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Index

• Dear Reader
• Diagnosing Problems in Soybeans
• Revisiting Integrated Pest Management
• Considering Fungicides?
• Manganese Deficiencies
• Soybean Rust Education Meetings

Dear Reader,

Maybe you bought a new drill this year and you're learning that setting it properly and running at the right speed is more critical than you thought. Maybe you've acquired some new land and problem areas are showing up. Maybe you should have controlled those weeds earlier. Maybe you're very pleased with a practice that you just implemented this year. The list goes on.

Most importantly, are you learning from your observations? July is a very good time to look over the soybean crop you've established, diagnose problems, and make good decision on how those problems can be overcome in the future.

In this issue, we'll focus on certain issues that might arise this summer and how decisions made regarding those issues can affect your bottom line.

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Diagnosing Problems in Soybeans

Most of our crops are at least a week ahead in their development this year. Corn is tasseling, cotton is flowering, and peanuts are pegging. Most of this early development is due to our unusually warm April and May. Soybean development is less affected by temperature. Instead, flowering is driven by photoperiod. When the days become short enough, flowering is initiated. Then, temperature takes over. So our soybean development is not necessarily ahead of schedule. But growth (in the areas with sufficient moisture) is good. If we can continue to receive some timely rains, the potential is there for another good crop.

But, all of our soybean fields are not looking that good. Why? Of course the answer to that question is field specific. You can sometimes solve the problem through a review of the field history, practices implemented this year, or by plant symptoms. In other cases, soil and/or plant samples may need to be sent to a laboratory for analysis. Diagnosing field problems can be a challenge. Visual aids can be of great value. Probably most important are the questions asked. Signs and symptoms don't always follow the textbook. Patterns don't always exist. But, by following some general guidelines, one can be quite successful at diagnosing problems. Below are some guidelines that I use.

Preliminary Fact Finding. Obtain information on each of the following:

• Cropping History (for at least the two previous growing seasons). What crops were planted? What is the typical rotation? Is this the first year that soybeans were grown in this field? Tillage used? Fertilizer, lime, and chemical applications? Any past problems with this or other crops in this field?
• Soil Information. Find out soil texture and classification. A soil map would be handy. Soil test results (Soil pH and levels for P, K, Ca, and Mg) are valuable. Plant tissue test results (major plus most secondary and minor nutrients) may be needed. What were the fertilizer and liming practices (time, rate, and method of application) for this season?
• Weather. Rainfall amounts, temperature, relative humidity during growing season are valuable. If chemical injury is suspected, then identify rainfall patterns (amounts, dates, light vs. heavy, etc.) and temperatures of soil and air before, during, and after application. What was wind speed and prevailing direction during and after the chemical application?
• Pest Management Information. This includes all herbicide, insecticide, fungicide applications and rates for this and the previous crop(s). Other valuable information includes past soil nematode assay results (species and population levels) and major weed or insect problems.
• Tillage and Other Cultural Practices. What were the planting procedures and equipment used? What was the soybean variety? Is the seed tag available? Saved seed? What was the germination?

The Field Visit. After obtaining as much information as possible before going to the field, follow the general guidelines listed below:

• Materials and Equipment Needed.
• Notebook, paper, pencil, complaint or diagnostic forms
• Mobile phone
• Camera and accessories. Digital cameras are excellent because images can be quickly emailed to specialists.
• Shovel or spade, pocket knife, trowel, other digging tools
• Soil probe, plastic mixing pail, soil sample boxes or bags
• Plastic bags for plant samples that need preserving, paper bags for plant nutrient analysis samples
• Reference books, product labels, other visual aids
• Penetrometer or other soil compaction measurement device (soil probe, pocket knife, metal surveying flag
• Pocket ruler, yard stick
• Magnifying glass, hand lens
• Windshield / Whole Field Investigation. Before looking at plants in the field, try to get a feel for the problem over the entire field. Are there any patterns or trends to the injury? Check neighbor's fields or other soybean fields on the farm.
• Above-Ground Inspection. Identify the soybean growth stage. Know the types of problems that can be experienced at this stage. Did the problem occur in the past or is it ongoing? All affected plant parts should be identified and noted. Compare symptoms with those found in a trouble-shooting guide. Note the occurrence of, identification, and growth of weeds present.
• Below-Ground Inspection. Check the soil texture, condition, moisture, hardness, etc. Inspect the root system. Dig; never pull the plant to inspect the roots. Pulling will dislodge roots and nodules. Is plant well nodulated? Are roots malformed or injured? Check for compaction.
• Take the Appropriate Plant or Soil Samples. In many if not most cases, you will not be able to fully diagnose the problem. Take plant and soil samples from the affected and unaffected area. Follow directions on diagnostic forms (see below). Remember, if taking a plant sample, dig up the plant (never just pull the plant from the soil). If you can hand deliver the sample, include the soil around the roots.
• Documentation. Record information in writing. This doesn't have to be written up as you are diagnosing the problem, but document the evidence before leaving the site. Use a prepared form (University, industry, or self-developed). Fill it out completely. This may be the only opportunity to gather the evidence, so get all of it on paper.
• Equipment Check. If you suspect that the problem may be related to a piece of equipment such as a planter or sprayer, then it would be wise to look at it. Check the general mechanical condition, settings, and spacing.
• Interaction with the Producer (for agents, consultants, company representatives, etc.) Be courteous and respectful. Approach the situation as a service opportunity to solve a problem. Be positive, but careful in your assessment. Know when you are over your head. Get help when you need it. "I don't know" is response that can gain respect.

Analysis of Data.

• Patterns. Look at any patterns that may be present (i.e., streaks, patterns of emergence, tire tracks, cultivation depth, planting depths, soil types, etc.)
• Look-Alike Symptoms. Many symptoms of nutrient deficiency, nematode damage, and herbicide injury look alike. One may be able to infer from field history information what the symptom can be attributed to. But, in many cases, further laboratory analysis will be needed.
• Interacting Factors / More Than One Problem. In most cases, the problem cannot be attributed to a single factor. Herbicide activity closely follows weather conditions. Nematodes can be more or less severe depending on the weather, soil fertility, or cultural practices. The general soil condition (organic matter, structure, etc.) will affect many other things. Compacted soils will enhance any other problem. Certain soybean varieties are sensitive to particular chemicals or combinations of chemicals.

Drawing a Conclusion. Review the facts and data. Evaluate the data regarding what is normal and abnormal. Eliminate unlikely causes. Validate the likely causes (for instance, streaks in the field are related to spraying, tillage, or planting equipment). Remember, a conclusion may not be able to be drawn in the field, especially if laboratory analysis is needed to confirm your suspicions. However, be prompt with you diagnosis. Solve the problem as soon as possible, so remedial actions can be taken.

Follow Up. If the problem was identified, did corrective actions resolve the problem? Re-visit the field. Gather and read any relevant information such as Extension publications, labels, journal reprints, etc. Forward relevant material to the producer or others involved.

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Revisiting Integrated Pest Management

For some reason, many of us sometimes ignore the consequences of our pest control tactics. I hope this is due to ignorance about the pest and/or agricultural system, and not a deliberate refusal to do what's right. For example, a grower may think that he is solving a problem with an early insecticide application to control a minor pest. There may be sufficient evidence (via research) that such an application is rarely beneficial. But, being unaware of this information, the grower goes ahead with the application. The practice could kill beneficial insects that would normally keep insect pests in check. Without this biological control, additional insecticide applications may be needed. We sometimes refer to this as the "pesticide treadmill." Once you get on it, it's very hard to get off. Plus, the yield loss due to the pest and the extra pesticide applications become very costly. Therefore, know the consequences of any action before taking it. Remember, when you pick up the tail of a snake, its head is at the other end.

Most farmers pay close attention to the economics of their decision. Generally, they will not apply chemicals unless they believe there is a return on their investment. But, in my opinion, here lies the problem ­ belief versus knowledge and understanding. Knowledge is acquired through thorough, conscientious, and reliable research. Belief, on the other hand, can be formed by a good sales pitch. Sometime the sales pitch is backed with data, sometimes not. But, without a clear understanding of the problem, the action taken because of a sales pitch could be incorrect. Only through knowledge and understanding of the pest and cropping system can good economic decisions be made.

There are always sales brochures and other advertisements out there that indicate the use of a particular product will always lead to a return on one's investment. Data is usually shown to back these claims up. But, in many cases, the data has been carefully selected to justify the conclusions (not all data or experiments are presented) or the information is from other regions of the country where pests and environmental conditions are much different. The data may be valid, but it may not be applicable to all circumstances.

My best advice is to beware of information that promises large yield benefits from a strategy that has not historically been used in our state or region. For instance, let's say a product claims to lead to a 10 bushel/acre yield advantage in soybean. Think about this. If your average yields are 30 bushels per acre, this is a 33% increase in yield! Even if you average 40 bushels per acre in certain fields, it's still a 25% increase in yield! Doesn't it seem a little odd that all of a sudden, we have this miracle product? I admit that such yield difference is extreme and few people would guarantee it. But it is not uncommon to hear one promote a 5 bushel advantage. This too is large. I'm not saying that in some parts of the country or under certain environments, such a response is not possible. I'm just saying that if the product shows such an improvement, university or cooperative extension tests would have confirmed it for a state or region.

Also, beware when the ads use testimonials of farmers clear across the country. I value testimonials; they can speak great truths. But, just because a product works well for someone in Louisiana, it doesn't mean it will work well in Virginia. This is especially true for pest management. A disease that is rampant in the Mississippi Delta may only be a minor problem in the Mid-Atlantic due to differences in weather patterns and cropping systems. Controlling weeds may be easier on a high water-holding capacity soil in the Midwest than on a sandy soil in the Coastal Plain where the weeds are under drought stress and don't translocate herbicide as well.

This all gets back the to the IPM definition. IPM uses the knowledge of a pest system to predict the ecological and economic consequences of pest control actions. Those who use IPM will base their recommendations on data and understanding of that data. We in the University and Cooperative Extension are obliged to use these criteria. Unless a practice can be proven by experimentation over time and location, we cannot endorse it. We don't always have the data for Virginia or even the region, but we usually have or can acquire the knowledge and understanding from someone with data. We also know how to interpret the data in a nonbiased way; many do not.

In summary, think about the consequences of your pest control actions. Ask yourself these questions. Will such an action consistently result in an economic benefit for my farm? Could this action cause future problems down the road? Is there local, unbiased data to justify the action? If so, is the data interpreted properly? Do experts or specialists in that field agree with the conclusions drawn from the data? If you can answer "yes!" to all but the second question, I would say that the consequences of your action will be positive. If not, then you should reevaluate your decision to act.

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Considering Foliar Fungicides?

First, let's address the need for fungicides if soybean rust were to arrive. That issue is simple. We have no other means to control rust other than fungicides at this point. Therefore, fungicides will be needed if soybean rust arrives in Virginia. But, what about other diseases? Would fungicides be beneficial even in the absence of rust? Soybean rust has many reconsidering fungicide applications. But, just like soybean rust, we shouldn't think that just because the disease is present in our region that we should be making a blanket application of fungicide to all of our acres.

What about the need for foliar fungicides on seed beans? This "insurance" treatment will generally improve seed quality, especially for full-season soybeans that are maturing during warm and moist conditions. Still, the best way to insure good seed quality in Virginia is to use a double-crop system and harvest in a timely manner. By pushing the maturity and dry down of the soybean into a cooler part of the fall and harvesting the crop soon after it matures, one can usually avoid seed quality problems. Even in 2002 when our seed quality greatly suffered, our double-crop soybeans faired well. But, seed producers may still want to consider fungicides. Seed beans are more valuable. Fungicides are an insurance treatment. If growing this crop in a full-season production system, if a timely harvest cannot always be expected, and if the producer has had seed quality problems in the past, then foliar fungicides may be warranted.

Now, let's address the rest of Virginia's acreage. In general we don't have a regular problem with foliar diseases. We don't use an early soybean production system that puts the reproductive stages into the warmer, more humid times of the growing season. We don't widely irrigate. Still, soybean disease is often present.

I occasionally seed frogeye leaf spot, but not in damaging levels. Brown spot and downy mildew are non uncommon, but again, not usually present in damaging levels. In 2002, we had some late-season infections of Cercospora leaf blight in several locations; I saw it once in 2003. This disease is more problematic when rainfall and humidity are high in late summer and early fall. Other foliar diseases such as aerial blight are sometimes mentioned in fungicide labels or other places. But, I've not seen that disease in Virginia. Although I see soybean diseases every year, most fields do not warrant a fungicide.

Below are descriptions of some common foliar diseases that might occur in Virginia. But a warning should be issued here. Be very careful trying to identify any disease by visual symptoms. The only sure way to identify a disease is to have it diagnosed by a trained plant pathologist at a disease diagnostic lab.

Brown Spot/Septoria Leaf Spot. This fungus (Septoria glycines) caused irregular, dark brown spots that range in size up to 4 mm or about the size of a pencil lead. Spots are on the upper and lower surfaces of leaves. The individual spots will grow together forming irregular shaped, brown blotches. Infected leaves will yellow and eventually drop from the plant. Symptoms will first develop on the lower leaves and progress upward during warm, wet weather. Yield losses have ranged from 8-15%. The disease is most severe when soybeans are grown continuously in the same field or not rotated with a non-legume crop. Soybean varieties vary in their susceptibility, but there is no known resistance. Control via tillage has not been consistent. To manage the disease, rotate to a non-legume crop.

Brown Spot, photo from U.S. Soybean Diagnostic Guide, United Soybean Board

Downy Mildew. This disease (Peronospora manshurica) is common, but is seldom of economic importance. Symptoms appear as light green to yellow spots on the upper surface of the leaflet. The spots can enlarge into yellow lesions and turn grayish to dark brown. On the lower surface, grayish tufts of mold grow during moist weather. The disease could be confused with other foliar diseases in early stages, but the mold on the underside will give it away. Pods can become infected and result in seeds having a thin crust of mold growth on the seed coat. There is some variety resistance, but is not usually listed on seed company brochures due to its relative non-importance. It can be managed by rotation.

Downy Mildew, photo from U.S. Soybean Diagnostic Guide, United Soybean Board

Frogeye Leaf Spot. Sometimes called Cercospora leaf spot, this disease (Cercospora sojina) occurs primarily on leaves, but sometimes stems, pods, and seed are affected. Symptoms are very small circular to angular spots that develop on the upper leaf surfaces. At first, the spots are dark and water-soaked in appearance. Later, the center becomes light brown to gray and is encircled by a dark reddish brown margin. These lesions may merge and drop out, giving the leaf a shot-hole appearance. If 30% of the leaf area is covered with lesions, a blighting phase can occur and leaves will wither and fall off the plant. Warm humid weather encouraged disease development. Young leaves are more easily infected; few lesions will develop on older, fully expanded leaves. The disease can be managed by using resistant cultivars. The disease can also be controlled with fungicides. Since the fungus survives on infested seed and residue, rotating out of soybean for 2 years is valuable.

Frogeye Leaf Spot, photo from U.S. Soybean Diagnostic Guide, United Soybean Board

Cercospora Leaf Blight. This is the same disease that causes purple seed stain. Cercospora kikuchii develops under warm and humid environments that are common to Virginia and the southeastern U.S. Cercospora blight and leaf spot has been reported to cause 15 to 30% yield loss in Brazil. It is not unusual to see symptoms of the disease in Virginia, but has not generally been a problem. The first visual symptoms appear during seed development. Upper leaves develop light purple areas that later become reddish purple, angular to irregular lesions on both the upper and lower surfaces of leaves. Severe infections result in defoliation in the upper leaves. This defoliation is sometimes mistaken for senescence; however, green leaves will remain below (just opposite of normal senescence). Although the same organism causes purple seed stain, foliar symptoms are not consistently related to stained seed. There is some variety resistance, but most seed companies do not list it in their publications. Fungicides are available for control.

Cercospora Leaf Blight, photo by David Holshouser.

Some Guidelines for Foliar Fungicide Applications. First and most important, foliar fungicides should not be applied unless the disease is present. There is no evidence of benefit from fungicides when diseases are not present. One should never make a blanket application to fields when they have not been scouted and there is no sign of disease. Virginia soybean growers should not take the "better safe than sorry" attitude. Soybean rust is not present yet and most other foliar diseases do not usually cause problems for us.

I've heard rumors that some are considering including a fungicide with their insecticide spray, or vice-versa. This is even more disturbing. Applying insecticides when they are not needed is a very good way to flare future problems, especially corn earworm. Beneficial insects and disease can keep insect pests in check. Killing the beneficials can lead to severe and costly pest problems. In addition, widespread pesticide applications can lead to resistant pest populations and we wind up losing the product due to lack of control. Reckless use of pesticides goes against every principle of IPM.

The following guidelines are suggested if considering fungicide applications in soybean. Keep in mind that most of these suggestions come from the Delta where disease problems are much higher than in Virginia. As stated earlier, we generally do not need fungicides for Virginia soybeans that are not to be sold as seed.

1. Scout the field and determine any problem.
2. If you discover a problem, consider fungicide applications if yield potential is high or if growing soybeans for seed.
3. Chose the best fungicide for your problem. There are only a few products labeled (see table below). Information from Arkansas and Louisiana indicate that Topsin-M, Quadris, and Bravo will control most disease, but Topsin-M works better on Cercospora and Frogeye leaf spot. Topsin-M does not control soybean rust.
4. Timing ­ Most labels say to apply between the R3 (early pod) to R5 (early seed), but it is more important to have the fungicide on the crop during wet conditions. Drought is not conductive of disease development, so don't apply under drought conditions.
5. Single vs. two applications. In Louisiana, when disease is present, yield increases ran from 3 to 5 bushels with a single application and 4 to 7 bushels with two applications. However, they found that a single application at the higher rate was more economical.
6. Spraying a fungicide will increase time to harvest, but only if diseases were present. Fungicides themselves do not cause the delay in maturity. Fungicides prevent diseases and allow the plant to live longer. If disease is present, fungicide could delay harvest by a week versus not spraying.
7. Application Volume. The more water the better for fungicides. Use at least 5 gallons by air and 15 gallons by ground. The products need to stay on the plant at least 4 hours. Hollow-cone nozzles are better than flat fans.

One final note is in order. If you see any of the diseases described above develop in your crop this year, consider changing varieties. Many varieties have some resistance to disease. This is the best preventative measure that we can take.

Foliar Applied Fungicides for Soybeans

Disease	Trade Name	Common Name	Rate (product/acre)	Application Direction / Remarks
Anthracnose, brown spot, Cercospora leaf blight, frogeye leaf spot, pod & stem blight, purple seed stain	Bravo Weather Stick® Bravo Ultrex®	chlorothalonil	1.5 - 2.25 pts. 1.4 - 2.2 lbs	Make first application at early pod set (R3, when the majority of the pods are 1/8 to 3/8 inch in length) and the second at beginning of seed formation (R5) which occurs about 14 days later. Bravo may be applied through sprinkler irrigation equipment. Do not exceed total of 3 applications or 6 pints per season. Do not apply within 6 weeks of harvest. Do not feed to livestock or allow grazing of treated fields.
	Quadris® Flowable	azoxystrobin	12.3 - 15.4 oz	Quadris applications should be made prior to disease development. Use the high rates under conditions favorable for severer disease pressure, dense plant canopies, or when susceptible varieties are planted. Applications may be made by ground, air or chemigation. No more than 2 foliar applications should be made per growing season. Do not make more than 1 application at 15.4 fl. oz. to soybean forage or hay. Do not apply within 14 days of harvest (seed).
	Topsin® M 70WP Topsin® 4.5FL Topsin® M WSB	thiophanate-methyl	0.5 - 1.0 lbs. 10 - 20 fl oz. 0.5 - 1 lbs.	Apply from full bloom to when pods are 1/8 to  inch. Make a second application 14 to 21 days later. Do not make the second application later than 14 days after pods average " in length or when beans form in the pod. Use the high rate under severe disease pressure. FOR SEED BEANS ONLY - For seed quality, make a single application at the high rate (1 lb per acre) when beans form in the pod.
Soybean Rust	Quadris® Flowable	azoxystrobin	6.2 to 15.4 fl oz	See remarks above. A non-ionic surfactant is recommended for the lower use rate for improved rust control.

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Manganese Deficiencies

• Scout your fields. Mn deficiencies may or not materialize. The only sure way to determine a deficiency is to observe the deficiency symptoms. The characteristic symptom is yellowing between the veins on new leaves. Mn is an immobile nutrient. Therefore, it will not move out of older leaves to the new leaves. Symptoms will appear when the plant can no longer extract sufficient amounts of the nutrient from the soil. The typical symptom is shown above.
• If Mn deficiencies are suspected due to high pH and no symptoms have yet appeared, you may want to consider taking a tissue sample. This can reveal deficiencies before symptoms appear. I would suggest this especially if lime was recently applied.
• To overcome a deficiency, apply 1/2 lb chelated Mn (elemental basis) or 1 lb inorganic Mn (elemental basis) per acre to foliage upon appearance of symptoms and prior to flowering. More than one application may be required to correct a severe deficiency.
• Note that many Mn products recommend applying lower rates of Mn. However, the label usually states that these are maintenance rates. Once a deficiency occurs, these lower rates will not correct the deficiency and the rates stated above will be needed.
• An alternate method of application can be used. Before a deficiency is evident an on soils that commonly show a deficiency, especially on soils recently limed, a lower rate (~  of that shown above) can be combined with another scheduled application. Such an application may include a postemergence herbicide.
• Be reminded that combinations with glyphosate (Roundup, Touchdown, etc.) will result in reduced weed control of certain weeds. Other herbicides have not shown to interact. This may be a sufficient rate to prevent a deficiency from occurring. But, continue to scout the field and take future corrective measures if deficiencies reappear. Symptoms like that shown on the previous page will still require the full rate. I will remind you that this is a preventative treatment. A deficiency may not occur. Furthermore, these are only maintenance rates and another application will likely be needed if the field is truly deficient.

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Eastern Shore to Host Virginia Ag Expo - August 12

The field day will be held on Woodlands Farm, which is 30 miles north of the Chesapeake Bay Bridge Tunnel and less than 1 hour south of Pocomoke, MD. Over 40 corn hybrids and over 30 soybean varieties are planted and will be taken to yield. There will be field exhibits where companies can showcase their latest products, equipment exhibits, and equipment demonstrations. Business and organization booths will be under cover in a large and handsome farm equipment shed. Lunch will be crab cakes, chicken salad, cole slaw, and potato salad and will be served between 11:00 am and 1:00 pm in what was the Sweet Potato House. There is a $5 pre-registration fee that will be refunded at the event.

If you prefer to travel by water, then you can take advantage of arrangements made for up to 150 participants to travel to the Expo by boat with Captain Rudy Thomas. The boat will leave Reedville by 6:45 am and return from Onancock by approximately 5:15 pm. For more information on the event, please contact me.

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Sincerely,

David L. Holshouser

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