Volume 10, Issue 6                                                                                                      May 3, 2002




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



We have started to see an increase in asparagus beetle egg laying activity on spears. A treatment is recommended if 2% of the spears are infested with eggs. Since adults will also feed on the spears, a treatment is recommended if 5% of the plants are infested with adults. Sevin, Lannate, Ambush, or Pounce will provide control.



Continue to check potatoes for an increase in Colorado potato beetle egg hatch. The treatment threshold is 4 small larvae per plant or 1.5 large larvae per plant. If both small and large larvae are present, these thresholds should be reduced by ½ for each.  Actara, Spintor or Provado will provide good control of adults and larvae. Corn borer moth populations are still low -- generally less than one moth per night. The most recent blacklight trap catches can be found at  http://www.udel.edu/IPM/traps/latestblt.html. Trap catches will be updated on the IPM website 3 times per week (Mon., Wed., and Friday) starting May 6.  As of this date, no potato leafhoppers have been found in potatoes.



As soon as plants are set in the field, you should begin scouting for cucumber beetles, aphids and spider mites. Since cucumber beetle populations were high at the end of last season and overwintering conditions were favorable, be sure to look for beetles, especially on field edges near overwintering sites. Foliar products can provide good cucumber beetle control; however, multiple applications of a pyrethroid or Sevin may lead to spider mite outbreaks later in the season. So be sure to scout fields and only treat if populations are causing damage. Admire or Platinum can also be applied through the drip and should provide both beetle and aphid control. There have been reports of low levels of aphids on plants in the greenhouse. If plants are ready to set out, the best option is to check plants for aphids as soon as they are set in the field. The treatment threshold for aphids is 20% infested plants with at least 5 aphids per leaf. Actara, Fulfill, Lannate and Thiodan are labeled on melons and will provide melon aphid control. These materials should be applied before aphids explode. Overwintering conditions were also favorable for spider mites so begin checking small plants for mites within a week of setting them in the field. If populations increase gradually and you find a high percentage of immature mites, Agri-mek has provided good control. However, if populations explode quickly and you are finding mostly adult mites, Capture, Danitol or Kelthane should be used. No controls should be needed until 20- 30% of the crowns are infested with 1-2 mites per leaf.



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


Section 18 Granted.

For the second year EPA has granted Delaware and Maryland a section 18 emergency exemption for the use of Acrobat (dimethomorph), manufactured by BASF, to control Phytophthora blight (Phytophthora capsici) in squash (summer, winter, pumpkins), cantaloupes, watermelons, and cucumbers. The section 18 label can be found at the following address: http://www.rec.udel.edu/Update02/Updatepdf.htm

in PDF format.  This product is labeled at 6.4 oz/A for a maximum of 5 applications per season and a 4 day pre-harvest interval. It is a useful tool in an overall program to manage Phytophthora blight. It must be tank mixed with another fungicide labeled for Phytophthora blight, eg., fixed copper, but not mefanoxam (Ridomil Gold 4E, UltraFlourish 2E) or metalaxyl.


Sweet Corn.

To control the flea beetles that transmit Stewart's wilt plant seed treated with Gaucho, apply Counter 20CR at planting or apply insecticides once thresholds are reached or at the spike stage of growth. Plant resistant varieties whenever possible.


Snap Beans.

To prevent Pythium damping-off apply Ridomil Gold in a band over the row at seeding or apply Ridomil PC 11G in the furrow. For added control of Rhizoctonia pre and post emergence damping-off use Maxim treated seed.



Pickling Cucumber Weed Control - Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu


Strategy is a pre-mix product from UAP that combines Command 3ME and Curbit 3E.  It is labeled for cucumbers, melons, pumpkins and squash.  In pickling cucumbers, it can be used as a pre-emergence material, not incorporated.  The two pint rate of Strategy equals 5.3 oz/A of Command and 17 oz/A of Curbit.  If using Strategy for pickling cucumbers, 8 to 15 ounces of Curbit should be added to obtain the desired Curbit rate of 1.5 to 2 pints/A.


Most pickling cucumber growers have been successfully using 4-5 ounces of Command 3ME plus 1.5 to 2 pints of Curbit per acre.


Breakouts of grass can be controlled with Poast.  Nutsedge can be controlled with Sandea, which received a 24c local needs label last year for cucumbers.



Field Crops


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



At this time, all spring planted fields should be sampled for leafhoppers. Within a week of first cutting, be sure to begin sampling all alfalfa fields for potato leafhopper adults. The first adults have migrated from the south and generally cause the most damage in spring planted fields. 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, Mustang, Pounce or Warrior all provide effective control.


Field Corn.

With recent rains and cooler weather, be sure to watch spike to 3-leaf stage corn for slug activity. Slugs can easily be found under the trash in no-till situations. Treatment options for slugs include the application of metaldehyde baits ( e.g.Deadline MPs and TrailsEnd LG) or the use of liquid nitrogen at the spike to one leaf stage. In general, both treatment options will help to reduce the slug activity buying time to enable the crop to outgrow the problem.


Small Grains.

In addition to grass sawflies, the first true armyworms have been found in wheat and barley in Kent and Sussex Counties. Since sawflies can quickly clip heads in both crops, early detection is critical. Be sure to shake plants to dislodge larvae feeding on the plants during the day. In both crops, the treatment threshold for sawflies  is 2 per 5 foot of row innerspace or 0.4 per foot of row. The armyworm threshold is one per foot of row in barley and two per foot of row in wheat.

Black Cutworm Pheromone Trap Counts

April 20 through April 26, 2002

Trap Counts Provided by UAP Inc., Seaford, DE and University of Delaware IPM


# Moths


# Moths

Argos Corner






Little Creek






















Harrington E




Harrington N


















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



Powdery mildew is increasing since the return of the cool weather and rain. Be sure to check your fields regularly for the presence of mildew. Most wheat is headed out so the window for fungicide application is narrowing. Fungicides (Tilt or Stratego) cannot be applied after flowering (Feekes Growth state 10.5). Many varieties have some mildew in the lower part of the canopy, but none in the upper part (the flag leaf and the two leaves below). If the wheat is flowering or has flowered and there is no mildew on the top three leaves, fungicides are not necessary for powdery mildew under most conditions. Some varieties such as Roane, Pocahantas, Century II, Coker 9025, need to watched. They have heavy infection levels in the lower canopy in our Middletown variety plots and have the potential for infection in the upper leaves as well if the current weather pattern continues.




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


Commodity Prices Await Market News

Weekly export inspections for the week ending 04/29 were friendly for U.S. wheat, with exports reported at 23.769 million bushels, well above trade expectations. Soybean exports totaled 9.767 million bushels, considered to be neutral to the market coming in the middle of trade guesses. Corn inspections were considered bearish, at 26.478 million bushels, coming in well below the low end of trade guesses.


Grain Stocks Decline

Stocks of grain held in terminals and elevators included in USDA's weekly Grain Stocks report dropped another 2%, to 38% last week. That's 5% below stocks at this time a year ago.


Marketing Strategy

We are currently getting a "mild" bounce in the corn and wheat pits. The bounce is said to be mild because there doesn't appear to be any news that can sustain much of a rally at this point in time. We are in a continuing holding pattern for advancing new crop sales for corn, wheat, and soybeans. With about 26% of the nation's 2002 corn crop planted, the market will be paying attention to the advancement of planting progress over the next three to four weeks. Corn needs to be planted on or before June 10th in the Central corn belt.



Yellowed Newly Emerged Corn - Richard W. Taylor, Extension Agronomist, rtaylor@udel.edu , Derby Walker, Jr., Extension Ag Agent, Sussex County, derby@udel.edu


In looking at fields early this week, we found that a number of newly emerged corn fields were showing up as bright yellow in color rather than the green one would expect.  In addition, wheat fields that had been dark green the week before were much lighter green in color and gave the appearance of loosing vigor.  These observations have not been limited to Sussex County, Delaware but are observable up and down the state and also appear in southern New Jersey.




We suggest that much of this yellowing that we’re seeing is due to the cloudy, cool, and moist weather the corn has been experiencing the past week to ten days.  Root growth has been slow, nutrient uptake has been below normal and subsequently the ability of the plant to produce chlorophyll (the pigment that gives plants their green color) has been limited, so the plants have turned yellow.  We would expect that with the long-range forecast predicting warm, sunny weather from Friday through the weekend that much of the poor coloration in corn and the lighter green color in small grains will disappear.




Keep in mind that plants growing under stress will not be as tolerant of herbicides.  Check the label before making any post treatments to avoid injury. Some materials will have a label statement “not to apply when corn is under stress (moisture, injury, poor growing conditions, etc) or below a minimum temperature”.




Frost Damage on Wheat - Richard W. Taylor Extension Agronomist, rtaylor@udel.edu , Derby Walker, Jr. , Extension Ag Agent, Sussex County, derby@udel.edu , Bob Uniatowski, Associate Scientist, bobuni@udel.edu


In the past few weeks, we’ve had a number of fields that have shown frost or freeze damage.  The injury occurred as late as last week when some small corn that was planted generally in fields protected from the wind showed severe frost damage.  In most, if not all cases, the below ground growing point was not injured so little permanent damage was done to the corn. 


For wheat injured last week, we were seeing dead growing points on small newly emerged tillers as illustrated in the photo below.  We suspect yield impact will be minimal since in the fields we looked at the number of tillers per plant was very high and only the small, weak tillers appeared affected.  Examination of some of the small tillers that were not injured showed heads in the boot with only about 6 potential kernels.  Keep in mind that these tillers often are too short to even get caught by the combine.



Another type of injury that we observed was leaf tip burn and chlorosis as illustrated in the photo below.  We were seeing it occur mostly on the flag leaf and symptoms and amount of leaf area affected was unlikely to impact yield potential.  It should be noted, too, that the wheat had actually begun to shed pollen which is about three weeks earlier than normal.




Finally, we also have seen wheat plants that were severely impacted by the hard freeze of several weeks ago.  The photos below show how the lower nodes of the primary tillers were killed by the freeze.  In many cases, the leaves above the injury point were still green and appeared alive although we suspect that the hot weather of last week finished the job the freeze injury began.  Most of the plants observed were sending out new tillers.  This damage was likely to severely impact yield even with the new tiller production.  We suspect that at harvest the field will have heads in all states of maturity as well as of variable size (number of kernels and grain height above the soil surface).




For more detailed descriptions and the implications of cold damaged wheat, please refer back to the Weekly Crop Update for April 19, 2002, volume 10, number 4, pages 8-10.






Strawberry Twilight


University of Maryland Wye Research & Education Center

Queenstown, Maryland

Thursday, May 16, 2002

6:00 pm- until



Special Guests and Topics:

Ø      Strawberry Nutrient Management: Dr. Gordon Miner, NCSU

Ø      SkyBit for Frost Protection: Dr. Joe Russo, Agricultural Meteorologist

Ø      Strawberry Weed Control: Scott Rowe and Dr. Ed Beste

Ø      Laminating Plastic Beds: Mike Newell and Paul Clarke

Ø      Plus: More on varieties, strawberry plasticulture, and carryover with Dr. Harry Swartz, Bob Rouse, and USDA.


For more information, call 410-827-8056, ext. 115






When:Tuesday, May 7, 20026:00 PM – till(?)


Where:University of Delaware Research and Demonstration Area

¾-mile east of Armstrong Corner, on Marl Pit Rd. (Rd. 429).



Come join your fellow farmers and our Extension Specialists for an interactive and hands-on experience as we address in-season  wheat/barley, corn, and soybean production issues to include:


·            variety trials,

·            agronomics and fertility,

·            insect, weed, and disease management.


As always there will be time to discuss your questions.



DDA will award (1) private applicator re-certification credit in the agricultural plant category. Credits will also be available for Certified Crop Advisors.


Whether or not you can join us on the 7th, stop by at your convenience throughout the season. Handouts and maps will be available in the plastic information box mounted behind the UD sign. This meeting is free, and everyone interested in attending is welcome. For more information or special consideration in accessing this meeting, please contact our office in advance at (302) 831- 2506.




Carl P. Davis

Extension Agent, Agriculture




Ag Fact



Americans spend 10% of their income on food; Japan 17%; and India 52%.  American farmers, on average, get 29% of the consumer’s retail dollar.  This ranges from 7% for the wheat producer, and near 100% for the pick-your-own farm operation.


Many people think processors and retailers extract an exorbitant share of the consumer’s dollar, but the record shows (through consolidations and closures), that the food industry is highly competitive and works on thin margins.




                       Weather Summary

Week of April 25  to May 1, 2002


April 25: 0.27 inches

April 27: 0.04 inches

April 28: 1.32 inches


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

Air Temperature:

Highs Ranged from 75°F on April 28 to 60°F on April 25 & 27.

Lows Ranged from 53°F on April 28 to 39°F on April 26 & 30.

Soil Temperature:

58°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, 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.