Vol. 5 No. 4 April 25, 1997

Weekly Crop Update

University of Delaware Cooperative Extension

Volume 5, Issue 24

September 11, 1997



Field Crops:

Field Crop Insects -

Joanne Whalen, Extension IPM Specialist.




As indicated in the last newsletter, we do not expect to see many fields with economic levels of corn earworm. Although moth catches in blacklight traps have increased to 20 to 50 per night, larval populations should be held in check by weather conditions that promote disease development in the larvae and cooler night temperatures that slow earworm development. Although larvae can be found in a few fields, very little pod feeding has been observed. Fields should be checked 1-2 times during the next 10 day period to determine if populations are declining naturally or if a treatment will be needed. Sprays should be delayed until at least 1/3 of the worm population is greater than inch in size and pod feeding is detected.



In recent years, Hessian fly populations have been increasing in areas where continuous wheat (double cropped with soybeans) has been grown. As you make plans to plant your wheat crop, be sure to consider using a combination of cultural practices to reduce the likelihood of damage. Chemical controls are not practical or effective. Resistant varieties developed in the mid-West have not performed well in our area. Therefore, you need to look for resistant varieties developed in the south that yield well in our area. In addition to resistant varieties, the following cultural management strategies should be used: 1.) plant after the fly free date for your county so that wheat will not be available for egg laying when flies emerge ( New Castle County - Oct 3; Kent County - Oct 8 and Sussex County - Oct 10) , 2.) destroy any volunteer wheat to eliminate early egg laying in the fall and reduce the spring fly population, 3.) avoid planting wheat in the same field two years in a row , and 4.) when possible, avoid the use of wheat as a fall cover crop in fields adjacent to wheat fields you intend to harvest next season.



Grain Marketing Highlights -

Carl L. German, Extension Specialist, Crops Marketing



The last private production forecast for the 1997 growing season was released September 9, 1997 reflecting estimates as of September 1. The average call for U.S. corn production by all forecasters was for a '97 U.S. corn crop of 9.379 billion bushels (ranging from 9.197-9.550 bil. bu.). The average call for U.S. soybean production was for a '97 U.S. soybean crop of 2.749 billion bushels (ranging from 2.690-2.792 bil. bu.). In August, the USDA forecast for corn was 9.276 billion bushels, and for soybeans 2.744 billion bushels. The official USDA forecast will be released Friday, September 12, 1997.


USDA's weekly Crop Progress report, released this week, was virtually unchanged from the previous week. U.S. corn earning good/excellent marks increased by 1 %, while soybeans with the same rating slipped by 1 %. It is generally thought that we are not likely to see any surprises in the USDA September report. In the event that we do, then we will be working to finish sales for the 1997 crop and at possibilities for making initial sales for the 1998 corn, soybean, and wheat crops.



Understanding High-Oil Corn: Part 2--Quality Characteristics

Richard W. Taylor, Extension Agronomist


Bob Uniatowski, Extension Associate - Field Crops



Interest in high-oil corn comes from changes in the quality components of the grain. Conventional corn hybrids average about 4 percent oil and are low in several essential amino acids, primarily lysine and methionine. As shown in Table 1, the high-oil corn has a higher energy content (in this Ohio State trial, approximately 150 Kcal/kg more than conventional corn), a higher protein content, improved amino acid distribution (more lysine), and can reduce the need for fat supplements in animal feeds. The higher oil content also benefits animal feed producers by reducing the amount of dust in processed feed.


High-Oil Corn Versus Conventional Corn:


Table 1. Quality characteristics of a conventional (low-oil) corn hybrid and several high-oil top cross blends. From Dr. Peter Thomison, Ohio State University.





Pioneer brand 3394

TC Blends*

% Oil



% Protein



% Starch



Energy (Kcal/kg)



% Lysine




* Average of blends in test on a dry matter basis.



Field Crop Diseases -

Bob Mulrooney, Extension Plant Pathologist




Phomopsis stem canker was recently diagnosed on scattered plants of a mid-season variety in Sussex County. The soybean stems were girdled and the top of the plant was dying. The infections originate from the petiole infections that progress into the stem and develop into reddish-brown lesions which can kill the plant. Crop rotation will reduce overwintering populations of the fungus.


Pre-harvest Aides in Corn -

Mark VanGessel, Extension Weed Specialist



To speed dry down of corn or weeds there are a few things available. Defol will dry down plants but it does not have herbicide activity. Defol is labeled for use at 1 gal/A. Dry down is slow, expect at least 14 days. Roundup can be used after the corn moisture is 35% or less (black layer formed), allow 7 days between treatment and harvest. Up to three quarts can be applied, only 1 qt by air. 2,4-D is also labeled up to 1 quart of a 4 lb gallon. Apply 2,4-D after the dent stage. Apply Roundup and 2,4-D with extreme caution because spray drift can be very damaging to trees, shrubs, and lawns at this time of year.


Vegetable Crops:

Vegetable Crop Insects -

Joanne Whalen, Extension IPM Specialist.



Blacklight Trap Catches.

We will not be running blacklight traps through the end of September; however, recent trap catches for corn earworm and corn borer indicate that egg laying and egg hatch will be high in peppers, lima beans and snap beans through the third week in September.



Maintain a 7 day spray schedule until the end of September except in the Harrington and Dover area where sprays are needed on a 5 day schedule.


Processing Snap Beans.

Fall snap beans are very susceptible to damage from corn borer and corn earworm at this time. In areas where corn borer catches have been 30 - 50 per night for 10 days and in areas where catches have recently exceeded 100 per night (especially the Harrington area and west of Laurel), you will need 3 Orthene sprays during bloom to avoid damage. As indicated in past newsletters, these sprays will need to be applied 5 days apart to be within the 14 day preharvest interval for Orthene. Also, you will need to add Asana to the pin spray for earworm control. In areas where corn borer catches are extremely high, you may need to apply Lannate within 3 days of the pin spray if populations remain high and then on a 4- 5 day schedule until harvest. In all other areas, sprays will be needed on a 4-5 day schedule after the pin spray until harvest.



Vegetable Crop Diseases -

Bob Mulrooney, Extension Plant Pathologist




Phytophthora crown rot has been diagnosed in a field of bell peppers. This is a disease that is very prevalent in the New Jersey growing areas using plastic culture and trickle irrigation. It can occur in flat culture as we see here on Delmarva if peppers are not rotated for long enough periods. Rotations of three years or longer are needed to reduce the threat of pepper blight. Symptoms of Phytophthora blight are blackened stems and wilting of the infected plants. Initially the roots are healthy, but may become infected later. The stem infections produce spores that are splashed to the leaves and upper branches of nearby plants that cause foliar and fruit infections. At this time of the season, applications of Ridomil/Copper can helpwith the foliar and fruit phase of the disease. Early season application of Ridomil Gold and planting on raised beds in addition to rotation is needed to protect plants from the crown and root rot phase.


Vegetable Diseases -

Kate Everts, Extension Specialist, Vegetable Pathology

Universities of Maryland and Delaware



Cucumbers. Anthracnose on cucumbers is present on Delmarva. Leaf symptoms are circular brown or reddish brown lesions. The centers may crack open giving the leaves a shot-hole appearance. Infection is favored by periods of 100% relative humidity for 24 hours. A chlorothalonil product (Bravo or Terranil) should be applied every seven days. Add Benlate (50WP) or Topsin M (70WP) at the rate of 0.25-0.5 lb./A.


After Harvest Sanitation. As harvest of vegetables is completed in fields, plow under crop debris at the earliest possible time. Foliar diseases can increase rapidly within a field once fungicides are no longer applied (ie. after harvest). This disease build-up may contribute to increased inoculum levels next spring and summer. However, plowing under debris will bury tissue, stop the current epidemic, and stop inoculum from building up. Once incorporated, the tissue will break down more readily in warm (early fall) soil than in cooler soil. Beginning the 1998 growing season with lower inoculum levels will reduce the extent of the early season epidemic and contribute to a healthier crop.





Quarterly Pesticide Training & Testing


Kent County Cooperative Extension Office



Sept. 16th - 8 a.m.- 4 p.m.

Sept. 17th - 8 a.m.-Noon



Sept. 17th - 1 p.m. - 4 p.m.



Weather Summary

University of Delaware,



Week of September 5 to September 11, 1997



0.06 inches: Sept. 10

0.63 inches: Sept 11

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





Ranged from 85 F on September 8 to 71 F on September 5.



Ranged from 69 F on September 11 to 45 F on September 5.



Soil Temperature:

68 F. Average for the week.




 Compiled & Edited By:

Tracy Wootten

Extension Associate - Vegetable Crops


Cooperative Extension Education in Agriculture and Home Economics, University of Delaware, Delaware State College 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, color, sex, disability, age or national origin.