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April 17, 1998 Vol. 98.3

IN THIS ISSUE:

Announcements:

New Agronomy Extension Faculty in Environmental Soils

Dr. Richard Stehouwer joined the Agronomy faculty in August, 1997 as an extension specialist in Environmental Soils. This extension program will address soil environmental issues ranging from restoration of contaminated soils, mine reclamation, and land application of residual and by-product materials. Rick came to Penn State from Ohio State University where he spent the past seven years as a research scientist studying the benefits and environmental risks from using by-product materials in mine reclamation and as agricultural soil amendments. Rick received his Ph.D. in Soil Science from Ohio State in 1990, and his M.Sc. in Agronomy from Cornell in 1981. Between those two degrees he worked in agricultural extension and development in Liberia, W. Africa.

The focus of the Environmental Soils Extension program as it relates to production agriculture will be on the use of municipal and industrial waste materials as soil amendments.

Municipalities and industries are increasingly promoting land application of residuals as an alternative to disposal. Such materials include sewage sludges, various composts, spent mushroom substrate, food processing residuals, spent lime by-products, coal combustion by-products, and others. Each of these materials has potential benefits for crop production as well as problems and risks. The goal for this part of the environmental soils extension program is to get information on the benefits/problems/risks of these materials to the farmers and consultants so that they can make informed decisions regarding if, when, and how to use them. Look for some articles on these topics in upcoming issues of Field Crop News. In the meantime, contact your local extension office or Dr. Stehouwer directly (814-863-7640) with questions in this area.

Rick Stehouwer

Mark Your Calendar:

1998 Penn State Agronomic Field Diagnostic Clinic

The dates and topics for our annual Diagnostic Clinic have been set. As in the past, the Clinic is a one-day event conducted at the Penn State Agronomy Research Farm near Rock Springs, PA. This year's Clinic will be held on Wednesday, July 22 and then repeated on Thursday, July 23, 1998. The topics include:

(CCA and pesticide applicators license credits will be offered.)

Registration forms are being mailed, so look for yours soon to register and to get additional information on each of the topics. The cost of this year's Clinic is $40/person. (Similar one-day Clinics in the Midwest can cost >$100/person.) If you do not receive a registration form within a couple of weeks and would like to attend, contact Lisa Crytser at (814) 865-2543. For additional information or comments about the Diagnostic Clinic contact Dwight Lingenfelter at (814) 865-2242 or by email, DXL18@PSU.EDU.

We look forward to seeing you at the Clinic!

Dwight Lingenfelter

Production:

Update on Pre-Sidedress Soil Nitrate Test for Corn

The Pre-sidedress Soil Nitrate Test (PSNT) for corn has been used successfully in Pennsylvania for several years. This N soil testing approach is based on taking soil samples just before sidedressing (after the spring wet period but before the period of major N demand by corn) and determining the nitrate-N available in the soil at that time. If the test level is greater than 21 ppm NO3-N, no sidedress N is recommended. If the test is below this level, the results of the test are then used to make sidedress N recommendations. This test is primarily recommended for use on fields where there are significant organic N contributions such as a history of manure applications or forage legumes in rotation. It does an excellent job of verifying when these organic sources of N are adequate for the crop. This test is of limited value on most fields without organic N contributions, because these fields generally have low levels and thus the standard recommendations are suitable.

Since this test is somewhat unique compared to regular soil tests; it is probably worth while to review the procedures for using the PSNT since it will soon be time to test. The PSNT procedure is as follows:

1. Only apply a minimum of fertilizer N in the spring. (Starter fertilizer and/or N used as a herbicide carrier.)
2. Apply manure based on the history of the field, a manure analysis, how the manure will be handled, and on crop requirements for N estimated from the expected yield and crop history.
3. Take soil samples when the corn is 12 inches tall or at least a week before planned sidedressing.
4. Sample the fields by taking 10 to 20 cores to a 12-inch depth if possible. If not, sample as deep as you can. Avoid starter bands and other atypical areas. Because of sampling problems this test cannot be used on fields that received injected fertilizer or manure.
5. Combine and crumble the cores and dry as quickly as possible. Spread the samples out in the sun or under a heat lamp in a well-ventilated area to dry. The samples must be dry within 24 hours.
6. The sample can be sent to a reputable soil testing lab for soil nitrate-N analysis. A reliable field-test kit for soil nitrate-N can be used to determine the nitrate-N level in the sample.
7. Calculate the adjusted sidedress N recommendation. (See Agronomy Facts #17)

There are several areas that seem to cause the most problems with the PSNT. First, many people try to take the test too early. It is important for the test to work properly that the corn be at least 12" tall at the top of the whorl when you sample. A second problem related to timing of sampling is taking samples immediately after a heavy rain. Experience has shown that the test works best if you allow 2 to 3 days following a heavy rain before sampling for the PSNT. Sampling too soon after a rain can give a false low reading indicating that there is less nitrogen available than there really is. Third, and this is the tough one, for the test to work the best the samples should be taken to a 12" depth. Unlike phosphorus and potassium, nitrate will readily move deeper into the soil. Everyone complains about this deep sampling but it could be worse because taking deeper samples would be even better. Some states recommend 2 or even 4-foot deep samples for nitrogen testing. This 12" depth seems to be a reasonable compromise between optimum accuracy of the test and sampling practicality. Finally, the samples need to be dried immediately. They should be completely dry within 1 day of when they are taken. I have seen sample nitrate nitrogen levels increase by a factor of 2 to 3 times just from sitting around damp over a weekend.

Samples can be analyzed by sending them to a soil testing lab such as the Agricultural Analytical Services Lab at Penn State (See your county agent for mailing kits). The samples can also be analyzed using a Quick Test Kit. Quick test equipment for the PSNT is available from Hawk Creek Laboratory, Inc., R. D. 1 Box 686, Simpson Rd. Glen Rock, PA 17327 (Phone: 800-637-2436). Hawk Creek also has a compete line of supplies for the Quick Test Kit. You should check your supplies of nitrate test strips, extracting solution, and nitrate standard. Old strips and standard should be used with caution because the strips do go bad with time, especially after they have been opened, and the standard can become contaminated with repeated use. County Extension Offices have received information on the Quick Test Kit and necessary supplies from Hawk Creek Lab.

Agronomy Fact sheet #17 "Presidedress Soil Nitrate Test for Corn", which explains the PSNT in detail, is available from Penn State Cooperative Extension offices.

Doug Beegle



Scouting Emergence Problems in Corn

Timely scouting for corn emergence problems is an essential part of a top corn management program. Early diagnosis of problem fields can lead to timely replanting decisions and management changes that can avoid future problems. Corn should begin emerging after about 100 to 125 GDDs have accumulated following planting. Here's a list of a few common problems encountered during this phase:

1) No seed present. May be due to planter malfunction or bird or rodent damage. The latter often will leave some evidence such as digging or seed or plant parts on the ground.

2) Coleoptile unfurled underground. Could be due to premature exposure to light in cloddy soil, planting too deep, compaction or soil crusting, extended exposure to acetanilide herbicides (e.g., Dual, Lasso, etc.) under cool wet conditions, or may be due to extended cool wet conditions alone.

3) Seed with poorly developed radicle or coleoptile. Coleoptile tip brown or yellow. Could be seed rots or seed with low vigor.

4) Seed swelled but not sprouted. Often poor seed-to-soil contact or shallow planting- seed swelled then dried out. Check seed furrow closure in no-till. Seed may also not be viable.

5) Skips associated with discolored and malformed seedlings. May be herbicide damage. Note depth of planting and herbicides applied compared with injury symptoms such as twisted roots, club roots, or purple plants.

6) Seeds hollowed out. Seed corn maggot or wireworm. Look for evidence of the pest to confirm.

Note the patterns of poor emergence. At times they are associated with a particular row, spray width, hybrid, field or residue that may provide some additional clues to the cause. Often two or more stress factors interact to reduce emergence where the crop would have emerged well with just one present. Also, note the population and the variability of the seed spacing. This information will be valuable in the future.

Greg Roth

Pest Management:

Watch Out For Those Weeds This Spring

With the mild winter and somewhat bizarre spring we have been experiencing this year, keep several things in mind when addressing weeds this year. First, with the lack of cold weather this winter, it is likely that most weeds will have survived the winter well. Winter annuals, biennials, and perennial weeds will be out in full force this spring and mother nature is on their side.

With the mild spring weather, many of the winter annuals are well ahead of where they might normally be. Red dead nettle, shepherd's purse, and chickweed have been flowering in many areas for several weeks. These larger more mature weeds are more difficult to kill with burndown herbicides, so adjust herbicide rates or programs accordingly.

On the other hand, perennials such as quackgrass, Canada thistle, and orchardgrass which appear to be abundant this year, may be more effectively suppressed with burndown herbicide treatments because of their "larger than normal" size. In general, make a systemic herbicide application to cool season perennials after they have at least 6 to 8 inches of new spring growth. The larger or more mature the perennials are at application time, may avoid having to return with a follow up postemergence treatment after the crop is up.

Also remember the factors that reduce Roundup and Touchdown activity; cold weather, hard water, mixing with residual herbicides (atrazine, metribuzin, etc.), and applying in 28% N instead of water. Add ammonium sulfate, increase the rate of glyphosate, don't tank mix, and reduce the volume of the spray carrier if these conditions are a concern with your application. Gramoxone Extra activity is also reduced under cold weather, water with high sediment content, too low a carrier volume or the inappropriate adjuvant.

Bill Curran



Herbicide Resistant Crops: Their Fit in the Northeast (Part II)

The following is the second of a three part series on herbicide resistant crops. This article discusses herbicide resistant soybean varieties available in the Northeast. The final article in this series will deal with the economics of using herbicide resistant crops. For a previous discussion about herbicide resistant crops and options for herbicide resistant corn hybrids refer to the March 20, 1998 issue of Field Crop News, Vol. 98:2.

Herbicide Resistant Soybean Highlights

Three herbicide resistant soybean types are available for Northeast agriculture: STS, Roundup Ready and Liberty Link.

STS soybeans

Roundup Ready soybeans

Liberty Link soybeans

SOYBEANS

The STS soybean/herbicide system enhances crop safety from certain sulfonylurea herbicides such as Pinnacle and Classic. Varieties were developed using tolerance selection methods to increase herbicide resistance. The STS seed/herbicide system is designed to provide good weed control without crop injury. Although these varieties were developed to be used in combination with STS labeled herbicides (e.g., Synchrony STS), these soybean varieties also provide greater safety from many of the ALS-type herbicides.

For more than 10 years, sulfonylurea herbicides have been widely used to control many kinds of weed species. The Classic+Pinnnacle+Assure II program provides good control of many common annual weeds in soybeans. However, because of the injury concern from Pinnacle and the higher rates of Classic and Pinnacle (i.e., a premix of these ingredients in Synchrony STS) required to obtain control of harder-to-control species, STS soybeans were introduced. Synchrony STS is a sound herbicide program, however, the frequent use of Synchrony or other ALS-inhibitor type herbicides has promoted weed population shifts and the development of resistant species. Eastern black nightshade, especially, is not controlled with Synchrony and has become more prevalent in the Northeast due to the use of this particular product. Several weeds, such as the pigweeds, mainly in the Midwest and South, have become resistant to sulfonylurea and other ALS-type herbicides. To prevent these problems be sure to tank-mix effective non-ALS type herbicides with Synchrony STS and rotate away from ALS-type herbicides in both soybeans and corn.

STS soybean seed costs slightly more than normal varieties, and generally, the total cost of the herbicide program is less or comparable to other traditional programs. Soybean variety trials as well as farmers have found STS soybeans to be competitive and comparable in yield to traditional elite soybean varieties.

Roundup Ready soybeans were developed using genetic engineering techniques. This system allows over-the-top applications of Roundup Ultra (glyphosate) to soybeans. The program provides broad spectrum control of many annual and perennial grasses and broadleaves. Sequential applications may be required for harder-to-control perennials and wide row plantings.

Roundup is effective in controlling numerous weeds including many perennial species. Roundup Ready soybeans have a wide application window¾from cracking through flowering¾which allows for timely Roundup Ultra applications when weeds are most susceptible. For control of most annual weed species, start with a clean field, and apply Roundup Ultra (1 qt/A) about one month after planting or when weeds are 4 to 8 inches tall. If the system is used properly, Roundup Ultra can provide effective annual weed control with one in-crop application in drill-planted or narrow-row Roundup Ready soybeans. Wide-row soybeans may require a sequential application or a herbicide tank mixture, since crop competition due to canopy closure is slower than narrow row soybeans and new weed flushes likely may occur during the season. (Monsanto does not recommend tank-mixing other herbicides with Roundup. However, other companies do allow tank-mixtures, so please refer to the tank mix partner label for specific recommendations.) Although, studies suggest that a single in-crop application of Roundup Ultra is adequate in narrow-row soybeans, residual pre herbicides or tank mixtures with Roundup may ensure better weed control and prevent weed population shifts or resistant weeds to occur. Although higher in cost, some research has found that a residual pre treatment followed by Roundup Ultra provided more flexibility in making a timely post Roundup application. This may be especially true when targeting a perennial at a susceptible stage of growth, since application timing is critical for longer-term control of perennials. If possible, apply Roundup Ultra when broadleaf perennials are in the bud to bloom stage and when perennial grasses are in the late boot stage. University studies show that Roundup Ultra applied in Roundup Ready soybeans can provide good control of hemp dogbane, wirestem muhly, and other perennials. Roundup Ultra tends to be weaker on morningglory, eastern black nightshade, and large velvetleaf and lambsquarters. Therefore, recommended rates and proper application timing are essential for good control of these species.

Despite higher seed costs, Roundup Ready soybeans are being widely accepted by farmers throughout the US. It is expected in the future that Roundup Ready soybeans may comprise as much as 75% of the soybean market. In most cases, it is a relatively easy-to-use system for broad spectrum weed control. However, keep in mind some of the concerns/risks associated with the use of HRCs, such as herbicide drift and misapplication, previously noted in this publication.

Liberty Link soybeans are genetically engineered to allow over-the-top applications of Liberty (glufosinate) herbicide. This program provides broad spectrum control of annual broadleaves and grasses in soybeans.

Liberty Link soybeans are new to the market. Although Liberty has been approved for use with Liberty Link soybeans, this herbicide seed system will probably not be marketed in 1998. Check with your local seed supplier for more information on Liberty Link soybean availability.

Liberty provides good control of small annual weeds. In narrow-row soybeans, a single application of Liberty may suffice. However, in wide-row soybeans or in severe weed pressure situations, Liberty may need to be tank mixed with a residual herbicide or applied sequentially. A typical program may include a preemergence application of reduced rates of Dual plus Sencor or Lasso plus Lorox followed by a post application of Liberty. Liberty could be tank mixed with a residual product (e.g., Pursuit) to enhance activity. Liberty may be tank mixed with other labeled soybean herbicides except Classic or Cobra. Liberty may be applied to Liberty Link soybeans from emergence to bloom.

Liberty is recommended at 16 oz to 28 oz/acre, with the 20 oz/acre application rate being the standard. Penn State research has shown that the higher Liberty rate (28 oz/acre) provides better control of most susceptible weed species. Include dry or liquid ammonia sulfate at standard adjuvant rates to improve Liberty performance.

Dwight Lingenfelter, William Curran, and Jayson Harper



Preservation of Conservation Measures and Herbicide Application Control

This has been a particularly hard winter on Pennsylvania crop fields and structural conservation measures. The rains have put constant pressure on residue covered fields and particularly grass covered conservation structures such as waterways, diversions, turning strips and access lanes. In some cases, the quality of grass cover has not been good enough to withstand these pressures and the resultant erosion and gullies have become commonplace.

As your employees head out to customers fields to custom apply herbicides, please take extra precaution to remind them to shut off spray rigs when crossing critical water control structures and service lanes. This will insure the survival of critical grass covers allowing them to continue to protect the field from the ravages of erosion.

Your consideration will:

Beside....gullies in that field next year will be hard on your equipment too! Please discuss this with your employees before they head to the fields.

Lee Bentz, IPM Coordinator for PDA and Winand K. Hock, PSU Pesticide Education



Seed Treatments for Corn

In 1997, many growers experienced poor corn stands because of the cold weather during May. There were many reports of corn seed being in the ground for 3-4 weeks before emergence. Even though a weather pattern similar to May 1997 might be considered unusual, many growers are planting earlier when soil temperatures are lower. The increased use of conservation tillage practices, particularly no-till, also results in seed being placed into cooler soils. These events have increased the interest in fungicide seed treatments on corn.

Essentially 100% of commercially sold corn seed is treated with a fungicide to aid in the control of seed and seedling diseases. Until recently, Captan was the fungicide used on nearly all corn seed. In 1997, about 40% of the corn seed planted in the United States was treated with a mixture of the fungicides Maxim and Apron. It is expected that the percentage of seed treated with Maxim + Apron will be considerably higher in 1998 although some companies are using a Captan and Apron mixture.

Captan is an excellent, broad-spectrum contact fungicide that has been used on corn seed for decades. Its primary weakness is that it has limited effectiveness against species of Pythium, a fungus that is almost always present in some amount in soils and takes advantage of the slow emergence and seedling growth that occurs with low soil temperatures. Captan treated seed is usually dyed pink and leaves a pink colored dust in the seed bag and planter box.

Apron is a narrow-spectrum fungicide with excellent activity against Pythium. Apron used with Captan has become more popular in recent years. Apron XL is a new product that contains a more active isomer of the active ingredient and can be used at a lower rate.

Maxim is a new broad-spectrum fungicide that is very effective against many soil fungi but is not effective against Pythium. Thus it is always used in combination with Apron.

Research conducted at Iowa State University, at other universities, and by seed companies suggests there is no difference in performance between Maxim + Apron and Captan + Apron. The switch to Maxim + Apron has occurred because of ease and safety of handling. Maxim is used at a much lower rate than Captan, and dust is reported to be 80% less than with Captan.

A possible disadvantage with Maxim-treated seeds is that with finger-type planters and flat seed, occasionally there is a lower than expected seed drop. Apparently, this is because Maxim-treated seed is more slippery than Captan-treated seed. Planters can be adjusted to offset this problem but growers must be aware of the problem. No problems have been reported with other types of planters or seed sizes. New formulations of Maxim will correct this problem.

Captan, especially with the addition of Apron, will remain an effective corn seed treatment. New formulations of Captan are being developed that should reduce the dust.

Besides planting high quality, fungicide-treated seed, there are other practices that can improve seed germination and healthy seedlings. Crop rotation will help as well as reducing the amount of residue over the row allowing the soil to warm more rapidly. Soil temperatures below 55° F are conducive to seedling diseases. A lot of corn seed in Pennsylvania is planted into soils with a temperature below 55° F so effective fungicide seed treatments are a must. Seed sitting in soils at these low temperatures will often result in reduced stands.

There are planter box and other on-farm seed treatments available. Most contain a combination of a fungicide and an insecticide. Usually, they are not needed for added disease control but can effectively control some insects. There are conditions, however, where additional fungicide could be beneficial. If growers know they are pushing the lower limits of soil temperatures at planting, the additional fungicide might help.

John E. Ayers
(Adapted from an article by Dr. Gary Munkvold, Iowa State University)



Soybean Inoculation - To Do or Not To Do

Each year there are questions about the need to inoculate soybean that are planted in fields with a past soybean history. It is well accepted that inoculation is key to successful production in fields with no soybean history. Recent experience here and in the midwest indicates that it does pay to inoculate even when planted on "old" soybean land. Research results from across the midwest show an average yield increase between 1.0 and 1.5 bushels per acre. Results from several field demonstrations, conducted by county agents in Pennsylvania and New Jersey and industry representatives in 1997, gave similar results.

There are several new technologies, available in both liquid and peat sources, for preparing and packaging the inoculant. The response from these products appear to be more consistent than the older peat methods. These new products still need to be carefully handled in order to maintain the viability of the bacteria. The following are suggestions for maintaining viability:

Elwood Hatley



Soybean Inoculant - Seed Treatment Compatibility

The trend toward planting soybean earlier, in cold soil conditions, has prompted questions regarding the use of fungicide seed treatments. A concern when using these seed treatments and other pesticides is the compatibility of the pesticide and the nitrogen-fixing bacteria inoculant used to enhance soybean yields.

Urbana Laboratories, St. Joseph, Missouri offers the following compatibility guidelines:

1. Insecticides are more toxic than fungicides which are more toxic than herbicides to nitrogen fixing bacteria.

2. In-furrow application methods for inoculants are the preferred method of adding inoculant when seed treatments of any type have been applied.

3. When an inoculant and seed treatment are combined on a seed, keep the exposure time as short as possible; less than four (4) hours is best.

4. Liquid interfaces speed up any detrimental activity. Therefore, if the chemical seed treatment is a liquid, it should be applied first and allowed to dry before the inoculant is applied.

5. Peat based inoculants are more protective of the Rhizobia (nitrogen-fixing bacteria) than liquid based inoculants. Exposure times, prior to planting, should be kept to a minimum.

Fields should be ranked according to their potential response to inoculation. The potential for the greatest response is in fields that have no previous record of soybean production. Delay planting these fields until the soil warms and the need for a seed treatment is reduced.

Fungicide seed treatments can be very helpful for soybeans planted early into cold, wet soils. But, growers need to be aware of compatibility problems and act accordingly. Check on compatibility before applying fungicides.

John E. Ayers
Elwood Hatley



Barley Leaf Rust

The Plant Disease Clinic recently received a barley sample that was inundated with barley leaf rust. The sample was collected in York County, and it turns out that the field was planted to barley in late-August which is much earlier than recommended. Our recommendation is that the grower wait until the crop reaches growth stage 8, then apply a fungicide labeled to control this disease. Growers should be alert for this disease. Normally, we would not expect to see barley leaf rust this early in the season. The mild winter probably allowed the pathogen to over winter. Don't forget to watch wheat fields closely, they are also susceptible to leaf rust.

John E. Ayers
Elwood Hatley



Insect Alert

Wireworm and white grub - This is the time of year to begin checking old pastures and other grassy fields where you plan to plant corn for these two pests. Both insects are associated with grasses and can cause significant stand reductions when present in a field. One option in managing these pests is to use a soil insecticide at-planting as insurance against their injury. This is not a good general practice since the likelihood of these pests being a problem is extremely low; and other pests that can occur when corn is planted into old pastures and grassy areas are easily managed with foliar insecticide applications after crop emergence. If there is a question about the presence of these two pests, monitoring methods are available to assess their population level before planting. If numbers exceed the economic threshold, then a soil insecticide should be applied at planting time.

Economic Thresholds:
Wireworm - 1 or more larvae per bait trap
White grub - 1 or more grubs per square foot of soil

Wireworm monitoring procedures: Monitoring can be initiated when the soil temperature reaches 55°F at a soil depth of four inches. At ten locations in the field dig a hole four to six inches deep and place one small bag, constructed from wedding veil material filled with a mixture of corn and wheat into the hole, and then cover with dirt (tie the bag with a rubber band or string). To help heat up the soil, lay a piece of black plastic over the soil and cover the edges with soil. Leave the bags in the field for one or two weeks. Remember to mark the location of each bait trap with a colored flag for easy location. After the one to two week period is over, locate the bags and dig them up. Open the bags and count the number of wireworms in each bag.

White grub monitoring procedures: At the same time that you monitor for wireworm, you can also check for white grub populations in the field. In the field dig up a one square foot area about four inches deep (root zone of grasses) and place it on a dark cloth. Shake the soil off the roots. Then break the sod apart and look for grubs that are close to the surface. Shift through the soil on the cloth. Count the total number of grubs per one square foot area. Repeat at the other nine locations in the field.

Treatment Options:

Option 1: If white grub and wireworm populations are below the economic threshold, then a soil insecticide is not needed. A planter box treatment is recommended as protection against possible seed corn maggot infestations.

Option 2: If white grub are not found in the field with wireworm, then a planter box seed treater will provide the same level of protection against wireworm as a soil insecticide. If a planter box treatment is chosen as an option, then the product should contain lindane or lindane and diazinon. This will also protect against seed corn maggot. The only exception is when extremely high numbers of wireworms are found in the field. Under these conditions a soil insecticide will provide slightly better protection of the seedlings.

Option 3: If white grub is also found in the field a planter box treatment will not provide adequate protection of the crop. In this situation, an soil insecticide with activity against wireworm and white grub should be selected. The soil insecticide will also provide protection against seed corn maggot. If seed or seedling rot is a concern, then you may still want to apply a planter box treatment that contains a fungicide. Foliar feeding insects that attack the crop after emergence can be controlled with an insecticide based on need. Scouting procedures are available to help locate and remediate any problems that may develop from these pests.

Seed corn maggot - This insect is primarily a problem in fields with high organic matter levels. Volatiles compounds given off during the decay process attract the adult flies to a field. For this reason, fields where green vegetation has been plowed under are at the greatest risk of attack. However, when fly populations are high and the conditions are right, any field can be attacked. The adult flies are drawn to a field by the volatiles from decay or carbon dioxide given off by germinating seed. During springs when the soil is cool for an extended time period and slow emergence is typically associated with a higher percentage of fields with stand reductions from the pest. The easiest and cheapest method to protect against loses from the pest is to use a planter box treatment at planting that contains diazinon as one of the active ingredients.

Flea beetle - The 1998 growing season may see increased pressure from adult flea beetle feeding and an increase in the incidence of Steward's wilt (a disease transmitted by the beetles during feeding). Increased populations of this pest have been associated with mild winters, particularly when the sum of the average temperature in January, February, and March equal 90 or more. The best protection is to plant a hybrid that has some level of resistance against the disease. Typical beetle populations are not high enough to cause economic damage from their feeding alone. However, if 50% or more of the foliage is removed on a plant or 5 or more beetles per plant are present prior to the 4th-leaf stage, then an insecticide application is warranted.

Bt - corn and European corn borer Management

Prior to the commercial release of Bt-corn hybrids, the chances of successfully controlling European corn borer (ECB) using foliar insecticide applications was extremely low. Scouting was difficult and costly and timing of the insecticide application was critical to obtain economic control. Because of these difficulties, management of ECB was not recommended in Pennsylvania.

Although, management was not recommended, the average corn field lost 6 to 7% of its yield to this pest. There simply was no economical management tactic to protect the plant from this loss. The introduction of Bt-corn hybrids has changed the status of European corn borer as a pest. We now have a management tactic that can protect most of the 6 to 7% loss caused annually by the pest. This does not mean, however, that all corn fields will economically benefit by the use of a Bt-corn hybrid. This article is designed to provide information that may help determine whether a Bt-corn hybrid has value on a farm or in a particular field.

Conditions that Are Conductive to Higher European Corn Borer Populations:

Although these conditions increase the attractiveness of a corn field to ECB moths looking for a place to lay their eggs, they will not always determine the final level of infestation. We do know that ECB moths lay more first generation eggs in early planted and taller corn fields and more second generation eggs in later planted fields. However, survival of these eggs to the damaging larval stage is dependent on a number of factors (i.e., level of parasitism, predation, and disease, and weather factors). The earliest and latest planted fields do not necessarily end up with the greatest amount of damage from the pest. Two years of research at Penn State has shown that the mid-planting dates, when injury from both ECB generations are combined, had the higher percentage of reduction in yield. However, these levels were only slightly higher than other planting dates. Because of the many variables that influence ECB population levels and subsequent damage in a field, planting date is not a reliable method of selecting fields for Bt-corn. This leaves few ways to help select which fields should be planted to Bt-corn. Here are some criteria that might help increase a farmer's chances of getting an economic benefit from a Bt-corn hybrid:

Other Factors to Consider When Selecting a Bt-corn Hybrid:

Table 1. Comparison of Bt Corn Technology Sources
Trade Mark Yield GardTM Yield GardTM Dekalb KnockoutTM NatureGardTM
Event MON-810 BT-11 DBT418 Event-176 Event-176
Bt Gene Used cry1Ab cry1Ab cry1Ac cry1Ab cry1Ab
Seed Companies with Technology Asgrow
Cargill
DeKalb
Holden's
Garden Harvest
Pioneer
Others		 Novartis
XtraTM		 Dekalb Novartis Mycogen
Have a Defined Insect Resistance Management Plan Requiring A Refugia Yes Yes Yes Yes No
Level of 1st generation ECB Control Control Control Control Control Control
Level of 2nd generation ECB Control Control Control Partial Partial Partial

The Bt corn technology is a good one to help protect corn yield from the pest. Because it is an excellent tool to manage the pest, there is a risk that usage levels will be high. If this occurs, then the likelihood of ECB becoming resistant to the Bt toxin will increase. For this reason, the US EPA is requiring that a resistance management plan be provided along with a company's application for registration and that farmers implement the plan. The main component of a resistance management plan is that farmers leave some areas in a field or in a nearby field planted to non-Bt corn hybrids where susceptible genetic types of the ECB can survive to mate with resistant individuals that do survive on Bt-corn. How this plan will be tactically implemented is still being debated and research is underway to help define the design of a resistance management approach in Pennsylvania.

Dennis Calvin

Precision Vision:

Well, spring is here. We have some cardinals in our yard and the early morning chirping is a delight and a reminder of new growth. On campus, students seem to be focused on getting as much sun as possible, on upcoming final exams and on dating. But, what's new? Seems so many years ago, I was doing the same.

The focus of this column for this month is on calibrating sprayers. But, first I thought I would also provide some interesting web sites on the Internet for those of you readers that are surfing the Internet. The Agricultural and Biological Engineering Department maintains a web site where you can view many of the Extension Fact Sheets. I have gotten all of the Extension Fact Sheets about sprayers that we have available entered into the website for your use. Using your browser, either Netscape or Microsoft Internet browser, type in the following URL (stands for Universal Resource Locator). http://server.age.psu.edu/dept/extension/Factsheets/b/ You will see a selection of the fact sheets we have on line. Each month, at the end of this column, I am going to supply a few of the web sites featuring precision agriculture subjects. Try them out and save the web sites in your bookmark section.

Special Topics Section: Sprayer Calibration Comments

In today's economic environment, the control of production costs is very important. An improperly calibrated sprayer has a potential for wasting substantial amounts of costly chemicals. Accurate calibration takes only a few minutes. Accurate calibration is very important for economy, efficiency, effectiveness, and safety.

Sprayer calibration simply means making a "check" or trial run to determine the actual application rate of the sprayer. Data in manufacturers' catalogs are adequate for selecting nozzles or flow control settings, but the application rate needs to be confirmed under field conditions. We usually calibrate a sprayer by measuring or timing an application of water over some known small area called a calibration test plot. We then determine the amount of water applied. Of course, proper nozzles, operating pressure or flow setting, and driving speed need to be selected before making the trial run. It should be noted that a calibration test checks only the application rate; it gives no indication of coverage or distribution.

Why Check Calibration?

There are four very important reasons to calibrate your sprayer:

1. Chemicals need to be applied at the proper rate to be effective and safe without causing pollution. The calibration test tells us the application rate with our selected nozzles (or flow setting), pressure, and travel speed.

2. The operator must know the application rate in order to determine the proper amount of chemical(s) to add to the sprayer tank. Once we know the actual application rate, we can easily determine the acres a tank full or part of a tank will cover. Then we can accurately determine and measure the proper amount of chemical(s) to add to the tank.

3. Applying chemicals at the wrong rate is a waste of money. Using more than the desired amount of chemical is wasteful, may be a violation of the label rates, and may pollute the environment. Too low an application rate probably will not be effective, and money will have been wasted for the material and its application.

4. Actual application rates may vary from nozzle catalog values due to pressure gage error, wheelslip, speedometer error, and friction loss. The catalog is satisfactory for selecting the nozzles but the sprayer must be checked at actual operating conditions to determine the exact application rate.

In other words, a calibration check is necessary to determine the actual application rate for the operating conditions.

Adjustments and Checks Before Calibrating

I. Before calibration, the sprayer must be operating properly. The following precalibration checks are suggested:

II. Check and clean all nozzles and screens. Replace any that are damaged.

III. Check hoses and fittings for leaks and cracks. Repair or replace as needed.

IV. Observe nozzle patterns with clean water; they should be continuously smooth with no skips or heavy streams. Replace any that are suspect. If you need to replace more than one or two, you probably need an entire new set.

V. Check the nozzle sizes for appropriate intended output (manufacturer's numbers).

VI. Check pressure gage. Pressure should be stable and at the desired level. If the gage fluctuates due to pump pulsations, install a damper between the line and the gage. The gage will be easier to read and it will last longer. Liquid-filled gages are recommended for long life.

Summary

Once you do a calibration test, you'll find it is easier than it sounds. Additional tests will be quick and easy. Be sure to record the conditions and results--nozzles used, operating pressure, travel speed or tachometer reading, gear used, and of course, gallons per acre applied--for future reference. The time invested in calibration will pay off in accurate application rates, more effective pest control, and peace of mind knowing you are doing your spraying accurately.



Interesting Websites:

http://w3.aces.uiuc.edu/InfoAg/

http://www.agriculture.com/agtalk/Ag_Groups.html (Choose the Precision Ag Section)

http://www.ppi-far.com/

http://pasture.ecn.purdue.edu/~mmorgan/PFI/graphic.html

http://nespal.cpes.peachnet.edu/pf/

http://www.pionet.net/~kuseld/arkmain.htm

David Wagner

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

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