| In this week's Ag News . . . |
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ECB moth flightEuropean corn borer moth flight began across eastern Nebraska last week. Light trap data from University of Nebraska sites can be accessed at: http://www.ianr.unl.edu/ianr/entomol/fldcrops/fldcrops.htmBob Wright, Extension Entomologist, South Central REC |
Initial hatch is very hard to detect in the field, as newly hatched rootworms are very small.
One method to detect hatch is to dig up corn plants, carefully shake off soil from roots and put roots over a coffee can containing water. A coarse wire screen platform can be placed over the top of the can to hold corn roots. As the root dries out rootworm larvae will fall out and drop into the water where they can be more easily seen.
After hatch occurs you should begin to scout continuous corn fields for corn rootworm larvae and damage, regardless of whether a soil insecticide was applied at planting. This will help determine whether an insecticide is needed, if one was not used at planting, and provide a check of the effectiveness of planting time insecticide applications. In case of poor control, this will allow you to apply a rescue treatment before too much damage has occurred.
To check for larvae in a field, dig a 7-inch cube of soil centered on the corn plant. Sample a minimum of two plants at each of five sites in a field. Carefully search through the soil and plant roots for larvae. There are three larval stars (stages). The greatest amount of damage is done in the last stage. Degree-day accumulations needed to complete development of different stages are shown in the table. The first instars are about 1/16 inch long and difficult to find without magnification. Often the first detected rootworms are second instars. Corn rootworm larvae are slender, cream-colored, with brown heads and a dark plate on the top side of the tail, giving them a double headed appearance. Mature larvae are 1/2 inch long. Searching through the soil and roots may be done over a sheet of black plastic to help you see the small white worms. There is no established treatment guideline for corn rootworm larvae, but some consultants advise treating if there are two or three rootworms per plant. The usefulness of this guideline is dependent on your ability to find rootworm larvae in the soil.
Cultivation time treatments of insecticides, if needed, should be applied soon after egg hatch begins. Cultivation time applications of insecticides are an effective means of reducing injury to com plants from rootworm feeding damage. Most planting-time granular soil insecticides (except for Aztec and Fortress) labelled for corn rootworms are also labelled for use at cultivation. Incorporate granules with 1-2 inches of soil after application; effectiveness may be decreased unless the insecticide is incorporated.
Other options include the use of Furadan 4F and the use of chemigation treatments with Lorsban 4E. Control with Furadan 4F generally will be improved if the treatment is cultivated into the soil, unless sufficient rainfall occurs after application to move the insecticide down into the root zone. Lorsban 4E applications should be timed for the first appearance of second instar corn rootworms. Additional information on suggested insecticides, rates and restrictions is available at http://www.ianr.unl.edu/ianr/ entomol/instabls/crwlarv1.htm.
Bob Wright
Extension Entomologist, South Central REC
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Since last September, the northeast, central, east central, south central, and southeast climatic districts received above normal precipitation only in February. The southwest district received above normal precipitation in February and March, and the north central district received above normal precipitation in September, February, and May.
A storm system late last week brought welcome precipitation and limited relief to north central and northeast Nebraska, often with 2-4 inches of rain. Unfortunately, the rains fell over several hours instead of several days, resulting in runoff.
In southern Nebraska rainfall was spotty at best, with most locations south of I-80 receiving less than 0.25 inch. Soil moisture conditions continue to deteriorate. From April 1 to May 19 precipitation has been less than 40% of normal for portions of southwest, south central, and southeast Nebraska. This has more than offset the above normal precipitation in February and the first half of March (see table, below).
The Panhandle has been the one bright spot during this ongoing drought. Precipitation across the northern Panhandle has averaged 150-200% of normal during the last nine months, with the southern Panhandle receiving 100-125% of normal precipitation. Above normal conditions also extend into the western third of the north central district.
The pattern of below normal precipitation is particularly dramatic across the eastern third of Nebraska. Since last September, precipitation in the east central and southeastern climatic districts was less than 50% of normal. Even with the recent rains in the northeast district, precipitation levels are still more than six inches below normal.
In historical terms, we have now entered the 2000 production season in worse condition than at the onset of the 1988 and 1989 drought years. Drought during those two years mainly resulted from a lack of growing season precipitation.
Even with the recent rainfall, 90% of the area east of the Panhandle has been identified as being in a severe drought, according to the U.S. Drought Monitor. Within the severe drought area, portions of Gage, Johnson, Lancaster, Nemaha, Otoe, Pawnee, and Richardson counties have now met the criteria necessary to be placed in the extreme drought category. (This classification requires that September, January, and April to date precipitation be less than 50% of normal.) In addition, rivers are running at 5-15% of historical flow rates in this region.
The Natural Resources and Conservation Service (NRCS) conducted soil moisture tests at 16 locations across the state May 8-12 (see table, below). These tests indicated that at 20 and 40 inches, nine of the sites had soil moisture levels below the wilting point. Of the remaining six sites, soil moisture was above the wilting point, but significantly below field capacity.
While the NRCS data was taken before the recent rains, we believe most locations failed to get recharge penetration down to 20 inches.
Planting progress and crop emergence is well ahead of schedule this year. Ninety-eight percent of the corn has been planted, with 85% of the crop emerged. This compares to the five-year average of 84% planted and 43% emerged. Soybeans are 82% planted and 44% emerged, compared to the five-year average of 35% planted and 7% emerged. Even sorghum is ahead of schedule with 56% planted and 16% emerged, compared to the five-year average of 24% planted and 0% emerged.
With emergence ahead of schedule, crop development is also running ahead of schedule. This means that crops will demand greater quantities of water earlier than expected. Most of the crop is in the late two-leaf to mid four-leaf stage. Evapotranspiration rates will rapidly increase during the next few weeks and crop water demands should approach 0.25 inches per day by June 10.
On average, most locations have less than 3 inches of available moisture. With crops already 7-10 days ahead of the five-year average and temperatures averaging 5oF above normal, this limited moisture will probably be used in the next two weeks. Unless significant moisture falls across southeast and east central Nebraska during this period, significant crop stress is likely.
Moisture stress for dryland crops is likely to be an ongoing factor in the 2000 production season. Crop rooting depths will be limited due to insufficient soil moisture below 20 inches and any moisture that does fall will be extracted more quickly from a smaller root zone.
The seriousness of the current situation has prompted governor Mike Johanns to write Dan Glickman, U.S. Secretary of Agriculture, about providing some fast-track assistance at the national level, if it becomes necessary. The first step would likely be the release of CRP acreage for grazing and haying. The state is still trying to sort out the best way to appease wildlife interests, alfalfa producers, and producers short of quality forage. Instead of releasing entire CRP blocks, forage may be limited to a percentage of qualifying CRP land blocks.
The 2000 production season will be a challenging one, to say the least. If long-lead models continue their accuracy, Nebraska can expect to receive above normal temperatures and below normal precipitation throughout the growing season. These models do offer a ray of hope for next year with a return to above normal precipitation.
Al Dutcher
State Climatologist
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Following several recent storms, some producers are looking at replant options for corn. This early in the season, replanting to corn is still a good option; however, as we move into June, corn becomes less of an option, forcing producers to replant to other crops. Many preemergence herbicides restrict replant options so before deciding what to do be sure to check product labels.
One method of planting into soil containing damaging herbicide residues is to set furrow openers on the planter to remove the surface soil. A heavy rain after planting would negate this technique and may result in the crop being "silted under." Use herbicides only "as needed" on the replant crop.
A sound strategy is to consider potential replant options when choosing a herbicide for a given site. Understanding that herbicide choice with respect to replant options is not always possible, the following table lists planting options based on our judgment for various herbicides with the time delay required between application and planting. These estimates can be influenced by several factors including application rate, soil organic matter content, and pH. Always read and follow the herbicide label.
Jeff Rawlinson
Extension Weed Science
Alex Martin
Extension Weed Specialist
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Alfalfa has matured much faster than usual this spring. For many growers, despite the best of intentions, alfalfa is going to be more mature than planned at first cutting.
At this point, raising the cutting height may be a wise management change. Normally it's best to leave as short a stubble as possible because that maximizes yield and doesn't affect rate of regrowth; however, late cutting is different.
Before cutting, walk into your alfalfa field and closely examine the base or crown of plants. Are short, new shoots starting to grow? These are the new plants for the second cutting. Are many of these shoots two or three inches taller than your usual stubble height? If you cut them off along with the first growth, your alfalfa plants will have to start a whole new set of shoots for regrowth. This could delay regrowth for the second cutting by as much as two weeks.
To avoid this delay, raise your cutting height a couple inches to avoid cutting most of these new shoots. Plus, the stubble you leave behind has quite low feed value anyway, so the yield you temporarily sacrifice is mostly just filler.
StorageTo maintain its nutritional value and worth store hay in a location and in a manner that will minimize nutrient losses caused by weathering. High value, high quality hay that will be sold or fed to high value animals like dairy cows and horses should be stored under cover. A hay shed, a partially used machine shed, an unused corn crib, or any other shelter with a roof will be better than exposing your hay to what Mother Nature dishes out this summer. Next best may be tarps, especially heavy-duty ones that can be tied down without tearing in the wind. Plastic also works, but it takes special care to fasten down plastic well enough so it doesn't get ripped during storms.
If uncovered storage is your only option, place bales and stacks on an elevated site with good drainage so moisture doesn't soak up from the bottom. Don't stack round bales or line them up with the twine sides touching — rain will collect where they touch and soak into the bale. Be sure to allow space for air to circulate and dry hay after rain.
Bruce Anderson
Extension Forage Specialist
An NU wheat plot tour will be 6 p.m. June 6 at Verle Schoenrock's farm in Jefferson County, 3 miles west of Fairbury at 564th Avenue, then 1 mile north to 713 Road, then 1/2 mile west, on south side of the road. For more information contact Paul Hay, Extension educator in Gage County, at (402) 223-1384.
For more wheat plot tour dates and locations, visit the Crop Watch Events page.
We are seeing typical barley yellow dwarf symptoms in both wheat and oats in eastern Nebraska. Kansas has been reporting a moderate level of barley yellow dwarf in their wheat for the last month. We noted symptoms in the wheat plots at Lincoln in early May and recently have been receiving occasional reports of the red leaf symptom in oats.
Barley yellow dwarf is diagnosed in the field when plants appear yellowish to reddish. The plants may be grouped or in a small patch that represent patterns of aphid feeding since this virus is aphid transmitted.
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The first symptoms of infection are yellowish-green spots or blotches near the tips of older leaves. Eventually these blotches enlarge and coalesce, turning various shades of yellow, red and brown. The entire leaf ultimately becomes a reddish-orange to brown or purple. Severely infected plants are shorter, produce lower test weight grain, and have more blasted florets.
Wheat: If winter wheat is infected in the fall, yellowing of leaves usually does not occur until mid-spring. In severe fall infections, some stunting and reduced tillering may develop. Barley yellow dwarf symptoms start to become obvious at about the jointing stage of growth.
Barely yellow dwarf virus does not produce a distinct mosaic pattern, as do wheat streak mosaic virus or soil-borne wheat mosaic virus. The pattern of symptom expression is similar to that in barley or oats.
Leaf symptoms begin as blotches near the tip, and with time these turn various shades of yellow, red or purple. Progression of symptoms is from leaf tip to base and margin to mid-rib. Symptoms are more pronounced under cool temperatures, causing the tips of flag leaves to sometimes become a reddish-purple.
The yellowing in wheat is not as brilliant as it is in barley, and the reddening of leaves is not as pronounced as it is in oats. In wheat, the pale yellowing of older leaves is the more typical symptom. The extent of yellowing, stunting and yield reduction is contingent on whether the plant is infected as a seedling or during post-seedling development. Leaves of some cultivars under some conditions remain green, but plants become stunted.
In the field, barley yellow dwarf first appears in small localized patches that increase in size as more and more infected plants show symptoms. Generally the plants in the center of these patches show more severe symptoms, with the symptom intensity decreasing toward the perimeter.
Early planted winter wheat and winter barley, late planted spring oats, and spring barley are the most susceptible to infection. Younger plants are more attractive to aphids than older plants. Planting winter cereals should be delayed until aphid populations decline to minimize barley yellow dwarf outbreaks. Proper seeding date allows the plants to develop when aphid populations are lowest.
Although early seeding of spring cereals does not give full protection against barley yellow dwarf, it allows plants time to develop past the seedling stage before they might become infected. This delay significantly reduces damage to the crown.
The more tolerant oat varieties such as Blaze, Chaps, Don, Gem, Horico, Jim, Jud, Larry, Ogle, Prarie, Rodeo, Settler and Troy will show subdued symptom expression compared to the susceptible varieties such as Garry, Rodney and Russell.
Insecticidal control of aphids in the fall may reduce the incidence of barley yellow dwarf infections; but if aphids escape the treatments or migrate in from untreated areas, insecticides are of little use except in reducing secondary spread within the field.
Insecticide treatment of spring cereals to control barley yellow dwarf rarely is justified. For insecticides to be effective, application needs to be timed to coincide with the migration of aphids into the field. This is difficult because there is not an adequate system of forecasting migration of cereal aphids in North America.
John E. Watkins
Extension Plant Pathologist
While the dry conditions have held back most foliar fungal diseases, spring black stem could still be a problem in some irrigated alfalfa. Spring black stem is a fungal disease whose peak period is in May when cool, wet conditions occur. The disease occurs on leaves, petioles and stems and can contribute to crown and root rot.
Symptoms include small black spots on leaves, petioles and stems of new shoots. Leaf lesions caused by spring black stem are irregular in shape compared to common leaf spot, which will be circular and small. Stem lesions will enlarge until most of the stem is black and girdled stems will die. The fungus also infects the crown and upper taproot leading to stand thinning and overall decline.
Spring black stem is normally not a problem after the first cutting. The best management option for this disease is to adjust the cutting schedule and harvest diseased fields early to reduce defoliation and maintain forage quality.
StorageTo maintain its nutritional value and worth store hay in a location and in a manner that will minimize nutrient losses caused by weathering. High value, high quality hay that will be sold or fed to high value animals like dairy cows and horses should be stored under cover. A hay shed, a partially used machine shed, an unused corn crib, or any other shelter with a roof will be better than exposing your hay to what Mother Nature dishes out this summer. Next best may be tarps, especially heavy-duty ones that can be tied down without tearing in the wind. Plastic also works, but it takes special care to fasten down plastic well enough so it doesn't get ripped during storms.
If uncovered storage is your only option, place bales and stacks on an elevated site with good drainage so moisture doesn't soak up from the bottom. Don't stack round bales or line them up with the twine sides touching — rain will collect where they touch and soak into the bale. Be sure to allow space for air to circulate and dry hay after rain.
Loren Giesler
Extension Plant Pathologist
How does early planting affect soybean crop development? Normally this is not much of a concern, but with good field conditions this spring some farmers finished their corn planting early and decided to plant their soybeans. There also has been discussion about very early soybean planting - dates before April 15. We don't have a lot of experience with very early planting, so this may be a good year to see how development is affected by planting dates and conditions.
2000 crop development modeled
The table contains projected dates of soybean development for a Group III variety planted at 10-day intervals starting March 1 near Fairmont. The dates were calculated on May 22 using measured weather data up to May 21, forecast weather through May 28, and long-term average weather data for the remainder of the year. The calculations are based on the day length and temperature relationships in SOYGRO and PCYield software developed by J. Jones and his collaborators. Weather data was provided by mPower3.
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Soybean is a "short day" plant. Research in growth chambers shows that soybean develops faster in short days, like those of early spring, and slower in the long days at the start of summer (see Fig. 1). You may have noticed that beans under a street light or by a road sign stay green longer in the fall. The lights make the plant believe days are longer than they really are, and crop development is slowed. In the field, away from the lights, temperature is the practical concern, not daylength. Even though days are shorter in March and April than in May (Fig. 1), cooler temperatures increase the number of calendar days between planting and flowering for the very early plantings. There can be a juvenile phase, starting at emergence, in which the plants wait before sensing daylength, but the juvenile phase is probably short or non-existent in varieties adapted to Nebraska. The table gives estimates for the date of flower induction - the time buds start their development into flowers. Flower induction is a hidden step because it happens chemically inside the cells. The speed of development from flower induction to flowering depends on growing degree days. Cooler weather will lengthen the period.
Weather plays a big role in the success of an early planting date. The chance of a freeze is low now, which is good news for those who planted early. Soil temperatures are warmer than average so beans should be germinating and emerging faster than last year. Farmers who planted their soybeans early are encouraged to observe and record crop growth stages this season. Watch for the date the first flowers appear and count the number of fully expanded leaves on the plant. Also note when pods and seed first form at the top four nodes of the plant. These observations will help you understand how well the development of the crop matches your particular environment.
For further information on soybean development, see: http://www.oznet.ksu.edu/__library/crps12/samplers/c449.htm or http://hancock134.exnet.iastate.eud/agriculture/soybean/bean_develop/.
Robert Caldwell
Extension Croping Systems Specialist
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The Entomological Society of America has published several insect handbooks which would be of use to producers and consultants.
The Handbook of Corn Insects provides growers and the experts that they rely upon with comprehensive information on preventing, detecting, and controlling insect pests in corn. With contributions from 37 entomologists who are experts in corn Insect pests, the handbook includes the latest techniques in corn pest management. It also features color photos of insects and insect injury, distribution maps, illustrated growth charts, a glossary sources of local information, and an important section on biological control. The book is 164 pages.
Other publications in the series are: The Handbook of Soybean Insect Pests, The Handbook of Turfgrass Insect Pests, and The Handbook of Household and Structural Insect Pests.
Cost is $35 for 1-4 copies, $24 each for 5-25 copies; $21 each for 26-50 copies; and $18 for 50+ copies. Shipping and handling is $5 for the first item and $1 for each additional item.
To order contact the publisher:
Bob Wright
Extension Entomologist, South Central REC
Imagine planting early spring, or even late fall, into cold soil and having the seeds lie there until the weather warms up later in the spring. Then the crop germinates and starts growing like it had just been planted. Though not yet on the market, that's the idea behind an exclusive new polymer seed coating being developed by IntellicoatTM Corporation of Menlo Park, California. The polymer coating prevents the seed from absorbing water when the temperature is cold enough to cause biological damage to the seed.
The coating, a fatty acid polymer made from corn and soybean oils, takes about 250 to 300 heat units to activate and allow water to penetrate the coating for absorption by the seed, according to Claude Butt, senior agronomist for Intellicoat. This delays germination by about 14 to 18 days when used in early May or about 35 to 60 days if planted in early March. However, with the warm March experienced this spring, that delay would have only been a couple of weeks. Any treated seeds would have germinated, emerged, and been susceptible to frost.
The breakdown of the polymer coating is heat unit related, not triggered directly by temperature. A series of warm days could lead to the accumulation of heat units, allowing moisture to penetrate the coating, even if the temperature wasn't high enough for germination. The porosity change of the polymer is slightly reversible if the coating starts warming and then cools back down; however, enough moisture may have entered the seed that its viability may be affected, so planting in the fall or very early spring will not be recommended.
Farther north in Canada, where the spring warmup is later and fairly quick, the polymer coating is being used on fall seeded canola, continues Butt. That far north, they have seen the potential for successful fall seeding and spreading the planting workload. But in the Midwest, there are too many warm days in February and March to consider fall seeding. For now, Intellicoat is focusing on relay cropping soybeans with wheat, planting coated soybeans into growing wheat about the first week of May before the wheat is heading. With the delayed emergence, the soybeans are then growing when the wheat is harvested, allowing double cropping to move northward into the central and northern Corn Belt.
Fielder's Choice DirectTM, an Indiana-based seed company owned by Intellicoat, has on-farm relay cropping research on about 900 acres with 40 cooperators in seven Midwest states, with one site in Nebraska west of North Platte, Butt said. Most of these cooperators are using a system based on 15 inch row spacing to allow room for interseeding soybeans into the growing wheat. With the higher rainfall of the eastern Corn Belt or with irrigation in the western Corn Belt, this would allow two crops in one year. (See www.relaycrop.com for more information.)
Butt reported that the Intellicoat Corporation was surprised at the interest producers had in using the polymer coating for early planting of both soybeans and corn to spread the planting workload. They have a couple of university trials this year and hope to do on-farm research next year. A coating may be available spring 2002 for several crops. They are experimenting with different additives to the coating, exploring options such as Rival and Vitavax for disease protection on soybeans and nutrients on corn.
About 15 to 20 seed corn companies are trying an Intellicoat coating this year on male inbreds used in seed production. This allows seedcorn producers to plant both the male and female inbreds at the same time, saving atrip across the field and guaranteeing that the male rows get planted in a timely manner. The coating delays the germination and emergence of the male rows to match pollination to silking. By varying the thickness of the polymer coating or by mixing with some uncoated seed, the pollination period can be extended.
The polymer seed coating has to be uniform on all sides of the seed to provide predictable and reliable delays in germination. Treatment involves spraying on the coating in a seed tumbler and using low heat drying.
The price of the seed coating has not been determined. Producers will have to balance the cost with the agronomic and machinery management benefits of an extended planting season.
Paul Jasa
Extension Engineer
Producers should begin scouting corn for common stalk borers when 1,300-1,400 growing degree days have accumulated,using a 41° F base.
With current prices for insecticides and beans, it would take approximately four to six beetles per plant to justify a treatment. Resist the temptation to throw in an insecticide with your Roundup (if you have Roundup Ready beans) just because it is convenient. Save some money and use economic thresholds to determine when treatment is most cost effective. Refer to the April 21 Crop Watch for treatment thresholds.
Winter wheat condition varies tremendously across the counties. Some fields have really shown the affects of WSMV the last 10 days or so. Fields at higher elevations have also been stressed and damaged by the freeze here May 13-14.
Alfalfa weevils continue to devour alfalfa and there has been much early harvesting and spraying. Flea beetles have been reported in corn, but numbers are not too heavy Corn and soybeans are quickly developing as are weeds.
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