Field Crop News

Website Address: http://fcn.agronomy.psu.edu/

Vol. 96:3

April 19, 1996

IN THIS ISSUE:

Certified Crop Adviser Corner

Production

- Field pH Test Kits
- Agrotain Urease Inhibitor
- Hi-oil Corn Hits the Market
- Alfalfa Frost Heaving: Assessing the Damage

Pest Management

- Pre-Plant Considerations for Alfalfa Insect Control
- Scout for Alfalfa Weevil
- Bt-Corn for Controlling European Corn Borer
- Look for Cereal Leaf Beetle in Small Grains
- Information Sources for Field Crop Insect Management
- Timely Kill of Cover Crops for Successful Corn or Soybean Establishment
- Command 3ME Receives Pennsylvania Registration
- Submitting Weeds for Identification
- Winter Wheat Disease Management

Observations around the Commonwealth

- Northwest

CERTIFIED CROP ADVISER CORNER

Minimum CEU Requirements For Registrants In Their First Renewal Cycle:

Due to the fact that the continuing education program is still under development in many states and sufficient educational opportunities may not yet be accessible to all registrants, the National CCA Board has temporarily relaxed the minimum CEU requirements for Certified Crop Advisers in their first renewal cycle. These are the CCAs that were required to have 40 CEUs by June 30,1996. Now registrants will be required to have at least 20 CEUs in their first two years to renew their certification. Registrants who have more than 20 CEU hours, but less than the
normally required 40 hours, must make up the shortfall plus their regular 40 hours required in the next renewal cycle. For example, if a CCA has 25 CEUs on June 30, 1996, he/she can renew their certification however, they will need to accumulate 55 CEUs during the next two year cycle. Registrants who fail to maintain the required 40 hours in their second renewal cycle, plus any shortfall from the first cycle, will have to petition their state board to remain certified. The local board will then determine if the registrant has made a good faith effort on his/her continuing education or if there are mitigating circumstances. If not, the registrant will be denied the ability to renew his/her certification.

Future Programs: (CEUs will be provided)

Environmental and Economic Aspects of Nutrient Management
June 4, 1996
Lebanon County Cooperative Extension Office
Contact: Peter Bohn, 814-865-3774

Crop Production
June 20, 1996
Landisville Research Station
Contact: Peter Bohn, 814-865-3774

Professional Nutrient Management Workshop
June 24-25, 1996
University Park, PA
Contact: Peter Bohn, 814-865-3774

Crop Diagnostic Clinic
July 23 and 25, 1996
Rock Springs
Contact: Dwight Lingenfelter, 814-865-2242

Conservation Management & Advanced Field Scouting
July 24, 1996
State College, PA
Contact: Elwood Hatley, 814-863-1013

PA Lime, Fertilizer and Pesticide Conference
January 21-23, 1997
State College, PA
Contact: John Ayers, 814-865-7776

Elwood Hatley, CCA

PRODUCTION

FIELD pH TEST KITS

In a recent soil test summary for Pennsylvania almost half (49%) of the samples run for agronomic crops had a soil pH in the low category (<6.5). Over 8% of the samples had a pH of less than 5.5! In spite of the fact that liming is one of the oldest soil fertility practices, low soil pH is still a significant problem in crop production. Thus regular soil testing, including tests for pH and lime requirement are a must. In addition to these regular soil tests, there are situations where a quick check on the soil pH may be helpful in making a management decision. One of the first things that I do when trying to diagnose a field problem is to check the soil pH. Many crop production problems can be related to pH including: reduced nutrient availability, poor root growth, and reduced herbicide activity. A second area where a quick check of soil pH is useful is where there is the potential for an acid roof in reduced and no-till fields. Repeated application of nitrogen fertilizer and manure to the soil surface without mixing by tillage can result in a very low pH at the soil surface. This acid roof may not be apparent in a routine soil sample taken to plow depth but can have significant detrimental effects on the crop and especially on herbicide activity. In this situation a field test kit can be used to check the pH in the surface inch of soil to determine if there is an acid roof.

In these situations a sample could be collected and sent to a soil testing lab for analysis but it is usually more desirable to be able to determine the pH immediately in the field. For this purpose you need a good field pH test kit. There are several different kinds of legitimate field pH test kits available. Following are descriptions of the most common types of field pH test kits that work well for soil testing.

Colorimetric kits. The most common kits are the colorimetric kits. With these kits, a few drops of a chemical pH indicator solution is added to the soil on a spot plate and the color of the resulting solution is compared to a color chart to estimate the soil pH. An example of this is the Cornell pH Kit which is widely used. Most garden stores also carry a similar type of pH test kit. These generally cost from $10 to $15.

Indicator strips. A second type of field pH test kit is based on the use of pH indicator strips. To use this type of test kit, a sample of the soil is mixed with an approximately equal volume of water. After the soil settles a pH sensitive strip is dipped in the water and the color of the strip is compared to a color chart to estimate the pH. These are also available in many garden stores and from scientific supply houses and generally cost from $10 to $15.

pH meters. Finally, today you can buy an actual pH meter that will fit in your pocket. These miniature meters, often called "pH pens", contain a pH sensitive electrode and the electronics just like in a lab pH meter. To use this type of test kit a sample of the soil is mixed with an approximately equal volume of water. After the soil settles the electrode built into the meter is dipped in the water and the pH can be read from a digital display. These meters also have to be calibrated against a known pH standard before use. While these may are also be available in some garden stores it is more likely that you will have to buy these from a scientific supply house. These generally cost from $40 to over $100.

I get a number of questions about where these kits can be purchased. Below is a list of places where these types of field pH test kits can be ordered if they are not available locally. This is not an exhaustive list of suppliers. If anyone knows of other places to buy these kits, let me know and I will add them to my list.

Cornell Nutrient Analysis Labs
Phone: (607) 255-4540

Hawk Creek Laboratory Inc.
Phone: (800) 637-2436

Nasco
Phone: (800) 558-9595

Ben Meadows Company
Phone: (800) 241-6401

Forestry Suppliers
Phone (800) 543-5368

Fisher Scientific
Phone: (800) 766-7000

AGROTAIN UREASE INHIBITOR

There is a new product on the market this year called Agrotain Urease Inhibitor being distributed by IMC-Agrico. This product is a fertilizer additive used with urea and urea based fertilizers to reduce the loss of ammonia when these materials are surface applied.

In the soil, urea reacts in the presence of the enzyme urease to form ammonium carbonate. The carbonate formed in turn reacts to dramatically raise the pH which results in the ammonium nitrogen being converted to ammonia gas. If this reaction occurs on the soil surface the ammonia gas is lost to the atmosphere. Losses of over 30% of the nitrogen applied as urea have been measured in no-till corn in Pennsylvania. If the urea is incorporated into the soil by tillage or rain, the reaction described above occurs but the ammonia formed is trapped in the soil and converted back to ammonium nitrogen thus volatilization losses do not occur.

The urease inhibitor, Agrotain, stops the activity of the urease enzyme for about 14 days. During this time the urea is not converted to ammonium carbonate, thus volatilization does not occur. Consequently, if rain or tillage occurs to incorporate the urea within this 14 day period, volatilization losses should be minimized when the urea finally does break down in the soil. If there will be immediate incorporation of the urea by tillage or rain, there is no benefit from a urease inhibitor.

Research from 295 comparisons conducted over 6 years in 19 states showed a 5 bu/A corn yield advantage from the same amount of urea with the urease inhibitor vs urea alone. This was for all comparisons. When the results are compared only on sites where there was a documented volatilization loss from urea, the corn yield advantage was 6.6 bu/A from the urea with the urease inhibitor compared to the urea alone. In 15% of these comparisons the yield advantage was over 20 bu/A. Using some of the same comparisons it was also determined that an average of 74 lb/A of additional unamended urea-N would be required to overcome the large losses of N that are prevented by using the urease inhibitor. Research by Dick Fox at Penn State, which is included in the summarized data just presented, showed a 14 bu/A advantage to using urea with the urease inhibitor on no-till corn grown under Pennsylvania conditions.

There is also the potential for volatilization loss from urea-ammonium nitrate solution (UAN) because approximately half of the N in UAN is urea. In 192 comparisons with UAN the corn yield advantage of UAN with the urease inhibitor was 2.8 bu/A compared to unamended UAN. This is consistent with the urea data since only half of the nitrogen in UAN is urea.

It would appear that there is a potential benefit from the urease inhibitor when used with urea nitrogen in situations where there is the potential for significant volatilization losses. This would primarily be on no-till corn when rain is not expected within a day or two after application. If rain is expected immediately after application or if the fertilizer will be incorporated immediately there is no benefit from a urease inhibitor. Hopefully the information provided above will help in evaluating the economics of using this product in your situation.

Urease inhibitors should not be confused with nitrification inhibitors such as N-Serve or DCD. These products inhibit the conversion of ammonium nitrogen to the more leachable nitrate nitrogen. Nitrification inhibitors have no affect on volatilization losses.

Douglas Beegle

HI-OIL CORN HITS THE MARKET

Several companies have begun marketing hi-oil corn hybrids and blends in Pennsylvania during the past two years. High oil corns, as their name implies, have elevated levels of oil in the kernel which can be beneficial in some processing and feeding situations. Normal dent corn contains 3.5% to 4.5% oil. High-oil commercial types often contain as much as twice this amount. Commercial high oil corn hybrids have not been used widely because their yield potential has been lower than normal hybrids.

Recently, an alternative system of producing hi-oil corn has been developed that consists of planting a blend consisting of about 92% of an adapted, but male-sterile (produces no viable pollen) hybrid and about 8% of a special hi-oil pollinator line. The pollen shed from these pollinator plants contains a special gene that cause a kernel to produce a much larger germ or embryo. The pollen from the 8% will pollinate the entire field. This results in higher oil and protein in the grain on the adapted hybrid plants. This system of producing hi-oil corn is known as the Topcross system and was developed by Dupont. Because the yield of the pollinator plants is low and pollination is dependent on 8% of the plants, there is some concern about the yield potential of these blends compared to the normal fertile hybrids. Despite the relatively few pollinator plants in the field, pollination is usually close to that achieved with fertile hybrids. Testing these blends is difficult, since they have to be isolated from normal corn and thus cannot be tested in conventional strip tests or small plot evaluations. Grain from these blends contains about 7-7.5% oil compared to 3.5 to 4.0% for normal corn. The higher oil content is offset partially by lower starch levels in the kernel, but the hi-oil grain contains higher levels of gross energy.

In a 1995 replicated Ohio State trial, gross energy levels for 5 normal corn hybrids averaged 1781 kcal/lb while the Topcross blends with similar genetic backgrounds had energy levels that averaged 1844 kcal/lb. Slight increases in lysine were noted with the Topcross blends as well. Yield levels in this trial showed the Topcross blends to be 6 bu/A less than their normal counterparts and 8 bu/A less than Pioneer 3394. However, two of the Topcross blends had yields that were similar or higher than 3394. A similar Wisconsin trial, conducted at four locations, showed that hi-oil Topcross blends yielded about 10% less than their fertile grain parent counterparts.

The adoption of hi-oil corn will depend on the availability of corn hybrids that yield consistently close to top hybrids and markets or feeding opportunities that show an economic advantage for hi-oil corn. At this point, the advantage of hi-oil corn appears to be greatest for swine and poultry rations. The advantage is less clear for dairy feeding.

Greg Roth

ALFALFA FROST HEAVING: ASSESSING THE DAMAGE

Alfalfa frost heaving, the repeated freezing and thawing of the soil causing the alfalfa crown to be pulled or pushed above the soil surface, is wide spread throughout Pennsylvania this spring. Here are some answers to commonly asked questions about frost heaving of alfalfa.

Is there anything that can be done to push the crown back into the soil?
No. While many people have tried cultipackers or lawn rollers to push the heaved alfalfa crown and root back into the soil, there is no data suggesting that any of these techniques are beneficial.

How much frost heaving is needed to justify rotating an alfalfa field into another crop?
The answer to this question depends on the severity of the heaving. Consequently a complete evaluation of the stand is needed. Depending on when the crowns were elevated above the soil, all of the crown buds could have been frozen and the plant is essentially dead. Look for green growth coming from the crown and count the number of these crowns per square foot. If there are an average of five or more live crowns per square foot then the stand is probably worth keeping at least through the first harvest.

Will the alfalfa that is still alive remain productive throughout the season?
Frequently, alfalfa plants that have heaved only a small amount (one inch or less) still have their tap root intact and can remain productive. Caution must be used to insure that the crown is not removed when cutting the alfalfa during harvest. These crowns will also receive additional damage from wheel traffic with each harvest which kills additional crown buds and exposes the crown to more diseases.

Fields in which alfalfa crowns have heaved a lot (greater than 1 inch) are strong candidates for rotation into another crop. However, if there are greater than five live plants per square foot then it may be best to take an early first harvest prior to rotating. Plants with their crowns elevated to this height generally have their tap root broken and will be more susceptible to drought stress (low production) this summer. In addition, crowns at this height can be cut off during the first harvest leaving the root with no growing points for herbage regrowth.

How can I tell if the alfalfa is worth keeping after the first harvest?
As mentioned earlier, the number of crowns per square foot is one method for determining alfalfa stand productivity. However, better than the number of live crown is the number of stems per square foot. As the stem number declines to 40 stems or less per square foot alfalfa fields begin to loose profitability and should be rotated out of alfalfa.

Will the heaved alfalfa survive another winter?
Unfortunately, the crown buds (from which spring growth comes from) of heaved alfalfa plants will be exposed to colder temperatures next winter because the crowns will not be insulated by the soil. Exposure to freezing temperatures next winter may kill the crown buds. If an alfalfa field with heaving this spring is kept until next spring it should be monitored very closely with anticipation that it should be planted to another crop.

Marvin H. Hall

PEST MANAGEMENT

PRE-PLANT CONSIDERATIONS FOR ALFALFA INSECT CONTROL

Stress to young alfalfa stands can affect vigor and later performance of the stand. In many years leafhopper populations can cause appreciable losses to new alfalfa stands. There are several strategies to deal with leafhopper problems: (1) monitor them with a sweep net; (2) apply Furadan 4F at planting; (3) apply Lorsban 4E at planting. The problem with applying insecticides at planting is that the leafhoppers may not be present at the time of application, and therefore the effort and material may be wasted. The materials mentioned above last only about 45-50 days, so they may not be effective when leafhoppers arrive, usually in mid-June. After the first cutting, watch closely for insects, starting when the regrowth is 2-3" tall.

SCOUT FOR ALFALFA WEEVIL

Scouting for insects in alfalfa at this time of the year centers mainly on the alfalfa weevil. The larvae are small, green and curved, with black heads. They typically finish growth by early June. The pupae (the stage after the larva) are present in small, round, delicate, loosely woven cocoons attached to leaves, stems and plant litter. Once you see these cocoons, you can consider damage to be finished from this insect this year, except for perhaps some adult feeding on new regrowth after the first cutting. The adults which emerge from the pupae will spend the summer around and in fields, but they are not damaging to the crop.

If you begin to see feeding damage on the plant tips, it is time to begin monitoring for the alfalfa weevil larvae; the month of May is the crucial time to monitor. Equipment needs are very simple: a 2 or 3 gallon plastic bucket. Based on the number of larvae found, the value of the crop, its growth stage and insecticide cost, a decision can be made whether to spray. For details on scouting for alfalfa weevil, see PSU Special Circular 284, A Pest Management Program for Alfalfa in Pennsylvania. Typically, the insect overwinters as an adult and lays eggs in April and May, leading to larval damage to the plants usually after mid-May. However, some eggs can be laid during the previous fall, particularly in fields which have not been cut or have plenty of foliage. These eggs are already present in the spring and can result in some earlier than normal damage.

Bt-CORN FOR CONTROLLING EUROPEAN CORN BORER

Transgenic plants are those which have a portion of a foreign genetic material, typically from bacteria, inserted into their own. We are familiar with the Bt's (products such as DiPel) made from the bacteria Bacillus thuringiensis, which kill insects via a crystalline protein produced by the bacterium. However, transgenic crops will now have the ability to produce this caterpillar-killing protein within their own tissues. The results so far indicate that these transgenic crops kill virtually 100% of a European corn borer population, compared to an average effectiveness of about 60% for a typical insecticide. In addition, with these transgenic crops, there is no cost of scouting or application of a pesticide to a crop, so the only additional cost will be the premium placed by the company on a bag of seed. Several companies have developed and patented the technology for these transgenic lines, and are working with several seedcorn companies. Several seed companies have Bt-corn available during 1996.

Economic analysis done by Dennis Calvin indicates that the economic benefit in Pennsylvania from using these transgenic corn hybrids will range between $6 to $26 per acre, depending on the conditions. There will be about a $7/acre premium on transgenic corn hybrids. Therefore the economic returns per acre will vary between $0 and $21 per acre. On average most corn fields will benefit economically from a transgenic corn hybrid. However, to assure an economic return, growers can better target corn fields at risk of economic losses. First generation corn borer is usually problematic in the earliest planted fields, because females from this generation seek out the tallest corn available. Conversely, the latest-planted fields will have greater second generation corn borer problems than the middle planted ones, because these later ones will be in the attractive tasseling and silking stages. Finally, the longer day hybrids will probably have more corn borer problems because they stay greener and more succulent for longer periods of time, and therefore can be attacked by both first and second generation corn borer. In summary, the fields most likely to have corn borer problems are the very earliest planted ones, the very latest planted ones, and the longer day hybrids.

A major concern with these transgenic crops is the potential for development of resistance of corn borer to the Bt toxin with overuse. Most insect populations, if they are exposed to a toxin excessively, can develop resistance, making pest control products less effective. Transgenic corn hybrids are no exception, because the crystal protein produced by the transgenic plant is simply another form of an insecticide. Any potato grower knows of this problem with Colorado potato beetle. Presently, the registration of these transgenic crops must include a resistance management program. Because a resistance management program is required by the EPA, the amount of transgenic corn available to an individual grower may be limited. For additional information on resistance management techniques, visit further with Steve Spangler, Dept. of Entomology, Penn State University at (814) 863-7791.

LOOK FOR CEREAL LEAF BEETLE IN SMALL GRAINS

The cereal leaf beetle (CLB) was first discovered in Michigan in 1962, but has probably been present in the U.S. since at least the early 1950's. Since then, it has spread throughout much of the midwest and eastern U.S., to where it now is spread across about 25% of the U.S. wheat acreage. Adults are about 1/4" long, with a shiny metallic, blue-black body, with a large red area behind the head. These emerge from protected overwintering places (in and around corn fields) during April, and feed for a couple weeks on wild grasses and winter grains. After this feeding, they begin to lay eggs. Preferred egg-laying sites are young plants such as spring planted oats and late planted winter wheat. Larvae hatch after 7 to 21 days and are yellowish in color, but because they cover themselves with a black or brown coating of fecal matter, they appear black or brown, like bird droppings. Larvae feed on leaves during May and early June in the mid-Atlantic region. The adults can completely chew through the leaves, whereas larvae feed only on the upper leaf surface, giving the leaf a whitish appearance. The tips of damaged leaves turn white, giving the field a "frosted" appearance.

There are several species of hymenopterous parasites (tiny wasps) which were released by the USDA to control CLB during the 1970's. They attack the egg and larval stages, and have been very successful in controlling CLB populations. For some reason, CLB populations have increased in recent years, and there is some thought that this is due to declining populations of the beneficial parasites. Economically damaging populations have been observed in various parts of the Commonwealth in recent years, including Perry, Cumberland, and York Counties. During 1995, the Pennsylvania Department of Agriculture will be conducting general surveys for the beetle, as well as for the beneficial parasites. There is also some discussion of the USDA becoming involved again in parasite releases.

To scout for CLB, examine 20 plants in five locations in a field, and count the number of larvae and adults on each stem. Also, note the number of flag leaves with feeding damage. If an average of one or more adult or larvae per stem or flag leaf is found, a treatment is suggested. A variety of control materials are listed in your Agronomy Guide, including Guthion, Sevin, Furadan, malathion, and Lannate.

INFORMATION SOURCES FOR FIELD CROP INSECT MANAGEMENT

Field Crop Scouting Manual. A Guide to Identifying and Diagnosing Pest Problems. Cooperative Extension, University of Illinois. Available from: Vocational Agriculture Service, College of Agriculture, University of Illinois, 1401 S. Maryland Drive, Urbana, IL, 61801. Telephone: (217) 333-3871. Price: $30.

Field Crops Pest Management Scouting Manual. Cooperative Extension, Purdue University, Publication IPM-1. Available from: Media Distribution Center, Purdue University, 301 S. 2nd St., Lafayette, Indiana 47905-1092. Telephone: 317-494-6794. Price: $40.

The Corn and Soybean Field Guide, Cooperative Extension, Purdue University, Publication ID-179. Available from: Media Distribution Center, Purdue University, 301 S. 2nd St., Lafayette, Indiana 47905-1092. Telephone: 317-494-6794. Price: $3.

Various 1-page PSU fact sheets on field crop insects, available from your local Extension office. Free.

Handbook of Soybean Insect Pests, edited by. L. Higley and D. J. Boethel. Available from: The Entomological Society of America, 9301 Annapolis Road, Lanham, MD 20706-3115. Telephone: (301) 731-4538.

A Pest Management Program for Alfalfa in Pennsylvania. Special Circular 284, Penn State University.

Corn Rootworm Management in Pennsylvania. Special Circular 333, Penn State University.

Color fact sheets of small grain and vegetable insects, University of Maryland. Available from: Dept. of Entomology, PSU. Telephone: (814) 863-7791. Price: $5.

The Penn State Agronomy Guide. Available from the Publications Distribution Center, The Pennsylvania State University, 112 Agricultural Administration Building, University Park, PA 16802-2602. Telephone: (814) 865-6713. Price: $7.00.

Steve Spangler & Dennis Calvin

TIMELY KILL OF COVER CROPS FOR SUCCESSFUL CORN OR SOYBEAN ESTABLISHMENT

There are a number of reasons for killing winter cover crops in a timely fashion. Larger covers utilize critical soil moisture, are more likely to attract certain insect pests, and may pose planter seed placement problems. In addition, small grain cover crops such as winter rye are often easier to kill whether it be with a herbicide or tillage, while small in the vegetative stage of development. Kill the cover one to two weeks before planting to insure adequate "dry-down" prior to entering the field with the planter or drill. The following information provides herbicide suggestions for killing several winter covers in spring.

Small grains (wheat or rye)
Roundup or Roundup Ultra 4L @ 12 to 48 oz/acre
The 12 oz rate controls wheat up to 18" tall and rye up to 12" tall. For these lower rates, you must use low rate/volume technology (3 to 10 gallons/A) (includes surfactant at 0.5% v/v with Roundup) and do not tank-mix with soil residual herbicides. Use 2 to 3 pt/A for high-volume-tank mix applications.

Gramoxone Extra 2.5SC @ 1.5-3 pt/acre
Higher rates are for larger plants. Apply prior to tillering or after the boot stage for best results (especially for wheat). Applications made from tillering to boot stage will generally not provide adequate control. Include a nonionic surfactant or crop oil concentrate and apply in a spray volume of 20 to 60 gpa. You may use certain liquid fertilizers as the carrier and including a photosynthetic inhibiting herbicide (atrazine, Bladex, Sencor/Lexone, or Lorox) may improve control.

Alfalfa or Other Perennial Legumes
Banvel 4E @ 1 pt
Do not apply in the spring prior to soybean or legume planting. Apply to the alfalfa after at least 4 to 6 inches of regrowth. Include 3 to 6 pt/acre Roundup in the mix if perennial grasses are present.

2,4-DLVE + Banvel 4E @ 1 pt + 0.5-1 pt
The combination of 2,4-D and Banvel will improve the control of the legume plus increase the effectiveness on other perennial broadleaves such as dandelion. For greater corn safety, make applications 7 to 14 days before planting. Include 2 to 6 pt/acre Roundup in the mix if perennial grasses are present.

Perennial Grasses (orchardgrass, bromegrass, timothy, etc.)
Roundup 4L or Roundup Ultra @ 2 to 6 pt/acre
For best results apply to actively growing plants in the boot to early head stage of growth. Adequate spring regrowth is necessary for successful control. Use the higher rates for orchardgrass, reed canarygrass, and fescues. Lower rates may require low volume technology - 3 to 10 gal/A, surfactant (not Roundup Ultra) and no tank-mixing of soil residual herbicides. A sequential application of atrazine will improve the control of most perennial grasses.

Gramoxone Extra + atrazine and/or Bladex @ 1.5 to 3 pt + 1 to 2 qt
Gramoxone Extra in combination with atrazine and/or Bladex will suppress or control certain perennial grasses such as timothy and bluegrass. This combination is not very effective on orchardgrass, bromegrass, or fescue sods. Rainfall within one or two days following application will improve the level of control.

Bill Curran

COMMAND 3ME RECEIVES PENNSYLVANIA REGISTRATION

Command 3ME herbicide has received registration for use in Pennsylvania. Command 3ME is a 3 lb ai/gallon, microencapsulated formulation that is labeled in soybeans, tobacco, and cotton. It must be used as a preemergent soil applied treatment without incorporation. Though this formulation reduces the volatility (off-target movement) of Command, buffers around housing developments, nurseries, desirable plants, etc. are still required. See current label for detailed information on these and other application instructions. Both the 4EC and the 3ME Command products are available this season, so precautions must be taken to avoid confusion between products, rates, application methods, buffers, etc.

Command 3ME will be a good fit for conservation tillage systems and can be applied alone or in tank-mix combinations. Command provides good control of velvetleaf, lambsquarters, jimsonweed, foxtails, and panicum. Tank-mixing improves control of pigweed and broadens the control spectrum.

SUBMITTING WEEDS FOR IDENTIFICATION

Every season and especially during the spring and fall, we receive numerous plant samples from individuals requesting their identification. Few of our faculty or staff are "expert" taxonomist and many samples require further investigation using several taxonomic reference guides. To ensure that you receive the "best" possible answer (or guess), please consider the following guidelines when submitting plant materials for identification.

For plant identification, collect a representative plant sample with intact roots. Seeds, flowers, or fruit, when available, should be collected as an aid in making positive identification of the plant (in particular, seed heads should be included with grasses). Prepare broadleaf plant samples submitted for identification by carefully arranging the leaves in a flat position and pressing the plants between heavy paper or cardboard. Turf, pasture, or weedy grass samples should be pressed only if they have an emerged seed head. Otherwise, prepare these samples as fresh plant samples (this is necessary since vegetative characteristics of the grass are used in making identification and desiccation may destroy these vegetative features). All other samples including samples submitted for injury diagnosis should be prepared as fresh samples.

Fresh samples are prepared by wrapping only the plant roots and soil, but not the foliage, in a moist paper towel. Cover the moist paper towel, not the entire plant, with a plastic bag and tie the top. Wrap the whole sample in dry newspaper or paper toweling. Place prepared samples in a crush-proof container marked "Plant Sample - Perishable". Address samples to the appropriate university department, extension personnel, or plant clinic. If in the area, hand deliver sample or mail sample immediately - early in the week to avoid weekend lay over in a post office (mail First Class). Keep samples refrigerated until mailed.

Dwight Lingenfelter

WINTER WHEAT DISEASE MANAGEMENT

The major diseases affecting the yield of wheat in Pennsylvania are caused by fungi (i.e. powdery mildew, septoria, leaf rust, take-all, head scab) and several virus diseases (barley yellow dwarf virus, soil borne mosaic virus). Cultural practices such as crop rotation and selecting varieties that are tolerant or resistant to these diseases are the main control methods for most wheat diseases. Of these only powdery mildew, septoria and leaf rust are controlled by applying foliar fungicides. In the last newsletter we briefly discussed the use of foliar fungicides for disease control. Making the decision to apply a fungicide involves integrating many factors. The following is a discussion on these factors and steps that can be helpful in making a decision on applying a fungicide.

Disease development depends on three factors; weather, host plant, and the presence of a pathogen. Knowing how the pathogen responds to weather patterns such as temperature, rainfall, and relative humidity are critical to making a decision. Powdery mildew requires a period of relatively cool (60 to 70 F) temperatures with high humidity. Frequent rainfall actually reduces mildew severity because this tends to wash the fungus from the leaves. On the other hand, septoria pressures increase with increasing rainfall because this aids in moving the fungus up the plant. It also requires cool temperatures. Powdery mildew and septoria are able to overwinter in Pennsylvania; however, leaf rust moves in on wind currents, in the spring, from the south. It requires higher temperatures (70 to 80 F) then mildew or septoria and tends to infect plants at later growth stages (Growth Stages 10 or later).

Knowing plant characteristics is also important in making spray decisions. If the variety of wheat seeded has resistance to the disease then the need for a fungicide is reduced. The growth stage of the plant when making the spray decision will affect the potential yield response from the spray. A single spray applied at Growth Stage (GS) 6 or earlier tends not be as effective as one applied at GS 8 or later. This is because the upper two leaves and the head, which appears after GS 8, produce the materials needed for grain production. The lower leaves contribute very little to grain production. Plant stand, vigor and yield potential also play important parts in the expected yield response from a fungicide. The yield response, in fields with a low yield potential, is small and in most cases uneconomical.

Finally, for a plant disease to cause an economic yield loss the pathogen must be present and above a certain level or threshold.

One of the most difficult wheat production decisions is to apply or not to apply a foliar fungicide. This is because there are so many variables entering into the decision: the disease susceptibility of the variety; yield potential of the crop; stage of growth; disease identification; disease severity; past weather conditions and future weather predictions; cost of application and grain price. Dr. Donald Hershman, Extension Plant Pathologist at the University of Kentucky has proposed several steps to use in making this decision which we feel can be helpful. These steps have been modified, in some cases, to fit conditions in Pennsylvania.

Step 1 - Commitment To Scout Fields:
If a producer is not willing to commit to field scouting (either doing it or paying to have it done), then the decision to consider using a fungicide should be questioned.

Step 2 - Determine The Number Of Sprays:
Competition for time and application costs indicate a one spray application program for Pennsylvania producers. This means that timing of the application is critical. Research and experience indicate that this is between GS 8 and 10. As discussed earlier, protection of the flag (F) leaf, or upper most leaf, and the F-1, or one leaf below the flag leaf, and the head is much more important to yield and grain quality than is protecting the lower leaves.

Step 3 - Know The Disease Reaction Of the Wheat Variety Planted:
Typically, foliar fungicides will not be necessary on wheat varieties rated as resistant or tolerant to a particular disease. However, this resistance can change in a relatively short period of time and for this reason these fields should be periodically scouted to assure that a disease buildup is not occurring.

Step 4 - Estimate Crop Yield Potential:
Remember that applying fungicides only protects yield already developed in the crop, they do not create additional yield. The higher the yield potential the greater the probability of a crop benefiting economically from a foliar fungicide if a disease becomes a problem.

Step 5 - Know The Diseases Present In The Field:
In an earlier discussion we indicated that foliar fungicides controlled only a few of the diseases affecting wheat. The diseases they control however, are the major foliar diseases which economically affect yield and quality in Pennsylvania. These diseases are powdery mildew, septoria, and leaf rust. Proper identification of wheat diseases is very important.

Step 6 - Scout Fields To Determine Disease Levels:
Scouting fields to determine crop growth stage and current disease situation is key to making good fungicide decisions. When scouting, it is important to walk the entire field. The key is to make a decision based on the average disease situation in the field. Begin scouting fields at GS 6 and continue every 7 to 10 days through GS 10 or a decision has been made to spray. Observations should be made at five or six locations in each field. Leaves on 20 to 25 stems should be examined and these observations averaged to determine the disease level in the field.

The following are guidelines (thresholds) to use for specific levels of disease on specific leaves at a specific growth stage. The thresholds were developed by Dr. Hershman at the University of Kentucky. The table has been modified slightly to fit Pennsylvania conditions. The thresholds should be used with other information. For example if a threshold is reached for powdery mildew and an extended period of hot, dry weather is predicted, spraying may not be needed. The thresholds indicate that a yield loss due to one or more of the listed diseases is likely; however, they do not mean losses will definitely occur. Weather can always intervene and reduce or increase a disease situation.

Threshold levels for leaf diseases on wheat.
Growth Stage	Diseases	Indicator leaf*	Threshold
GS 6-first node visible	Powdery Mildew Septoria Leaf Rust	Uppermost fully expanded green leaf Do not spray at this time Do not spray at this time	Average of 10 pustules per leaf
GS 7-second node visible	Powdery Mildew Septoria Leaf Rust	Uppermost fully expanded green leaf Uppermost fully expanded green leaf Any green leaf	Average of 10 pustules per leaf 25% of leaves examined with blotches Average of 1 pustule per leaf
GS 8-Flag leaf emerging	Powdery Mildew Septoria Leaf Rust	F-2 leaf F-2 leaf F-3 leaf	Average of 5 pustules per leaf 25% of leaves with blotches Average of 1 pustule per leaf
GS 9 to 10.5-Flag leaf fully emerged to flowering	Powdery Mildew Septoria Leaf Rust	F-1 leaf F-2 leaf and above F-2 leaf and above	Average of 5 pustules per leaf 25% of leaves with blotches Average of 1 pustule per leaf

* F = flag leaf; F-1 = one leaf below flag; F-2 = two leaves below flag; F-3 = three leaves below flag leaf

Step 7 - Understand Risks:
One of the problems of using a foliar fungicide is the inability to determine if disease favorable conditions will persist after a fungicide is applied. Fungicides are valuable only if yield and quality are threatened by disease. Similarly, fungicides will be of limited value if other diseases develop that are not controlled by foliar fungicides. Examples are take-all, loose smut and head scab. Also, fungicides may be of limited value if yield and quality are reduced by nondisease factors such as lodging, delayed harvest, and short grain fill period. Unfortunately, these factors will always be a risk when using foliar fungicides.

Disease Observations: We are starting to receive questions about diseases from the field. The visual symptoms indicate virus diseases, in particular soil borne mosaic. We experience this in springs when the soil remains cold and wet for long periods. Once these environmental conditions change and things warm up, the wheat plants out grow the symptoms.

John Ayers, Dept. of Plant Pathology and Elwood Hatley, CCA, Dept. of Agronomy

OBSERVATIONS AROUND THE COMMONWEALTH

NORTHWEST

It looks like early green-up seems to be coinciding with tax day this year (Got to be some irony there somewhere?!?). A lot of ground got plowed in late March and early April. Those getting the plowing done early were generally surprised with the relatively dry soil conditions, especially for our soils at this time of year. So far, our usual abundance of spring rains has not really begun. In addition, the 100 plus inches of snow this winter somehow did not translate into excessive soil moisture this spring. The winter did apparently result in more heaving of alfalfa than usual. Likewise, some winter wheat damage and perhaps some less winter hardy forage species damage has been observed. Planting wise, some oats have been planted, hopefully on some of the drier ground. I suspect though that most of the oats remain to be planted as growers took advantage of relatively dry soil conditions and kept plowing. A few more acres than usual of oats and spring barley will likely get planted by dairy producers looking to come up with some additional non structural carbohydrates for the ration before next fall. This is probably a good idea in light of the poorer quality of a lot of the corn silage this year. Like everywhere else, corn planting intentions seem to be pretty high. I believe I have seen quite a bit of sod turned under and know of some fallow ground being brought back into production. That's all well and good, but I hope that with these high corn and feed prices that producers will focus hard on maximizing quality forages! Finally, a strong marketing effort for the "Rawson zone tillage system" has been fairly effective locally, creating more than a little interest, and quite a number of customers. Some bought into just the three coulters per planter unit, but others also got on board with the additional deep strip tillage package. At about $1000 per unit for either part of the system, it's a rather significant investment either way. On the one hand, I am glad to see the interest in wanting to make no-till work up here, but I fear that maybe the emphasis should be placed more on technique and less on the tool. I am curious if other areas have seen a similar surge in interest and sales of this system.

Joel Hunter, Crawford/Erie Counties

William S. Curran
Associate Professor Weed Science
email: wsc2@psu.edu

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Website Address: http://fcn.agronomy.psu.edu/