Volume 11, Issue 3                                                                                                    April 11, 2003



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


Section 18 Approved for Provado on Stone Fruits.

Provado 1.6F has been approved for use on peaches, nectarines, plums and apricots in Delaware to control aphids, including the green peach aphid, a vector of Plum Pox Virus.


A maximum of 4 applications at the rate of 5-6 fl. oz. of product/A (0.06-0.08 lbs. a.i./acre) of Provado 1.6F may be made by ground equipment.  No more that 24 ounces of the product (0.32 lbs a.i.) may be applied per acre per year.





Watermelon Promotion Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu


The National Watermelon Promotion Board has received approval from the USDA for a new logo that emphasizes watermelon as the “lycopene leader in fresh produce.”  Research has indicated that lycopene, a cartenoid, may help reduce the risk of prostrate cancer and heart disease.  Another good reason for consumers to buy Delmarvalous watermelons.






Wet Conditions and Potato Weed Control Decisions Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu


The continuing wet conditions have obviously delayed much of the potato planting progress.  In some cases, the weather may have eliminated the opportunity for pre-emergence treatments of herbicides.  However, there are excellent post-emergence materials available. 


If no pre-emergence materials were applied, a Matrix (rimsulfuron) and Sencor (metribuzin) combination will control many grass and broadleaf weed species.  While the Matrix rate is 1 ounce/acre, a reduced rate of Sencor (metribuzin) at 1/3 lb./acre should be used when mixed with Matrix.  Use non-ionic surfactant at 1 quart per 100 gallons of spray.  Always check the label for additional instructions and restrictions.  This must be applied before the potatoes are 14 inches tall.  Of course, the earlier the application, the better the weed control.


The post-emergence grass materials, Select or Poast, can also be used as separate applications to control escaped grasses.



Vegetable Diseases Kate Everts, Extension Plant Pathologist, Univ. of MD and Univ. of DE; everts@udel.edu



Ozone injury on watermelon.

Bifacial necrosis of old watermelon leaves.



Photo taken from the USDA-ARS, North Carolina State University Air Quality Research Unit at the following address:



Ozone Damage in Watermelons. 

Ozone injury to watermelons is common in Delaware and on the Eastern Shore of Maryland.  Symptoms include flecking, premature chlorosis, and necrosis (yellowing and tissue death) of crown leaves.  In severe cases, the leaves will become skeletonized.  A recent study conducted by Dr. Gerald Holmes (NCSU) showed that seedless cultivars tended to be more tolerant of ozone damage than seeded cultivars.  He did not find a relationship between cultivar fruit size or shape and ozone damage.  Crimson Sweet, Sentinel, and Tri-X-Palomar were more sensitive to ozone than the average cultivar tested.  Mardi Gras, Revolution, SeedWay 4502, HMX 8914, TRI-X-313, Millionaire, Freedom, and Millennium were more tolerant of ozone damage than the average cultivar tested.  Cultivar tolerance to ozone damage is the only available management tool we have for this problem.




Field Crops


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


Supply and Demand Report Viewed as Uneventful

Commodity analysts are reporting no big surprises from the April 10th Supply and Demand report. The numbers most watched in this report were ending stocks for U.S. corn, soybeans, and wheat. The ending stocks for all three commodities were well within pre-report estimates.


Corn ending stocks are now listed at 1.009 billion bushels vs. the average trade guess of 999 million bushels. Ending stocks for corn were reported to be 5 million bushels less than last month's estimate.


Soybean ending stocks are down to 145 million bushels, vs trade guesses ranging from 125 to 150 million bushels. Soybean stock estimates are down 15 million bushels from last month.


Wheat stocks are down 20 million bushels from last month. The decrease in wheat stocks, now placed at 445 million bushels is due primarily to a 25 million bushel increase in domestic feed and residual use and a 5 million bushel increase in imports on the supply side.


CBOT Launches Mini Agricultural Futures Contracts

The Chicago Board of Trade launched CBOT mini corn, wheat, and soybean futures contracts on Monday, April 7. The trading hours for these 1,000 bushel contracts will be from 9:30 a.m. to 1:45 p.m. These contracts replace the mini contracts that were formerly traded at the Mid-America Commodity Exchange. If interested in getting further information contact Carl German, clgerman@udel.edu




Is It Too Late to Apply Nitrogen to Small Grains? - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu ; Derby Walker, Jr., Sussex County Extension Ag Agent; derby@udel.edu


The question being raised after the most recent period of bad weather is if it still is worth while fertilizing small grains.  An important component of the answer is the determination of the stage of growth of the crop.  Where you haven’t been able to apply fertilizer yet, you should take the opportunity to scout a field for the crop’s growth stage while you wait for it to dry.  Examine a number of plants across the field and determine growth stage by looking closely at the primary tillers on each plant.  Check tillers to see if you can feel a swelling that indicates node development.  Another way is to pull back leaf sheaths to expose the growing point and see if more than one or two internodes (the space between two nodes) are present.  Also, observe how far above the soil surface the growing point is.  The jointing stage of growth begins when the first node appears above the soil surface and jointing progresses as more and more nodes occur above the soil surface until boot stage when the seed head can be felt within the leaf sheaths.


Once the space between the nodes begins to lengthen and pushes the growing point that ends in the seed head above the soil surface, the likelihood of doing at least some damage to the crop by driving across a field to spread fertilizer is great.  After several internodes are visible, the chance of having a large impact on yield by applying nitrogen (N) diminishes.  Another helpful indicator will be the intensity or greenness of the crop or signs of N deficiency on the lower leaves.  The number of leaves per plant showing N deficiency symptoms relates to the amount of N stress and that corresponds to loss of yield potential.  When combined with plants at later stages of development (late jointing or early boot), the damage caused by N stress reaches the point where additions of N will no longer boost yields enough to be profitable.  The earlier you can apply N the more yield response you are likely to see.  By boot stage, N will have little impact on yield potential although it can still influence the grain N content.


Another question asked is whether wheat that recently came up will yield?  This question is harder to answer because wheat requires a period of cold temperatures to change it from vegetative state to a reproductive state.  Winter wheats require more cold weather than spring wheats and southern varieties of winter wheat can be switched to a reproductive state by fewer days of cold than varieties developed further north.  The problem with deciding if a field will move to the development of grain (yield) is knowing when the crop germinated enough for the cold temperatures to begin the process of vernalizing the crop and switching it to a reproductive state.  With a microscope or a very good hand lens (and good eyesight), you might be able to dissect plants and identify the developing panicle if it has switched to the reproductive state.  At the growing point even when it is very tiny, you can identify the developing panicle or seed head since it looks like a miniature wheat head.  Even if you find that the crop has vernalized, the yield potential is an open question.  Experience suggests wheat that emerges in late February can produce 50 to 60 bu/A but we’ve not had experience with wheat emerging later than that date.


Avoiding Leaf Burn from UAN on Small Grains - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu; Derby Walker, Jr., Sussex County Extension Ag Agent; derby@udel.edu


Several years ago Ron Mulford, the farm manager for University of Maryland’s Popular Hill Research Farm, passed along to Derby Walker the following dilution values for 30 percent UAN (urea-ammonium nitrate) solution.  The dilution should be enough to prevent the leaf burning of small grains when liquid nitrogen (N) is broadcast applied under warm conditions (60˚F and higher). 


If you have to apply UAN under warm conditions, you may want to follow the guidelines below to possibly reduce the potential for leaf burn.  Since weather conditions may be forcing many producers to apply N much later than they like, preventing even the mildest of stress such as the temporary leaf burn UAN can cause can be worth the extra effort.


Table 1.  Approximate dilutions for UAN solutions when topdressing small grain to reduce the potential for leaf burning under warm conditions (60˚F and higher).


Gallons of UAN


Gallons of Water

N Application Rate

Total solution volume

Lb N/a



28% UAN






















30% UAN






















32% UAN
























Preemergence Herbicide Rates In Corn - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu


There have been changes in formulation and ratios of products for many pre-packaged herbicides over the past few years.  As a result, check the label for your product of choice since often the new formulations recommend lower use rates than what as previously labeled.  Below is a chart on rates of the most common pre-packaged mixtures used in the area, and general use rate and what the products they are providing:







(grass herbicide)

Bicep II Magnum

1.6 qts

1.24 qt

1.0 pt Dual II Magnum



2.7 qts

1.1 qt

2.0 qt Topnotch


Guardsman Max

1.5 qts

1.25 qt

14 oz Outlook


Harness Xtra  5.6L

1.7 qts

1.1 qt

0.76 qt Harness



2.5 qts

0.625 qt

1.76 pt Dual II Magnum

AND 5.4 oz Callisto **


    **Callisto is not a chloroacetamide



Conventional Soybean Herbicides - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu


I have had a number of questions about herbicides for non-Roundup Ready soybeans.  There is interest in growing conventional varieties for a number of reasons.  Most sound herbicide programs will require a broadleaf plus a grass herbicide at planting.  The Delaware/New Jersey Soybean Weed Management Guide available free at the county offices or online at http://www.rec.udel.edu/weed_sci/WeedPublicat.htm will provide useful information for selecting herbicide programs for the specific weed problems you need to handle.  As always, there is not one program available that will fit all situations.  Be sure to consider all factors, including effectiveness, application timing, and rotational restrictions.  Contact your county agent if you want to review your options.




Supplemental Labeling of Roundup Products for Glyphosate-Resistant Horseweed (Marestail) - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu


Monsanto has issued supplemental labels for control of glyphosate-resistant horseweed in all of DE, NJ, and eastern shore of MD.  For all

Monsanto’s glyphosate products (Roundup Ultra, Roundup UltraMax, and Roundup WeatherMax),



they are requiring 1 pt of 2,4-D to be applied to plants 6 inches or less.  I have concerns that the rate of 2,4-D will not control the glyphosate-resistant horseweed, and I would encourage the use of 1 qt/A of 2,4-D (in areas where it is appropriate and where a 30 day interval between application and planting is acceptable) for better and more consistent control.




Do Not Overuse Roundup Ready Crops - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu


Avoid the temptation to use Roundup Ready corn in the same fields where you are planting Roundup Ready soybeans.  Relying on glyphosate (whether it is Roundup products, Touchdown, Glyphomax or others) every year for postemergence weed control is not a sound, long-term weed management program.  As a general rule, do not use Roundup Ready crops more than once out of two years for a given field.




Delayed Burndowns For Corn - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu


Due to the spring rains a number of fields for no-till corn have not been sprayed yet.  As a result, what works when burndowns are applied in March may not work this year because the weeds are likely to be larger than normal.  Be sure to use a full rate of the non-selective (burndown) herbicides.  Gramoxone Max at 1.25 pts and full rate of glyphosate products should be used since many of the winter annual weeds will be larger due to the later application timing.  Also, if considering using 2,4-D, be aware there are restrictions on time from application to planting (commonly 7 to 14 days) and it is not recommended on coarse-textured soils with low organic matter (refer to label of the product you are using).  Remember, if trying to combine nitrogen applications with the burndown herbicides, Syngenta recommends increasing the rate of Touchdown by 0.5 to 1.0 pt/A while Monsanto does not recommend nitrogen carriers where annual ryegrass, barnyardgrass, fall panicum, or broadleaf signalgrass are present.  Finally, if you typically use Princep (simazine) when burning down no-till fields early, you should still use it with the burndown mixture to help with residual control of crabgrass or fall panicum.  Princep will not help with controlling those plants already out of the ground, but will provide residual control.


Changes in Pesticide Regulations as Related to Applying Pesticides When Using a Tractor With An Enclosed Cab Tracy Wootten, Extesnion Associate – Vegetable Crops; wootten@udel.edu


The following information was taken from James Belote’s Accomack Ag News, March 2003 Issue.


The American Society of Agricultural Engineers (ASAE) is no longer certifying closed cabs as equivalent to the protection of a respirator.  As a result, when the label requires a respirator, applicators must wear one, even if using a tractor with an enclosed cab.


The problem has occurred because no tractor manufacturer or government agency has declared in writing that the enclosed cab of any tractor with its properly functioning ventilation system will provide respiratory protection equivalent to or greater than the vapor-or gas-removing respirator specified on a pesticide product.


As a result, growers using enclosed cab tractors and applying products that require respirators are required to wear respirators when in the cab.




                   Weather Summary



Weeks of April 3 to April 9, 2003


0.58 inches: April 7

0.01 inches: April 8

0.94 inches: April 9


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

Air Temperature:

Highs Ranged from 62°F on April 3 to 40°F on April 8.

Lows Ranged from 44°F on April 3 to 38°F on April 8 & 9.

Soil Temperature:

48°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, 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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