Volume 6, Issue 17                                                                                           July 17, 1998


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


Mite activity has remained steady in most fields with a slight increase in egg laying activity. In later planted fields, watch for an increase in mite activity due to warmer weather. Fields should be sprayed when 10-15% of the crown leaves are infested. Agri-Mek and Kelthane have provided the best control. Melon aphid populations have also started to increase in spots throughout fields. Populations can explode quickly so be sure to check fields carefully, especially later planted fields. The treatment threshold is 20% infested plants with 5 or more aphids per leaf or runner. Lannate will provide melon aphid control but coverage is important, especially if leaves have begun to curl.


Continue to maintain a 7-10 day spray schedule for corn borer and pepper maggot control. Once corn earworm catches increase to 20 or more per night, you will need to switch from Orthene to Lannate or a pyrethroid. In general, Orthene provides poor earworm control.


Scattered populations of aphids can be found in most fields throughout the state. At this time, only late planted fields should need to be treated if populations explode as a result of the recent warmer weather. The treatment threshold is 4 aphids per leaf until 2 weeks from harvest when this threshold increases to 10 aphids per leaf. Since the green peach is the predominant species being found, Provado or Monitor are the materials of choice.

Snap Beans.

Processing snap beans should be sprayed at the bud and pin stages with Orthene (1 1/3 lb/acre) for corn borer control. A third application with Lannate will be needed within 5 to 7 days from harvest. When moth catches increases, you may need between 2 and 4 sprays after the pin spray. Also, as corn earworm catches increase, you will need a tank mix of Asana plus Orthene at the pin spray to achieve control of corn borers and corn earworm. Continue to spray fresh market snap beans on a weekly basis with Lannate starting at the pin stage and continue until 5-7 days from harvest.

Sweet Corn.

Fresh market silking sweet corn should be sprayed on a 4-5 day schedule throughout the state. *

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


With powdery mildew pressure increasing I wanted to clarify some points in regard to the two Section 18 fungicides Quadris and Nova. First, the powdery mildew rate for Nova is 2.5 oz./acre, not 4 oz. I had suggested using both fungicides no more than twice in sequence. Ideally they should be used in alternating sprays. Spray Bravo/Terranil on 7- day interval until powdery mildew is seen then add Nova to the Bravo followed by Quadris alone, then Bravo + Nova, etc. Nova and Quadris should be applied on a 7-10 interval depending on the weather. The Quadris rate should not be reduced any lower than 11.0 oz per application and does not need to be tank mixed with Bravo/Terranil. The full rate is needed to reduce the development of resistance.

Pumpkins are beginning to run or develop fruit and will need to be checked for powdery mildew. When one lesion per 45 old leaves is found add Nova to the Bravo/Terranil or mancozeb spray, then alternate with Quadris as for cantaloupes.


Late Blight Update

DSV accumulations as of July 13, 1998 are as follows:

Location/Emergence Date

DSV's July 9

DSV's July 13


Baldwin - 4/20



7-day, mid rate

Jackewicz - 4/20



7-day, mid rate

Zimmerman - 4/23



7-day, mid rate

Baker - 5/1



7-day, mid rate

If you are growing early blight susceptible cultivars and you are not ready to dig them yet, the high rate of a protectant fungicide is suggested.

Digging has begun at many farms now. We will continue the late blight FAX reports until the end of July and make a decision then whether to continue depending on how many potatoes are left and the condition of the crop at that point.

Remember, if you see any potatoes with pink rot, please save me 4-5 infected tubers, refrigerate them, and let me know so I can get them. Phone: 302-831-4865, FAX 302-831-0605. Thanks.

The Late Blight Report is also posted electronically at the UD Extension IPM website: http://www.udel.edu/IPM   *


Vegetable Diseases - Kate Everts, Extension Plant Pathologist, University of Maryland and University of Delaware ; everts@udel.edu, Phil Shields, University of Maryland, ps136@umail.umd.edu

MELCAST for Fungicide Application on Watermelons.

Do not use MELCAST if there is a disease outbreak in your field, it is a preventative program. Below are the EFI values from weather stations located on the Eastern Shore July 8-15. Any questions please call Phil Shields at (410) 742-8788 or e-mail: ps136@umail.umd.edu

EFI Values



















Wootten Farms, Galestown,MD









Mark Collins, Laurel, DE









U of D, REC Georgetown, DE








Vincent Farms Laurel, DE









Watermelon Fields should be sprayed with a fungicide when 30 EFI values have been accumulated by the weather station nearest your fields. Add 2 points for every overhead irrigation. After a fungicide spray, reset your counter to 0 and start over. If a spray has NOT been applied in 14 days, apply a fungicide and reset the counter to zero. The first and last day above can be partial days so use the larger EFI value of this report and other reports for any specific day. *

Laurel Farmer's Auction Market Report

July 9- 15, 1998

Quantity Produce Price
50,802 Cantaloupes  



Super Star

0.85 - 0.95






20 Honeydews 1.65
5986 Sugar Babies 0.75-2.10
5085 Watermelons  

Crimson Sweet


12 up


15 up


20 up






Royal Majesty


20 up



40 Peppers 6.50-9.50
502 Tomatoes  




1401 Sweet Corn Doz. 1.00-2.05
52 String Beans 8.00-14.00
88 Cucumbers 2.50-8.50
263 Squash  




4 Potatoes  




2 Eggplant 7.00

Field Crops

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


Continue to scout fields for potato leafhopper adults and nymphs. If fields have already turned yellow, it is generally best to cut the field and spray when re-growth is one to two inches tall. Although rain can help to slow down leafhopper activity, it will not significantly reduce populations if threshold levels were present before the rains. Baythroid, Dimethoate or Warrior will provide effective control. *


Soybean Twilight Tour - Mark VanGessel, Extension Weed Specialist ; mjv@udel.edu

A tour of the soybean plots at the University of Delaware’s Research and Education Center in Georgetown will be held on July 22 beginning at 6:30 p.m. The Research and Education Center is located on Route 9 midway between Highways 13 and 113. Soybean varieties, weed control, and current research on production practices will be highlighted. Tour is open to everyone. Refreshments will be provided. One pesticide re-certification credit can be earned. Contact Mark VanGessel or Mabel Hough, 302/856-7303, if you have any questions. *


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

Commodity Markets Hammered by Favorable Growing Weather and July Supply & Demand Reports

Old crop carryover estimates (1997-98 marketing year) were raised for U.S. corn, although they were lowered slightly for soybeans and wheat in USDA's July crop reporting estimates. Simultaneously, the National Weather Service forecasted favorable growing conditions for the corn belt and surrounding areas through the 20th of July. The window of opportunity for a heat-related pollination problem appears to be closing. The favorable weather forecast has had more of an effect upon price direction this past week than any other factor currently influencing commodity prices. Commodity traders view the favorable growing conditions as a strong indicator that 1998 U.S. corn and soybean crop size, forecast to be quite large, is likely to get larger.

The balance sheet for new crop (1998-99 marketing year) carryover estimates did not fare so well. U.S. corn, soybean, and wheat carryout estimates for the new crop year were all increased from the June estimates. The increases in carryover estimates were 235 million bushels for corn (now forecast at 1.844 billion bushels), 10 million bushels for soybeans (at 435 million bushels), and 41 million bushels for wheat (at 868 million bushels). *


Replicated Strip Trials and Yield Monitors - Richard W. Taylor, Extension Agronomist ; rtaylor@udel.edu

The following information was extracted from a two-year study reported by Dr. Greg Roth, Lynn Hoffman, Dr. Elwood Hatley, and Mark Antle from The Pennsylvania State University.

Six strip trials were conducted over two years (1996 and 1997) using six hybrids and three replications. Strips were six rows wide of varying lengths (600 to 1,600 feet). A John Deere 4435 combine equipped with an Ag Leader yield monitor was used. The yield monitor and a weigh wagon were calibrated prior to harvesting using field scale loads weighed on a certified scale with moisture tested on a certified Motomco moisture meter.

LESSON NUMBER 1: The reliability of your strip yield trials increases with your experience in using yield monitor equipped combines and up-to-date equipment. In the first year of their study, Dr. Roth and colleagues reported finding errors in the 62 strips tested that ranged from -9.0 percent to +22.0 percent. The average error (the difference between the yield reported by the yield monitor and the actual weight of grain) was 5.8 percent with a standard deviation (67 percent of the observations if done an infinite number of times, an estimate of the reliability of the average error) of 6.9 percent. In 1997 when they used an updated version of an electronic chip in the yield monitor and when they had another year’s experience with the equipment, the yield prediction errors ranged from -7.9 percent to +5.8 percent. The average error was only +0.3 percent with a standard deviation of 2.6 percent.

LESSON NUMBER 2: Careful calibration for both weight and grain moisture are essential. Yield errors can be influenced by both errors in estimating the moisture content of the grain and by errors in estimating the weight of grain harvested. Careful calibration of both factors is essential to ensure accurate weights with low standard deviations.

LESSON NUMBER 3: Calibrate over the entire expected moisture range but, if you exceed this range, be extra wary of the data. In the Penn State study, moisture was a significant source of error especially when hybrids had grain moistures above 27 percent.

SUMMARY: What must I do to use a yield monitor for testing new hybrids on my farm? The reported study recommends that your strips be long and narrow and grain loads should be at least 4,000 pounds (that’s about 0.7 acre per strip at a yield level of 100 bu/A or over a third of an acre at 200 bu/A). Also, grain moisture should be less than 25 percent and the combine/yield monitor should be up-to-date and carefully and fully calibrated. Even with all this, individual strip yield errors of more than 5 percent (that’s 10 bu/A for tests yielding near 200 bu/A) may be present in some cases so use your data with care. *

Annual Grain Crop Field Day

Tuesday, July 21, 1998

9:15 a.m. – 1 p.m. (Lunch at Noon)

Location: Marl Pit Road (R.d. 429, approximately 2 mile east of the intersection with Del. Rt. 71/U.S. 301 (Armstrong’s Corner). Look for the University of Delaware signs on the left.

Come join your neighboring farmers, agribusiness respresentatives, and the Extension Staff as we view and discuss this year’s field trials to include: small grain variety trials, full-season and double-crop Roundup Ready and non-Roundup Ready soybean variety trials, Bt corn hybrid and date-of-planting trials, a corn phosphorus fertility study, and two Roundup Ready soybean weed management trials. In addition, we plan a brief in-field insect identification and management training session.

We expect t have the 1998 wheat and barley variety trial results for distribution and discussion. During lunch, the Extension Specialists will present disease, insect and weed situation updates including comments on Hessian fly in small grains.

Credit toward Delaware pesticide license recertification will be awarded.

A boxed lunch will be available for $5 by reservation only. Please call by Thursday, July 16, to insure that we have a lunch reserved for you.

The meeting is free and everyone interested in attending is welcome. To reserve a boxed lunch, for more information, or for special consideration in accessing this meeting, please contact the New Castle County Extension Office at 302-831-2506.*

Upcoming Events…

July 21, 1998

Annual Grain Crop Field Day

Time: 9:15 a.m. – 1 p.m. (Lunch at Noon)

Location: Marl Pit Road, New Castle County

For More Information: see previous article.

July 22, 1998

Soybean Twilight Tour

Time: 6:30 p.m.

Location: U of D Research & Education Center, Georgetown

For More Information: see article on page 3.

August 12, 1998

Farm & Home Field Day

Time: 8:30 a.m. - 1:00 p.m.

Location: U of D Research & Education Center, Georgetown

For More Information: Contact the REC at 302-856-7303.

August 26, 1998

Irrigation Field Day

Time: 9:00 a.m. - Noon.

Location: Thurman Adam's Farm

For More Information: Mabel Hough at 302-856-7303.

Weather Summary

Week of July 10 - July 16

Readings taken for the previous 24 hours at 8 a.m.
Air Temperature:
Highs Ranged from 90 F on July 15 to 81 F on July 11.
Lows Ranged from 69 F on July 15 to 55 F on July 12.
Soil Temperature:
75.6 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 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. 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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