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July 10, 1998 Vol. 98.9

IN THIS ISSUE:

Production:

MID SEASON CORN MANAGEMENT

Once the middle of the summer arrives, many folks forget about the corn crop even though it is growing fast and determining much of its yield potential then. There are a number of things corn growers should be considering during July and August. Here's a brief rundown of a few of them:

Set some time aside to assess the effectiveness of some of your input choices. Did herbicides and insecticides perform as expected? Is N deficiency appearing on lower leaves?

Start managing wheat stubble fields for next year's corn. Get lime, nutrients and manure on if necessary while the fields are dry. Also, control annual weeds before they go to seed. This is also an excellent time to control perennials.

Consider some rotation alternatives. With prospects for good forage supplies this winter, it may be a good year to do some rotating to forage crops. Rotation is one way to help rebuild soils that had such poor quality in many areas this spring.

Consider some cover crops this fall for the same reasons. In addition, relatively low small grain prices should make cover crop establishment more economical.

Start scouting corn fields and make fall harvest decisions. Fields with corn borer, disease, bird damage, etc. should be harvested early to avoid crop losses.

Finally, develop a marketing plan well before harvest. Marketing is always more difficult when corn is plentiful and if our crop continues to rebound, we may have a large crop this fall.

Greg Roth, Agronomy,
Corn & Sorghum Management

Pest Management:

Newsworthy - The following four articles were recently published in the American Society of Agronomy's "Agronomy News". I thought they were newsworthy and might interest you, if you hadn't already heard about these items.

EU APPROVES GMO LABELING

After nearly two years of sometimes contentious discussion, European Union (EU) farm ministers approved rules that will require labeling of foods that can be proved through testing to contain genetically modified organisms (GMOs). The plan calls for food processors to undertake mandatory DNA testing or other lab tests to determine whether a product contains GMOs. The ministers scrapped plans for a label that would have stated that foods "may contain" genetically modified corn or soybeans if it was unclear whether they were present or not. Ministers also agreed to draw up a list of processed products that are made from genetically modified corn or soybeans which, due to the production process, lose the DNA of the GMO. Products on that list would not be subject to labeling requirements.

U.S. food processors, as well as some small European food manufacturers, say the mandatory testing requirement will prove too costly, an argument that so far has swayed neither EU farm ministers nor members of the European Commission.

The agreed labeling requirements appear to be largely the responsibility of food processors and will not extend to the farm level. For example, farmers will not be required to segregate GMO from non-GMO crops. Strict segregation, beginning at the farm level, is a major objective for a number of European and consumer groups.

AND THE WINNER IS...MONSANTO FOR $4.2 BILLION.

Wall Street Journal, 12 May 1998. Monsanto has purchased both Dekalb Genetics and Delta & Pine Land Company for a combined $4.2 billion. Dekalb will sell for $2.3 billion with Monsanto paying $100 per share. The Journal said, "Though expensive, the acquisitions would give Monsanto an army that rivals the muscle of the alliance between Pioneer and DuPont. The deals could thwart the plans of some European chemical companies to become players in biotechnology." The losing bidder for Dekalb was Novartis.

MONSANTO ACQUIRED.

Wall Street Journal, 1 June 1998. American Home Products, makers of Advil and Chap Stick and owners of American Cyanamid, will acquire Monsanto for $34 billion. American Home Products was recently in the news when its agreement to be acquired by Smith Kline Beecham fell through. Monsanto shareholders will receive American Home Products shares and will have a 35% stake in the new company. Monsanto said the combined company will have a new name and global operations for its agricultural division. The companies said they expect to realize $1.5 billion over the next three years in cost savings. The CEOs of the two companies will become co-CEOs of the merged companies.

AgrEvo ANNOUNCES EPA APPROVAL FOR STARLINK.

AgrEvo press release, 19 May 1998. The USEPA has approved StarLink brand Bt corn hybrids to control European corn borer larvae and include resistance to AgrEvo's Liberty herbicide. AgrEvo says that the StarLink Bt is unique because it contains Cry9C protein, which has a different site of action in the insect gut then current Bts on the market. They believe this is an important step to reduce the risk of resistance to Bt. The Garst Seed Company will be the first to market StarLink and hybrids will be available this year.

Bill Curran, Agronomy, Weed Science

INSECT ALERT

The following insects can be active during this time period. This does not mean they have been seen in the State, but it is the period of time when they can injure crops. Insects that have been reported are shown in bold type and specifics about their management are presented in individual articles. Pictures of each corn insect species, economic thresholds, and scouting guidelines can be seen on the world wide webpage, http://www.fra.cas.psu.edu/.

Corn
Corn rootworm adults and larvae
grasshoppers
stalk borer		 European Corn Borer larvae
Japanese beetle
thrips		 fall armyworm
slugs
true armyworm
Soybeans
bean leaf beetle
green cloverworm
potato leafhopper
two-spotted spider mites 		cabbage & soybean loopers
Japanese beetle
stinkbug		 grasshoppers
Mexican bean beetle
Alfalfa
alfalfa blotch
leafminer
Meadow spittlebug
Spotted alfalfa aphid 		clover leaf weevil
pea aphid 		grasshoppers
potato leafhopper
Small Grains
grasshoppers True armyworm  

Corn Rootworm Larvae - The majority of larval feeding is completed, although some larvae can still be found feeding on roots. Adult beetles are beginning to emerge in central Pennsylvania and warmer areas of the state. Peak adult emergence should occur during the third or fourth week of July. This will be about one week earlier in southern warmer regions of the state and one to two weeks later in cooler areas (See Tables 1 and 3 for degree day information for your area). Some plant lodging is becoming apparent in corn fields. A number of fields have significant root pruning, but are still standing well. Because most fields have good moisture levels, plants in these fields should soon expand their brace roots and develop new fibrous roots to provide adequate structural strength and root surface area for proper growth and development. However, a storm with strong winds could cause significant lodging if it hits before the brace root expand. Because of the significant rainfall this spring and early summer, fields where more water soluble soil insecticides were used may sustain higher levels of root damage than those fields treated with less water soluble products.

European corn borer - First generation larvae are reaching the final two instars of development in central Pennsylvania. A few pupae can be found. Warmer southern areas should have late instar larvae, a large number of pupae and possibly the beginning of the second generation flight. Based on the age of larvae, the second flight should begin about the third week of July and about the first or second week of August in central Pennsylvania. In warmer areas the flight should be about one week to 10 days ahead of central Pennsylvania (See table 1 and 3 for degree day requirements in your area).e Bt-corn event registration to check these fields can result in a loss of their registration of the product.

Economic Thresholds Values - See the "Field Crop IPM Training and Reference Manual" for methods to calculate specific thresholds which vary based on plant growth stage, yield potential, percentage control, and market value of the crop.

Potato leafhopper - Leafhopper numbers are moderate in Pennsylvania alfalfa fields this summer. A high percentage of second cutting fields were treated. Watch the new regrowth as it reaches 2 to 12 inches for development of potato leafhopper infestations. See the Agronomy Guide for Insecticide Options.

Economic Threshold Values - See the Publication, "A Pest Management Program for Alfalfa in Pennsylvania", for specific thresholds.

Threshold Ranges:
For 0 to 4 inch high alfalfa - 0.2 to 1.0 leafhoppers per sweep
For 5 to 8 inch high alfalfa - 0.3 to 1.7 leafhoppers per sweep
For 9 to 12 inch high alfalfa - 0.8 to 5.0 leafhoppers per sweep

Slugs - Slugs continue to be found in corn and soybean fields in the state. The warm weather should help most fields keep ahead of their feeding injury; however, a few late planted soybean and corn fields may still be susceptible to injury. Watch late planted soybeans and corn fields, particularly those planted no-till, for slug feeding. If slug feeding is significant as the plants begin to emerge, a broadcast treatment of Deadline MP at 10 lb per acre should be considered. Remember soybeans are particularly susceptible to slug injury because the growing point is above the cotyledons. Plants consumed below this level will die. Once plants are emerged follow the listed economic thresholds in making treatment decisions

A new slug species, Arion subfuscus (the dusky slug) has shown up in some Pennsylvania corn and soybean field in high numbers this year. This slug species has been causing problems in Ohio for several years and was present in low numbers in Pennsylvania. However, the mild winter and late planting of corn and soybeans increase crop susceptibility to the pest. The dusky slug is an imported species and has several color variations, which can look similar to the banded slug. Reddish, orangish, light brown and dark brown individuals occur and can be found in the same field. Their presence can be verified by the orange slime trails they leave in a field. This species is commonly associated with woodlands and is thought to feed primarily on fungus (mushroom, etc). When found in a corn or soybean field, they feed primarily on the stems, cotyledons, and roots of plants, but will also feed on the leaves. Leaf feeding damage differs from the gray garden slug in that leaves look stripped rather than having irregular areas removed. Once the soybean trifoliate leaves are actively expanding, their damaging potential declines rapidly.

Economic Threshold Values: 50% of leaf area removed per plant and plants are less than V6 (6 leaves with the collar showing outside whorl).

Dennis Calvin,
Entomology


Precision Vision:

SOIL SAMPLING - DO I AVERAGE OR MAP MY SAMPLING DATA?

What is the typical scenario in getting soil samples? Sometimes the farmer takes a soil sampling probe or a shovel and gets a few typical samples from around the field to send to the soils lab for analysis of phosphorous, potassium, pH, etc. In other cases, the lime or nutrient supplier agrees to take the soil samples for the farmer and to provide the proper amount of lime or fertilizer. Other scenarios include, crop consultants taking the soil sample, and making application recommendations. Typically, the samples are mixed in the pail and put into the sample bag and mailed with the information sheet. A week or two later, nutrient and lime recommendations are received from the soils lab. Fertilizer and lime supplies are ordered or the custom applicator is called and applications are scheduled. If you count the cost of the nutrients and lime, it is a significant production cost of the harvested crop. All the costly crop inputs are dependent on a decision made on a soil sampling procedure.

The point where crop management and cost control starts is the moment the decision is made to collect soil samples. Sure, the cost of each sample may run $6.00 or more and to get even one soil sample for each field on the farm may run to a hundred or so dollars. How to sample is one of the decision points:

The subject of this article is whether to mix the soil samples or to keep them separate. There are arguments for both situations. I believe that a farmer who tills and harvests his own land gets to know the ground very well. There is great value in this accumulated knowledge, gained from driving the tractor or the combine or the forage chopper and baler. Before we can talk about mixing or keeping samples separate for analysis, we have to examine another problem; that is, how many samples to take and where to take them. To take the "scientific" approach involves many statistics and more room than is available for this article. Consider any farm field in Pennsylvania. If the farmer has been farming the field for several years, the farmer will have developed a "feel" for the variability across the field -- wet/dry soils, high/low yield, flat/hilly, light/dark soil surface, clay/loam/sandy texture, etc. This intuitive knowledge guides the decision on where and how many soil samples to take. The general rule is to take samples so each area of the field that has some distinct characteristic is represented by a number of soil samples in proportion to the percent of the field taken up by that distinct characteristic. What a mouthful!

Here is an example: if a field has 25 percent of the area in a low, flat, high organic soil and the rest of the field, 75 percent, is taken up by hillside, droughty, lower organic soils, then take enough samples, (say two or three) to represent the 25 percent of the field in high organic. Then take three times more samples (say six to nine), scattered around the hillside areas. This means that 25 percent of the samples represent 25 percent of the field area and 75 percent of the samples represent 75 percent of the field. If the samples are mixed, at least each portion of the field will be properly represented. If the samples are analyzed separately, then much more will be known about the different areas of the field for future variable rate or precision application technologies.

Say a farmer has just rented a new farm and knows nothing about the field soil nutrient or pH characteristics. Then a different method of sampling has to be taken. The most common approach is to divide the field into a minimum of four or five sections, or grids, and take a sample at the center of each grid. Have each sample analyzed separately. This initial sampling will show the general soil characteristics and the analysis will also show how much variability is present. Then, a second soil sampling can be designed to more thoroughly investigate the variability with perhaps a sample for each acre or each two acres, not in a regular grid pattern, but spaced as described in the preceding paragraph.

Now we can talk about mixing, or compositing soil samples. If the fields are small and there is not much variation shown by soil sampling or the farmer's experience from yield observations, then there may not be a need for keeping the samples separate. If it is not justified to vary the application of nutrients or manure across the field, there is a good argument for just mixing the soil samples together for analysis. At minimum, the samples from each major section of the field can be mixed for analysis.

Now the tough situation. If there is significant variation in the field, and the field is larger, there can be shown some potential for changing the rate of application of manure or nutrients depending on the variability in the field. That gets into the area of precision farming that I have been talking about in previous columns in Field Crop News.

If a Global Positioning System (GPS) is used to log the geographic location of each soil sample and had each sample analyzed separately, then a variety of soil characteristics maps could be generated that could be stored in a Geographic Information System (GIS). These GIS maps become one of the decision inputs that allows a farmer or consultant to look at a variety of conditions that affect the growth of the crop, not only as an average for the field, but for every square yard of the field individually. These soil characteristics maps could be then compared to yield map and other types of field maps to generate a "prescription map" for applying lime or nutrients to the field. Applying the proper mix of pH control and nutrients is possible so that each part of the field could be managed to yield its most profitable level of crop production. The most profitable level of production is dependent on many conditions. A single mixed sample that tries to represent average conditions in the field will not allow good management of the various ideas to the field.

To mix or not to mix that is the question. Mixing depends on the field size, the variability, and the need for the information both for the present and in building a base of data to guide future decisions for that field. If a farmer is planning on getting into yield monitoring, and variable rate application, then it makes sense to spend a little more money on good soil sampling analysis with adequate soil sampling strategies. Penn State agronomy specialists and precision farming specialists can help you with these decisions.

David Wagner,
Ag & Bio Engineering, Precision Ag


Agents Corner:


ADAMS COUNTY

Crops seem to have grown exponentially the last several weeks after their slow start. There are approximately 300 acres of snap beans growing in our area with harvest still several weeks away. Mexican bean beetle hatch has occurred, along with pressure from leafhoppers and pale stripped flea beetles.

Corn is in varying stages of growth from just planted to emerging tassel. Most sidedressing was completed this past week. The first adult rootworm beetles were seen on July 3. Fields that are second year corn or continuous corn, without insecticide, are showing root pruning and the stalks are developing the characteristic "goosenecking." European corn borer feeding in the whorl is becoming evident.

Soybean growth is leveling out and the fields appear more uniform as compared to the uneven emergence. Groundhogs are out helping to control growth.

Alfalfa second cutting has been completed with above average forage quality. Sweeps at green-up are showing threshold levels of leafhoppers. With the recent storms, scouting third cutting regrowth is most warranted.

Finally, barley and wheat harvest is complete. Test weights have been extremely light on the barley and normal to light on the wheat.

Larry Swartz
Adams County

BRADFORD/SUSQUEHANNA COUNTIES

The word from this corner of the state is ugly. This might seem a little strong coming from the optimist I consider myself and perhaps it is, but the crops sure aren't pretty around here. It does make you wonder if credence ought be given to the adage that 'a dry one can only scare you, but a wet year will starve you to death.' We simply can't get much, if anything, done.

Our corn crop looks poor and is extremely variable. Yes, decent corn can be found growing on some better drained soils particularly if manure was incorporated but most of our ground, heavy and poorly-drained, is taking its toll on our corn crop. A significant amount of corn has drowned or is yellow from soil nitrogen losses and is struggling to remain viable. Numerous fields have been replanted or the populations have been augmented by another planter pass. Corn planted late seems to be the least vigorous and in the most peril. Fortunately, our weed control programs for the most part are working well but that offers only moderate solace at this point. We're looking forward to the dusty days of summer here.

Mark Madden
Bradford/Susquehanna Counties

CENTRE/CLINTON COUNTIES

Adequate rain combined with warm temperatures the past couple of weeks to push most corn well passed the "knee high by the 4th of July" standard by which corn is gauged. Although many fields emerged unevenly, they seem to be growing well now. Second cutting of hay is in progress, but getting it adequately dry has been a challenge.

The soybean crop is also progressing well, although milkweed and burdock have been a problem in many fields. A lot of Roundup Ready beans have been planted, and will serve a good test this season on their fit in controlling perennial or other hard to kill weeds. Small grains are coming off now. Reports from growers indicate light test weights in barley, but average yields. Wheat harvest has just begun.

Blue mold was diagnosed in a tobacco field in Loganton, Clinton County. This year's weather has provided favorable conditions for blue mold growth, and tobacco crops have required constant scouting. All in all, it has been a good growing season so far.

Gary Dauberman
Centre/Clinton Counties

FAYETTE COUNTY

Producing crops in the southwest is really a challenge this year. For the past two weeks of this writing (6/22/98), very little field work has been done due to the weather. About 50% of first cutting hay is still to be harvested, growers who are trying to cut barley, in between the rains, are having a really difficult time, and weed outbreaks in corn fields are getting ahead of post emergence herbicide applications.

The positive side is the oats crop looks good and the wheat that is still standing is maturing nicely. Also, hay crop producers that harvested in that May window of opportunity, have a really good second cutting ready for harvest.

Don Fretts
Fayette County

LAWRENCE COUNTY

In general, we are having a good growing season here in the West Central region. The corn crop is progressing well, although moisture levels are somewhat inadequate for much of the area. Prior to a shower last evening, some of our areas well-drained fields and those no-tilled later into sod were showing wilt. Weed control has been somewhat variable as we experienced a dry spell for much of May which allowed for weed escapes, mostly nutsedge, lambsquarters, and velvetleaf, necessitating more postemergent applications than usual.

On a positive note, we have been receiving some positive feedback from producers who have tried zone tillage for the first time this year; however, no-till fields have seemed to struggle this year for any number of reasons, some of which remain unclear to this writer.

Second cutting of alfalfa is continuing on many farms and yielding quite well. However, leafhoppers have reached threshold levels in many fields and some second cuttings have been stunted. For the most part, spring seedings of alfalfa yielded excellent stands, but we must continue to monitor them closely for leafhopper feeding.

The wheat harvest is continuing ahead of schedule with good yields in general. The early harvest of small grains has spurred an interest in double crop beans which is somewhat rare in our location. With a few exceptions, the bean crop is looking great. We did experience severe slug feeding in some no-till fields and in a few cases, fields had to be replanted. We're also concerned that some non-Roundup Ready fields may have been or will be sprayed too late for good post emergence weed control, as the beans and weeds really took off over the last several weeks.

Following Craig William's lead, we have been evaluating 11 herbicide treatment options for controlling multiflora rose over the last several years. At a recent field day, those in attendance observed that Roundup applied in the fall, or Ally applied at flower or in the fall provided the best results. These observations have been consistent over the four locations in the study.

Ryan Hockensmith
Lawrence County

SCHUYLKILL COUNTY

There appears to be an increase in no-till corn and beans this year, primarily related to an effort to save fieldwork time and put planting on schedule.

The early season lack of uniformity in the corn fields rapidly disappeared when the warm moist weather arrived. However many of the fields that were not sidedressed show signs of N deficiency.

There is a lot of late planted corn and beans. With beans it is difficult to distinguish between the full season and late planted crop. Planting was more or less a continuous process from mid-May through late June.

Perennial weeds seem to be more of a problem this year.

The grass hay crop grew well but harvest as high quality bailed hay was extremely difficult.

J. Allan Shoener
Schuylkill County

WAYNE COUNTY

The northeast did not enjoy the rain-free period during late May and early June that much of the rest of the state experienced. In fact, I don't think we have had more than three consecutive days without rain since April - or at least it seems that way. The rainy weather, along with the somewhat poorly drained soils in the area, has combined to delay planting and forage harvest and make many farmers rather grumpy.

Corn fields range from 6 inches to waist high with the majority of the fields in the 20-inch range. Fields that were planted in a timely manor on better drained soils look fantastic. Later planted and/or wet fields look less impressive. Yellow, stunted corn (in wet spots) is the most common problem throughout the area. Limited PSNT results indicate lower than expected N levels in most fields. Producers are currently sidedressing as part of their normal routine or in an attempt to "boost" stressed fields. Weed control has been very good so far; although I am guessing we will see late flushes of weeds in this year of frequent rains. Slugs have been the most common pest this season. They are present in most fields but are rarely severe enough to warrant a treatment. Other pests of note include a few severe infestations of seed corn maggot, some black cutworm, and the ever present four-legged pests. Many fields were planted late so early frosts will become a concern this fall. We're keeping our fingers crossed. Overall, I would estimate the yield potential of the corn to be average to slightly better than average if our current weather continues.

The rainy weather has caused a lot of problems with the forage harvesting. Many producers are well into their second cutting; although there is still a lot of first cutting that remains to be harvested. (Does anyone need mulch hay?) Potato leafhoppers are present in the alfalfa growing regions of the northeast, but they have not increased in numbers like expected. Few acres have needed an insecticide application for leafhoppers.

Dave Messersmith
Wayne County

Degree Day Accumulations:

1998 DEGREE DAY ACCUMULATIONS

To track corn and insect development, compare the 1998 cumulative degree-days shown in Table 1 to the required values in Tables 2 and 3. Choose a location that is closest to your site when making a comparison.

Table 1. Cumulative Degree Days for Corn and Insects for the Period Ending July 6, 1998
Corn Insects
County Location 1998 30-year ave. SCM/SB AW BCW CRW ECB
50F 50F Diff 40F 48F 50F 53F 55F
Erie Waterford 964 836 128 2050 1268 1095 862 723
Crawford Meadville 1026 896 129 2161 1350 1173 933 788
Mercer Mercer 1028 896 132 2179 1360 1181 939 794
Bradford Towanda 1015 900 115 2166 1346 1169 926 780
Lycoming Montoursville 1081 962 119 2297 1439 1256 1005 853
Tioga Mansfield 954 836 118 2054 1264 1090 856 716
Susquehanna Montrose 872 758 115 1933 1167 997 771 638
Butler Butler 1085 951 133 2292 1441 1257 1007 856
Indiana Indiana 1072 941 131 2287 1433 1248 998 847
Lawrence Lawrence Jct 1036 907 128 2166 1358 1181 940 796
Blair Martinsburg 1031 900 131 2232 1388 1204 956 808
Centre State College 1029 903 126 2213 1376 1194 948 801
Columbia Bloomsburg 1093 974 119 2335 1462 1277 1023 869
Clearfield Curwensville 1022 895 127 2189 1361 1182 938 792
Dauphin Elizabethville 1129 1005 124 2414 1517 1328 1067 910
Bedford Bedford 1103 971 133 2373 1491 1301 1042 887
Mifflin Belleville 1095 969 126 2340 1468 1281 1026 873
Northumberland Sunbury 1134 1012 122 2411 1517 1329 1070 912
Lehigh Trexlertown 1150 1028 122 2467 1551 1359 1095 934
Schuylkill Hegins 1089 968 121 2341 1464 1278 1022 869
Westmoreland Greensburg 1073 938 135 2295 1438 1252 1001 850
Somerset Somerset 935 794 141 2076 1268 1089 850 711
Washington Washington 1138 998 140 2413 1527 1336 1076 919
Franklin Chambersburg 1181 1049 132 2530 1601 1405 1135 972
York York 1215 1085 130 2608 1652 1453 1178 1011
Lancaster Ephrata 1146 1021 125 2472 1554 1361 1095 935
Berks Hamburg 1164 1041 123 2489 1568 1376 1110 949
Corn degree-days based on a May 1 starting date. Insect degree-days based on a January 1 starting date.


Table 2. Cumulative Degree-Days Required for Insects to Reach key Periods for Scouting or Management
  Maturity rating (days)
80 90 100 110 120
50% Silking 1100 1150 1250 1300 1400
Black Layer Formation 1900 2100 2300 2500 2800


Table 3. Cumulative Degree-Days Required for Insects to Reach key Periods for Scouting or Management
  Stalk Borer Alfalfa Weevil Black Cutworm* Corn Rootworm European Corn Borer Seed Corn Maggot
Adlt Emrg 5% Hatch 1st Gen 2nd Gen
SB AW BCW CRW ECB1 ECB2  
Initiation 1400 300 91 1283 380 WCRW** 558 1550 450***
Termination 1700 500 430 2253 478 NCRW** 1228 2045  

*Degree-day accumulation should begin at first moth capture in a black light or pheromone trap.
**These values represent degree day accumulations for optimal timing of Furadan 4F post emergence applications. WCRW-Western Corn Rootworm, NCRW-Northern Corn Rootworm
***This number of degree days represents the number of degree days required from plowdown of green vegetation until it is safe to plant corn or soybeans and avoid seed corn maggot injury.

Dennis Calvin, Entomology

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

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