Volume 7, Issue 7                                                                                         May 14, 1999


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

Crop Pest Hotline.

If you want information on the most recent blacklight trap catches of corn borer and corn earworm, you can call the Crop Pest Hotline at 1-800 345-7544 (in-state only), 302-831-8851 (out of state) or visit the University of Delaware IPM website at www.udel.edu/IPM


Melon aphids have increased in the greenhouse on transplants and are easily found on plants recently set in the field. Lady beetles and syrphid fly larvae can also be found in many fields. In some cases, these beneficials can control moderate populations of aphids, especially if you do not have a history of virus in your area. However, if you have experienced virus problems in the past or leaves have begun to curl, a treatment should be applied if 10 to 20 percent of the plants are infested with aphids. Lannate should provide control.


Adult Colorado potato beetle activity and egg laying remains light throughout the state. With the warmer weather this week, you may see egg hatch by next week. European corn moth activity is still less than 5 per night in most areas with the highest counts in the Greenwood area. We have seen the first egg masses being laid in the earliest planted potatoes. Therefore, begin scouting the earliest planted potatoes for egg masses or infested terminals. A treatment should be applied if you find an average of one egg mass per plant or 25% infested terminals. If you are unable to scout, then the first spray should be applied one week after finding 8 –10 moths per night in local blacklight traps.

Sweet Corn.

Flea beetle and cutworm activity has increased above threshold levels in scattered fields throughout the state. The treatment threshold for flea beetles is 5% infested plants and the cutworm threshold is 10% leaf feeding or 3% cut plants. A pyrethroid will provide cost effective control of both insects. v

Vegetable Diseases - Kate Everts, Extension Vegetable Pathologist, University of Delaware and University of Maryland; everts@udel.edu


Control of cucumber beetles is important in prevention of bacterial wilt in muskmelon, cucumber and squash. Protect seedlings and maintain control of the beetles until flowering.

Check flats of watermelon and muskmelon transplants as they go into the field for signs of gummy stem blight. If disease is present discard infected plants and apply a fungicide spray to non-symptomatic transplants before or just after transplanting.

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

Late Blight Update.

Severity value accumulations have exceeded the 18 DSV threshold for potatoes that emerged (green row, 50% emergence) before May 5. We experienced a favorable weather period statewide last Wed., Thurs., and Fri. For Potatoes reaching green-row after May 7, there are not enough severity values to recommend a spray at this time. No severity values have accumulated since last Friday, Present conditions are not favorable for late blight. There is no need for alarm, but now is a good time to apply the first fungicide spray to those early potatoes.

DSV accumulations as of May 10, 1999 are as follows:


Emergence Date


May 10


Baldwin – 4/19


7-day, low rate

Jackewicz – 4/30


7 day, low rate

Art Wicks – 4/26


7-day, low rate

Ken/Chris Wicks – 5/3


7 day, low rate


Just a reminder to growers that may be using mancozeb fungicides such as Dithane DF or Penncozeb DF that these products contain 75% active ingredient and 15 lbs./acre of these products per season is the limit.

If you are not comfortable with the DSV’s and the late blight predictions, begin sprays when the plants touch down the row. v


Field Crops


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


The first leafhopper adults have been detected in alfalfa. This insect will cause the greatest damage when plants are small and in spring planted fields. After the first cutting, begin sampling for leafhoppers on a weekly basis. On alfalfa, 3 inches or less in size, the treatment threshold is 20 leafhoppers per 100 sweeps. In 4 – 6 inch tall alfalfa, the threshold is 50 per 100 sweeps. Since many fields are drought stressed, a pyrethroid (Ambush, Baythroid, Pounce or Warrior) will provide the best control.

Field Corn.

As indicated by the most recent pheromone trap catches, black cutworm moth activity has increased this past week. We are starting to see an increase in leaf feeding but only an occasional cut plant. Based on trap catches and degree-day accumulations, we expect to see an increase in the percentage of cut plants by next week. Be sure to watch fields closely at emergence for cutworm activity. In one-two leaf stage corn, a rescue treatment will be needed if you find 10% leaf feeding or 3% cut plants. When plants reach the 3-4-leaf stage, the treatment threshold increases to 5% cut plants. A pyrethroid will provide cost effective control.

Small Grains.

Continue to check wheat for cereal leaf beetle feeding. In some cases, larvae can be found feeding on the lower part of the plant as well as on the top 3 leaves.

At this time, the treatment threshold is 0.5 larvae per stem. Once wheat reaches the late dough stage, no treatment will be needed for cereal leaf beetle. The first armyworms and sawflies have been detected in wheat in Sussex County. Most of the grass sawflies are still small and will be most easily detected with a sweep net. Once larvae are found, you need to examine 5 linear foot of row in 5 – 10 locations for larvae and head clipping. A treatment is recommended if you find 2 sawfly larvae per 5 foot of row innerspace. Be sure to include an edge sample in your sampling sites since larvae will often be detected in rank areas on field edges. Sawflies are also spotty in their distribution throughout a field so a representative sample is necessary. Populations generally peak by the end of May. If you find twice the number of clipped heads compared to sawfly larvae it is usually too late to treat. In comparison, armyworms are nocturnal feeders so they are generally found at the base of the plants during the day. Armyworm larvae now range in size from to inch long. Remember that armyworms will clip heads faster in barley so the treatment threshold is one per foot of row. In wheat, the threshold is 1 to 2 per foot of row. Parathion can still be used in wheat and barley but it must be applied by air and there are set back restrictions. Lannate and Warrior can be used in wheat; however, only Lannate can be used on barley. v


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


Continues to look very good where adequate water is present. Powdery mildew is causing less of a problem and as flowering of wheat approaches, the threat from mildew and other fungal diseases is lessened. Generally speaking, applications of fungicide after flowering are not cost effective. I am still waiting to hear if the wheat viruses diagnosed last week (wheat soilborne mosaic, wheat spindle streak mosaic) were confirmed by lab tests. Septoria and tan spot have not been seen yet.

Be on the lookout for take-all now that wheat is heading. Stunted plants with white heads in spots in the field are good indications of a potential take-all problem. Infected plants have a very limited root system and can be pulled out of the ground easily. The base of the stem, after you take away the sheath, will have a shiny black discoloration. You may need to look at several plants to find the back discoloration, and the roots will be rotten or non-existent. Rotation away from small grains for several years will help control this soilborne fungus disease.


I was in a field of Nomini barley this week that had a very random infection of barley kernel blight. This bacterial disease was very prevalent last season on Nomini and Wysor. The bacteria are common and live primarily as epiphytes (live on the surface of plant leaves) not disease causing microbes (pathogens). Wet weather early at heading is probably important for infection. In this field, the number of infected heads was very low and only a few kernels per head were infected. The base of the glume close to where it is attached to the head is discolored and a reddish brown band of infected tissue can be seen easily. Unless you were walking the field looking, you would not notice the discolored kernels. The bacteria are present on many grasses and can be seedborne as well. This disease can look like glume blotch and has probably been misdiagnosed in the past. There are no controls, but fields that have high infection levels should not be saved for seed. Unfortunately there is little. v


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

The Weather Market Arrives

Patience remains the key to advancing grain and oilseed sales this marketing year. Prices for soybeans and wheat are at very low levels, with corn not far behind (although December corn futures are now within a cent of where they were on December 14, 1998). The good news is that the demand for corn is extremely high at this time. Foreign buyers are said to be more concerned about prices turning higher than they are about commodity prices turning lower. Although commodity traders have not responded, the market is now finding value. Chances of the market moving higher from current levels are much greater than a sharp sleigh.

The most recent Weekly Crop Progress report placed corn plantings at 55%, just ahead of the five year average, and soybeans at 12% complete. Even though this report placed corn plantings ahead of the five year average, the fact remains that the corn belt is under going a wet spring. Approximately, one month remains from today's date to get the U.S. corn crop planted, before farmers begin switching to beans.

There were no major surprises and very little market reaction to USDA's May Supply & Demand Report. Market traders are, for the moment, taking the position that most negative news has been discounted into commodity prices. A worthy note to keep in mind is that December '99 wheat is 24
cents higher on the board than July '99 futures.

With commodity prices so low, particularly for soybeans and wheat, an alarming fact has come to any astute marketer's attention and that is "there are no marketing tools currently available to us that we can use to make sales for 1999 production". That is the reason that we need to remain patient. The weather's effect upon crop development this growing season will drive commodity prices for the next few months.

Incidentally, the Russian nuclear reactor scare remains unconfirmed and any changes in how LDP's might be made are stalled in USDA. Considering that the Russian economy is so weak, commodity traders did something they don't normally do. They 'ignored' the rumor. The old adage is 'buy the rumor - sell the fact'. v

Drought Stress is Affecting Wheat - Richard W. Taylor, Extension Agronomist ; rtaylor@udel.edu

I’ve seen many fields with a wide range of symptoms. We have had dry spring weather over most of the region. Because of this, drought stress may be combining with the usual range of virus diseases (wheat spindle streak, barley yellow dwarf, and soil-borne wheat mosaic) and fungal diseases (in particular, powdery mildew) to create a complex of differing symptoms. Lower leaf scorching or firing has been characteristic of this complex in most fields.

What can you do about it? For most growers, there is little that can be done other than to pray for rain. However, for growers with the capacity to irrigate and who are raising either seed wheat or ICM wheat, irrigation may help preserve yield potential. Research is underway to provide preliminary guidelines on how to irrigate wheat. At this point, my best advice (or guess, to be honest) is that you should provide water on an as needed basis up to head emergence or first flowering. During flowering, you should try not to irrigate since this could encourage the development of scab on the wheat. If irrigation becomes necessary during flowering, limit the time you apply water to early in the day so the wheat can dry before evening. After flowering, apply up to about 1.5 inches of water per week but try to limit the number of weeks that irrigation is applied. In the study last year, there was a trend for lower yields when irrigation continued for three or four weeks after flowering. v


Soil-applied Herbicides With No RainMark VanGessel, Extension Weed Specialist; mjv@udel.edu

Soil-applied herbicides need to be incorporated into the soil in order to be effective. Incorporation can be done mechanically with a field cultivator or finishing tool. Or they are incorporated with rainfall or irrigation. The amount of water needed to move the herbicide into the soil depends on the herbicide. Dual, Lasso, Harness, Topnotch, and Frontier (these are the residual herbicides in Bicep, Bullet, Harness Xtra, Fultime, and Guardsman, respectively) need less water than atrazine. Princep or simazine needs the most amount of water (it’s based on the water solubility of the herbicide). But with the lack of rain in most areas over the last 2 to 3 weeks, many of the fields treated with soil-applied herbicides have not received enough rain to "activate" them. This is of particular concern for Dual, Lasso, Harness, Topnotch, and Frontier which control grassy weeds, because these herbicides are absorbed by the shoot of the weed as it emerges from the ground. Root uptake is not very effective for providing control. So rainfall is needed to activate these herbicides before the grassy weeds emerge. This generally occurs 1 to 2 weeks after the field is tilled or "burn-downed" depending on soil temperature and moisture.

What can you do? Rotary hoeing can be provide good control of small emerging grasses. But this is generally not an option in no-till. Bladex 90DF applied before the fifth leaf of the corn plant is visible, with a non-ionic surfactant. Expect some marginal leaf burn with this treatment. Basis Gold or Accent are also labeled for emerged grasses. Both these products are not particularly effective on crabgrass. They must be applied before crabgrass is over one inch tall. Do not use Basis Gold if Counter 15G or Counter 20 CR was used regardless of application method due to potential injury. Also, do not use Accent if Counter 15G was used regardless of application method; or Counter 20 CR if it was applied in the furrow; T-banded applications of Counter 20 CR with soils organic matter less than 4% (specified on Accent label). Early applications of either Basis Gold or Accent will allow for lower use rates.

Atrazine is absorbed by roots, so it can kill small weeds that emerge before rainfall. Atrazine will provide control of broadleaf weeds not grassy weeds.


2,4-D Rates for No-till Soybeans - Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

The ester formulation of 2,4-D should have an interval between application and planting. The interval for one-half pint rate is 7 days and for the full pint the interval is 30 days. Spraying no-till ground at this time, should use the half-pint rate.


Pesticide BriefsSusan Whitney, Extension Pesticide Educator; swhitney@udel.edu

Pesticide Container Recycling

Free of Charge
Sussex Conservation District Maintenance Yard
Shortly Road, Georgetown
9:30 am - 1:30 pm
May 27, June 24, July 22, August 19, September 16,
October 28

Sponsored by DDA in cooperation with Sussex Conservation District and USAg Recycling, Inc.
Only properly rinsed plastic pesticide containers accepted. For more information, contact: Grier Stayton or Bill Millikin, DDA 739-4811; www.usagrecycling.com

Comments needed on azinphos methyl.
If you use azinphos methyl, get ready to make comments on its risk assessment. On May 19, EPA will sponsor a technical briefing for this insecticide. The briefing will provide an opportunity for the public to learn about the data, information, and methods that the Agency used to develop and revise the risk assessment. This will be the first such meeting to present to the public a revised risk assessment for an organophosphate pesticide. Representatives from USDA will provide ideas on possible risk management. Following the briefing, EPA will release the revised risk assessment for public availability. The public will be encouraged to submit risk management ideas and proposals. Comments will be taken until July 19. Contact Susan Whitney (swhitney@udel.edu; 302-831-8886; fax: 302-831-3651) if you would like a copy of the risk assessment. Additional information can be found at:


Upcoming Meetings…


Twilight Crop Management Session

When: Tuesday, May 18, 1999

5:30 PM – till(?)

Where: University of Delaware Research and Demonstration Area; -mile east of Armstrong Corner, on Marl Pit Rd. (Rd. 429).

What: Come join your fellow farmers and Extension staff for an interactive and hands-on experience as we:

Wheat and Barley


Nutrient Management

Discuss and demonstrate the use of the Pre-sidedress Nitrogen Test (PSNT).


Discuss timely questions/issues.

We’ll wrap the session up with a dessert treat and more chance to continue discussion.

Important: DDA will award (2) private applicator re-certification credits in the Agricultural Plant category. Certified Crop Advisor credit(s) will also be applied for.

For more information or special consideration in accessing this meeting, please contact our office in advance at (302) 831-COOP (2667).




Small Grain Twilight Tour

University of Maryland, Wye Research and Education Center, Cheston Lane, Queenstown, MD

Thursday, May 20, 1999

6:30 p.m. until 8:00 p.m.

Dr. Jose Costa, Assistant Professor, Small Grains Breeding: Will review the state trial of 62 varieties and four new hybrids of wheat as well as 34 varieties and experimental lines of barley.

Dr. Galen Dively, Associate Professor, Integrated Pest Management: Current small grain insect problems and hessian fly update using resistant wheat varieties.

Dr. Arvydas Grybauskas, Associate Professor, Diseases of Field Crops: Examination of various fungicide treatments pertaining to prevalent Maryland small grain diseases, e.g. powdery mildew and septoria; seeding rates in no-till wheat production; and review of fungicide treatments under no-till wheat management.

Mr. Ted Haas, Regional Agronomy Specialist: Review of small grain inputs and their potential Return on Investment (R.O.I.)

For More Information and directions to the meeting, call: 410-827-8056.


Weather Summary

Week of May 6 to May 12

0.02 inches: May 6, 1999
Readings taken for the previous 24 hours at 8 a.m.
Air Temperature:
Highs Ranged from 83F on May 8 to 63 F on May 6.
Lows Ranged from 58F on May 8 to 48F on May 11.
Soil Temperature:
73F 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.


Black Cutworm – Pheromone Trap Catches – 1999 Season

Data Provided by Terra Inc., Bridgeville, DE

Trapping Period : May 2 – May 9 , 1999

NOTE: Moth catches ranging from 7 to 15 moths per 7 day period have been associated with a moderate to high potential for cutworm outbreaks. Once moth catches in an area reach this level, the first larvae are generally seen within 300 degree days (using a temperature base of 50 degrees F). Since April 4, 175 degrees days have accumulated at the Research and Education Center located in Georgetown , DE .



Location # Moths/7Days
American Corner, MD


Lewistown, MD


Argos Corner, DE


Magnolia, DE


Atlanta, DE


Mardela Springs, MD


Bayard, DE


Marydel, MD


Berlin, MD


Milford, DE #1


Bethel, DE


Millsboro, DE


Bridgetown, MD


Milton, DE


Bucktown, MD


Newark, MD #1


Burrisville. MD


Newark, MD #2


Cambridge, MD


New Church, VA


Clarksville, MD


Oak Orchard, DE


Dagsboro, DE #1


Pocomoke, MD #1


Dagsboro, DE #2


Pocomoke, MD #2


Delmar, DE


Preston, MD


Denton, MD


Public Landing, MD


Easton, MD


Redden, DE


Eldorado, MD


Reids Grove, MD


Ellendale, DE


Reliance, MD


Farmington, DE


Rhodesdale, MD


Federalsburg, MD


Ridgely, MD


Georgetown, DE


Seaford, DE #1


Goldsboro, MD


Seaford, DE #2


Greenwood, DE


Selbyville, DE #1


Hurlock, MD #1


Selbyville, DE #2


Hurlock, MD #2


Snow Hill, MD #1


Laurel, DE # 1


Snow Hill, MD #2


Laurel, DE # 2


Snow Hill, MD #3


Laurel, DE # 3


Trappe, MD


Leipsic, DE


Vernon, DE


Lewes, DE


Wyoming, DE


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