Volume 12, Issue 22                                                                     August 20, 2004



Update on Post-Emergence Weed Control in Spinach Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

Stinger is labeled as a post-emergence herbicide for use on spinach.  It can be applied when the spinach is in the 2 to 5 leaf stage of growth.  It is useful for control of Canada thistle, sow thistle, black nightshade, clover, cocklebur, common groundsel, jimsonweed, prickly lettuce, pineappleweed, and ragweed.  Check the label for the proper rate for each weed species.  Scouting fields early for weed escapes is important to time Stinger applications for early weed control.




Downy Mildew on Cucurbits Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu


Over the past few weeks, we have written much about the control of Downy mildew on cucurbits.  It has been devastating, with serious yield loss on watermelons, significant damage to pumpkin vines, and very serious yield loss and quality damage to pickling cucumbers.  In the case of pickles, even with good yields at the beginning of the season, final production may only approach 50% of intended production.


With the innoculum coming to us early in the season and in apparently unprecedented amounts, this threat was compounded by cool, wet weather that favored the development of the disease.  In the 46 days between July 1 and August 15, it rained 28 days; or 60% of the days experienced rain.  There were two stretches of six consecutive days of rain during this time frame.  There were no days in this period with temperatures above 90oF at the University of Delaware Research & Education Center’s weather station near Georgetown.


As reported earlier, a period of at least six hours of 100% relative humidity at the leaf surface is required for the disease organism to produce sporangia.  We certainly had extended periods of these conditions, which helped launch and maintain the epidemic of Downy mildew.


Some observers have inquired about the appearance of the plants and possible fertility deficiencies.  The pale, weakened appearance is a result of the Downy mildew, not plant nutrition problems.  The rates applied this year are consistent with previous years, when vine growth was aggressive, in fact, perhaps too aggressive.  We have one field with over 175 pounds/A of nitrogen applied in an attempt to stimulate the plant, and are not seeing any significant response.


Many fields still exhibit the symptoms and damage continues.  However, we are seeing some plantings that were sprayed frequently and often, holding their own.  While we work towards solutions for this year’s crop, we are turning our attention to avoiding and preventing a similar situation next year.  Although in the unlikely event the weather pattern repeats itself, the battle will be engaged again.


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



Continue to sample fields for diamondback and cabbage looper larvae. Economic levels can now be found.  A treatment should be considered if you find 5% of the plants infested and before they move into the hearts of the plants. If both species are present, Avaunt, a Bt, Proclaim or  Spintor  will provide control. If cabbage looper is the predominant species, a pyrethroid, Intrepid, or Confirm  will also provide control.

Lima Beans.
Continue to scout for  lygus bugs and stinkbugs as soon as pin pods are present . Treatment should be considered if you find 15 adults and/or nymphs per 50 sweeps. Since earworm continues to be found in lima bean fields, be sure to scout fields with pin pods for corn earworm. A treatment will be needed if you find one corn earworm larvae per 6 ft of row. Capture, Lannate, Mustang or Warrior will provide earworm control. The higher rates may be needed if population levels are high and worms are large at the time of treatment.


Be sure to maintain a 5-7 day spray schedule for corn borer, corn earworm, beet armyworm and fall armyworm control.


Snap Beans.
At this time, all fresh market and processing snap beans will need to be sprayed for corn borer and corn earworm control from the bud stage through harvest. Remember, Orthene provides poor corn earworm control. Since trap catches change quickly and we are seeing another spike in corn earworm moth catches, be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in processing snap beans. http://www.udel.edu/IPM/traps/latestblt.html

and http://www.udel.edu/IPM/thresh/snapbeanecbthresh.html). 



Since webworm and beet armyworm moths are both actively laying eggs, be sure to watch for both worm pests as soon as plants emerge.  Controls should be applied when worms are small and before they have moved deep into the hearts of the plants. Also, remember that both insects can produce webbing on the plants. Since beet armyworms are more difficult to control, chemical selection is important. Confirm, Intrepid or Spintor will be needed for beet armyworm control. If webworms are the predominant species, permethrin, Confirm (8 oz/acre),or Intrepid (8-10 oz) should be used. Generally, at least 2 applications are needed to achieve control of webworms and beet armyworm.


Sweet Corn.
With the recent increase in corn earworm trap catches, a
ll fresh market silking sweet corn should be sprayed on a 2-day schedule.  Be sure to check trap catches frequently. You can check trap catches and treatment decision guidelines on our website (http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/silkspraythresh.html).



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

Lima beans.

Downy Mildew Alert. Downy mildew, caused by Phytophthora phaseoli, was positively identified in two samples from the Frederica-Bowers Beach area in Kent County. As we had stated before the weather has been very favorable for infection and continues to be favorable. Growers with beans that have pods should be applying protective fungicides for downy mildew. Remember that there are three diseases that can infect pods and may look similar namely, downy mildew, lima bean pod rot caused by Phytophthora capsici and white mold caused by Sclerotinia. If you see infected pods it is important that you get the disease correctly identified before applying a control. Fungicides for white mold and downy are very different and one fungicide will not control both diseases. White mold is controlled with Topsin M, Rovral, or Endura. Downy mildew is controlled by growing resistant varieties and applying fungicides preventatively. In order of effectiveness, Ridomil Gold/Copper is the best and most costly and is recommended if downy is found in the field followed by a copper spray 7 days later. It is also great preventatively. Phostrol as mentioned in earlier issues is also available and is an excellent preventative fungicide if used according to the label, 4 pts/A at weekly intervals. Phostrol will not control downy if infection has already occurred. Copper sprays (Champ DF and Kocide 2000 at 2.0 lb/A, Cuprofixx 3 lb/A) have also performed very well when used preventatively and weekly.



Downy mildew on lima pod.                     Downy mildew on pin pods.





LATE BLIGHT ADVISORY.  NOTE: This will be the last potato disease advisory.


Disease Severity Value (DSV) Accumulation as of August 18, 2004 is as follows:

Location: Joe Jackewicz Farm, Magnolia, DE. Greenrow: April 25, 2004





Daily DSV


Total DSV

Spray Recommendation














































































Application rates for protectant fungicides (Dithane, Bravo, etc.) should be at the high end of the rate with the amount of foliage present. For specific fungicide recommendations, see pages F132-33, 2004 Delaware Commercial Vegetable Production Recommendations Book. EB 137.


No late blight has been seen in DE-MD-NJ area on potatoes.


Note:  Late blight has been confirmed on tomato in Burlington and Sussex counties in NJ and is present in southeast PA on tomato as well. Growers with late potatoes and those that may have tomatoes nearby should continue to spray and scout for symptoms. There have been no new reports on tomato from these areas.




Field Crops



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


Continue to scout fields for soybeans aphids.  Although populations have not reached threshold levels we can still find them on stems as well as leaves. At this point, the highest populations can be found in New Castle County. You will need to look at the entire plant when sampling for aphids. The treatment threshold is 250 per plant up to growth stage R-3/R-4 with 80% of the plants at that level. After R4, the threshold increases to 1000-1500 aphids per plant. Numerous products are now labeled for soybean aphid including Asana, Baythroid (suppression only), Mustang MAX, Warrior, and  Lorsban. Dimethoate has not provided adequate control and Furadan 4F only has a 2ee label for the Midwestern states.


We continue to find hot spots of economic levels of defoliators in later planted double crop fields. In most cases, the predominant insects are grasshoppers and green cloverworms. Before bloom, the defoliation threshold is 30% and once fields begin to flower the threshold drops to 15% defoliation. You should also watch for diseased cloverworms which can help to crash populations.


We are still finding very low numbers of corn earworms and beet armyworms in double cropped fields. As in most years, double crop fields will be most susceptible to attack. A treatment should be considered if you find  3 corn earworms per 25 sweeps in narrow fields and 5 per 25 sweeps in wide row fields ( 20-inches or greater). With the recent increase in trap catches, be sure to watch fields carefully during the next 3 -4 week period. As far as beet armyworms, remember they are primarily defoliators unless populations are high. Therefore, you should use the defoliation thresholds when making a treatment decision.


We have also seen some isolated pod damage from stinkbug and possibly bean leaf beetles in full season fields. Although we have not seen problems in the past, stinkbug populations are higher this year. The following information on stinkbugs in soybeans comes from the most recent Virginia report:


Unusually high stink bug populations in soybean (Ames Herbert, VPI)
We are experiencing more stink bugs than normal in our soybean crop. We are finding two species, green and brown, and both undergo about 3-5 generations per year. They feed on a lot of different weed hosts and crops and move from one to another to seek the freshest food source. Populations have been unusually high this spring and summer, with large numbers in corn and cotton. Now they have moved into soybeans. They damage soybeans by their feeding when they pierce the pod and seed to feed on plant juices, simultaneously injecting digestive enzymes. Feeding can cause shriveling and abortion of young pods, and shriveled discolored seed on older pods. Both seed quality and yield can be reduced if populations exceed threshold levels. Our threshold is set at 1 stink bug per foot of row (if using a drop cloth) regardless of row spacing, or 2.4 to 3.6 per 15 sweep net sweeps in 7 to 21-inch, or greater than 21-inch row spacings, respectively. Stink bugs are the primary soybean pest in
Georgia and their thresholds are higher, set at 2 per foot of row when seeds are just forming, and 3 per foot of row after mid pod fill. Stink bug feeding can also result in maturity delay. Pod damage during pod set to pod fill can slow maturity and result in green fields or areas of fields at harvest. We are recommending that growers scout fields using either the drop cloth (in 21-inch or wider row spacings) or the sweep net (row spacings less than 21 inches) and consider treatment if thresholds are found. We also recommend using pyrethroids. Pyrethroids will do a good job on any corn earworm populations, a good job on green stink bug, and a fair job on brown stink bugs if higher rates are used. To maximize control, use the high rates listed for stink bug.


As far as bean leaf beetle pod damage, we have rarely seen pod damage from this pest. It is generally a pest that has caused more damage in the mid-west as well as some areas of PA. In North Carolina, they report that pod damage is usually limited to the outer layers of the pod, the developing seeds being infrequently attacked.  However, if you are interested in more information on bean leaf beetle management (remember that thresholds from other regions have not been tested in our area), you may want to consider visiting the following websites: (http://www.uky.edu/Agriculture/Entomology/entfacts/fldcrops/ef131.htm)






Field Crop Diseases - Bob Mulrooney,

Extension Plant Pathologist, bobmul@udel.edu



Frogeye leafspot was identified this week in soybeans. This disease is caused by the fungus Cercospora sojina and can be destructive late in the growing season. This disease prefers the cool, humid weather we are experiencing now. The disease is characterized by the the “eyespots” on the leaves. These spots are generally circular to angular and have gray to tan centers with purple-brown to red margins. Heavily infected leaves fall prematurely. Frogeye can also infect stems and pods and cause some purple stain as well. The more common and less yield impacting fungus Cercospora kikuchii is our principle cause of purple seed stain and produces very different leaf symptoms and no defoliation. Control frogeye by plowing the field in the fall to remove any overwintering spores and infected plant material. Foliar fungicides can be helpful if applied between R2 and R5 stages of growth (late flowering to early seed growth). If soybeans are beyond R5, little effect will be seen with a fungicide application. Quadris and Bravo are labeled for soybeans and should provide some control if needed. Follow labels for rates and other information. The price of soybeans may justify control if favorable weather for infection continues and defoliation is prevented.



Frogeye leafspot on soybean


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

Strong Exports Reported for Corn and Wheat.
Weekly export sales of 41.2 million bushels were reported for corn this morning, well above last week's 31.9 million bushels. Wheat sales were reported at 27.3 million bushels. The trade was expecting wheat sales between 14.7 million and 22 million bushels. Export sales for soybeans were within the expected range, with shipments of 1.6 million bushels as compared to 2.7 million bushels last week.

Selected Highlights.
Competition for wheat export sales is said to likely increase in the coming weeks ahead, as the rest of the world finishes up wheat harvest. This is likely to play havoc with wheat prices.

Corn and soybean prices have a tendency to flatten out this time of year. Where prices head from this point depends in part on the 'frost factor'. If an early frost occurs in the Northern Plains then corn and soybean prices are likely to get a fast and furious rally. The potential rally is being termed fast and furious because, if an early frost occurs the price benefit is likely to come and go in a matter of a mere few days. The advent of an early frost is not easy to predict. The last time an 'early' frost occurred (defined here as one that happened before mid-September) was on September 9th in 1924. On that date it was 34°F in Mason City, Iowa. The most recent date for an 'early' frost was September 29th in 1992 when 32°F was recorded in Cedar Rapids, Iowa. Of course, it needs to be made perfectly clear that the actual date that a frost will arrive can not be predicted with much accuracy. However, according to Dr. Harry Hillaker, Iowa State University Climatologist, Statistics would say that the odds of a frost and/or freeze in the Corn Belt in September this year are high, but it is impossible to say exactly when that freeze would occur. The earlier the date of a frost, the greater the impact on yield and production for corn and soybeans. Remember, no one is guaranteeing an early frost event. This subject was alluded to in today's column because it was duly noted that temperatures dipped into the 30s and 40s from Northern Iowa through the Dakotas and Minnesota by 5:00 a.m. this morning




Delaware Corn Hybrid Test Derby Walker, Sussex County Extension Ag Agent, derby@udel.edu


The Delaware Corn Hybrid test is located at the Georgetown Research and Education Center Farm, near the Chestnut Grove.  Use Experiment Station Road (right across from the office), turning left on the third dirt road on the left.  The corn was mowed off in front of the plots. Signs are located in the plots.  If you would like a plot plan to identify the varieties, copies of the plans are in the rack in the hallway of our office. Feel free to stop by and pickup a copy to review the commercial varieties.










AUGUST 23-24, 2004








August 23, 2004


Linvilla Orchards, Media PA

Funks Farm Market & Garden Center, Millersville

Brown’s Orchard & Farm Market, Loganville, PA

Maple Lawn Farms, New Park, PA

Hickory Bridge Farms, Orrtanna, PA.

Hotel Liberty


August 24, 2004

Lady Moon Farms/Trickling Springs Creamery

                                                Chambersburg PA

Willow Pond Farm, Fairfield, PA

Adams County Winery, Orrtanna, PA

Quaker Valley Orchards, Biglerville, PA



We are inviting all of you to join us.  Transportation, lodging, meals taxes and gratuities are included.  The cost is $ 80.00 per person double occupancy.


We will leave Dover at 7 AM on MONDAY 8/23  return TUESDAY night at 9:30 PM


PHONE 302-730-4000 by August 19th if you will be going on this tour, or email Gordon Johnson (gcjohn@udel.edu). For more information contact our office at 302-730-4000.  


Tour sponsored by the University of Delaware Cooperative Extension, The Delaware Department of Agriculture, and  The Northeast Center for Risk Management Education.  




Wicomico Farm and Home Show


AUGUST 19- 21 2004



Located at the Wicomico Equestrian Center, Winterplace Park, Rt. 50 & Hobbs Rd., Salisbury, MD  21801

12 NOON...............................................SHOW OPENS
12:30 pm. ........................Children's activities & games
1:00pm.................................Compact Tractor Contest
5:00 pm ...............................................Livestock Show
5:00 - 7:00 ......................................MAX Radio Station
6:30 pm ..............................................Livestock Show
7:00 pm ........................................................Cruise-In
7:30 - 9:00 pm. ..............................Karaoke by DAWN
9:00 pm...............................................SHOW CLOSES
9:30am.................................................SHOW OPENS
10:00am..............................................Livestock Show
10:00 am. - 2:00 pm......................Tractor & Car Show
10:30am.................................TRAINING WITH TRUST       KENNY HARLOW(horse clinician and trainer)
11:00 am...............................................Livestock Show
11:00am.-1:00 pm............................Karaoke by DAWN
1-4pm.............KENNY HARLOW will work with horses
1:30 pm...........................................4H Fashion Show
2:00 pm......................................Pedal Tractor Contest
2:00-5:00 pm. ...................................Steel Drum Band
4:00 - 5:00 pm. ..Being A Better Partner for Your Horse
5:00 pm.................................................Benefit Auction
                                            Auctioneer: Doug Marshall
7:30 pm.......................................Awards Presentation
8:30 pm. ...........................................SHOW CLOSES

There will be a dunking booth on Friday & Saturday.


Anyone wishing to enter into the Tractor Show and/or Classic Car show may go directly to the website.




For more information, contact Susan Lewis at 410-749-7151(ph), 410-742-5436 (fax) or email at www.farmersandplanters.com

*For more information on 4-H activities, call the Wicomico County Extension Service




                     Weather Summary


Week of August 13 to August 17, 2004


0.16 inches: August 13

1.38 inches: August 14

0.15 inches August 15

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


Air Temperature:

Highs Ranged from 82°F on August 17 to 74°F on August 14.

Lows Ranged from 68°F on August 13 to 62°F on August 17.


Soil Temperature:

76°F average.

(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

Sussex County Extension Agent – Horticulture

University of Delaware


Emmalea Ernest

Extension Associate – Vegetable Crops

University of Delaware




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



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