Volume 11, Issue 1                                                                                                    March 14, 2003

The Weekly Schedule Begins – April 4, 2003

 

This newsletter is designed to provide subscribers with the latest information on disease and insect problems, weed control information, crop progress reports, and other timely topics related to agronomic and vegetable crop production in Delaware.  University of Delaware Extension Specialists and Agents provide information for the newsletter.  The weekly issues will begin on April 4, 2003 and continue through the month of September.  The Weekly Crop Update can be obtained by mail, fax (subscription cost is $30) or from the Internet at http://www.rec.udel.edu/TopLevel/Publicat.htm for free.  Use the enclosed form to subscribe. We also offer a weekly email reminder to those of you who wish to receive one.  Please forward your email address on the enclosed form or to my email address below.  I ask those of you who plan to access the newsletter from the Internet to please notify me of any problems you may encounter during the season.  Please forward any comments or concerns to me at

302-856-7303 or at wootten@udel.edu .

 

 

Has the Winter Weather Affected Insect Populations? - Joanne Whalen, Extension  IPM Specialist;   jwhalen@udel.edu

 

Entomologists are often asked if extremely cold or mild winter weather has an impact on insect populations in the spring. Most would agree that there is no one answer to this question. Although mild weather conditions enable some overwintering insects to survive, winter weather has little or no impact on other species.

 

If you look at the major insects that attack field and vegetable crops, some general principles can apply ---

(a)    Overwintering Stage: Insects that overwinter in the soil in the egg stage are generally not affected by cold winter temperature. The best example is the corn rootworm. In comparison, insects that overwinter in the adult stage, especially beetles can be more affected by cold winter temperatures. However, the heavy snow cover can negate these affects because it offers some degree of insulating protection.

(b)    Overwintering Location: Insects that overwinter deep in the soil -- like grubs and wireworms -- are generally not affected by the cold winter temperatures. Spring conditions including early planting followed by cool, wet weather can favor damage from these pests.

(c)    Natural Protection: The European corn borer (ECB), which overwinters as a full grown larva, has an antifreeze type material in its body that protects them from cold winter weather. Vacillating temperatures (from very cold to very warm) in the winter can have a greater impact on reducing overwintering ECB populations.

(d)    Migratory Species: Obviously, winter conditions in our area have no affect on migratory species like the potato leafhopper, cabbage looper and beet armyworm.

So, predicting the potential for infestations based on winter weather conditions is often not very accurate. It has been the experience of most entomologists that spring weather conditions have the greatest impact on insect populations and determine if an insect will become a pest problem. The only way to know if you have a problem is to understand which cropping systems favor certain pests and plan to scout fields on a routine basis in-season.

 

Fruit

 

Fruit Insects - Joanne Whalen, Extension IPM Specialist;   jwhalen@udel.edu

 

Peaches.

A Section 18 Emergency Use request was again submitted to EPA in February for the use of Provado on stone fruit to control aphids that vector the Plum Pox Virus. There is also a possibility that the full Section 3 federal registration may come through before this use season. We will let you know as soon as we get a response from EPA.

 

 

Vegetables

Vegetable Insects - Joanne Whalen, Extension  IPM Specialist;   jwhalen@udel.edu

 

Seed Corn Maggot (SCM).

With the recent cool, wet weather, SCM management should be considered in most spring planted vegetables including cabbage, peas, snap beans, spinach and sweet corn.

 

Peas and Snap Beans.

The only available control options are a seed applied Lorsban SL treatment (must be done by a commercial treater) or a hopper box treatment of diazinon 50W. Gaucho is no longer labeled on snap beans for seed corn maggot control. In recent years, diazinon 50W has provided good SCM control. It should be applied at a rate of ˝ oz per bushel of seed and graphite added to prevent bridging in the planter.  As of November 2002, this is the only diazinon formulation registered for use on peas and snap beans. We will have this label until July of 2004, but it is in jeopardy of being lost. We will need to hear from growers and processors interested in maintaining this registration. Documentation and information regarding the importance of this material for your operations will be needed. Please contact Joanne Whalen at

302-831-1303 for more information.

 

Spinach.

The only available option is a broadcast application of 3 qts/A of diazinon applied right before planting and immediately incorporated 2-3 inches deep. Diazinon should not be incorporated too deeply and the ground should only be worked once after application.

 

Sweet Corn.

In addition to hopper box treatments, a number of seed applied treatments including Lorsban SL, Gaucho and Cruiser are available for sweet corn. Soil insecticides including Force, Lorsban, Fortress, Furadan and Counter are also labeled for SCM control in sweet corn.  Under heavy pressure, a soil insecticide and a seed treatment may both be needed. Furadan and Counter are the only two soil insecticides that will also provide flea beetle control. Gaucho and Cruiser will also provide flea beetle control.

 

 

Sandea Herbicide Receives Federal Label for Several Vegetable Crops Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

 

In December, EPA granted a federal registration for Sandea, a broadleaf weed herbicide for use on cucumbers, cantaloupes, pumpkins, tomatoes, winter squash, and asparagus as post-plant preemergence or post-emergence treatments.  It is also labeled for use in the row middles for peppers and summer squash.

 

Sandea provides excellent control of yellow and purple nutsedge, as well as many other broadleaf weeds.  Pre-emergence applications require 0.5 to 1.0 ounce per acre.  Post-emergence applications should be applied at the 2-5 leaf stage, with the 3 leaf stage being ideal.  Rates for post-emergence applications are 0.5 to 0.66 ounce per acre with a non-ionic surfactant.  Irrigation should be delayed until 2 to 3 days after application and cultivation until 7 to 10 days after application.  Both applications should be applied in a minimum of 15 gallons of water per acre.

 

Sandea does not control grasses.  Therefore, herbicides that control grasses should be used as part of the weed control program.  The selection of the grass herbicide will vary with the crop.

 

Please read the label carefully before purchasing and using Sandea.  More details about Sandea on a crop by crop basis will be published in future Weekly Crop Updates.

 

 

Pictsweet Frozen Foods Changes Plans Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

 

In early March, Pictsweet Frozen Foods chose not to exercise its option on land south of Bridgeville, Delaware.  The company had been planning to build a raw product receiving and cooling station to receive lima beans, peas, and possibly sweet corn.  Pictsweet was also developing plans to build a complete frozen food factory at some point in the future.

 

While these plans have been dropped, the company is committed to contracting and receiving 3,000 acres of lima beans this year and in the foreseeable future.  Pictsweet is contracting with growers for delivery of raw product in Delaware, then cleaned and cooled for shipment to their plant in Bells, Tennessee.  With the investment required in harvesting equipment, it is also foreseeable that peas, which are harvested by the same equipment as lima beans, may be handled in the future.

 

While the news is disappointing in light of the company’s original plans, Pictsweet’s interest in procuring lima beans from Delaware is a strong positive.  Delaware grower’s ability to produce lima beans efficiently and consistently is why this new “book of business” has found its way to Delaware.

 

 

Vegetable Diseases - Bob Mulrooney, Extension Plant Pathologist, bobmul@udel.edu

 

Stewart’s Wilt of Sweet Corn.

For control of Stewart's wilt, which is vectored by the corn flea beetle, it is important to control the flea beetle. Plant resistant varieties and control the beetles early. The following index predicts conditions favorable for overwintering flea beetle populations not the abundance of the bacteria. The prediction has its limitations including the influence of snow cover on survival, but indicates that flea beetles should be reduced compared to most seasons. The question always becomes how much bacteria is available for them to spread. It’s interesting to note how cold this period was compared to previous seasons, in case you had not noticed.

 

Winter Temperature Index For Predicting Stewart’s

Wilt in Delaware Sweet Corn, 1994-2003.

 

Average monthly temperatures in oF at Georgetown, DE. REC. 1994-2003

 

2002-03

2001-

02

2000-01

1999-00

1998-99

1997-98

1996-97

1995-96

1994-95

December

36.7

43.2

31.2

40.3

41.3

39.3

42.0

33.5

43.0

January

28.9

40.0

33.8

33.9

39.5

42.6

35.0

33.5

39.0

February

33.8

39.9

38.8

39.7

38.7

40.6

41.5

34.7

33.8

INDEX

99.4

123.1

103.8

113.9

119.5

122.5

118.5

101.7

115.8

 

Average monthly temperatures in oF at Newark, DE Experiment Station. 1994-2003.

 

2002-03

2001-

02

2000-01

1999-00

1998-99

1997-98

1996-97

1995-96

1994-95

December

33.5

43.3

31.1

39.1

41.0

38.4

40.9

32.1

41.8

January

27.1

39.6

31.5

32.6

34.8

40.9

33.2

30.9

37.6

February

29.5

40.1

38.4

37.8

38.0

40.6

40.3

34.7

31.7

INDEX

90.1

123.0

101.0

109.5

113.8

119.9

114.2

97.7

111.1

 

Severity Index: <90, usually absent; 90-100, intermediate; >100, usually severe.

 

Prediction for 2003:

Newark:          Absent-Intermediate

Georgetown:  Intermediate - Severe

 

 

Vegetable Diseases - Bob Mulrooney, Extension Plant Pathologist, bobmul@udel.edu

 

Fungicide Update.

There have been some new fungicide additions for 2003 that will be welcome additions for control of troublesome plant diseases. Specific use information can be found in the 2003 Commercial Vegetable Production Recommendations E.B. 137.

  • Benlate use is now expired and is not legal for use.
  • Omega from Syngenta Crop Protection is labeled for use on potatoes for late blight and white mold control.
  • Switch also from Syngenta is a mix of fludioxonil plus cyprodonil is labeled on strawberries for Botrytis gray mold control.
  • BASF labeled the active ingredient pyraclostrobin for use on vegetables and field crops. For vegetable crops the product is called Cabrio and for our area labeled vegetables include: carrots, cucurbits, peppers, and tomatoes. For potatoes and field crops the same active ingredient is labeled as Headline. For potatoes, Headline will be useful for early blight control and also has a 2ee label for black dot (Colletotrichum coccodes) as well. This fungicide is in the same class as Quadris and Flint (Gem on potatoes) and needs to be rotated with fungicides in other classes.
  • Several years ago there was a new potato seed treatment labeled called MonCoat MZ (combination of flutolanil and mancozeb) for suppression of black scurf , Fusarium, silver scurf and Rhizoctonia stem canker. This season another new product with a similar name called Moncut 70DF is now available. This systemic fungicide is used as an in-furrow spray and is not a seed treatment. It contains the fungicide flutolanil as well.
  • Acrobat 50WP received a full federal label for cucurbits (downy mildew and fruit rot) as well as bulb vegetables and lettuce. No more need for section 18’s for Acrobat.
  • Ronilan is now labeled on lettuce and snapbeans only for white mold control. This use will be ending at the end of 2005.
  • Cuprofix Disperss is a new copper formulation of basic copper sulfate manufactured by Cerexagri. It is labeled for many bacterial and fungal diseases of vegetables, fruits and field crops including downy mildew of lima bean.

 

 

 

Field Crops

 

Field Crop Insects - Joanne Whalen, Extension  IPM Specialist;   jwhalen@udel.edu

 

Alfalfa.

Although alfalfa weevil populations have been high the past 2 seasons, winter weather conditions may help to reduce some of the overwintering adult and egg populations. However, heavy snow cover can negate this affect since it produces an insulating effect. So, you should begin sampling fields for early feeding signs by the last week in March. Look for small larvae feeding in the tips of plants producing a round, pinhole type of feeding. Once you detect tip feeding, a full field sample should be taken. You will want to avoid treating fields too early since it may result in multiple applications. In general, no treatment should be needed before you observe 50 percent of the tips with feeding damage.

 

Field Corn.

New Registration – On February 25, 2003, Monsanto received a full approval for YieldGard Rootworm Bt corn. While YieldGard Corn Borer corn protects plants from attack by ECB and a few other caterpillars, YieldGard Rootworm corn protects only against corn rootworm attack. It will not provide control of secondary soil insect pests like wireworms and white grubs. YieldGard Rootworm corn has been approved for all end uses in the U.S. and has completed regulatory review in Japan. In 2003, this trait will be available in corn hybrids sold through Monsanto’s branded seed business ( DEKALB and Asgrow) as well as through licensed, independent seed companies. An important part of this product’s stewardship program is the use of insect resistance management practices to delay the potential development of resistance. The EPA requires growers using YieldGard Rootworm corn to plant a minimum of a 20 percent refuge of non YieldGard Rootworm corn adjacent to or within the YieldGard Rootworm field. This resistance management plan was developed by a collaborative team including Monsanto and a committee of both university and government scientists considered to be the nation’s leading corn rootworm experts.

As you make plans to plant field corn, understanding the factors that favor soil insect pests can be used when making a treatment decision and selecting the best treatment option:

 

Seed Corn Maggot (SCM).

This insect overwinters in the pupal stage and becomes active at temperatures as low as 40 degrees F. Although we have not observed any egg laying activity, we know that cool wet conditions at planting, the use of manure and/or plowing under of green cover crops close to planting all favor maggot problems. Since the recent weather trend has been cool and wet, most early planted conventional corn and all no-till plantings will be susceptible to seed corn maggot attack. In addition to granular and liquid soil insecticides, seed treatments can provide effective control. Hopper-box treatments containing diazinon or permethrin as well as seed commercially treated with imidacloprid (Gaucho or Prescribe) or thiamethoxam (Cruiser) will provide seed corn maggot protection. In fields with the potential for heavy pressure (i.e. manure has been used, or a spring cover crop is plowed under), a soil insecticide plus a seed treatment may be needed.

 

Wireworms (WW).

High soil organic matter, sod covers, and heavy grass weed pressure the previous season all favor wireworm populations. Fields having a combination of high organic matter and heavy grass weed pressure are the most susceptible to damage. Wireworm larvae spend multiple years in the larval stage and the larvae move up and down in the soil profile following moisture gradients. Therefore, good control is often difficult to achieve. Seed treatments containing diazinon/lindane or permethrin will only control larvae feeding on the seed. The Gaucho label states seed protection only and the Cruiser label states early season seedling protection. Soil insecticides including Regent, Force, Fortress, Lorsban, Counter, and Warrior are labeled for wireworm control. All materials must be placed in-furrow to get effective control. The Mustang MAX in-furrow label for field corn only has cutworm control on the label and Baythroid does not have an in-furrow label. Remember, the use of Capture or Empower (both formulations of bifenthrin) is prohibited on field corn grown in coastal counties.

 

White Grubs.

In general, grubs are favored by a number of factors including planting into double crop soybean stubble, old sod, hay, pasture or set-aside acreage. The most accurate way to measure the potential for a grub problem is to sample fields for grubs before planting, but it should be done before a field is tilled. The most accurate results will be obtained when the soil temperatures at 6-inches deep are at least 45 degrees F. At each site, sample one square foot of soil dug six inches deep. One to two samples should be taken for every 10 acres with no less than 10 samples per field. A treatment is recommended if you find 1-2 grubs per foot in heavy soils or 0.5 – 1 grubs per foot in sandy soils. Soil insecticides need to be placed in-furrow to get effective grub control. Under high population pressure, the most consistent grub control has occurred with Counter or Force. Remember, both materials need to be placed in-furrow for grub control and they need rainfall to be activated. In terms of seed treatments, Gaucho and the low rate of Cruiser will only provide early season seedling protection.

 

Black Cutworm.

This insect is favored by late planting, broadleaf weed growth (especially chickweed) present before planting, poorly drained field conditions and reduced tillage. Rescue treatments can be applied for this soil insect if you are able to scout fields twice a week once leaf feeding is detected. If you are unable to scout and you have conditions favoring cutworms, a pyrethroid  tank mixed with a herbicide and applied close to planting has provided effective control. The granular insecticides Force and Lorsban are labeled for cutworm control, but must be applied as a T-band to be effective. The new BT insect protection trait, Herculex, has also provided good control of cutworms. However, fields should still be scouted especially if pressure is high or large worms are present at the time of planting. In some cases, a rescue treatment may still be needed.

 

Wheat.

Although we continue to find spotty distribution of Barley Yellow Dwarf Virus (BYDV) in the state, aphid management can play an important role in reducing losses from BYDV. It still appears that the most important time to control aphids and help reduce problems from BYDV is the first 30 to 60 days after plant emergence.  Although many fields are small and it is possible to have virus vectored in the spring, if you see BYDV in wheat this spring it was likely vectored late last fall and early winter.  Information from Kentucky indicates that there is generally no yield impact after Feeke’s growth stage 4 (stem elongation).

 

The aphid still causing the greatest amount of damage in recent years has been the greenbug. This aphid can be easily identified by the green stripe down the center of the body. Although this aphid can vector barley yellow dwarf, the main damage occurs when it injects a toxin into the plants. Feeding damage initially appears as small reddish pinspots which lead to yellowing of leaves that eventually turn brown and die. Although this aphid causes the greatest damage from mid to late fall, it was still causing damage in early January and can be present throughout the winter and into the spring. So, be sure to check fields at least once in March to early April for overwintered populations. Dimethoate, Lannate, Malathion, Penncap and Warrior can be used for greenbug control in wheat.  The following greenbug thresholds are used in other areas of the country and can be used as a general guideline in our area:

 

 

 

 

 

 

  

 #/Foot of Row

Plant

Height

Time of Year

20-50

4-6 "

Fall - late Winter

200

7 - 10 "

mid-March

300

18-20 "

mid-April

800

30 + "

mid-May

 

 

Precautions for Herbicide Use with Nitrogen Applications to Small Grains - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu

 

It is common to add herbicides when nitrogen is applied to small grains and small grain-legume mixtures.  These precautions are from manufacturer’s label:

 

Harmony Extra or Harmony GT- slurry in water first and may result in temporary crop yellowing.  If liquid nitrogen is less than 50 percent of the spray mix, then include a surfactant.  For 2,4-D it varies with the formulation.  The ester formulation can be mixed directly with nitrogen, but labels recommend good agitation.  Amine formulation of 2,4-D should be mixed with 3 to 5 parts of water before adding it to the nitrogen solution.  Buctril label cautions about potential leaf burn when mixed with liquid fertilizer, but leaves emerging after application are not affected.  For MCPA, it varies some with the manufacturer.  The ester formulation should not be applied with liquid nitrogen.  The amine formulation varies, ranging from no mention of liquid nitrogen to application is allowed.

 

 

Small Grain Weed Control - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu

 

It is time to consider your weed control for the small grain crop.  Fields that were no-tilled or chickweed emerged shortly after planting in the fall are fields to check first for spring treatment.  If you have wild garlic or Canada thistle, the time of application should be delayed since you need to spray these weeds when they have fully emerged.  Coverage is important for these species.  If weed pressure from winter annuals is great, it may not be possible to get control of the winter annuals and perennials with one application.  In that case, two applications maybe required.  You can mix your Harmony Extra with nitrogen.  If spraying Harmony Extra with nitrogen be sure to pre-mix it in water first.  If using nitrogen as your carrier, no need for a surfactant unless wild garlic is over 8 inches tall.  Applying Harmony Extra in nitrogen diluted with water, use a non-ionic surfactant at ˝ to 1 pint/100 gallons of solution.  If applying it in water use non-ionic surfactant at 1 qt/100 gallons.

 

Have you considered resistance management with your small grains?  Most of the small grains get treated only with Harmony Extra, which contains two ALS-inhibiting herbicides (some types of herbicides as Pursuit, Accent, Classic, etc).  And many weeds have developed resistance to herbicides that have this mode of action.   Consider how often a field is planted to small grains and how often it gets treated with Harmony Extra.  If this rotation is short, 3 years or less, consider tankmixing another herbicide with Harmony Extra to minimize the risk of developing herbicide resistant weeds.

 

Finally, the following are the timing limitations for small grain herbicides.  The timing restrictions are based on crop safety.

 

2,4-D - up to jointing stage (pre-jointing)

Banvel/Clarity - up to jointing stage (pre-jointing)

Buctril - up to boot stage

Harmony Extra - up to flag stage (pre-flag leaf)

 

 

Control of Horseweed (or Marestail) in No-Till Soybeans When It’s Small - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu

 

The presence of glyphosate-resistant horseweed has made no-till soybean burndown programs more challenging.  This species is not a problem in tilled fields (because it emerges before the tillage is completed, so tillage kills it) or in corn (because atrazine is pretty effective on it).  Rather the problem has only been showing up in no-till soybean fields where glyphosate alone has been used for burndown control prior to planting.  The presence of glyphosate-resistant horseweed is so wide-spread and it moves so easily with the wind, you have to assume that the horseweed plants in your field are resistant and not rely on glyphosate to control them. 

 

What to use??  Paraquat sometimes will not effectively control all the plants and it often requires two applications for excellent control.  There is concern about excessive use of ALS-inhibiting herbicides such as Amplify, FirstRate, Canopy, or Canopy XL that could lead to additional resistance.  That leaves 2,4-D.  The pint rate of 2,4-D ester is only marginal on horseweed (particularly when the plants are 4 inches or taller).  A quart rate of 2,4-D ester is needed to consistently control this species.  A quart rate requires a period of 30 days from time of application until soybeans can be planted.  So this treatment should be made as early as possible due to controlling small weeds and allowing the time interval prior to planting.  Additional flush of weeds is possible with this early application, so an application of paraquat at planting may be necessary if significant number of weeds emerge.

 

If you cannot treat your no-till soybean fields until 30 days or less before planting, use a pint rate of 2,4-D plus paraquat (this must be applied at least 7 days prior to planting).  (Paraquat is the active ingredient in Gramoxone Max and formulations are available).  If 2,4-D is not a viable option for a variety of reasons or spraying less than 7 days before planting, use sequential applications of paraquat made 3 to 5 days apart.

 

 

New Weed Control Guides For Corn and Soybeans Available - Free - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu

 

Available from your county extension office are two weed management guides for assistance in weed control in corn and soybeans.  The first half of each guide deals with soil-applied herbicides and the second half is for postemergence herbicides.  These guides have pre-mixes and what is in the pre-mix, expanded weed control tables, information on application timing, comments for each of the herbicides, and much more.  Contact your county extension office for these free guides.

 

 

Grain Marketing Highlights - Carl German, Extension Crops Marketing Specialist; clgerman@udel.edu

 

Key Supply/Demand Numbers in USDA's March Report

 

Ending Stocks for the '02/'03 MarketingYear

Ending Stocks for U.S. soybeans were estimated at 160 million bushels, down 5 million bushels from last month and within the range of pre-report expectations of 140-165 million bushels.

 

Ending stocks for U.S. corn were estimated at 1.004 billion bushels, a 75 million bushel increase over last month and within the range or trade expectations of 900 million-1.06 billion bushels.

 

Ending stocks for U.S. wheat were placed at 465 million bushels, a 20 million bushel increase over last month and well within pre-report trade expectations of 430-480 million bushels.

 

U.S. Export Projections for the '02/'03 Marketing Year

Soybean exports increased 20 million bushels from last month, now estimated at 960 million bushels. This is on the high side of pre-report trade expectations.

 

Corn exports placed at 1.750 billion bushels are estimated to be 75 million bushels less than last month, and below pre-report trade guesses of 1.775-1.8 billion bushels.

 

Wheat exports place at 875 million bushels are 25 million bushels less than last month and within trade expectations.

 

Southern Hemisphere

Argentine soybean production was indicated at a new record 35 mmt, 1.5 mmt more than last month's estimate and above pre-report trade estimates of 34-34.5 mmt.

 

Brazil Soybean Production at 51 mmt is unchanged from last month's record level forecast.

 

General Comments

Today's report contains few surprises to commodity traders with the exception of the larger than expected drop in U.S. corn exports and the larger than expected increase in Argentine soybean production. The drop in U.S. soybean ending stocks was expected. The trade also expected the projected increase in U.S. corn ending stocks.

 

Market Strategy

The only new crop sales opportunity presented at this time is in new crop corn. The CBT Dec '03 corn futures price currently at $2.39 per bushel is expected to soften from current levels.

 

Some market observers are anticipating some winter crop damage to the mid-western wheat crop, although the extent of damage is not likely to be known until harvest.

 

Dry weather concerns in parts of the Corn Belt are not influencing commodity markets at this time. It is generally believed that timely rains during the growing season can offset the dry winter conditions.

 

Dry February's do not automatically equate to reduced crops. Therefore, commodity traders are currently bidding the impact of trend line yields and world supply/demand into '03 new crop futures prices.

 

 

Assessing Small Grain Stands This Spring - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu

 

After the ice, snow, and rain-fed ponds disappear from small grain fields this spring, growers and consultants will be left with the problem of assessing the extent of damage to these fields.  The easiest portion of the task will be calculating the proportion of a field that died as a result of ice sheeting or long-term emersion under water (see Photo 1).  Ice sheeting and ponding can rapidly eliminate stands in affected areas.  Visual estimates of the proportion of the field affected can give you a working estimate for calculating acres needing fertilization, although actual measurement of the affected areas is best.  Using GPS and GIS to plot maps and estimate acreage will be the most accurate method.  If you need assistance in calculating area of various shapes, please contact the author.

 

Photo 1.  Ice formation in fields can lead to carbon dioxide toxicity in most plants especially in areas where a porous underlayer of snow does not exist (Photo by R. Taylor).

 

A more difficult question will be how to evaluate for water damage from water logged conditions where the plants have not died.  It’s been my experience that recovery of small grains in areas water logged for a period of time is very slow and grades outward from the lowest spot.  Often as much as a half to two thirds of the badly affected area will show only minimal recovery even with additional fertilizer.  The outer quarter to a third although delayed often shows significant recovery and growth.  The problem in many water logged areas is that the root systems are severely damaged and the wet conditions mean that the soil is much slower to warm up than surrounding drier areas.  The saturated conditions often result in denitrification and inhibit (low soil oxygen levels as well as colder temperatures) mineralization of nitrogen (N) from the soil organic matter pool.  Applied nitrate in these areas can be rapidly lost because of localized areas of anaerobic conditions and thus denitrification.  An ammonium source for N will help those plants still alive recover better.

 

For water logged areas, again estimate the area of the field affected and figure that no more than about half will recover adequately to have a fair to average yield potential.  If the areas are large enough to be able to adjust your N application pattern, then limit the amount and type of N applied to these areas.  Otherwise because of the high cost of N this year, you may want to recalculate your yield potential and decide how much N the lowered yield potential for the field will justify.

 

A third question concerns the problem with damage from geese feeding on the small grains.  If the damage relates to stand loss because the geese are pulling the small plants out of the ground and either eating them or leaving them to wither on the soil surface, an evaluation via stand counts after the geese have left will provide a reasonable estimate of yield potential for the field.  This also assumes that the geese do not feed past about mid-March.  Take stand counts on either a foot of row basis or on a plants/ft2 basis from 20 to 30 areas in the field and take an average.  If stand counts are 30 or more plants/ft2 (15 per foot of row on 6 inch rows or 18 to 19 per foot of row on 7 or 7.5 inch rows) or 70 or more tillers/ft2 (a tiller has 3 leaves emerged) at spring green-up time, yield potential will be maximized for the growing conditions expected in the spring.  At counts of 15 to 20 plants/ft2, yield potential is reduced by about 10 to 15 percent.  If counts are 10 to 15 plants/ft2, Kentucky data and our own data indicate that yield potential is 70 percent or less as well as being very variable from season to season.

 

If geese are grazing the wheat, the timing of when the geese leave the field will be critical in determining yield potential.  In the Deep South, wheat is often grazed until early to mid-March or a week or two before it begins to joint without any detrimental effects on yield.  Bare in mind that the yield potential is on the order of 30 to 50 bu/A, not at our higher yield potential.  Still, if you can keep the geese away from the field or they leave on their own, one to two weeks before jointing (if the wheat has tillered) or three to four weeks before jointing (if the wheat has not tillered), you can expect yield potentials of 50 bu/A or better assuming other problems have not limited yields.

 

 

Considerations for Rutted Fields - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu

 

Beginning with a 7-inch rain in early September last fall, rainfall was significantly above average across much of Delaware.  Harvest pressures from rain delays lead to damage on many fields from ruts.  Ruts can increase compaction, reduce drainage, slower infiltration rates, and delays in spring tillage and planting time.

 

What occurs when ruts are made in a field?  Under saturated conditions, there may be less compaction than you might expect since the soil may flow rather than compact.  In Photo 1 you can see how the side ridges show the flow of soil during saturated conditions.  In these situations, there may be less deep compaction, but sidewall compaction is still likely.  For unsaturated soil conditions (Photo 2), flow is minimal so the pressure results in both surface and side-wall, plus deep compaction.  Photo 3 shows one of the problems experienced this spring when high rainfall and snow amounts result in significant ponding in the fall ruts.

 

Photo 1.  Fall compaction under saturated soil conditions leading to some soil flow and moderate deep soil compaction (Photo by R. Taylor).

 

Photo 2.  Fall compaction under unsaturated soil conditions leading to significant surface, side-wall, and deep compaction (Photo by R. Taylor).

 

Photo 3.  Heavy winter snow and rain can lead to significant ponding problems in fall ruts (Photo by R. Taylor).

 

There are fall options available that need not be considered here except for mention of planting cereal rye to help reduce compaction effects.  Rye reduces or moderates the effects of compaction, increases water infiltration rates, speeds the process of drying the following spring, improves tillage effectiveness in the spring, and rye roots help tillage break up the compacted soil.

 

What should be done about ruts this spring?  There are three potential situations that can arise, a dry spring, wet spring, and normal spring (however you would define the term normal or average).

 

In a dry spring, as soon as the ruts dry out they should be evaluated to determine the extent and severity of compaction.  As a handy tool, a simple wire flag can be used to assess the extent and possibly severity of the compaction.  Although it is unlikely this spring will be dry enough for deep tillage to be effective if the soil does dry out completely, deep ripping can be used to help alleviate severe compaction.  Straight-type ripping coulters have been shown to be the most effective tool for shattering deep compacted layers.  Much more likely is that the soil will remain too wet for effective soil shattering during deep ripping.  Ripping will need to be postponed until this fall when dry soil conditions are more likely and ripping is generally more effective.  To remove ruts, chisel plow or disk to smooth the ruts and prepare a seedbed.  A dry spring can help make planting on time possible.

 

If the spring is wet, evaluation of ruts for compaction severity will be delayed, but should take place as soon as possible.  Determine if compaction occurred along the sidewalls or whether you will have to contend with deep compaction.  Delay tillage until ruts dry out and then either disk or chisel plow to smooth out the ruts and prepare the seedbed all in one pass.  Plant as soon as the soil is ready but expect to be delayed past the normal planting time.  If compaction in the rutted areas was severe, plan to deep rip in the fall when the soil is dry.

 

Time your tillage this spring for when the soil in the ruts dries out enough to support tillage equipment.  Again, the best options are chisel plowing and disking. However, if you are set up to handle in-row ripping during the planting process and compaction occurred when the ruts formed, this practice may help improve yield this coming growing season.  You will likely have to consider using deep ripping in the fall to completely eliminate the compaction problems from the ruts.

 

If the field was no-tilled, you can limit the area tilled to the damaged areas and till them as early in the spring as possible.  Emerging weeds should be controlled with herbicide at planting time.  The damaged areas will again need ripping in the fall and then the areas can be reestablished in a no-till system.

I want to acknowledge and thank several soil scientists who helped in preparation of this article.  They include Dr. Bruce Vasilas, University of Delaware, and

Dr. Jeremy Singer and Dr. Tom Kaspar from the USDA-ARS National Soil Tilth Laboratory in Ames, IA.

 

 

Managing Wheat After a Late Wet Fall Planting Season - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu; Derby Walker, Jr., Extension Agent, derby@udel.edu

 

After an extremely dry summer last year, the fall turned off wet and cold.  While August was warmer than average with 2.25 inches below normal rainfall, Sept. was 5 inches of rainfall above average, Oct. almost 3 inches above average, Nov. 2 inches above average and Dec. about average.  Daily high temperatures averaged 2, 4, and 2˚ F. below the 20 year average for the period Oct. thru Dec., respectively.  This meant that many small grain fields were planted late, planted in wet soil, and made little growth in the fall.  The heavy snow fall this winter and periods of ice sheeting have also taken a toll on small grain stands and vigor.

 

First, fields should be evaluated for the proportion of the field that has maintained a stand that should produce harvestable yield this spring (refer to the article on assessing small grain stands this spring included in this Weekly Crop Update issue).  Yield potential should also be estimated for those fields that did not tiller at all last fall.  The combination of percentage stand and yield potential can be used to estimate nitrogen need of the crop.

 

In the past, we often found that many small grain stands could produce maximum economic yields with only 60 to 80 lbs N/A applied in one application either early at spring green-up or later (if well tillered) at early jointing.  Due to high N prices, variable stands, cold-wet soils, and the likelihood of an abbreviated growing season (at least between now and jointing), growers and consultants should consider limiting N rates to about 60 lb N/A on wheat and 40 to 50 lb N/A on barley.  Exceptions are for those fields that were planted early and have come through the winter with minimal damage.  In other studies and experiences we’ve had, wheat that emerged very late in the fall or early spring and had few if any tillers visible at green-up time produced yields in the 40 to 60 bu/A range.  A nitrogen rate of 60 lb/A applied as early as feasible should be enough to reach the expected yield potential for these fields.  Keep in mind that with very low tiller counts, early N application will be critical to encourage tillering especially after the excess of fall rainfall.

 

If wet soil conditions are expected to significantly delay spring N application, it might be worth considering at least a minimal amount be applied by air.  As long as the weather stays cool, urea with 46 percent nitrogen will be a good choice even though some N will be loss because of urease activity causing release of urea as ammonia.  If the urea can be applied before a rain event or irrigation event, the N will be carried into the soil and transformed into ammonium and then nitrate as the soil warms.  Wheat does have a preference for the ammonium form of N, so uptake of N from urea should begin quickly.  This procedure will also protect one from additional denitrification losses in wet areas of the field.  Since denitrification can occur in a matter of hours to a few days, calculate your nitrogen rate for very wet fields using only the urea and ammonium nitrogen proportion in your fertilizer.  A 30 percent UAN solution weighs 10.83 lbs/gal and has 3.249 lbs N/gal and of this 0.80 lbs/gal will be N as nitrate so figure that the 30 percent UAN will give you 2.45 lbs N/gal.  Also note that the denitrification loss will only occur in very wet areas where the soil is anaerobic for a period of time and this often does not involve the entire field.

 

For fields that were not as severely impacted by last fall’s weather or the winter weather this year, information available from studies conducted at Virginia Tech may be useful in planning nitrogen (N) applications this spring.  With wheat in many fields still in the very early tillering stage or not yet to the point of tillering, growers should use their fertilization practices to boost the tillering potential of wheat.  When fields are fairly uniform, maximum yield potential in wheat requires a stand count of 30 or more plants/ft2 (15 per foot of row on 6 inch rows or 18 to 19 per foot of row on 7 or 7.5 inch rows) or 70 or more tillers/ft2 (a tiller has 3 leaves emerged) at spring green-up time.  For stands this good, use your regular fertilizer program, but split the N with 1/3 to 1/2 of the total N at green-up and the remainder at Feeke’s growth stage five.  Early season N tends to stimulate more vegetative growth, taller plants, and more potential for lodging.  Growth stage five (initiation of jointing) N improves yield and protein content of the grain.  For stands with counts well below 30/ft2 and tiller counts of 50 to 70 tillers/ft2 or less, early N at green-up will help stimulate further tillering and maintain current tillers.

 

Although split applications can improve yield potential, early spring weather conditions warrant applying most, if not all, the N to small grains as soon as possible.

 

For no-till wheat, data from several sources indicate that an extra 20 lb N/A (applied at green-up) will be needed. Apply a larger proportion of total N at green-up if splitting N applications.  Why?  Conditions in early spring are more unfavorable for growth with no-till compared to reduced or conventional till wheat.  The extra N improves the plant’s growth and vigor.

 

 

Pest Management Recommendations for Field Crops 2003 Available

 

You may obtain copies of the Pest Management Recommendations for Field Crops 2003 from the Research & Education Center by mail, cost is $15.00 (includes shipping and handling), or purchase a copy for $13.00 by stopping by the Research & Education Center in Georgetown.  Please use the enclosed form and make checks payable to “University of Delaware” and allow one week for the delivery of the books.

 

 

Crop Profiles For Delaware -  Susan Whitney, Extension Specialist, Pesticides, Urban Entomology, swhitney@udel.edu

 At a recent Extension/Grower meeting on lima beans, a representative from EPA talked about using Crop Profiles to make pesticide regulatory decisions. Crop Profiles are descriptions of crop production and pest management recommendations for major commodities. In Delaware, we have written Crop Profiles on lima beans, snap beans, sweet corn, peaches, green peas, potatoes, spinach, squash, watermelons and wheat. To read these Profiles, go to: http://www.nepmc.org/CropProfiles/

We are also writing Pest Management Strategic Plans that address pest management needs and priorities for individual commodities. EPA has said that they will use these plans when making regulatory decisions on pesticides affected by the Food Quality Protection Act. The draft plan for lima beans will soon be in Grower/ Processor review. Next year we plan on preparing a plan for spinach. Contact Susan Whitney (swhitney@udel.edu) if you have questions about Crop Profiles or Pest Management Strategic Plans.

 

 

UPCOMING MEETINGS:

 

Profiting From A Few Acres – Growing for Market in Delaware

An introduction to growing for and selling at Farmer’s Markets or your own “Farm Stand”

 

Dates: Friday, March 21, 2003, and March 28, 2003

Time: 6-9 pm

Location: Univ. of DE Paradee Center, Kent Co. Ext. Office, Rt. 113, Dover, (next to DelDOT).

Registration: Phone (302) 730-4000 to register

For more information, contact: Gordon Johnson at (302) 730-4000 or Gary Petitt at (302) 698-4500.

 

 

The Basics of Greenhouse Production as a Business or Enterprise

An Introductory Course for those Considering a

Green house Business

 

Southern Delaware Location for the Short Course

Introductory Session:

Monday, March 24, University of Delaware Research & Education Center, 6-9 pm.  Directions: 4.5 miles west of Georgetown, DE. On DE, Rt. 9

 

Greenhouse Tour:

Saturday, March 29, Lakeside Greenhouses, Laurel, DE, 9 amNoon.

Additional Sessions will be scheduled according to participant interests.

 

Pre-registration is required.  To register contact Sharon Webb at (302) 856-2585 ext.318 For more information concerning this workshop, contact Jay Windsor at 302-856-7303, or windsor@udel.edu

 

 

 

                Weather Summary

http://www.rec.udel.edu/TopLevel/Weather.htm

Weeks of March 1 to March 11, 2003

Rainfall:

0.33 inches: March 2

0.37 inches: March 5

0.49 inches: March 6

 

Readings taken for the previous 24 hours at 8 a.m.

Air Temperature:

Highs Ranged from 65° F on March 5 to 36° F on March 7 & 11.

Lows Ranged from 38°F on March 2 & 5 to 18° F on March 4.

Soil Temperature:

40°F average for the week.

(Soil temperature taken at a 2 inch depth, under sod)

 

Web Address for the U of D Research & Education Center:

http://www.rec.udel.edu

 

 

Compiled and Edited By:

Tracy Wootten

Extension Associate - Vegetable Crops

 

 

 

Cooperative Extension Education in Agriculture and Home Economics, University of Delaware, Delaware State University and the United States Department of Agriculture cooperating, Robin Morgan, Director.  Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914.  It is the policy of the Delaware Cooperative Extension System that no person shall be subjected to discrimination on the grounds of race, sex, disability, age or national origin.

 



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