Volume 9, Issue 7                                                                                      May 11, 2001



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



Both imported cabbageworms and diamondback larvae can be found in cabbage in Kent and Sussex Counties. The treatment threshold is 5% infested plants. Avaunt (3.5 oz/acre), Spintor (3 oz/acre) or a BT insecticide will provide control of both worm species. With the dry weather, thrips populations are also starting to increase. On susceptible varieties, a treatment should be applied as soon as you see thrips populations increasing. On all other varieties, the treatment threshold is 20% infested plants. Spintor, Provado or Warrior will provide good thrips control.



Low levels of spider mites and aphids can be found on the earliest set plants. Populations are lower compared to this time last year. If populations increase gradually and the populations are predominately immature mites, Agri-mek should provide good control. However, if populations explode quickly and you are finding mostly adult mites, Capture or Danitol should be used. No controls should be needed before 20% of the crowns are infested with 2-5 mites per leaf. The treatment threshold for aphids is 20% infested plants with at least 5 aphids per leaf.



The first Colorado potato beetle eggs have hatched and we are starting to see small larvae. The treatment threshold for Colorado potato beetle is 4 small larvae per plant or 1.5 large larvae per plant. If both small and large larvae are present, the threshold of each should be reduced by ½ for each. Spintor or Provado will provide good control of adults and larvae. Corn borer moth populations are low at this time. The first European corn borer moths were caught during the last week. The most recent blacklight trap catches can be found at  http://www.udel.edu/IPM/traps/latestblt.html . (See page 8 for trap catches April 30-May 6). Trap catches are updated on the IPM website 3 times per week (Mon, Wed and Friday). As of this date, no potato leafhoppers have been found in potatoes.


Sweet Corn.

The most common insect being found is the cutworm. The treatment threshold is 10% leaf feeding or 3 % cut plants. Low levels of flea beetles can also be found. The treatment threshold is 5% infested plants.




Processing Vegetable Industry Changes – Vlasic Sale is Approved – Hanover Foods Purchases Saulsbury Brothers – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu


The purchase of Vlasic Foods by Hicks, Muse, Tate, & Forest is approved by the U.S. Bankruptcy Court in Wilmington, Delaware.  The sale is schedule to be complete on or near May 22, 2001.


The price was $370 million plus warrants to purchase 15% of the common stock of the “acquiring entity created by HMTF and additional consideration, subject to working capital adjustments.”


This sell includes the Vlasic Foods International’s North American Businesses, Vlasic Pickles, Open Pit Barbecue Sauce, and Swanson Frozen Foods.  These three business have combined annual sales of $750 million.  They have 2,700 full time employees, and 550 seasonal employees.  Further information can be obtained from the website Vlasic.com.


Hanover Foods has purchased the Saulsbury Brothers plant property and equipment in Ridgely, Maryland.  Hanover Foods has indicated they will continue to freeze vegetables at the site.



Basagran Injury on Peas – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu


We have seen some flecking or chlorosis on peas associated with Basagran.   Plantings sprayed two or three days before the 90 degree temperatures that occurred on May 3 and 4 experienced some injury.  Typically, the peas grow through the symptoms without much effect.  An occasional field has exhibited very noticeable injury; these fields have had a surfactant applied.  That coupled with the heat caused the injury.  Remember, Basagran on peas should have no crop oil or surfactants.



Watermelon Markets in North Florida – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu


Last week, in conversation with two different chain store watermelon buyers, two very different market assessments were made.  One said weather and other factors have really hurt supply, the other felt he was getting good supply.  I guess it depends on your perspective.


As of May 8, Northern Florida shipping points are reporting moderate demand, market lower.  On a F.O.B. shipping point basis, Red Flesh Seedless, in bins, for 15 to 18 pound melons, price is $23-$26 per cwt., with some as low as $21, some as high as $28.  Sangria types, in bins, for 15 to 18 pound melons, price is $10 to $12 per cwt., for 18 to 24 pounds melons, price is $13 - $14 per cwt.


There are so many variables on supply and demand, it is pointless to predict price for Delmarva at this point, but we will bring occasional reports as the watermelon season moves up the coast.



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


Gummy Stem Blight Resistance to Quadris.


Ø      Last summer there were several complaints that Quadris did not control gummy stem blight (GSB) on watermelon in Sussex and Wicomico counties.  Personnel from Syngenta (the company that makes Quadris) collected a large number of isolates of Didymella bryoniae (the fungus that causes GSB).  Laboratory tests confirmed that a high percentage of isolates were not sensitive to Quadris.  Unfortunately, all the strobilurins affect fungi the same way (have the same mode of action) and therefore, resistance to Quadris likely means that these isolates will be resistant to other strobilurins (for example, Flint). 


Ø      Growers in Sussex and Wicomico counties should not use Quadris for GSB control in the 2001 growing season.  For GSB, the best fungicide available is a chlorothalonil product such as Terranil, Echo or Bravo. 


Ø      Growers in other counties should alternate Quadris with another fungicide that has a different mode of action (on a strict 1:1 rotation). 


Ø      The strobilurin fungicides like Quadris, have been a valuable tool for growers.  To avoid (or at least delay) additional problems with resistance, follow good management practices. 1) Never apply Quadris (or other strobilurins) below the label rate for the crop you are spraying (labeled rate for Quadris on watermelon is 11-15.4 oz.).   2) Follow the recommended rotation (for Quadris 1:1) with a product that has a different mode of action.  3) Only apply the number of sprays that the label allows (for Quadris on watermelon, 4 ).  4) Finally, do not apply Quadris when more than 20% of the vines are affected by GSB.


Ø      Several other diseases are caused by D. bryoniae (gummy stem blight on other cucurbits and black rot on pumpkin).  Where a resistant population exists, Quadris will not control these diseases. 


Ø      In fields sprayed with Melcast the interval between sprays is often lengthened.  Therefore, it is especially important to use an effective product such as Bravo in these fields. 



Watermelon Seedling Diseases in the Greenhouse.


Many abiotic problems (scorch from high temperatures, excess nutrients and chemical burn) may cause spots on the leaves of plants in the greenhouse.  There are also several seedborne watermelon diseases that may show up on seedlings in the greenhouse.  Gummy stem blight (GSB) is the most common, but Alternaria leaf blight and anthracnose also affect watermelons.  There are several greenhouse practices that minimize infection by the pathogens of these diseases, including GSB.  The greenhouse should be disinfected before planting (benches, walls, walkways, etc.).  The seed source should have tested negative for the pathogen with a minimum assay number of 1,000 seeds.  Use clean transplant trays (disinfect trays if they will be reused) and new soil.  Destroy any volunteer seedlings and keep the area in and around the greenhouse weed free.  Avoid overhead watering if at all possible, or water in the middle of the day so that the plants dry thoroughly before evening.  Keep relative humidity as low as possible through proper watering and good air circulation in the greenhouse.  As the seedlings develop, inspect them carefully. Infected seedlings will have small brown lesions on the leaves and water-soaked lesions on the stem. Initial infections will occur as ‘foci’ or clusters of diseased plants. 


If the seedlings have lesions or appear diseased, destroy the flats where any seedlings show symptoms.  Remove adjoining flats to a separate area for observation.  Monitor these seedlings daily and destroy those that develop symptoms.  Do not ship any trays containing plants with symptoms of GSB.  Spray with a labeled fungicide when symptoms are observed and continue until plants are shipped.


Bacterial fruit blotch (BFB) of watermelon is caused by a bacterium that may also be seedborne.  Initial symptoms of BFB are water-soaked areas on the lower surface of the cotyledons.  Lesions turn necrotic often with yellow halos, are frequently deliminated by veins and subsequently the seedlings collapse and die. 



Postemergence Herbicides for Sweet Corn - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu


The following herbicides are labeled for use on sweet corn and have shown fair to excellent crop safety:  atrazine, Basagran, Laddok S-12 (combination of atrazine and Basagran) and Aim.  2,4-D is labeled but injury has been observed on a number of varieties, particularly super sweets and many fresh market varieties.  Use 2,4-D only with caution and experience.  Finally, Sempra and Accent are labeled.  Both of these are ALS-inhibiting herbicides and cannot be used if Counter was applied at planting.  Both can injure and stunt corn, even those varieties listed on the use label.  One of the considerations for use of either of these herbicides is weed control versus crop safety.  More information on postemergence herbicides can be found under the Sweet Corn Weed Management Guide available online at www.rec.udel.edu (look under publications).



Field Crops


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



Within a week of first cutting, be sure to begin sampling fields for potato leafhopper. The first adults, who are migratory, can now be found in Delaware. The treatment threshold is 20 per 100 sweeps in alfalfa 3 inches tall or less. In 4-6 inch tall alfalfa, the threshold increases to 50 per 100 sweeps. Ambush, Baythroid, dimethoate, Pounce or Warrior all provide effective control.


Field Corn.

Be sure to watch for cutworms feeding above and below ground. We continue to see an increase in feeding activity. A treatment in 1-2 leaf stage should be applied if you find 3% cut plants or 10% leaf feeding. A pyrethroid will provide the best control. We are also seeing bird damage in early emerging corn. Although birds can cut plants off at the soil surface, they tend to pull plants out of the ground. In addition, if you look closely you will see " bird prints" near the missing plants so do not confuse it with cutworm damage. In general, birds will pull plants out of the ground instead of cutting.



At this time, all fields should be sampled for cereal leaf beetle larvae. Economic levels are being found in Virginia, southern Maryland and southern Sussex County. Remember that larvae can quickly cause damage if the weather turns warm so fields should be watched closely. The treatment threshold of 0.5 per stem will work if fields are scouted routinely. As wheat heads emerge, begin checking for small sawfly and armyworm larvae. We are finding moderate levels in the earliest planted wheat fields in Kent and Sussex Counties.  The armyworm threshold is one per foot of row in barley and two per foot of row in wheat. The sawfly threshold is 2 per 5 foot of row innerspace. If both are present, the threshold for each should be reduced by 1/3 to 1/2. Warrior or Lannate will provide control of all 3 insects. Remember that Warrior is not labeled for barley.



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


USDA's May Supply and Demand Report Not Likely to Have Major Impact on Commodity Prices
The May 10th USDA Supply and Demand Report appears to be in line with pre-report trade guesstimates. Ending stocks for U.S. soybeans, now placed at 295 million bushels, are 5 million bushels less than last month and just on the high side of pre-report trade estimates. Ending stocks for U.S. wheat were placed at 825 million bushels, just 4 million bushels less than the April 10th report. This is said to be largely due to the largest abandonment of wheat acres in the plains states in nearly 30 years. Ending Stocks for U.S. corn, now placed at 1.998 billion bushels, are 47 million bushels larger than the April 10th report, and on the high side of the pre-report trade estimates.

Commodity markets are expected to open lower on the contents of this report, according to one Chicago Board of Trade Floor Trader. This report is not viewed as a disastrous report, yet by tomorrow's opening bell we are likely to be back to weather.

Export Sales Summary Comments
U.S. wheat sales were reported to be 15 percent above the previous week, but 21 percent below the 4 week average. Wheat sales will have to hurry in order to make USDA's yearly projection, which expires in June. Corn sales were reported to be 27 percent below last week, yet exceeded the 4 week average by 37 percent. U.S. corn sales are not expected to make USDA's yearly projection which expires in September. Soybean exports were 38 percent below the previous week, and equal to the 4 week average. U.S. soybean sales are expected to meet and/or exceed USDA's yearly projection, which also expires in September.

General Comments
Dec. corn new crop futures are currently trading at $2.24 per bushel, which is about a nickel lower than recent highs. A quick check of local new crop corn basis bids of 10 to 20 over reflects a current forward cash pricing opportunity of $2.34 to $2.44 per bushel. Those with all of their 2001 corn crop unpriced are likely to want to take advantage of pricing 10 to 30 percent of intended new crop production at this level. Nov. soybean new crop futures are currently trading at $4.29 per bushel. With local basis offerings at 15 under this translates to a forward contract price of $4.14 per bushel. This is well below the soybean loan rate of $5.36 per bushel. This early in the season, pricing new crop beans at this level does not appear to be advisable. For new crop wheat, July futures are currently trading at $2.65 per bushel with a local basis of 30 under. The Delaware loan rate for wheat is $2.67 per bushel. Even if we consider pricing new crop wheat into December delivery, where wheat futures are reflecting a 26 cent per bushel premium, the net price obtainable still comes in under the loan rate. The big play in U.S. commodity markets now becomes heavily dependent upon weather.   



New Weed Fact Sheets on the Web - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu


There are two new fact sheets available on the UD-REC website (www.rec.udel.edu, under publications).  The first one is a list of herbicide site of action of the most common herbicides used for corn, soybeans, small grains, and forages.  This has the herbicides listed by site of action.  This will be very helpful in developing herbicide programs to limit the potential for herbicide-resistant weeds and help understand which herbicides are similar.  The point is you do not want to repeatedly use herbicides with the same site of action.  The second fact sheet is designed to help when you are questioned about a field as a potential site for glyphosate-resistant horseweed.  This covers the basic questions to ask and details to be considered when thinking of a site as a potential for glyphosate-resistant horseweed.



Organophosphate and Postemergence Herbicides for Corn - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu


There are precautions on the label of many postemergence herbicides regarding the potential interaction with organo-phosphate insecticides.  These precautions are on the labels of ALS-inhibiting herbicides.  In the past there have been a number of situations where an ALS-inhibiting herbicide was sprayed over corn treated with Counter insecticide and no injury was observed.  The environment needs to be right in order for the interaction to occur.  One situation that favors this interaction is a dry spring with little to no rain to “activate” the insecticide.  Then after the corn has emerged there is a rain shower and the postemergence herbicide is applied within a short time.  This may be the situation we are facing this year.  Read the herbicide label and observe the precautions because the injury to the corn crop can be severe.



Zinc Deficiency on Corn - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu ; Gordon Johnson, Extension Ag Agent, gcjohn@udel.edu


Last year under wet, cold spring conditions, we were called in to look at several fields across Delaware that showed poor and sometimes within row plant-to-plant variable growth.  Symptoms consisted of a pale yellow to almost white color for the newly emerging leaves and/or white striping on the most recently fully-expanded leaves.  This latter symptom occurred more frequently in plants that appeared to be recovering.  Symptoms sometimes were variety specific.  A soil insect survey within the row showed little insect feeding.  Corn planted no-till was 4 to 8 inches tall.  Soil test extractable phosphorus (P) levels were high but not unusually excessive.  Tissue samples were taken and showed marginal zinc (Zn) tissue concentrations but several Zn ratios with other nutrients were out of line.


Zinc is an unusual micronutrient in that it interacts with not only environmental conditions, but also several soil and another factors.  Zinc deficiency is most common in cool, wet springs and is impacted by soil type, past erosion history, soil pH, extractable soil P, and extractable soil Zn.  Hybrids and even seed lots can differ in their zinc seed reserve status and, under marginal Zn availability conditions, high Zn seed reserves can prevent or minimize early season symptoms.  Zinc deficiency is often more frequently seen in no-till systems and on low-organic matter sandy soils.  As soil test extractable P and soil pH increase, plant available Zn decreases.  The critical tissue concentration of Zn is 17 ppm in the ear leaf at silking.


Foliar Zn applications can alleviate symptoms.  However, since Zn deficient plants are often significantly reduced in size compared to normal plants, absorption of adequate foliar Zn can be difficult.  This was observed last year when foliar applications improved the general field vigor but failed to allow the smaller more severely impacted plants to recover.  With that said, it should be noted that the grower averaged over 170 bu/A dry corn from the fields showing deficiency symptoms.


Broadcast soil application of Zn as zinc sulfate (ZnSO4) can effectively increase ear leaf Zn concentrations not only in the application year but for many years following application.  Broadcast of 10 to 20 lbs Zn/A on soils with Mehlich III soil test extractable P in excess of 150 lb/A is the rate recommended.  Research in Kentucky by Murdock and Howe showed that Zn concentrations in the ear-leaf increased by about 1.75 ppm for each 5 lbs Zn/A up to the top rate of 30 lbs Zn/A.


As corn begins to emerge, growers and crop advisers should observe fields closely for symptoms of Zn deficiency.  This will be especially true for no-till corn and if the weather becomes cool and wet again as it was earlier this spring.  Fields with a history of Zn deficiency should be watched for reoccurrence unless a recent broadcast Zn application of 10 to 20 lbs/A has been applied.  Low organic matter sandy fields with high or excessive soil test extractable P levels, moderate to high pH especially in the immediate rooting zone, and low soil test extractable Zn levels also should be priority fields to watch.  For fields where the problem is reoccurring, broadcast soil application of ZnSO4 is recommended especially if plants are small at the time symptoms appear.  Foliar application of Zn can be a less expensive option, but will be effective only when plants are of a size that allows adequate coverage of the foliar spray.



Dry Weather and Irrigated Corn - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu


Soil conditions across the area are becoming critical for available moisture.  Although we do not often think of the impact of dry weather on irrigated corn at this time of year, it can cause yield reductions.  Too often, we assume that emerging corn or small two to four leaf corn is using too little water to need irrigation.  While it is true small corn uses very little water per day, the cumulative effect of transpiration and the loss of available soil moisture during the initial tillage prior to planting can result in little available water in the surface 8 to 12 inches of soil.  Another important consideration is activation of herbicides, insecticides, and starter fertilizers as well as the initiation of ear shoots around the fourth to fifth leaf stage of growth.


Bottom line, if you in the least suspect that your corn could be running short of water, start your irrigation equipment and put water on the field.  You do not want corn to begin pulling moisture from the deeper soil layers at this time.  If the dry weather persists, even running irrigation constantly can sometimes not provide enough available water to refill or keep the deeper soil layers filled with water for crop growth during the hottest, driest portion of the summer.





Pesticide Container Recycling


MAY 17, 2001




Sussex Conservation District Maintenance Yard

Shortly Road, Georgetown, DE

Collections from 9:30-1:30 p.m.




All containers must be properly rinsed.


Questions? Call Delaware Department of Agriculture at 302-739-4811 or 1-800-282-8685.



                               Weather Summary

Week of May 3 to May 9, 2001



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

Air Temperature:

Highs Ranged from 87°F on May 4 to 60° F on May 7.

Lows Ranged from 60°F on May 4 to 40°F on May 8.

Soil Temperature:

69°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

Black Cutworm Pheromone Trap Counts - April 30- May 6 , 2001 

Provided by UAP Inc and Syngenta



# Moths 


# Moths 

Bridgeville, DE


Lincoln, DE


Bucktown, MD


Little Creek, DE


Cheswold, DE


Magnolia, DE


Cordova, MD


Mardela, MD


Crumpton. MD


Marydel, DE


Delmar, MD


Middletown, DE


Denton, MD


Milford, DE


Dover/Wyoming, DE


Millsboro, DE


East New Market, MD


Milton, DE


Easton, MD


New Church, VA


Eldorado, MD


Newark, MD


Ellendale, DE


Pocomoke, MD


Farmington, DE


Preston, MD


Federalsburg, MD


Princess Anne, MD


Felton, DE


Queen Anne, MD


Frederica, DE


Rhodesdale, MD




Salisbury, MD


Goldsboro, MD


Seaford, DE


Greensboro, MD


Selbyville, DE


Greenwood, DE


Smyrna, DE


Harbeson, DE


Snowhill, MD


Hebron, MD


Sudlersville, MD


Hickory Hill, DE


Trappe, MD


Hurlock, MD


Vernon, DE


Kenton, DE


Vienna, MD


Laurel, DE


Westover, MD


Leipsic, DE


Willards, MD



Cooperative Extension Education in Agriculture and Home Economics, University of Delaware, Delaware State University and the United States Department of Agriculture cooperating, John C. Nye, Dean and 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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