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Click here to download a printable version of Virginia Soybean Update Newsletter - PDF format
Survey Background: This survey is a cooperative effort that takes place each year to provide Virginia producers with a pest alert regarding corn earworm/cotton bollworm. Each year we sample cornfields in July to determine corn earworm population levels and what to expect when the pest moves from corn into the next series of host crops, which includes soybean, cotton and peanut. Field corn serves as a 'nursery' crop for earworm in July. Larvae feed and develop in corn ears where they are protected from natural enemies (predators and parasites) by the ear shucks. After they have developed, they bore out through the side of the ear, drop to the ground and burrow into soil chambers (about 2 to 3 inches deep) where they form pupae. In about 1 week, adult moths emerge from those pupae and fly to new host crops to lay eggs and begin the cycle again. In the survey we visit most of the major soybean/cotton producing coastal plain counties where corn earworm is a potential pest. We sample up to 5 fields per county, 50 corn ears per field. Survey results allow us to predict what general level of infestation is expected, and to some extent, whether fields will be invaded early or late relative to other years.
2001 Survey Results: Percent corn earworm infestation in corn was lower compared with the previous year throughout most of eastern Virginia (see Table). Infestation levels decreased from an average of about 29% on Eastern Shore in 2000 to about 8%; decreased from 36% to 15% in the mid-eastern counties; decreased from about 27% to 4.5% in the Northern Neck; and decreased from about 26% to 0.2% in the Northern counties surveyed. These 2001 levels are the lowest we have seen in several years. However, we need to be somewhat cautious for two reasons. First, when we initiate the survey, we try to target the time when most corn in the east is at the right stage to sample - when silks are dark and dry. As indicated by cooperators, in several counties (Mathews, Gloucester, Caroline, Spotsylvania) there was a lot of late planted corn and plants were in the tasselling or green silk stages during the survey week. These situations may have resulted in 'false negative' data which lowered overall county infestation averages. We suggest that corn in those counties might need to be sampled again in the next few weeks to determine if infestation levels have increased. Second, although infestation levels in corn were overall very low, there was a lot of variability among fields. This could lead to sporadic and localized differences in both moth activity and incidence of worms in soybean and other crops.
2001 CORN EARWORM SURVEY
Table 1. Corn fields in 31 eastern counties were surveyed for presence and age of corn earworm larvae in ears. Percent ears infested are used to predict infestation severity in soybeans and other crops.
| County | # Fields | # Ears Sampled | 2001 % Ears Infested | 2000 % Ears Infested |
|---|---|---|---|---|
| Eastern Shore | ||||
| Accomack | 5 | 250 | 5.6 | 34.4 |
| Northampton | 5 | 250 | 16.4 | 24.4 |
| Regional avg. % | 8.2 | 29.4 | ||
| Mid-Eastern | ||||
| Amelia | 5 | 250 | 20.8 | 44.0 |
| Charles City | 5 | 250 | 16.0 | 42.4 |
| Essex | 5 | 250 | 8.4 | 20.8 |
| Gloucester | 5 | 250 | 18.4 | 50.4 |
| Hanover | 5 | 250 | 8.8 | 22.0 |
| Henrico | 5 | 250 | 25.6 | 20.4 |
| James City | 5 | 250 | 14.4 | 38.8 |
| King and Queen | 5 | 250 | 20.4 | 35.6 |
| King William | 5 | 250 | 4.0 | 38.8 |
| Mathews | 5 | 250 | 20.8 | 38.0 |
| Middlesex | 5 | 250 | 5.6 | 28.0 |
| New Kent | 5 | 250 | 12.8 | 34.0 |
| Nottoway | 5 | 250 | 22.8 | 60.8 |
| Regional avg. % | 15.3 | 36.5 | ||
| Southeast | ||||
| Chesapeake | 5 | 250 | 22.4 | 48.8 |
| Dinwiddie | 5 | 250 | 27.6 | 55.2 |
| Greensville | 5 | 250 | 45.6 | 82.4 |
| Isle of Wight | 5 | 250 | 18.8 | 54.0 |
| Prince George | 5 | 250 | 15.2 | 32.0 |
| Southampton | 5 | 250 | 24.4 | 67.2 |
| Suffolk | 5 | 250 | 38.0 | 65.2 |
| Surry | 5 | 250 | 17.6 | 56.8 |
| Sussex | 5 | 250 | 12.0 | 46.8 |
| Virginia Beach | 5 | 250 | 42.8 | 45.6 |
| Regional avg. % | 26.4 | 55.4 | ||
| Northern Neck | ||||
| Lancaster | 5 | 250 | 3.6 | 28.4 |
| Northumberland | 5 | 250 | 2.8 | 34.4 |
| Richmond County | 5 | 250 | 3.2 | 32.4 |
| Westmoreland | 5 | 250 | 8.4 | 14.8 |
| Regional avg. % | 4.5 | 27.5 | ||
| Northern | ||||
| Caroline | 5 | 250 | 0.4 | 29.6 |
| King George | 5 | 250 | 0.0 | 22.0 |
| Regional avg. % | 0.2 | 25.8 | ||
The 2001 Virginia Corn Earworm Survey was conducted by Ames Herbert and Mike Arrington (VPI&SU, Tidewater AREC), Donna Tuckey (VCE, Middlesex Co.), Glenn Chappell (VCE, Prince George Co.), Jack Speese (VPI&SU, Eastern Shore AREC), Sam Johnson (VCE, Westmoreland Co.), David Moore (VCE, Middlesex and Gloucester Cos.), Ginny Barnes (VCE, Northumberland and Lancaster Cos.), Keith Balderson (VCE, Essex Co.), Chris Lawrence (VCE, King and Queen and King William Cos.), Paul Davis (VCE, New Kent Co.), Mac Saphir (VCE, Caroline Co.), and Vernon Heath (VCE, Charles City Co.).
A total of 155 corn fields (7,750 ears of corn) in 31 counties were sampled for corn earworm/cotton bollworm between July 19 and July 25.
All stages of worms (small, medium, large, and exited worms) were present at the time the survey was conducted. This population 'age structure' indicates that moth flights out of corn may be erratic and occur over a longer period of time. This may make threshold determinations more difficult (see below).
Survey Predictions: Based on the survey results, we should expect relatively light infestations in most soybean fields. However, because of the situations mentioned above, the possible 'false negative' corn fields and the variation in infestation levels among corn fields, we can expect a lot of variability with some fields having moderate, even high levels of worm pressure. Because of the relatively low, erratic, and all-worm-stages population, we can expect field thresholds to develop slowly and be less pronounced. This may mean a few extra field visits, but it will also mean that field scouting, if done well, will pay off by allowing producers to protect fields at risk but save inputs on fields below threshold.
Blacklight Trap Catch (see attached Table): Moth catches are increasing very slowly and are somewhat behind compared to this time in previous years. Moths are just now beginning to move out of corn at the Tidewater Center here in Suffolk. We expect to see numbers increasing in most southern locations by the end of next week, and by the following week north of the James. Weekly moth trap catch summaries will be available at all Virginia Cooperative Extension county offices through mid September. Call your local office for weekly updates, or access my home page at http://www.vaes.vt.edu/tidewater/faculty/herbert/advise.html, or contact Linda Byrd-Masters at 1-757-657-6450, ext. 126 for assistance.
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August is the time of the year when we often see signs and symptoms of insects, diseases, or nematodes that attack the soybean crop. Although many of these pests are present every year, economic infestations are not usually widespread. Regardless, below is a diagnostic guide that my help with identifying the culprit. Remember, the diagnosis of disease and nematodes should never be based solely on symptoms, because they can resemble problems cause by nutrient deficiencies, poor drainage, drought, or other pests. Laboratory analysis is usually needed. Virginia Tech's Plant Diagnostic Clinic can provide some analyses.
Pods are damaged or lost
Leaves and/or stems are physically damaged
Leaves and/or stems discolored and/or stunted
Plants stunted with possible abnormal growth
Plants in spots of the field remaining green past maturity of the rest of the field
Plants are wilted or dead
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I've noticed a general increase in the number of soybean 
fields in Virginia that show virus-like symptoms (Figure 1). In many cases, these symptoms are cause by herbicide or other factors. But, in others, we have identified the problem as a virus. Although, soybean viruses have not caused widespread yield losses for Virginia growers, their incidence may be on the rise.
There are about 50 viruses reported to infect soybeans and cause symptoms such as stunting, yellow or crinkled leaves, green stems late in the season, and mottled seed. While such symptoms can indicate presence of a virus, few of these symptoms are sufficiently distinct to diagnose which virus is present. Plus, infection and degree of symptom will vary with variety and the time at which the plant became infected. Therefore, symptoms alone are not sufficient to identify the virus; serological laboratory techniques are necessary to correctly classify the disease. Serological laboratory techniques measure the reaction of viral particles in leaves or seeds with antibodies that are specific for that particular virus. Although Virginia Tech's Plant Disease Clinic does not run specific diagnostic tests for viruses due to the expense, several commercial companies will conduct a diagnosis for a fee.
The viruses most likely to be encountered in Virginia are soybean mosaic virus (SMV), peanut mottle virus (PMV), and bean pod mottle virus (BPMV). Other viruses such as tobacco ringspot virus (TRSV) and tobacco streak virus (TSV) that causes the disease known as bud blight may also be found, but are less common. Below are excerpts from Dr. Sue Tolin's chapter on soybean diseases in the Virginia Soybean Production Guide.
Soybean mosaic virus (SMV): Mosaic is the most widespread viral disease of soybean. Symptoms vary with variety but leaves generally have a light-green/dark-green mosaic pattern and are no longer flat but have raised areas and a blistered appearance particularly between veins. Leaf edges are wavy or curled downward, often narrowing the leaf surface considerably. Plants may be stunted and have fewer pods. Pods that do develop are often smaller and in many cultivars have no hairs giving a shiny appearance. There are fewer seeds per pod, and seeds are often mottled. Soybeans become infected with SMV from seed, which contain virus, or by aphids, which spread the virus from one plant to another. Control of SMV is through elimination of virus-infected seed lots, and by resistant varieties.
Peanut mottle virus (PMV): When soybean are grown in close proximity to a peanut field or following peanut, PMV may be present. The virus is inoculated to soybean by aphids, which pick up PMV from peanut, in which it is seed borne but causes very mild symptoms and nearly no yield loss. PMV has also been found in several weedy leguminous plants. Symptoms of PMV on soybean are similar to those caused by SMV, except that leaves show more distinct yellow or green patches or rings and are not as extremely blistered or curled as are SMV-infected leaves. Seeds can be mottled, depending upon variety. PMV can be controlled by use of resistance varieties.
Bean pod mottle virus (BPMV): Soybean leaves infected with BPMV show a slight pucker and fine pattern of green and pale-green areas between the fine, tertiary veins. Foliar symptoms are very difficult to distinguish from those caused by SMV. Plants infected with BPMV may have green stems after the pods have matured, and may retain petioles after leaves have fallen. If plants are infected by both BPMV and SMV, yield losses are much more severe than those caused by either virus alone. BPMV infections are the result of virus transmission by several species of leaf-feeding beetles. Bean leaf beetle is the primary vector in Virginia. There is no evidence of transmission of BPMV through soybean seeds, although virus can be detected in seed coats. Thus the virus source is postulated to be perennial hosts such as Desmodium or overwintering beetles. BPMV incidence was once concentrated in the mid-south soybean-growing areas, but in recent years has spread into the mid-western states. Its incidence is also increasing in Virginia and middle-Atlantic regions. There are no cultivars of soybean that are resistant to BPMV. Having SMV resistance will decrease severe losses caused by dual infection with the two viruses.
Other Viruses: Tobacco ringspot virus (TRSV) and tobacco streak virus (TSV) may be associated with plants showing symptoms of "bud blight" in which the terminal growing point curves downward and dies. Pods on such plants are often very limited in number and may be filled by only one, large seed. The main stem usually remains green, but leaves and petioles fall off. Both viruses are known to be transmitted through seed, and has been reported to be carried between plants by various species of thrips. Both viruses have an extremely wide host range and may be harbored in any of several perennial, dicotyledonous plants surrounding or in soybean fields. However, no recent work has been done to confirm these reports though the symptom is becoming quite prevalent. No work has been done on assessing cultivars for resistance or susceptibility.
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But, which piece of equipment should be used to plant the soybeans? We have long known that reducing the row width of soybean from 30 or greater inches to less than 20 inches will increase our yield. Although additional yield increases may be realized by further reductions in row width, the data for this is inconsistent. In my research, an additional yield increase of 4 to 10% was obtained by narrowing row width from 18 inches to 9 inches over a wide range of populations. Therefore, there may be a benefit to using the drill versus a narrow-row or split-row planter for soybeans.
However, in my experience, a drill does not uniformly meter the seed out. Versus a planter, the soybean stand from a drill is spotty and non-uniform. My row spacing research was conducted using the same planter and the stands were uniform, regardless of row spacing. Because of the potential of more gaps between soybean plants seeded with a drill, the yield increase that I showed with drill-width rows may not be realized. I've also observed that to make up for this spottiness, producers generally plant more seed with a drill versus a planter in order to compensate for the created gaps. This of course increases seed costs. So, again I ask the question, which is the best combination of planters and drills that will utilize all equipment to its fullest potential and be most profitable?
At the Soybean Field Day hosted by the Eastern Virginia Agricultural Research and Extension Center (EVAREC) in cooperation with the Virginia Soybean Association and local agribusiness, we intend to provide some information that can answer this question. At this field day, one will be able to see large, replicated field plots that compare a Kinze 3600 23/12-row planter, a Great Plains Solid Stand 1200 no-till drill, and the newly introduced Great Plains 1520P "Precision Seeding System."
The Kinze planter would be able to plant corn in 30-inch rows and soybeans in 15-inch rows. I've noticed a move back to using this type of split-row planter for soybeans throughout the nation. I began seeing the move back in the mid-90's when I was located in Nebraska. Growers generally were not happy with the soybean stand they were getting with drills and they felt that it was affecting yield. Now, I'm seeing that same logic working in Virginia. Clearly, the metering system of a drill is not up to par with that of a planter. But, does it really make that big of a difference?
Enter the Great Plains 1520P, a drill that now has a metering system very close to the double-disk openers. In our stand counts that we made on the plots, we are clearly seeing that this drill is giving stands nearly as uniform as the Kinze planter. Therefore, the metering problem with drill seems to be at least partially solved. Another advantage of this drill is that the manufacturers claim that it can plant corn as well! We're not testing this and I would not assume that this is true. But this possibility increases the value of this drill immensely.
At the field day, Bobby Grisso, Virginia Tech's new Extension Agricultural Engineer, will go over the differences between the planters, and their advantages and disadvantages. He will also discuss techniques to properly set and adjust the equipment. All equipment used to plant the plots will be present at the field day. I will present information on our past research comparing row spacing plus look at the stand differences between the plots. Participants will also be able to view these stand differences for themselves. We've also planted all plots at 5 and 7 mph, so the effect of planting speed on emergence can be evaluated.
But even if the precision drill does all that it claims to do, is it the more profitable option? Or is utilizing a no-till drill for soybean and wheat plus a standard 30-inch planter the most profitable? Or will using a standard drill for wheat plus a split-row planter for corn and soybean come out ahead? That's what we're trying to find out. Therefore, at the field day, J. D. Hutcheson, Extension Farm Management Agent, will present an economic analysis of these three scenarios. Assuming the 1520P will be able to seed all three crops may be a big assumption, but such an assumption may be needed; seed savings over a regular drill and yield increases over either the drill or planter may not alone justify its purchase at today's crop prices. Of course, we will not yet have yields of the plots, but some assumptions will be made. A final analysis of this year's research will not be completely until the winter. I hope to repeat this experiment next year also in order to be more confident in our results.
In addition to this tour comparing planters and drills, the field day will also include a second morning tour centered on soybean variety selection and pest management. Highlights of this tour includes an introduction of some public Roundup-Ready varieties by Dr. Glenn Buss, a discussion by Dr. Sue Tolin on viruses in soybean, and a weed management and herbicide injury discussion by Drs. Henry Wilson and Scott Hagood. Dr. Ames Herbert will also be present to present his soybean insect research and give an update on the status of the corn earworm infestation, Virginia's most destructive soybean insect pest. Mr. Glenn Chappell (VCE, Prince George Co.) will round out the morning tour schedule with a demonstration on grain fumigation.
Lunch with be provided and the lunch program will focus on "Fueling Up With Soybean Biodiesel - The Intelligent Answer to Our Energy and Environmental Concerns." Susan Haller, the Virginia Soybean Association's Executive Direction will be the keynote speaker on this important issue. Finally, after lunch, Dr. Glenn Buss will take participants on a quick 1 _ hour tour of the soybean breeding plots at the Center. The EVAREC is the hub of Virginia Tech's soybean and small-grain breeding programs and contains tens of thousand of individual breeding line plots. Areas of emphasis in this tour will be ultra-early maturing, Roundup resistance, low saturated fat, low linolenic acid, and small- and large-seeded food type varieties.
In summary, the Soybean Field Day should be one of the better field days that growers, Extension Agents and Specialists, researchers and crop advisors can attend this summer. Hopefully, many questions can be answered and new ideas communicated. Bob Pitman, Superintendent of EVAREC, along with the field day committee has put together an excellent program that highlights much of the valuable research being conducted relating to Virginia soybean production. The Field Day is scheduled for Tuesday, Aug. 14 at the EVAREC located on Route 690 in Warsaw, VA. Registration begins at 8:00 am and the tours begin at 8:30.
Continuing education units for Certified Crop Advisors have been requested from the Mid-Atlantic CCA Board and Private Pesticide Applicator Licence credits can also be obtained.
 Loading seed into the Kinze 3600. |  The Kinze 3600 23/12 Split-Row Planter. |
 The Great Plains Solid Stand 1200 |  The Great Plains 1520P Precision Seeding System |
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Sincerely,
David L. Holshouser
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