Weekly Crop Update

University of Delaware Cooperative Extension

Volume 5, Issue 19

August 7, 1997



Crop Management Tour

August 21, 1997

9:00 to 12:00

Lunch - 12:30


A half-day tour with a free Eming's Barbecue Lunch at 12:30.


The tour will feature several demonstrations at the University's Warrington Farm on Rt. 5, south of Harbeson. Included are: 15" vs. 30" row lima beans, High available phosphate corn designed to reduce phosphorous content of poultry feeds, Deer management ideas, Irrigation scheduling for corn and lima beans, Bt corn and insect resistance, Nitrogen management on corn, weed management on corn and lima beans under irrigation.

The variable rate precision manure spreader will also be demonstrated.

To reserve a place on the air-conditioned bus and for lunch, please call us at 302-856-7303.

Field Crops:

Field Crop Insects -

Joanne Whalen, Extension IPM Specialist.



Unfortunately, spider mites continue to be the main pest problem in soybeans. In addition, egg laying continues to increase and weather conditions favorable for population crashes (moderate temperatures and high humidity) generally do not occur until later in August. At this time, edge treatments will not be effective. In general, populations have spread throughout the entire field and hot spots of activity can be found within most field interiors. In areas where plants are extremely drought stressed, a contact treatment of Parathion (aerial application only), Lorsban or Penncap will be your best choice. Unfortunately, you will need to plan on 2 sprays spaced 5 days apart. If you have received rain or have irrigated soybeans, dimethoate should provide adequate control. If spraying by ground or air, crop oil or organosilicone should be used. The best control will be achieved with the addition of an organosilicone.


Every year we can easily find aphids feeding in the center of whorl stage plants. In most cases, the predominant species is the corn leaf aphid and generally no controls are needed. Beneficial insects are very active and helping to crash the populations. Controls may be justified if: (1) the greenbug is the predominant species. (Yellowish-green aphids with a green stripe down the middle of its back), (2) natural enemies can not be readily found, (3) greenbug populations are readily increasing, AND (4) a few leaves are starting to die. Dimethoate is the material of choice for control.

Small Grains Variety Results are Available

Richard W. Taylor, Extension Agronomist


Bob Uniatowski, Extension Associate, Field Crops


Preliminary results from the 1997 Small Grain Variety Trials are now available from your County Agricultural Agent. Varieties of wheat and barley were tested at 3 locations: Middletown, Camden, and Georgetown.

Barley yield averages range from 78.6 bu/A at the Camden location to 113 bu/A at the Middletown location. The most consistent top yielding varieties across all locations were Pennco and Acton. While Starling and Luttrell performed well in the souther half of the state, Pennbar 66 did well in the northern half of the state. For long-term yield averages, the top varieties at the 3 locations were: Starling, Pennco, and Pennbar 66 at the Camden location: and Pennco, Starling, Nomini, and Acton at the Georgetown location.

Wheat yield averages range from 86 bu/A at the Camden location to 94.7 bu/A at the Middletown location. The most consistent top yield varieties across all locations were: AgriPro brand Hickory, Jackson, Northrup King brand Coker 9663, Agra brand GR 962 (new to the trials), Hoffman brand 14, and Pioneer brand 25R57 (new to the trials). For long-term yields at the Middletown location, the best varieties were Pocahontas (2 years only), Northup King brand Coker 9663 (2 years only), Gore, Jackson, Andy, Pioneer brand 2552, and AgriPro brand Hickory. For long-term yields at the Camden location, the best varieties were AgriPro brand Hickory, Jackson, Pioneer brand 2552, Southern States brand FFR 555W, AgriPro brand Sawyer, Northrup King brand Coker 9663 (2 years only), and Gore. For long-term yields at the Georgetown location, the best varieties were: Northrup King brand Coker 9663 (2 years only), Hopewell (2 years only), Jackson, Northrup King brand Coker 9835, Verne, Wakefield, Pioneer brand 2552, and Glory.

The results will be available at Field Day, August 13, at the R & E Center.

Vegetable Crops

Vegetable Crop Insects-

Joanne Whalen, Extension IPM Specialist



All fields should be sprayed on a 7 day schedule except in the Harrington area where sprays are needed on a 4-5 day schedule. Orthene or Lannate should be used. Green peach aphid populations are also starting to increase. Lannate, Orthene, or Provado will provide control.


Begin scouting fields for diamondback and cabbage looper larvae. A treatment should be applied when you find 5% of the plants infested, especially if they are feeding in the hearts of the plants. A Bt plus a pyrethoid should provide the best control. If you plan to use Monitor for the first spray, it will provide diamondback control but has not provided adequate cabbage looper control in recent years.

Snap Beans - Processing.

All fields should be sprayed at the bud and pin stage for corn borer control. In the Harrington and Dover area, sprays should be applied just before the bud stage to prevent entrance into the stems and again at the pin stage. After the pin spray, sprays should be applied on a 5 day schedule except in the Harrington area where sprays are needed on a 3-4 day schedule.

Sweet Corn.

All fresh market silking sweet corn should be sprayed on a 3 day schedule. If a single insecticide is used, Warrior or Lannate are the preferred materials. If Ambush, Asana, or Pounce are used, the mid-range rate should be used in combination with Lannate LV (1.5 pt/A or larvin (30 oz/A).


As you make plans to plant fall spinach in the next week to ten days, be sure to consider a pre-planting treatment for seed corn maggot. Treatment will be needed in fields with heavy organic matter or crop residue plowed under immediately before planting. Diazinon Ag500 should be broadcast at a rate of 3 qts pr acre. It also must be incorporated in the to 3-4 inches immediately before planting.

U of D Crop Pest Hotline: In State: 1-800-345-7544

Out-of-State: 302-831-8851

Spinach Weed Control

Ed Kee, Extension Vegetable Specialist


Ro-Neet applied pre-plant incorporated if used alone at 3 pints/acre. However, with the Section 18 for Dual on spinach, Ro-Neet should be applied at 1 quart/acre, preplant incorporated 7 days prior to planting. Dual should then be applied after planting, but preemergence at 1 pint/acre by ground equipment only and when sprinkler irrigation is to follow within two days.

UpComing Events...









8:30 a.m. - 1:30 p.m.


For more information contact:

Mark Isaacs or Jay Windsor

University of Delaware

Research and Education Center

RD 6, Box 48

Georgetown, Delaware 19947

(302) 856-7303


Grain Market Update

Carl German, Extension Market Specialist



Spark's August crop estimates (released pre-USDA) have forecast U.S. corn production at 9.470 billion bushels and soybeans at 2.686 billion. This compares to a July USDA forecast of 9.7 billion for corn and 2.690 for soybeans. FCC (another private forecaster) has made an August estimate of 9.582 billion bushels for corn and 2.731 billion for soybeans. The market tended to react to these estimates in a friendly manner, since the estimated carryover for both crops was slightly reduced from July forecasts. Nevertheless, the August 12th USDA forecast will become the standard, in the near term, for determining price direction in the commodity markets. The most significant development this week is the change in the forecast for the mid-west corn belt, with rain predicted for the dry areas of the corn belt. Significant rainfall will result in major price declines for new crop corn and soybean prices. Yet, "only light showers" are forecast for the dry areas of the corn belt. The amount of rainfall will be critical to U.S. crop size and commodity prices. For further information contact Carl German @ 302-831-1317.

Late Blight Update

August 7, 1997

Delaware Cooperative Extension

Bob Mulrooney, Extension Plant Pathologist


DSV accumulation as of August 4, 1997 are as follows:


Location/ emergence date

DSV July 28

DSVs August 4


Baldwin - 4/20



10-day, high rate

Jackewicz - 4/26



10-day, high rate

Zimmerman - 4/28



10-day, high-rate

Baker - 5/7 -5/9



10-day, high-rate


This will the last FAX update. I will be updating the Late Blight Hotline on Friday and you can call if you need information on DSV accumulation. Hot line number is 1-888-831-SPUD. The weather has not been favorable for late blight recently. There are still some late potatoes that may benefit from fungicide applications at this time.

A recent tuber sample that I examined was infected with Pythium which causes leak. When tubers are cut open the infected tissue is a smoky gray color and does not have the foul smell of bacterial soft rot. The infected tissue has a cheesy texture and large amounts of clear liquid can be squeezed from the infected tissue. The disease is favored by high soil temperatures and wounds. Rotation and foliar applications of Ridomil Gold

MZ as for pink rot are recommended for control.

Weather Summary

University of Delaware


Week of August 1 to 7, 1997


0.21 inches: Aug. 6

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



Ranged from 90oF on Aug. 4 &

to 78oF on Aug. 7


Ranged from 57oF on Aug. 1 to 73oF on Aug. 3

Soil Temperature:

74.5oF Average for the week

Compiled & Edited by

Ed Kee

Extension Vegetable Crops Specialist 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.



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