Volume 10, Issue 1                                                                                                    March 15, 2002

The Weekly Schedule Begins – April 5, 2002

Issue 1 of Weekly Crop Update is a sample of the type of information you will receive each week with a subscription or access via the Internet.  This newsletter is designed to provide subscribers with the latest information on disease and insect problems as they are developing, 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 5, 2002 and continue through the month of September.  The Weekly Crop Update can be obtained by mail, fax or from the Internet at http://www.rec.udel.edu/TopLevel/Publicat.htm .  If you would like to receive Update by mail or fax, the cost of subscription will remain at $30 (same as last year).  Use the enclosed form to subscribe.  If you can access the Internet, there is no charge for the newsletter. Weekly Crop Update is mailed each Friday.  If you choose to receive the newsletter by fax, it will be sent to subscribers on Friday evening.  The newsletter is placed on the Internet by 4:30 p.m. on Fridays.  We also offer to send an email reminder to those of you who wish to receive one each week.  Please forward your email address on the enclosed form or at my email address below.  I would like to ask those of you who plan to access the newsletter from the Internet to 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 .




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



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. We will let you know as soon as we get a response from EPA.





Agricultural Fact -

46% of Delaware’s land area is in farms.  Kent and Sussex Counties are in the top 100 counties in the United States in value of vegetables produced.




Pea Planting Has Begun – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu


Pea planting on Delmarva began in late February and subsequent plantings have occurred as weather and temperature allow.  Approximately 275,000 acres of peas for processing are grown in the U.S. each year; 9-10,000 are planted in Delaware each year.  Minnesota has 25% of the acreage, Wisconsin has 22%, Washington has 16% of the acreage, and Oregon has 12%.  Per capita consumption has declined from 4.7 lbs. per year in 1975 to 3.6 lbs. in 1999.




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


Back to Basics: Root Rot Control in Peas, Lima Beans, and Snap Beans.


Root rot diseases are widespread and often cause significant yield losses. These diseases usually appear every year to some degree depending on weather and soil conditions. Root rot diseases are most severe and damaging when we have cool, wet conditions early in the season, followed by dry periods or other stresses like herbicide or insect damage, other diseases, or fertility problems. Poor soil conditions such as poor soil drainage and soil structure, low organic matter, low fertility and compaction make root rots worse.


Symptoms of root rot damage include poor seedling emergence and establishment, damping-off, stunting and uneven growth, chlorosis, and lower yield. Decreased root size, discoloration and decay characterize damage from soilborne fungi such as Rhizoctonia, Pythium, Fusarium on beans and Aphanomyces, Rhizoctonia, and Fusarium on peas. Many times, more than one pathogen is present which makes visual diagnosis difficult.


Management of these diverse soil fungi is difficult if you only utilize one management option. Effective management will be possible if you use an integrated approach of using a combination of cultural, biological and/or chemical control with appropriate soil management practices.


It is known that almost all crop and soil management practices have a direct or indirect impact on root disease incidence and severity. The use of cover crops and green manures can reduce or increase root rot. Cover crop grain rye was shown in New York to significantly increase snap bean yield, while hairy vetch resulted in the lowest yield and increased root rot. Rotations of two successive seasons with field corn, sweet corn and/or small grains are beneficial. Soybeans are not a good rotation crop to reduce root rots in beans and peas. Applications of manure and other soil amendments in combination with cover crops and green manures are helpful in reducing root rot and increasing productivity. Tillage practices such as planting on raised ridges when practical will help reduce root rot in early-planted snapbeans. Subsoiling in the fall to reduce compaction especially where heavy equipment is employed will help reduce root rot. In New York State research, it was shown that roto-tilled and chisel-plowed plots with high levels of root rot had higher root rot ratings than plots that were moldboard plowed.


In summary, root rot can be reduced if you can follow these steps:

·        Use high quality disease-free seed treated with the appropriate fungicide for the pathogens you are likely to encounter.

·        Practice crop rotation.

·        Utilize cover crops, green manures and compost whenever possible.

·        Reduce compaction and improve soil tilth.

·        Plant at the appropriate time, depth and density.

·        Select the best-adapted and tolerant varieties, if available.


Adapted for Delaware from material presented by Dr. George Abawi, Dept. of Plant Pathology, Cornell University.




Vegetable Diseases -  Kate Everts, Extension Vegetable Pathologist, University of Delaware and University of Maryland;  everts@udel.edu


Pickling Cucumbers.

Phytophthora fruit rot is a disease that can infect all cucurbit fruit including pickling cucumbers.  Fruit rot is a different phase of crown and root rot, all caused by Phytophthora capsici.  The symptoms of fruit rot are large water soaked lesions, which develop a white dense growth on the fruit. The disease can spread rapidly, causing fruit collapse during the growing season and after harvest.  Like the crown and root rot phase, high soil moisture (typically standing water) for two days allows the sporangia to form and release zoospores.  Secondary infections then occur.  Heavy rain events, such as those resulting from hurricanes, may lead to complete crop loss.  High disease levels can also occur in fall pickles that follow a spring crop that was under standing water. 


Growers that have suffered losses due to this disease should plan ahead to minimize damage.  Water management is critical to reducing damage from Phytophthora fruit rot.  Select fields that have excellent drainage and avoid planting susceptible crops in low-lying areas where standing water is common.  Plant on raised beds and subsoil (or “V-rip”) before planting to avoid soil layers that are impervious to water.  A three-year rotation is important.  Crops to avoid in the rotation are: cucurbits (including melon, watermelon, squash and pumpkin), pepper, tomato and eggplant.  Broadcast soil fumigation can provide some benefit (for example, K-Pam and Telone list Phytophthora diseases on their labels).  If fumigation is used, prevent nontreated soil from washing into the treated area. 


Use of fungicides during the growing season is not always effective because of the presence of resistant strains of the fungus, difficulty obtaining adequate coverage and the aggressiveness of the disease when environmental conditions are favorable.  However, Ridomil Gold Bravo applied when the vines begin to run, on a 14-day schedule may provide some disease control.


2002 Commercial Vegetable Recommendations Guide Available at Local Extension Offices




You may obtain copies of the Commercial Vegetable Recommendation Guide from your local county Extension office or by mail from the Research & Education Center in Georgetown.  The cost for the Commercial Vegetable Recommendations Guide is $8.00.  Please use the enclosed form and make checks payable to “University of Delaware” and allow one week for the delivery of the books.




Field Crops


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


New Field Corn Registrations for Soil Insect Management 2002:

September 28, 2001 - Mustang (FMC) - label only states control of cutworms

February 28, 2002 - Warrior (Syngenta) - 2 (ee) registration for control of seed corn maggot, wireworms and cutworms; only suppression of white grubs and rootworms.


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).

Since winter temperatures have been warmer than normal, we are starting to find seed corn maggot flies laying eggs in recently plowed and/or manured fields. Cool wet conditions at planting, the use of manure and/or plowing under of green cover crops close to planting all favor maggot problems. Depending on spring weather conditions, most early planted conventional corn and all no-till plantings will be susceptible to seed corn maggot attack. In addition to soil insecticides, seed treatments have provided effective control. Hopper-box treatments containing diazinon or permethrin as well as seed commercially treated with imidacloprid (Gaucho or Prescribe)  will provide effective seed corn maggot control. A new 2(ee) registration was issued on Feb 28, 2002, for the use of an in-furrow application of Warrior for SCM control at a rate of 3.2 oz/acre. It can be applied through spray nozzles or microtubes behind the planter furrow opener and in front of the press wheels. Warrior may be applied with water or liquid starter fertilizer. This registration applies only to the following states: Delaware, Colorado, Illinois, Indiana, Iowa, Kentucky, Missouri, Kansas, Nebraska, Minnesota, South Dakota, Wisconsin, Michigan and Pennsylvania.



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 lindane or permethrin will only control larvae feeding on the seed when population levels are low to moderate. They will not control larvae that have moved to the growing point of a plant and started to feed. However, Gaucho and Prescribe seed treatments have provided excellent control of both seed and seedling damage from wireworms under high population pressure. Soil insecticides including Regent, Force, Fortress, Furadan, Lorsban and Counter have provided control. All materials must be placed in-furrow to get effective control and applied at the higher end of the labeled rate. If Regent is used, fields can not be planted to leafy vegetables for one month, root crops for five months, or small grains and other rotational crops for 12 months following an application. The new 2(ee) registration for Warrior also applies to wireworm control and should be used  at a rate of 1.92 oz/acre.


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. Overwintering populations were higher this season and warmer soil conditions may have favored survivorship. However, spring conditions as well as the recent cooler weather may help to reduce populations. 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. Counter, Force, Fortress, Regent and Prescribe will provide effective control. Remember,  at planting insecticides are only designed to provide control of grubs present at planting time. You should not expect control of larvae present in August and September that resulted from eggs laid in early July.


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 (Ambush, Asana, Pounce, Mustang or Warrior) tank mixed with a herbicide and applied close to planting has provided effective control. Pounce, Mustang and Warrior can also be applied as a liquid t-band application at planting for cutworm control. The granular insecticides Force, Lorsban and Fortress are labeled for cutworm control, but must be applied as a T-band to be effective.  Pheromone traps placed in the field by mid-March can be used to determine when to look for cut plants as well as areas of the state most likely to experience economic levels. Look for pheromone trap counts in future reports.



 Although we still 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. Information from Kentucky indicates that there is generally no yield impact after Feeke’s growth stage 4 ( stem elongation). Remember, symptoms of BYDV you see this spring is generally a result of what happened in the fall.


The aphid causing the greatest amount of damage last fall was the Greenbug. This aphid can be easily identified by the green stripe down the center of the body. The most significant losses occurred on the eastern shore of Maryland; however, we did have fields affected in Kent and Sussex counties. 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 leads to yellowing of leaves that eventually turn brown and die. In Maryland, entire fields were killed by greenbug feeding. Although this aphid causes the greatest damage from mid to late fall, it can be present throughout the winter and into the spring, so be sure to check fields at least once in March 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



Time of Year




4-6 "

Fall - late Winter




7 - 10 "





18-20 "






30 + "





Greenbug Aphid with green stripe down the back




During the last two growing seasons, alfalfa weevil populations have been higher than normal. A combination of warm winter weather and dry conditions could result in early feeding damage this season. Therefore, 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% of the tips with feeding damage.




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% 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.




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


Commodity Markets Rally on China News
General consensus at the Chicago Board of Trade among commodity traders is that we need some fresh fundamental news to help provide price direction in the trading pits. News along that line came at the end of last week as the rumor hit the market that China is believed to be softening its GMO policies. This was viewed as price positive during Friday's trading session for two reasons: first, the markets were caught in an oversold position and second, the rumor that China may soften its GMO policies is viewed as price positive in that this move could possibly bring more export business to the U.S., particularly for corn and soybeans.

Other News in Brief
The Southern Hemisphere harvest is well underway. Preliminary reports from South America are indicative of a very large crop, although not anticipated to be quite as large as originally expected.

The corn market has held steady in spite of recent, large cancellations of U.S. corn exports. Market analysts have indicated this to be a signal that the lows are in for corn.

Market Strategy
Price level has much to do with deciding what one's marketing strategy should be. Current price levels for soybeans and wheat are too low to make advancing sales an attractive venture, at this point in time. The corn market has now nearly recovered to its mid-January price level, when farmers were advised to make their first new crop corn sale on 10 to 30% of intended new crop production. For the time being, we'd like to see a Chicago Board of Trade price of $2.40 per bushel or better (with a basis of 10 over or better) before advancing new crop corn sales.




Small Grain Fertilization in 2002 - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu


I just want to make a few comments on wheat fertilization from the perspective of the advanced crop maturity status of wheat and barley this year.  The highly variable weather we’ve experienced this fall and winter seems to have small grains advancing far ahead of their usual pace.  Many fields appear well along in the jointing stage when normally it is the end of March before they reach this point.  For this reason, growers who had been planning to split nitrogen (N) applications may want to consider applying all their needed N now, rather than some now and some later in the spring.  In our usual pattern, we have or will be applying the first “at greenup” application in late February or early March and the second split application just prior to jointing in late March.  With many fields already jointing, it is critical to get the recommended rate of N applied.  As a caution, we do run the risk of loosing some N, if we get heavy rains in the next couple of weeks.  However, much of the small grain crop is large enough to rapidly take up the N that is applied.




Irrigating Small Grains - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu


The prolonged dry weather we’ve experienced since last fall has lead many growers to reconsider if irrigation of their small grain crops might pay off.  I thought it would be helpful to review the research on the topic and then offer my advise for what its worth.


You may recall an article from the April 2000 issue on this topic.  In it, I reviewed the results of two years of work on irrigation timing on winter wheat.  The study used a high-yielding, disease resistant wheat variety that was heavily fertilized with split applications of nitrogen including fall-applied nitrogen.  Excellent stands were achieved both years.  Fungicide was applied to minimize disease impact on yields and insecticides were used when needed.  Irrigation treatments began one week after the wheat flowered.  The crop was irrigated with 1.5 inches of water per week less the amount of rainfall received.  Irrigation treatments were a control that received no irrigation, and irrigation for one, two, three, and four weeks following flowering.  The center of a 30 by 30 foot plot was combine harvested for a yield estimate.


No significant differences were observed between the control and any irrigation treatment.  Although not significant, the trend both years was for lower yields with longer periods of irrigation and especially when irrigated for three or four weeks.  Test weight was not affected significantly by irrigation.


What about work done prior to the above study?  I read back through the old Wheat and Barley Reviews and found that Frank Webb had done work on both wheat and barley with and without irrigation.  The timing of water applications varied a little from year to year, but in three of the four years, water was applied in mid- to late-March, late-April, and mid-May, and in the fourth year irrigation was not needed until mid-May and mid-June.  In the first year, there was a significant decrease in yield of wheat with irrigation.  Across the four years, there were no significant differences between irrigation and no irrigation for barley or wheat.  The numerical difference between the treatments was a 2.7 bu/A increase for irrigated barley and a 0.6 bu/A decrease for irrigated wheat.  The wheat data follows very closely with the data I developed during the 1998 and 1999 growing seasons.


Should you irrigate small grains?  This question ultimately must be answered by individual producers.  Certainly, based on my research in 1998 to 1999 and research from the early 1980’s, irrigation of wheat or barley will not pay economically.


If you intend on irrigating wheat anyway, follow these guidelines.


Ž     Irrigate only the best fields with high yield potential.

Ž     Limit the number of irrigations while building the soils available water to near maximum.

Ž     Do not irrigate during flowering.

Ž     Stop irrigating by two weeks after flowering.

Ž     Irrigation prior to heading should occur only under extreme drought conditions.


This year many folks are asking about irrigation because it has been such a dry fall and winter season.  Some wheat is far advanced and is already jointing, but has been burned by the on again-off again cold weather we’ve been experiencing [do not confuse the leaf scorching with nitrogen (N) deficiency].  Others want to irrigate to be sure that any N fertilizer they applied is moved into the soil to reduce the chance that the urea component of the 30 percent UAN solution is lost by volatilization.  The recent rain we had should have taken care of this latter concern.


If you feel you must irrigate, the most useful thing you can do for both your small grain crop and your planned following crop is to irrigate enough to bring not only the top soil, but the subsoil that’s in the rooting zone of the crops to field capacity.  Because of the occasional yield reductions we’ve seen with irrigated wheat, I would not irrigate after getting the soil up to field capacity.  What rainfall we receive should be enough to take the crop on through to maturity especially since these crops appear not to need a large amount of water.



Pest Management Recommendations For Field Crops 2002 Available at Research & Education Center


You may obtain copies of the Pest Management Recommendations for Field Crops 2002 from the Research & Education Center by mail or by stopping by the Research & Education Center in Georgetown.  The cost is $12.00.  Please use the enclosed form and make checks payable to “University of Delaware” and allow one week for the delivery of the books.




New 911 Address for the University of Delaware Research & Education Center



Please make a note of the new address for the University of Delaware Research & Education Center (and Sussex County Extension Office).


University of Delaware

Research & Education Center

16483 County Seat Highway

Georgetown, DE 19947






Pesticide Briefs On-LineSusan Whitney, Extension Specialist, Pesticides, Urban Entomology, swhitney@udel.edu


Pesticide Briefs

Short news articles from EPA, USDA, and the Pesticide Industry. Our goal is to promote informed regulatory decisions on registered pesticides.








Pesticide Applicator Training and Testing:


Date:   March 22 (Friday) and 25 (Monday), 2002.

Location: New Castle Co. Extension Office.


Date:   March 27-28, 2002.

Location: Sussex Co. Extension Office.


Date:   June 12-13, 2002.

Location: Kent Co. Extension Office.

The first day is training -- 8:15 am - 4:30 pm. Training continues the morning of the second day, 8:15 am - noon.  Be sure to bring your Workbook!  The exam starts at 1:00 pm the second day. Closed book!!  Be sure to bring your calculator for the calibration questions.


For more information, contact Susan Whitney (swhitney@udel.edu) at 302-831-8886 or your local extension office: New Castle – 302-831-2506, Kent – 302-730-4000, Sussex – 302-856-7303.




Variety Trial Results Online



Variety trial results for Small Grains, Grain Sorghum, Soybeans, and Corn can be found at the following address:



or contact your county cooperative extension office for a copy.




                            Weather Summary

Week of March 1 to March 7, 2002


0.52 inches: March 2

0.29 inches: March 3


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

Air Temperature:

Highs Ranged from 66° F on March 7 to 40° F on March 5.

Lows Ranged from 42°F on March 3 to 16° F on March 5.

Soil Temperature:

43.3°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:




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, John Nye, 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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Please send check and this form to:

            Tracy Wootten

            University of Delaware Research & Education Center

            16483 County Seat Highway

            Georgetown, Delaware 19947