July 12, 2002
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Corn Production
Insect Management
Wheat Alfalfa and Pasture Management Management Resources AgNews
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For most of the state, the next few weeks will be critical to corn yields. Robert L. Shaw of the Department of Climatology and Meteorology at Iowa State University, reviewed many drought-stress experiments and summarized the data (see Figure 1). He found a 3% reduction in yield per day of stress early in growth. In some experiments that same rate of yield loss occurred throughout the season (lowest line of shaded curve), but on average (middle line) there was a pronounced increase in corn's sensitivity to drought starting around the time of silking and continuing for about two weeks. Yield losses can jump to 8% per day of stress during that period.
As temperatures soar and with tasseling in progress, we should be concerned about pollen viability and silk receptivity. Pollination is a critical period for corn development and yield. Pollen shed occurs over a two-week period. For kernels to develop, silks must emerge and be fertilized by viable pollen. Silks grow about 1 to 1.5 inches a day and will continue to elongate until fertilized. Temperatures greater than 95oF with low relative humidity will desiccate exposed silks but not impact silk elongation rates greatly. Pollen is killed by temperatures in the mid 90s or greater, especially with low relative humidity. Fortunately, pollen shed usually occurs from early to mid-morning when temperatures are lower.
When poor pollination does occur, it can lead to spotty kernel set. The kernels that pollinate properly often grow extra-large in the absence of neighboring kernels. Even if pollination is 100%, drought stress can reduce the number of kernels set by the crop.
After seeds are pollinated, plants seem to decide how many seed they can support and then abort the extra, starting with kernels at the end of the ear and moving toward the base. The rate of plant photosynthesis during that period appears to be the deciding factor. Low photosynthesis per plant leads to high kernel abortion. Other stresses also can cause corn to react in the same way: nutrient deficiencies, temperatures too high or too low, populations too high, and low solar radiation can affect yields by reducing photosynthesis and thereby increasing kernel abortion.
This phenomenon has been an active area of research for crop physiologists in recent years. The table summarizes how drought stress at different points in the life cycle can influence corn yield. At harvest, to find out how drought stress may have shaped your yield, check the components of yield: note the stand (plants/acre), ears/plant, kernel-rows/ear, kernels/kernel-row (spotty? or kernels lost at tip?), and weight/kernel. These yield components often reflect the plant's stress history throughout the season.
The bottom line is that high temperatures will not severely stress corn if soil moisture is adequate. Obviously we don't have to tell farmers to keep up with irrigation at this time of year. It is one of the best ways to reduce the impacts of high temperatures on corn pollination and fertilization.
Rain-fed fields are more of a concern. Drought stress with high temperatures at pollination and silking can have serious effects. If the current dry-hot conditions continue, we would expect to see major differences among fields based on management practices and hybrids.
Practices that conserved soil moisture this spring or last year such as no-till or reduced till will improve a crop's performance during drought. Early-season hybrids probably will do better than other hybrids if pollination occurred before temperatures soared or moisture reserves were depleted. Full-season hybrids with good stress tolerance may do better than others with less stress tolerance."
Bob Caldwell
Extension Cropping Systems Specialist
Southeast and Northeast REC
Roger Elmore
Extension Crops Specialist
South Central REC
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Leaving standing residue also can pay longer term benefits for next year’s crop by reducing wind erosion, limiting weeds, helping conserve moisture and capturing snowfall.
Corn can be harvested as hay (much like cane hay, with a thick, slow drying stalk that can be difficult to windrow), as silage, or grazed.. The producer's choice of use may be affected by the amount of nitrate present in the crop. Many times drought or hail stressed crops contain high levels of nitrates.
If nitrate levels are high, the field may need to be harvested differently than originally planned or feed rations may need to be mixed differently.
These fields have the potential to solve much of the forage/feed shortage caused by the current drought, although getting corn forage to the animals or bringing animals to the forage remains a logistics challenge.
Haying
Harvesting corn for hay presents several challenges, which the producer should carefully consider:
Forages that contain high nitrate levels can be diluted in the diet with grains or with other forages low in nitrates. Energy from the grain apparently helps complete the conversion of nitrate to bacterial protein in the rumen.
Greenchop
Greenchop is very effective at harvesting most of the feed nutrients available from the crop and making them immediately available. Greenchop is the most hazardous feed to use, though, when nitrates are high. Never allow greenchop to sit in feed bunks or feed wagons and heat. Nitrates get converted into nitrites during this heating process, and nitrates can be as much as 10 times more toxic than nitrates. Thus, only chop and feed what the animals will eat in one single meal. To further minimize nitrate risks, leave a tall stubble in the field.
Silage
Harvesting the field for silage is an excellent choice for reducing nitrate problems -- an average of one-third of nitrates are neutralized during fermentation. Using silage too quickly after chopping, however, can be deadly. During the first few days of early fermentation the chopped forage begins to heat, converting nitrates into nitrites. Nitrites are as much as 10 times more poisonous to cattle than nitrates. These nitrites are then converted into other compounds that make them less toxic.
To avoid feeding high nitrate or high nitrite silage, wait four weeks after chopping before feeding. Crops normally have lower nitrate levels at maturity, so harvest when the crop is as near maturity as possible. If the corn or sorghum field being harvested as silage has been identified as or is suspected of having high nitrate concentrations, raise the cutter head to selectively avoid stalk bases that have the highest nitrate concentration.
Even in dry fields, moisture may be a problem and may delay harvesting the field for silage. The stalk retains moisture and may remain too wet for a long time. To overcome the moisture problem, wait until the crop dries to desired 65% moisture before chopping. Another option is to windrow it and allow field wilting to reduce moisture. A final alternative is to mix wet chopped stalks with dry feeds like corn grain or chopped hay.
Silage does not transport well, so it makes for a poor cash crop unless livestock are near.
Grazing
Nitrate poisoning is less of a concern with grazing than with the other options, but it can still be a problem, depending on how completely animals are forced to eat the lower stalks. Providing fencing and adequate water may be bigger hurdles with grazing corn fields. Grazing management, such as strip grazing, will be needed if efficient use is desired, otherwise cattle will trample and waste a huge portion of the crop. A single electric wire often is all that is necessary to restrict animal access to a limited area if animals are trained and familiar with electric fence. Cows should receive only as much corn as they will finish in two or three days, then be given a fresh strip. Dairy cattle or stockers should receive fresh corn to graze every day or two.
Nutritionally, this drought damaged corn should be adequate for beef cows, dry or with suckling calves, and for replacement heifers and steers. TDN will be around 65 and crude protein about 12%. Small calves may struggle some with grazing without the cow and eating unground hay.
Bruce Anderson
Extension Forage Specialist
One of these challenges is grasshopper control and grazing restrictions. Use of insecticide
treated crops for forage and feed is often restricted. Because restrictions vary for different
insecticides, producers are reminded to read the insecticide label and discuss grazing restrictions
with their chemical dealer.
For example, the following restrictions apply to these common insecticides registered for use in
field corn and/or grain sorghum for grasshopper control.
Asana XL
Capture 2 EC
Dimethoate 4 EC
Furadan 4 F
Lorsban 4 E , Nufos 4 E
Mustang
Penncap-M
Of course other label information (e.g. post harvest intervals for grain, cumulative application
limits) also is important for the producer to consider. More information on pesticide labels can
be found in the on-line Greenbook at http://www.greenbook.net/.
Tom Hunt
During late July and August these beetles will be laying eggs in corn fields. These eggs
overwinter in the soil, hatch into rootworms in the spring, and feed on corn roots if continuous
corn is grown. However, not all continuous corn fields have economic infestations of corn
rootworms. Weekly scouting of adult rootworm beetles in July and August will provide you with
information to decide whether a rootworm insecticide is needed next year. People using adult
beetle control programs should base the decision to treat and spray timing on information from
field scouting.
Begin scouting for corn rootworm beetles soon after beetle emergence begins and continue
scouting weekly until threshold levels are exceeded or beetle activity stops. Examine 50 plants
per field, taking samples from each quarter of the field. Sampled plants should be several paces
apart, so that examining one plant doesn't drive beetles off of the next plant to be sampled. The
most reliable method is to examine the whole plant for beetles. Beetles may hide behind leaf
sheaths or in silks, so care is required to observe all beetles present. An alternative method is
check for beetles only in the ear zone (the area including the upper surface of the leaf below the
primary ear and the under surface of the leaf above the primary ear).
In continuous corn if beetle counts exceed 0.75 beetle per plant, damaging populations of corn
rootworms are possible in that field next year. In first year corn, there is a higher proportion of
female beetles, so the threshold is lowered to 0.45 beetle per plant. These thresholds are based on
a 24,000 plant population per acre. The number of beetles per plant to equal a threshold level
should be adjusted for different plant populations. (See table or NU NebGuide, Western Corn
Rootworm Soil Insecticide Treatment Decisions Based on Beetle Numbers", G86-774.) If you
use the ear zone method for scouting, divide the above thresholds in half, since on average only
50% of the beetles on a plant are counted using this method.
To prevent economic damage, rotate the field out of corn or use an insecticide at planting or
cultivation time. Fields remaining below the threshold level do not need to be treated with a
rootworm insecticide next year.
Individuals using adult beetle control programs should begin treatments when the beetle
threshold is exceeded and 10% of the female beetles are gravid (abdomen visibly distended with
eggs). This is an important point since the first beetles to emerge are mostly male, and females
require at least 10-14 days of feeding before they are able to lay eggs. Treatments applied too
early may be ineffective if large numbers of females emerge after the residual effectiveness of the
treatment has dissipated. Continue to monitor fields weekly after treatment for rootworm beetles.
If beetle numbers exceed 0.5 beetles per plant, retreatment is warranted. Late maturing fields are
particularly susceptible to corn rootworms moving into them from nearby earlier maturing fields.
A complete discussion of adult corn rootworm management can be found in the UNL
Cooperative Extension publication, "Adult Corn Rootworm Management," MP 63 by UNL
Entomologist Lance Meinke.
Be aware that reduced adult rootworm control with foliar insecticides due to insecticide
resistance has been documented in parts of south central Nebraska (see Adult Western Corn
Rootworm Insecticide Resisistance in Nebraska, NebFact 99-367). If you experience poor
control with repeated applications of foliar insecticides, and high numbers of beetles are still
present, consider rotating that field out of corn next year rather than continuing to treat for
beetles.
Bob Wright
Corn earworms are known to feed in the whorl. This feeding will produce ragged holes in the
leaves as they emerge. Earworms may also feed on the developing tassel in the whorl. In field
corn they would rarely need to be treated unless 50% or more of the plants were damaged and
had live worms present.
Bob Wright
The lack of rainfall both in the fall and spring plus little moisture from snowfall contributed to
shorter wheat and lower yields in much of the state. In addition many fields were cut and baled.
These fields will need special care to avoid problems. Some of these fields may be planted back
to wheat this fall.
Controlling weeds after winter wheat harvest will be a challenge. Surveys taken after winter
wheat harvest in the past in west central and southwest Nebraska usually show barnyardgrass and
green foxtail as the leading summer annual grasses infesting winter wheat fields. Other grassy
weeds include sandbur, stinkgrass, and witchgrass. Broadleaf weeds such as kochia,
lambsquarters, morning-glory, common sunflower, toothed spurge, and wild buckwheat are also
present in some fields. However in 2002 many fields have few weeds. Slimleaf lambsquarters is
the most common broadleaf weed. Some fields that caught a timely rain have low densities of
green foxtail, stinkgrass, witchgrass, and longspine sandbur.
Challenges to weed control
The effectiveness of post-harvest weed control is influenced by production practices associated
with the previous wheat crop, such as winter wheat variety selection, fertilizer practices, row
spacing, planting date, and seeding rate. Others factors influencing weed control include: weeds
that are too large; cutting off weed tops with the combine; crop rotation; temperature when
spraying; rain the day of spraying; streaks caused by sprayers, terraces, dust, straw, chaff, and
weed seed distribution. The lack of residue from the winter wheat crop makes this crop less
competitive with weeds.
Weeds under moisture stress are difficult to control. If you can wait to spray after a rain, control
will improve. It's a general rule with wheat in a three-year rotation that you can wait a maximum
of 30 days to spray; however, if wheat was planted without a 11- to 14-month fallow period, it
should be sprayed within 15 days after harvest. With one of the driest years on record and only
scattered rain, each field should be examined before spraying. The key is to prevent weeds from
using soil water and producing weed seeds.
Split treatments
Split treatments have been especially effective and with the earlier harvest this year their
advantages will be even greater. In Kansas there was a 20 bushel increase in corn yields the next
year for treatments applied in July vs mid-August. With the split treatment, apply the glyphosate
products alone (surfactant if needed plus the ammonium sulfate) as the first application in July.
Sufficient surfactant is included in RT Master, Roundup Ultra, Roundup Ultra Max, and
Landmaster BW. Many other brands of glyphosate need a surfactant. Check labels. For all
brands of glyphosate add ammonium sulfate (spray grade) at 17 lb per 100 gal of spray solution.
The ammonium sulfate is the first item put into the spray tank after the water. Ammonium
sulfate is especially helpful when stress conditions are present. Liquid ammonium sulfate, with
or without a drift retardant, is also available.
It is difficult to recognize weed stress; therefore, it's wise to always add ammonium sulfate.
Improve control by increasing the rate of glyphosate. Allow at least six hours for the glyphosate
products to become rainfast. Some weeds require more time than others. Barnyardgrass control
may require as much as 24 hours without rain for maximum control. A spray volume of 5 to 10
gallons per acre should be used with the glyphosate products. Do not use glyphosate products on
days when temperatures reach or exceed 95oF.
A second treatment in September should contain at least 1/2 pound per acre of atrazine and
possibly Gramoxone Extra (add surfactant), depending on the amount and size of volunteer
winter wheat, downy brome or jointed goatgrass present. Several options are available for using
nonselective herbicides with difficult-to-control weeds. With Gramoxone Extra use a minimum
of 2 pints of X-77, or equivalent surfactant, per 100 gallons of solution. Use 2 quarts of
X-77/100 gallons of spray solution if using less than 20 gallons of carrier. The atrazine rate
varies with soil and rainfall patterns. In southwest Nebraska, use at least 2 quarts per acre of
atrazine, but in the Panhandle, 1/2 quart per acre is often the maximum in one season.
The advantage of split treatments is that they provide excellent control of volunteer winter wheat
and other winter annual grasses. Control of volunteer wheat is especially helpful in reducing the
spread of wheat streak mosaic disease. Using one quart or less of atrazine before September 10
allows winter wheat to be planted 12 months later in most areas. If sufficient soil water is
available the following spring, corn could be planted or if moisture is limited, the field could be
fallowed and winter wheat could be planted in the fall.
Integrating control measures
Many options besides increasing herbicide rates are available for weed control after wheat
harvest. It takes a total package to obtain maximum weed control. Stands of vigorous winter
wheat will compete better with weeds, allowing you to concentrate on weed control in the fallow.
Preparing a good firm seedbed, controlling weeds in a timely manner, fertilizing if needed,
seeding properly, planting during the optimum time, selecting a competitive winter hardy winter
wheat variety, and controlling weeds in the growing wheat offer the best chance of reducing
weed population and vigor after harvest. In addition, it's essential that you watch closely and
spray at the proper time to control weeds. Most labels state that weeds must be treated before
they are 6 inches tall. If weeds are under severe drought stress, wait for rain and spray about a
week later.
If downy brome is a problem and a winter wheat-fallow rotation is being used, tillage is usually
recommended immediately after harvest to plant the seeds and ensure maximum weed
germination during the fallow period. But with the limited amount of crop residue this year,
tillage should not be used because of the possibility of soil erosion. Herbicides are available to
control downy brome in the growing winter wheat and are best applied early post in the growing
winter wheat. If jointed goatgrass and/or feral rye is a problem, use a rotation where wheat is
not planted for at least three years under good moisture conditions and even longer under dry
conditions.
Herbicide-tolerant winter wheat varieties are available in limited quantities this year for the
grower that has a jointed goatgrass or feral rye problem. Beyondr herbicide is then applied in the
growing wheat. A grower is required to take training before purchasing this herbicide. Be sure
to check the label for additional information.
Robert N. Klein
Usually, however, it may be worth more to leave it on the field than its value for animal feed or
bedding, especially with the limited amount of residue produced this year.
The more residue there is, the more weeds are suppressed and the more wind and water erosion
will be reduced. This is especially important, given the small amount of residue produced this
year. Removing crop residue, either by baling and/or tillage, could make the fields very
susceptible to soil erosion.
Stubble height may be as important as the total quantity of residue remaining in the field.
Kansas research showed corn yields increased 15 bushels with a stubble height of 15 inches
compared to a height of 7.5 inches. Both research and field observations over the years have
revealed a 20 bushel per acre yield loss when one ton per acre of straw was removed. In one
example, where straw was left on the field, the yield was 117 bushels per acre and where it was
removed it was just 97 bushels per acre. The additional crop residue also may carry the crop
longer before it needs a rain since it reduces evaporation.
Research also has shown that grain sorghum fields with more winter wheat residue are less susceptible to greenbugs. Maximum corn yields are usually obtained with 6000 pounds of evenly spread winter wheat residue, or the amount of residue from a 60 bushel per acre wheat crop.
Let’s examine that 20 bushel/acre corn yield decrease resulting from straw removal. If the price of corn is $2/bushel, that amounts to $40/ton for the straw. We also would have the cost of baling and treating if we feed the straw. The value of the straw for feed needs to be compared with hay prices. Summer forage crops may be a better alternative for hay supplies than using wheat straw.
Robert N. Klein
"With the continued hot, dry weather the decision to open the remaining roadsides was absolutely necessary," Gov. Johanns said. "Unfortunately, it doesn't appear that conditions will improve, so I wanted to take action before the roadside hay loses its forage quality."
In conjunction with the roadside haying release, the Governor is asking Nebraskans to consider donating their roadside hay or any other types of forage through the charitable relief organization, Orphan Grain Train. Based out of Norfolk, this nonprofit organization has volunteered to serve as a clearinghouse and distribution arm for donated hay.
Permits for roadside haying are available from designated Nebraska Department of Roads offices. Contact your closest office for more information. Roadside hay can be cut for private use only and can not be sold. There is a per mile/per side fee for roadside hay, which will be waived on donated hay.
To make a donation to Orphan Grain Train or to find out more information about the program, call (402)640-5528.
Contact your local Farm Service Agency office for further information and permits. Haying is authorized until Aug. 31, 2002, or until disaster conditions no longer exist, whichever
comes first. CRP participants who do not own or lease livestock may rent or lease the haying
privilege to an eligible livestock producer in an approved county.
Generally, to be approved for emergency haying and grazing, a county must have suffered at least
a 40% loss of normal moisture and forage for the preceding four-month qualifying period. At
least 50% of the CRP contract acreage must be left unhayed for wildlife. Hay harvested from
CRP acreage may not be sold.
USDA offers other programs to assist drought stricken producers, including emergency farm
loans, federal crop insurance, the emergency conservation program and the noninsured crop
disaster assistance program. Since the beginning of the year, areas of 16 states have been
declared drought disaster areas, making farmers in those areas eligible for emergency farm loans.
For more information, producers should contact their local FSA office or visit FSA's website at:
http://www.fsa.usda.gov.
Weed control authorities use leafy spurge flea beetles to control the noxious weed that is found
throughout Nebraska and infests irrigation ditches, roadsides, fields, woodlands, shelter belts,
rangeland, and sub-irrigated meadows.
Merlyn Carlson, Nebraska's agriculture director, said landowners can buy the beetles, or in some
areas, beetles may be available free. "I urge landowners to contact their local county weed superintendents who may have the necessary resources to find free beetles," Carlson said.
Leafy spurge flowers from May to September and is considered toxic to cattle. The weed is one
of seven noxious weeds in Nebraska.
These are the first in a series of publications to provide color photos of common diseases for
Nebraska crops. These are intended to be used with another Cooperative Extension publication,
"Diseases of Nebraska's Field Crops" (EC1880), which provides further details. Contact your
local Cooperative Extension Office to get your copy. Each publication costs $1.
Loren J. Giesler
Noel Mues, Extension Educator in Furnas County: Crop conditions are deteriorating rapidly. We've received about 4.5 inches of rain since early March. About 1.3 inches were recorded in June with none received so far in July. Temperatures in the upper 90's and 100's, along with high
winds, have added to the severity of the drought.
According to the
USDA-Ne-Crop-Weather report filed by Agricultural Statistics, top soil
moisture for south central Nebraska rated 73% very short, 22% short, and 7%
adequate while subsoil moisture rated 64% very short, 31% short, and 5%
adequate. Irrigators haven't been able to keep up and there is tremendous
concern as we enter into the "HOT" part of the summer. It is almost a
given that surface water irrigators won't be able to stretch their water
supplies beyond mid-August.
Ecofallow corn and sorghum, that was planted into wheat stubble, are starting to show evidence of drought. Many livestock producers are considering early-weaning their calves, heavy
culling of cows, and using alternative feed sources, such as, grazing
standing corn.
USDA's Nebraska Agricultural Statistics Service: Last week's hot temperatures and minimal rainfall pushed wheat harvest, accelerated crop
development, and continued the deterioration of dryland crop conditions, according
to the USDA's Nebraska Agricultural Statistics Service. Localized rainfall was beneficial except
where damaging floods occurred on Saturday in southern Keith and northern Perkins counties.
Grasshopper infestations were being treated when growing crops were affected. Producer
activities included weed control, irrigation activities and harvesting of wheat, oats, and hay.
Temperatures averaged from two to six degrees above normals across the state. Precipitation
was scattered and light across the state, except for specific locations in the west and southeast,
with flooding in Ogallala and in Perkins and Arthur counties.
Irrigated corn condition improved and rated 63% good and excellent, but below the five year
average of 76.
Dryland corn declined and rated 19% good and excellent, well below the average of 69. Crop
development progressed with 7% silked as of July 7, sllightly ahead of last year at 6% and an
average of 5%.
Soybean condition declined last week and rated 5% very poor, 21% poor, 44% fair, 27% good,
and 3% excellent, below last year and average.
Sorghum condition declined and rated 6% very poor, 25% poor, 47% fair, and 22% good, below
last year and average.
Wheat harvest continued at a strong pace about 1.5 weeks ahead of average.
Dry bean emergence slowed with 89% of the crop out of the ground to date, a week and a half
behind last year's 100 and average of 99. Blooms had set on 2% of the acreage, the same as last
year but behind average at 6. Condition declined and rated 16% poor, 37 fair, 44 good, and 3
excellent.
Alfalfa condition declined and rated 15% very poor, 31% poor, 32% fair, 18% good, and 4%
excellent, well below last year and average.
Pasture and range conditions remained below average and rated 32% very poor, 34% poor, 26%
fair, and 8% good. Pastures in many areas of the state are not regrowing after grazing, prompting
some producers to provide supplemental feedstuffs.
The full crop condition report for the week ending July 7, 2002, is at
http://www.nass.usda.gov/weather/cpcurr/ne-crop-weather. Individual county reports are
available at http://www.agr.state.ne.us/agstats/cropwthr/cmts_cur.htm
Check insecticide label before switching to forage or feeding
The drought experienced in much of Nebraska has caused forage and feed shortages for many
livestock producers. The use of corn, sorghum, or soybean for hay, as silage, or for grazing has
the potential to alleviate the forage and feed shortage; however, there are several challenges a
producer must consider before taking this option.
For field corn: Do not feed or graze within 14 days of last application.
For grain sorghum: Do not feed or graze within 28 days of last application.
For soybean: Do not feed or graze within five days of last application.
For corn: Do not feed forage, cut, or harvest within 30 days of last application.
For soybean: Do not graze or feed foliar-treated forage to livestock or cut for silage or hay.
For corn: Do not allow livestock to graze in treated areas, and do not harvest treated corn silage
as feed for meat or dairy animals within 14 days after last treatment. Do not feed treated corn
fodder to meat or dairy animals within 35 days after last treatment.
For grain sorghum: The treated crop is not to be used for grain, forage, hay, or silage within 30
days after application of 1 pint of Lorsban-4E per acre or within 60 days after application of rates
above 1 pint.
For soybean: Do not allow livestock to graze in treated areas or otherwise feed treated soybean
forage, hay, and straw to meat or dairy animals.
For corn: Do not apply within 30 days of harvest for grain and fodder (stover) and 60 days for
forage (silage).
For grain sorghum: Do not apply within 14 days of harvest for grain and fodder (stover) and 45
days for forage (silage).
For soybean: Do not graze or harvest treated soybean forage, straw, or hay for livestock feed.
For field corn: Do not harvest, cut for forage, or graze within 12 days of application.
For soybean: Do not apply within 15 days of harvest or grazing.
Extension Entomology Specialist
Haskell Agricultural Laboratory
Beetles emerging before silk emergence may feed on corn leaves. They feed by scraping the
surface tissue, leaving a white parchment-like appearance. Once silks emerge this is the favored
food. The earliest silking fields in an area often are most heavily damaged as beetles move
around in search of green silks. There are no thresholds for silk-clipping damage based on beetle
numbers because damage levels are not correlated well with beetle densities. Usually an average
of at least 10 beetles per ear are required to seriously affect pollination. Severe silk feeding at
25%-50% pollen shed may indicate the need for an insecticide, especially in seed production
fields. See the Department of Entomology web site for a list of insecticides labeled for adult rootworm control.
Adult western (left) and northern corn rootworms (Jim Kalisch, UNL Entomology) 
Leaf feeding by western corn rootworm adults.
Extension Entomologist
South Central RECAverage number of western corn rootworm beetles present in cornfields that may produce an economically damaging rootworm population in corn the following year. 14,000 1.28 0.64 0.96 0.48 16,000 1.12 0.60 0.84 0.42 18,000 1.00 0.50 0.75 0.37 20,000 0.90 0.45 0.68 0.34 22,000 0.81 0.40 0.61 0.30 24,000 0.75 0.37 0.56 0.28 26,000 0.69 0.34 0.52 0.26 28,000 0.64 0.32 0.48 0.24 30,000 0.60 0.30 0.45 0.23 32,000 0.56 0.28 0.42 0.21 1Based on a 50:50 ratio of females to males. 2Based on a 70:30 ratio of females to males. 3Use this threshold for continuous corn fields that did not have larval populations earlier in the season (adult beetles are immigrants, similar to first year corn). Earworms damaging whorl stage corn
I have received several reports of corn earworms feeding in whorl stage corn in York, Adams,
and Buffalo counties, with 5% to 25% of the plants affected. Corn earworm larvae are variable
in color, from green to brown to pink. They are over 1.5 inch in length at maturity. A key
characteristic visible with a hand lens is the presence of microspines, giving the skin a coarse
appearance.
Extension Entomologist
South Central REC
Controlling weeds after wheat harvest
The 2002 winter wheat crop varied from fair to good in most areas, but there was even some 80
bushel dryland winter wheat. Conditions last fall resulted in good stands and much of the late
planted wheat became well established. The late fall also contributed to increased spread of
wheat streak mosaic. This spring cutworms were present in many wheat fields.
Extension Cropping Systems Specialist
Drew J. Lyon
Extension Dryland Crops Specialist
Gail A. Wicks
Extension Weeds Specialist
Standing wheat may offer highest value for straw
Determining the value of wheat straw left in the field depends on several factors. It may be
beneficial to remove straw from the field if the crop residue was not spread at harvest, making it
difficult to control weeds, including volunteer wheat. Planting in heavy residue also could be a
problem and might lead to poor stands, although that's not very likely with the small amount of
residue produced this year.
Extension Cropping Systems Specialist
West Central REC
Drew J. Lyon
Extension Dryland Crops Specialist
Panhandle REC
Governor releases roadsides for haying
Due to deteriorating drought conditions, all counties in the state have now been released for roadside haying.All Nebraska counties now approved for CRP haying, grazing
All Nebraska counties have been approved for emergency haying and grazing of
Conservation Reserve Program acreage, according to the Nebraska Farm Services Agency office.Free weed-loving beetles
Landowners trying to control leafy spurge on their property may be able to use a free biological
control effort.Farm bill information and updates
Several sources are available on the Web to provide further information about the 2002 farm bill.
They include:
New crop disease publications
to help with field scouting
The extension plant pathology team has developed two new publications to help with field
scouting. The publications are entitled, "Corn Disease Profiles (EC1883)" and "Soybean Disease
Profiles (EC1882)". These are single page publications printed on heavyweight paper with full
color pictures of the top diseases of the prospective crop on one side and descriptions of the
diseases on the back.
Extension Plant Pathologist
Field updates
Andy Christiansen, Extension Educator in Hamilton County: Field borders are being treated for
grasshoppers. The western bean cutworm flight has been large and very similar to 2000 when we
had many acres treated and damaged by this insect. The dryland corners are drying up and alfalfa
and pastures are not producing. Fields began tasseling the week of July 7.
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Published by University of Nebraska Cooperative Extension in the Institute of Agriculture and Natural Resources Cooperating with the counties and the U.S. Department of Agriculture University of Nebraska Cooperative Extension educational programs abide with the non-discrimination policies of the University of Nebraska-Lincoln and the United States Department of Agriculture.
