripe and leaf rusts may not need to be treated, unless race changes occur in the rust population forming new races capable of overcoming plant resistance. However, those that are moderately susceptible or susceptible to one or both of the rusts need to be watched closely. Some of the more popular varieties such as Jagalene and Jagger, listed as resistant to leaf and stripe rusts, are showing higher rust severity levels this year than in past years and may need to be treated to protect yield potential.
Stand quality: In April assess the quality of the stand coming out of dormancy. Dryland wheat should have a yield potential of 40-50 bu/ac, and irrigated wheat should have a yield potential of 75-85 bu/ac to justify treatment.
Rust buildup in the southern plains: If either or both stripe or leaf rust are developing rapidly in Texas and Oklahoma during April and in Kansas during May, the probability is high that Nebraska will have a rust problem. Rust levels are already building rapidly in those states.
Earliness or lateness of the crop: If cool weather slows maturity, the window for disease development is extended and the impact on the crop is greater than if the crop is maturing early.
Weather conditions: These diseases need moist conditions, so if the long range forecast for May and June predicts above average rainfall, the disease risk is higher. Dry conditions lessen the threat to dryland wheat but may increase it for irrigated wheat because of more frequent irrigation. So far the weather in May has been perfect for rusts and powdery mildew.
Estimated price of wheat: If wheat is selling for $3.50/bu or above, treatment is more appealing than if the price is below $3.00/bu.
In general, if trace amounts of rust, powdery mildew or leaf spot are present on the flag-1 and flag-2 leaves by Feekes stage 9 (flag leaf fully expanded) and infection below the flag leaf is moderate to moderately severe, the likelihood is high that this disease will become severe enough on the flag leaf to affect yields and applying a fungicide should be cost effective.
Profitability of treatment
Applying a foliar fungicide to wheat does not guarantee higher yields. Consider it equivalent to health or home insurance. You pay a premium for protection that you may not need. If you get seriously ill or your house is severely damaged, the premiums were worth the cost, but if you don’t file any claims or the claims are small, you will have paid out more in premiums that you received from claims. This same principle applies to treating wheat.
In the event of serious disease pressure, timely application with the right product will protect yields, thus the investment was worth the cost. But if you treat the field and the disease levels never develop beyond light or moderate, the return on your investment will be less favorable and could be just a break even or even a loss situation.
The cost of treatment will range from $15 to $19 per acre depending on the product used and method of application. Many producers growing wheat under irrigation for maximum yield or for seed feel this investment is justified. However, the justification for treatment under a dryland cropping system is not as clear cut, and using the criteria provided becomes much more critical in making that decision.
Table 1 illustrates the potential net profit of treating wheat if various yield losses were to occur. In general when losses are greater than 10%, treatment with a foliar fungicide would have been cost effective. The potential net profit illustrated in Table 1 relates to common sale prices of wheat. Farmers also need to consider the effect on LDP payments and crop insurance coverage and indirectly to farm program and counter-cyclical payments which may make treatment a more favorable option.
John Watkins
As of May 5, 2005 the projected July wheat prices for central and western Nebraska with the historic basis differences from Kansas City wheat futures is near $2.65/bushel. With the current value of gain for stocker cattle, wheat may be worth more per acre harvested as pasture this year rather than being cut for grain. This is especially true if recent cold temperatures or disease have damaged wheat and will reduce grain yields.
Stocker cattle can be expected to gain well on wheat during May and early June. With the stress of the recent multi-year drought on perennial pastures and current moist soil conditions, wheat could provide excellent grazing while resting perennial pastures. Resting these pastures early in the growing season will improve plant vigor and overall production. In addition grazing winter wheat with cows that are close to or are currently being bred provides a high level of nutrition which will support and encourage conception rates. The multiple benefits of grazing wheat at this time when compared to the relative value of grain suggests that those who can graze without major fencing, water or labor issues should seriously consider it.
If cattle grazing is not feasible, harvesting wheat damaged by disease or cold as hay may potentially net more dollars per acre than harvesting the crop as grain. Producers considering these options should put together a partial budget that analyzes estimated costs and projected revenues associated with grazing cattle, cutting hay or harvesting wheat for grain. These options should also be evaluated in light of the potential effect that they will have on subsequent crop production, insurance and potential government payments.
The following resources from the University of Nebraska Cooperative Extension are available to help producers evaluate these opportunities:
Leaf rust found in central Nebraska winter wheat
Consider treatment criteria and profitability of fungicides
Leaf rust, stripe rust, powdery mildew, tan spot and Septoria leaf blotch comprise the primary foliar diseases in the central Great Plains.
Extension Plant Pathologist
Injury and economics may suggest grazing wheat
Producers should consider the value of harvesting wheat as forage rather than combining wheat for grain.
Aaron Berger
Extension Educator in Kimball, Banner, and Cheyenne counties
David Baltensperger
Crop Breeding Specialist
Panhandle REC, Scottsbluff
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The real soil moisture problems continue to occur throughout western and southwest Nebraska, where some areas are facing their sixth straight year of drought. The U.S. Drought Monitor currently rates much of the Panhandle and southwest Nebraska as being in “severe drought” while the remaining western half of Nebraska is described as being in “moderate drought.”
Current water storage in Nebraska reservoirs
The following table lists the storage in acre feet and the percent active conservation pool for early May of this year and last year. With reservoirs having limited storage, the quantity of water, as well as the time and length of delivery will be a problem again this year. For early or late crops, water will not be available when needed.
North Platte River in Wyoming
Current water storage, in reservoirs on the North Platte River in Wyoming, is still far below where we would like it to be this time of year and has changed very little from last year. It will take about a year and a half for the snow melt in the mountains of northern Colorado and southern Wyoming (on the upper reaches of the Platte) to reach Lake McConaughy. Seminoe and Pathfinder are the first two (and largest) reservoirs on the North Platte River in Wyoming. They each hold a little over one million acre-feet of water when full.
Noel Mues
Extension Educator in Furnas County
In the last three years, university extension weed specialists have been receiving phone calls and complaints on glyphosate failing to control certain weed species, including some “new weeds.” The list of such species includes: marestail (horseweed), morningglory (common and ivyleaf), wild buckwheat, Pennsylvania smartweed, lady’s thumb, Venice mallow, yellow sweetclover, field bindweed, waterhemp, kochia, Russian thistle, primrose species and volunteer Roundup Ready corn.
If these weeds are not controlled, their seeds will become a major problem, especially in no-till systems where tillage is not used for weed control. Such shifts to more tolerant weeds is already resulting in increased weed control costs due to additional herbicide applications or increased glyphosate rates.
This article summarizes preliminary data from studies conducted in 2004 at the University’s Haskell Ag Lab near Concord and the West Central Research and Extension Center at North Platte. The research tested six soil-applied herbicides for control of the previously named weed species. The six broadleaf herbicides were: Authority 75DG (5 oz/acre), Sencor 75DF (8 oz/acre), Canopy XL 56DG (6.5 oz/acre), Commit 3ME (1.5 pt/acre), Pursuit Plus 2.9EC (2.5 pt/acre), Scepter 70DG (2.8 oz/acre) and Steel 2.6 EC (3 pt/acre). These herbicides were applied to the soil after planting weed seeds.
The level of weed control at 40 days after planting varied by the weed species and herbicide. For example, Sencor provided excellent control (100%) of kochia, velveltleaf and Venice mallow, compared to a lower control level (37%) of ivy leaf morningglory (Table 1). For control levels for each weed species and herbicide see Table 1.
The results indicate a potential to effectively control most of these weed species with various pre-emergence herbicides applied to the soil after soybean planting. Soil-applied herbicides also would provide an additional mode of action for weed control, reducing the likelihood of developing weed resistance. Soil-applied herbicides also would provide a longer “comfort zone” for weed control early in the season by delaying the critical time for weed removal and reducing the need for multiple glyphosate applications later in the season.
Using various weed control tools is not a new thing -- we only “forgot” about it since the introduction of Roundup Ready crops. Rotating herbicide modes of actions is a basic tenet of an Integrated Weed Management (IWM) program where several weed control tools are integrated to provide weed management. Integrated systems are especially important when combating weed resistance/tolerance issues. Roundup Ready technology can fit under the umbrella of an IWM system but it will need to be preserved through proper management and reduced overuse.
In essence, the development of an IWM program is based on a few general rules that can be used on any farm. These include:
For more details on integrated weed management see the University of Nebraska Extension Circular, Guide for Weed Management in Nebraska (EC130). The concepts of IWM become even more important when other Roundup Ready crops become more readily available (e.g. Roundup Ready corn, Roundup Ready alfalfa).
It is easy to fall into a trap of overusing glyphosate when one glyphosate-tolerant crop is grown after another. Proper use of this technology as part of an integrated weed management program, is the key to preserving the long-term benefits of this technology while avoiding many of the concerns about its use or overuse.
Watch future issues of CropWatch for two more parts to this story: glyphosate pre-mixes and glyphosate rates needed to control problem weeds in Roundup Ready soybean.
Stevan Knezevic
Effective weed control for the first 30 days will give sorghum a head start on weeds and pay big dividends in sorghum yields. Fortunately there are several effective preemergence herbicides registered for use in sorghum. It is important to target annual grass weeds with a preemergence treatment as post-emergence options are limited.
Essentially all sorghum seed is now treated with a safener required for use of most preemergence herbicides. Atrazine (the only one of the group not requiring safened seed) provides fair control of many annual grasses and good control of broadleaf weeds. Bicep II Magnum, Bicep Lite II Magnum, Bullet, G-Max Lite, and Guardsman Max provide control of annual grasses and broadleaf weeds.
Large seeded broadleaf weeds including sunflower, cocklebur, velvetleaf and morningglory are often not adequately controlled with preemergence treatments. A postemergence treatment may be required to control these weeds. Dual II Magnum and Outlook control annual grasses and small seeded broadleaves. Application rates of these herbicides vary with soil properties. Check the product label or the University of Nebraska - Lincoln Cooperative Extension 2005 Guide for Weed Management in Nebraska (EC 130) for details.
Postemergence treatments that provide broadleaf weed control include atrazine, Aim, Ally + 2,4-D, Marksman/Sterling Plus, Banvel/Clarity, 2,4-D, Buctril&Atrazine, Peak and Permit. Many of these herbicides can be combined to broaden the spectrum of weeds controlled. Starane is an herbicide recently registered for use in grain sorghum. Starane controls many broadleaf weeds including kochia and triazine-resistant and ALS-resistant biotypes.
Paramount and Paramount plus atrazine provide postemergence grass control, especially of green foxtail, and broadleaf weed control.
Herbicide application rate, sorghum and weed growth stage, and spray additives are all important in attaining maximum performance of postemergence herbicides. Consult product labels or EC 130 for details. Alex Martin
Authority® will require a Special Local Needs (SLN) 24(c) label. The Nebraska Department of
Agriculture and Nebraska Pesticide Board must approve Section 24(c) labels, and only received
the request for Authority on May 5. Due to the extensive review process required for state
approval of a Section 24(c) request, the Authority label may not be approved in time for use on
this year's sunflower crop.
Drew LyonControlling problem weeds in Roundup Ready soybean
Many farmers are reporting that glyphosate used alone does not work as well today as it did five or six years ago. Nebraska’s fields appear to be experiencing a slow shift in weed species.
Combining agronomic practices based on these rules will allow agronomists to design an IWM program for any field. The bottom line is that an IWM program is not a one-size-fits-all solution. Rather, it needs to be changed and tailored to a particular farming operation. Since the eradication of weeds isn’t possible, the goal is to manage weeds.
Extension Weeds Specialist
Haskell Ag Lab, NEREC
Target weeds in sorghum early in the season
Grain sorghum planted in mid-May grows slowly for the first two to three weeks in contrast to corn and soybean. Many early season weeds including lambsquarters, Pennsylvania smartweed, common sunflower, velvetleaf and even foxtail grow faster than sorghum. For this reason early sorghum is less competitive with weeds than corn and soybean, emphasizing the need for early weed control.
Extension Weeds Specialist
Two products in line to aid herbicide crunch for sunflower
The limited supply of Spartan® herbicide is causing concern for sunflower growers in the state. In response to this shortage, the National Sunflower Association has worked to get other sulfentrazone products labeled in sunflower. These other products include Blanket® herbicide,
which is marketed by Tenkoz, and Authority® herbicide, which is marketed by DuPont.
Blanket® now has a supplemental label that includes sunflower in the states of Colorado,
Kansas, Minnesota, North Dakota, Nebraska, Oklahoma, South Dakota, Texas and Wyoming.
Applicators will need to have the supplemental label in their possession when making the
application.
Extension Dryland Crops Specialist
Panhandle REC, Scottsbluff
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Scouting and rescue treatments
Remember that early detection of a problem is essential because most of the cutting occurs within seven days of plant emergence. Generally, a rescue treatment should be considered if 5% or more (an average of at least 1 plant in 20) cutting is observed and the worms are one inch or less in length.
Rescue treatments are effective in controlling soil cutworms. Ambush 2E, Asana XL, Baythroid, Lorsban 4E, Mustang Max, Warrior, Proaxis, and Pounce 3.2EC (or generics) all will give satisfactory control as postemergence sprays. If the soil is dry or crusted, rotary hoeing immediately before or after Lorsban application may enhance control. The other insecticides are pyrethroids and should not be incorporated. See a full list of products and rates on the Department of Entomology Web site.
For more information on managing this pest, see the University of Nebraska Cooperative Extension NebGuide, Corn Cutworms (G93-1153).
Southern corn leaf beetles
A relatively new pest of corn - the southern corn leaf beetle – has caused damage periodically in southeast Nebraska since 2000. This insect has been reported to damage corn in northeast and north central Kansas over the last few years, and also has been reported in Missouri, Iowa and Illinois.
The adult overwinters in sheltered areas and becomes active in April. In addition to corn it may feed on weeds, especially cocklebur. The adults are 3/16 inch long, dark brown and often covered with soil particles, making them difficult to see. They hide in the soil during the day and are difficult to find. They feed on the stems of corn seedlings and may cut stems, causing damage similar to cutworms on seedling corn. They also feed on the edges of leaves, producing a notched appearance, similar to leaf feeding by cutworms. If abundant they may severely damage seedling corn.
Economic thresholds have not been researched for this insect, but use of thresholds similar to those for cutworms has been suggested. The same insecticides labelled for postemergence use against cutworms would be appropriate for southern corn leaf beetles.
Robert Wright
Extension Entomologist
Keith Jarvi, Extension Assistant
Integrated Pest Management
Northeast REC
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If you were still aerating grain when air temperatures were well below freezing, hopefully you took advantage of periods in the early spring when we had cool, relatively dry, air to push a warming front through the grain. A final grain temperature of 30-35oF in March would have been ideal. Even high moisture corn keeps well at low temperatures. This provides a window of time to wait for conditions when the grain can be dried to safe storage moisture content using natural air.
Research under controlled laboratory conditions has shown 19% moisture corn held at a constant 30oF with aeration has a shelf-life of nearly 10 months and 17% moisture and 30oF corn has a shelf-life of about 22 months. Shelf life is defined as the time grain can be stored before losing 0.5% of its dry matter content. The shelf-life of corn in a bin that is not being aerated to maintain constant temperature is approximately one-third as long.
Avoid holding frozen, high moisture grain until late spring
To illustrate the seriousness of holding frozen, high moisture, corn into May, lets assume a bin of grain was cooled to 20oF and no further aeration was done until the air is 60oF and 50% relative humidity. Radiant and convective heating would have warmed the grain near the bin walls but the grain in the lower center of the bin will have stayed cold. Air at 60oF and 50% relative humidity has a dew point temperature of 41oF. Since the grain close to the bin walls was warmer to start with, it will be warmed to above the dew point temperature and moisture won’t condense from the aeration air. More airflow is required to warm the colder grain in the center of the bin. More airflow means more water condensation into the cold grain since the grain temperature is below the dew point. The danger comes when the grain is below freezing. The moisture will turn to ice in frozen grain and enough ice could form to block airflow through the grain.
Air always takes the path of least resistance. This scenario could result in a pocket of frozen wet grain in the lower center of the bin that cannot be penetrated by air. You likely may not know you have this problem. Eventually, the grain in the middle of the bin will warm up and the scenario becomes more ominous because of the wet grain. Now you have a pocket of high moisture corn at higher temperature buried in the least accessible spot in the bin. Corn at 19% moisture and 65oF has a shelf life of about one month with aeration and about 10 days without aeration.
What should be done with frozen, high moisture grain in May?
The first priority is to bring the temperature of the grain above freezing. If possible, find a time when the relative humidity is low, then start the aeration system. Ideally, one would want to find a time when the dew point temperature of the air is no more than ten degrees higher than the coldest grain in the bin before starting the aeration system. These conditions are not likely to occur in mid May if grain is below freezing. In the future, aerate your grain regularly to maintain the proper grain temperature and avoid this problem.
If your drying bin is equipped with a stirring device, make certain you can manually turn the stirring augers to make certain they are not stuck in frozen grain before proceeding. If they are free, make a round with the stirring device before starting the aeration fan to help equalize the grain temperature in the bin.
Continue running the stirring device while aerating until the grain has been warmed to 40oF. Once the grain reaches a uniform 40oF, discontinue stirring natural air drying systems and allow a drying front to form and move through the grain. If the bin is not equipped with a stirring device, you can achieve greater airflow and faster warming in the center of the bin by unloading several hundred bushels of grain prior to starting the aeration fan. This will leave a crater in the center of the bin which will lower resistance to airflow and encourage greater airflow through the center of the grain mass. After a warming front is pushed through the center of the bin, the grain can be loaded back into the bin or the grain could be leveled to restore uniform airflow through all the grain in the bin.
Continue to run the fan until the grain moisture content is below 16%. If you can carefully monitor the grain for heating, fans could be run intermittently until the grain is dry. Base fan operation on the equilibrium moisture content table found in Natural Air Corn Drying (UNL NebGuide 760).
References
Tom Dorn
Extension Educator
Lancaster County
William Campbell
Extension Agricultural Engineer
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Gary Lesoing, Extension Educator in Nemaha County: I don't believe there was major damage to corn, alfalfa and wheat in the area due to the recent series of frosts. Most of the corn had not emerged due to the cold temperatures and I don't think wheat was far enough along in development to cause major damage.
The alfalfa may have been stunned by the cold, but should recover. There were good field conditions last week for farmers to really make significant progress in planting crops. Producers are generally winding down on corn planting and many are planting soybeans. Some of the corn has been in the ground for two to three weeks which has caused some concern, but the warm temperatures late last week and early this week should help corn and soybean emergence. Farmers also have been in the midst of herbicide applications the past few days.
Karen DeBoer, Extension Educator in Cheyenne County: Fieldwork includes corn planting, working summer fallow, and spraying weeds. We received some moisture mid-week that slowed field work progress. Wheat is growing well, however, we still need warm temperatures.
Wheat streak mosaic virus is in some fields. There has been Russian wheat aphid activity, however, we haven't received reports of populations reaching economic thresholds. At the start of the week, winter wheat leaf tips were brown in some fields. We should be able to determine the full extent of frost damage after four to five days of warm weather.
Other field work includes spraying for weeds in wheat, disking wheat stubble for summer fallow, preparing seedbed for spring seeded crops like proso millet and planting irrigated corn.
We have found wheat curl mites, the vector for wheat streak mosaic virus and High Plains virus, in wheat fields in northwest Cheyenne County.
Delroy Hemsath, Extension Educator in Dakota and Dixon counties: Most of the corn has been planted in northeast Nebraska and soybeans are being planted as the soil dries out from the recent rains.
The frosted alfalfa is recovering. I have only seen one field that was cut in order to stimulate the regrowth. The corn was not damaged as most was not emerged. There has been an abundance of shepardspurse and mustards in the fields, most of which has been sprayed with herbicides. There is quite a bit of tillage in corn stalks to plant soybeans. Oats look weather stressed -- they're yellow and needing warmer weather.
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In Webster County, southern Adams and eastern Franklin counties wheat condition is varied. We have a lot of yellow wheat fields that I believe are mostly related to environmental conditions. We endured five straight nights of freezing temperature and in some areas it got down as low as 25oF. Patches of a field may be brown (mostly low areas) while other areas of the same field look good. There is frost "scorching" on most of the wheat on early leaves but not enough to hurt anything. It is difficult to determine accumulative damage because of the cool weather and lack of growing days. The only thing consistent in the wheat fields is the lack of consistency.
We have received reports of some fungus diseases coming in to our area, mostly due to the weather conditions. These include: septoria, powdery mildew, and tan spot. Some fields on flatter ground are in excellent condition. Overall the wheat is behind normal for this time of year with the condition slipping. At this time, I would expect harvest to be later than usual.
We are experiencing similar problems in alfalfa. We had some freeze damage of leaves but I couldn't find any affected growing points. Up until last week the alfalfa looked really good. Our biggest problem right now is alfalfa weevil -- some fields are lousy with them. Ironically some fields were sprayed for weevil just before the frost so cutting the freeze damaged alfalfa was not an option. Some farmers that hadn't sprayed are clipping the frost damaged alfalfa to control the weevils.
In both wheat and alfalfa fields we are finding more weeds than usual, including a lot of winter annuals that are not normally in the fields (i.e. henbit). I also don't recall seeing this much pennycress in many years.
Gary Zoubek, Extension Educator in York County: We've had good rains in April, but we're getting dry and have had considerable crusting in fields planted prior to the heavy rains. Many pivots have been run to help with crusting problems and, in several situations, it has helped improve the final population. Planting has progressed rapidly with most of the corn in and many producers nearing the end on soybeans.
Steve Melvin, Extension Educator in Frontier County: Wheat should be able to outgrow the freeze damage to leaves. Alfalfa also suffered freeze damage. Some producers are harvesting it, while others are waiting to see if it continues growing. Most of the corn is planted and first planted is just emerging. Soybean planting is just getting started.
The publications are Soybean Rust: How Great is the Threat for Nebraska?, which is NebFact NF05-633, and Fungicides to Manage Soybean Rust: What are the Product Differences?, which is NebFact NF05-634. Both are available online or from local extension offices across Nebraska, said Loren Giesler, plant pathologist in the university's Institute of Agriculture and Natural Resources.
Soybean Rust: How Great is the Threat for Nebraska? offers information about the disease, including its symptoms, life cycle, host range and potential impact on Nebraska soybean production. While soybean rust has not been detected in Nebraska, monitoring and catching it early are critical steps in controlling this new, potentially devastating soybean disease, said Giesler, who is heading the university's soybean rust efforts. The publication also discusses characteristics that make soybean rust potentially devastating and its management.
Fungicides to Manage Soybean Rust: What are the Product Differences? includes information about fungicides if Nebraska soybean producers need to apply them this year. Based on experiences in other parts of the world, it is critical that a fungicide application be made before significant disease development in the field, Giesler said. The publication discusses resistance management issues, fungicide names and application methods.
UNL releases new soybean rust publications
Two new University of Nebraska Cooperative Extension publications will help soybean producers learn more about soybean rust and its control.
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