Volume 11, Issue 14                                                                                                    June 27, 2003




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



Continue to scout all fields for cucumber beetles and aphids. Fresh market cucumbers are susceptible to bacterial wilt, so treatments should be applied before beetles feed extensively on cotyledons and first true leaves. Pickling cucumbers have more tolerance to wilt, but a treatment may be needed if you find 2 or more beetles per plant and significant damage can be found on the cotyledons. A treatment should be applied for aphids if 10 to 20 percent of the plants are infested with aphids. Actara, Fulfill, Thiodan or Lannate will provide aphid control. Be sure to watch for bees foraging in the area and avoid insecticide applications on blooming crops. 



Continue to scout all melons for aphids, cucumber beetles, and spider mites. We are staring to find economic levels of spider mites so sample all fields carefully for spider mites. The recent hot weather has resulted in an explosion in both immature and adult mite populations. A treatment will be needed if you find 20-30% of the plants infested with 1-2 mites per leaf. If populations of mites have exploded and adult mites are the predominant life stage, Capture or Danitol should be used. If the population is a mixture of eggs, immature mites and lower levels of adult mites, Agri-Mek should be used at 8 oz/acre. A second miticide application may be needed in 3-7 days depending on the population level at treatment time. In the past, dimethoate has provided poor mite control; however, last season there were reports of good control. In recent years, Kelthane has provided fair to good mite control when used in the rotation to help avoid the development of resistance. If populations are heavy or numerous eggs are present at the time of treatment, at least 2-4 miticide applications will be needed.



In areas where corn borer trap catches are above 2 per night and pepper fruit is ˝ inch in size or larger, fields should be sprayed on a 7-10 day schedule for corn borer control. As soon as fruit are present, you will also need to treat for pepper maggot. If you are using acephate (Orthene or Address),  it will provide pepper maggot control. Otherwise, dimethoate is the best option for pepper maggot control.



Continue to sample fields for Colorado potato beetle adults and larvae. Remember Actara or Provado should not be used in fields where Admire, Platinum or Tops MZ-Gaucho were used at planting to avoid the development of resistance. You will need to use Spintor, cryolite, or Avaunt plus PBO. Continue to scout for potato leafhoppers. Adults and nymphs can both be found. Controls should be applied if you find ˝ to one adult per sweep and/or one nymph per every 10 leaves. Dimethoate, a pyrethroid, Actara or Provado will provide control.


Snap Beans.

Continue to scout for leafhopper and thrips activity. We have seen a significant increase in potato leafhopper and thrips populations. The thrips threshold is 5-6 per leaflet and the leafhopper threshold is 5 per sweep. If both insects are present, the threshold for each should be reduced by 1/3. Dimethoate, Lannate, Asana, Capture, or Warrior will provide control of both insect pests. If plants are approaching the bud stage, Orthene will control thrips, leafhoppers and corn borers. Once corn borer catches reach 2 per night, fresh market and processing snap beans in the bud to pin stages should be sprayed for corn borer. Orthene or Address (acephate) should be used at the bud and pin stages on processing beans. After the pin stage, a third application will be needed 7 days from harvest if trap catches are above 2 per night. Once pins are present on fresh market snap beans and trap catches are above 2 per night, a 7-10 day schedule should be maintained for corn borer control.  Lannate, Asana, Capture, Warrior or Mustang are labeled. Acephate has a 14-day wait until harvest.


Sweet Corn.

If corn borer populations were well above threshold at the mid-whorl stage, multiple whorl sprays and an early silk spray are often needed to provide corn borer control.  The first silk sprays will be needed as soon as ear shanks are visible. Silk sprays are needed on a 3-4-day schedule in Kent and Sussex Counties. Be sure to check our website (http://www.udel.edu/IPM/traps/latestblt.html) for the most recent moth catches in your area.




Field Crops


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



Continue to scout all fields for potato leafhopper. Remember that once yellowing occurs damage has already been done. The treatment threshold is 20 per 100 sweeps in alfalfa 3 inches tall or less, 50 per 100 sweeps in 4-6 inch tall alfalfa, and 100 per 100 sweeps in 7-11 inch tall alfalfa and 150 per 100 sweeps if alfalfa is greater than 11 inches tall. Early cutting can be used as a control strategy if you plan to cut in 5-7 days.  A pyrethroid, Furadan or Lorsban will provide control.


Field Corn.

Be sure to sample fields for grasshoppers. A grasshopper treatment should be considered if you find 5-8 grasshoppers per square yard. Asana, Dimethoate, Lorsban, Furadan and Warrior will provide control, but multiple applications may be needed.  Even though armyworm populations were low in small grains, be sure to check field edges for armyworms moving out of grains. A control will be needed if worms are less than one-inch long and 25% of the plants are infested.


We are also finding corn borer larvae in the earliest planted non-Bt field corn. Infestation levels range from 25-30%-infested plants. No controls are needed in dry-land corn until 75% of the plants are infested. The threshold in irrigated corn is 50% infested plants. A pyrethroid, Lorsban or Penncap-M will provide the best control.


Soybeans - Continue to watch all emerged fields for bean leaf beetles and grasshoppers. A treatment for bean leaf beetle will be needed from plant emergence to the second trifoliate when you find 2 beetles per ft. row and a 25% stand reduction. A pyrethroid, dimethoate or Lorsban will provide control. The treatment threshold for grasshoppers is 1 per sweep and 30% defoliation. Asana, Furadan, Lorsban, or Warrior will provide grasshopper control.

We are starting to see an increase in thrips activity. No controls should be needed until plants are stressed and you find 8 thrips per leaflet. Continue to sample for spider mites in soybeans. With the recent hot weather, you can expect to see mites in the earliest planted fields. Look for the white stippling at the base of the leaves, which indicates the presence of mites. Treatment will be needed when you find 20-30 mites per leaflet or 10% of plants with 1/3 or more leaf area damaged. Dimethoate, Lorsban and Parathion (aerial application only) are still the only available options, so early detection and control will be critical.



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


Tight Old Crop Bean Supplies Keeping Market in Check?

New crop soybean prices have shown an amazing resiliency lately due primarily to tight old crop supplies. That resiliency may be about to fold as the U.S. crop is reported to be developing into one of the best we've seen in quite some time, and may well register at record levels before this year's harvest is completed. Illinois, Iowa, and Nebraska are reporting the best crop conditions for this time of year in nine years. That factor alone would have very likely taken another 10 to 20 cents per bushel out of new crop soybean prices this week if it had not been for the old crop supply situation. However, it is important to keep in mind that the old crop supply situation is not the same as for the new crop. Another development that supported the soybean price this week was China's cancellation of soybean purchases from the Southern Hemisphere that were replaced by the purchase of U.S. beans. This was an unusual development that Chicago traders rewarded in both old and new crop soybean bids. That blip in the market is now considered already factored in. Trader attention is now turning back to expectations for the next crop report. Some private analysts have predicted larger domestic corn and soybean plantings than those indicated in USDA's June report.


The Answer to Last Week's Key Question

Last week's issue raised a question regarding tight world corn supplies and a pending record U.S. corn crop, the question being which factor would drive U.S. Corn prices into the '03 harvest. The answer, believed to be correct, is the pending size of the U.S. corn crop. Why? One reason, that's the way it generally happens. In recent memory, U.S. crop development and the size of the U.S. corn crop generally drives new crop corn prices. Another reason, the U.S. historically held about 25% of world corn stocks. Today the U.S. holds 42% of world corn stocks. One can deduct that since the U.S. holds a larger share of world corn stocks that the pending size of this year's domestic corn crop will be the driving force behind '03 corn prices.


Marketing Strategy

As we observe the corn, soybean, and wheat pits getting whip sawed this week, it is likely to be pre-mature to suggest a definitive price direction. New crop wheat prices are under harvest pressure and have declined considerably over the past two weeks. Now is not the time to make sizeable wheat sales, if any.


The corn market is likely to be driven by the funds over the next few weeks, although much depends upon weather developments and growing conditions. New crop corn prices are likely to need to bid higher before farmer interest picks up in advancing new crop sales. That somewhat depends upon the level of coverage previously taken and whether any opportunities arise before the release of the next crop report. An opportunity defined here would be a 10 cent or better rally in Dec '03 corn futures. 


The soybean market will also continue to catch the attention of fund traders over the next six weeks. Strong demand may help to boost the soybean market here and there, however, eventually pending U.S. '03 production will take the driver's seat. Those that are well covered (30 to 40% of new crop sales covered) can place advancing sales on hold. Those that have not done anything should seek technical assistance. A large U.S. crop and increasing Southern Hemisphere production points toward new crop soybean prices moving much lower than current levels. What we need now is another weather rally in the market as the Eastern Shore soybean crop begins to go into the ground.




Burndown Control for No-Till Soybeans - Mark VanGessel, Extension Weed Specialist, mjv@udel.edu


Due to the weather, many no-till soybean fields have not been sprayed, and it will be difficult to achieve good control.  Some fields may need to consider tillage, particularly those with excessive weed growth, where spray coverage will be reduced.  Herbicides are wonderful tools, but they have limitations.


Those situations where you want to try to control the weeds with herbicides, including Canopy or Canopy XL with paraquat or glyphosate will help with large horseweed plants.  You may want to consider including Dual or another chloroacetamide herbicide and try a soil-applied herbicide program.  Then use a postemergence application of glyphosate (or another herbicide) in those fields where needed.  Normally I would not suggest the use of Canopy or Canopy XL for control of large horseweed due to resistance management, but this is such an unusual year, our options are very limited.



Do Not Assume a Second Application of Glyphosate Is Always the Answer - Mark VanGessel, Extension Weed Specialist, mjv@udel.edu


In many Roundup Ready soybean fields, if the level of weed control is less than acceptable, the automatic response is a second application of glyphosate.  A second glyphosate application will certainly help with many species that glyphosate provides only marginal to fair control (morningglory, smartweed, velvetleaf, etc).  However, where control was poor for only one species (all other species were controlled) and there is not an apparent reason, you may want to consider an alternative herbicide rather than using more glyphosate.  University of Delaware Weed Science as well as reports from Ohio State University, indicate populations of lambsquarters that are more difficult to control with glyphosate than other lambsquarters populations.  Situations where only one species experience less than expected control should cause you to think about alternatives to additional glyphosate applications.




Harvest Aid for Small Grain - Mark VanGessel, Extension Weed Specialist, mjv@udel.edu


Roundup WeatherMax (up to 0.7 qt/A) or Touchdown (up to 1 qt/A) are labeled as harvest aids in winter wheat and barley.  Applications must be made after the hard-dough stage and at least 7 days prior to harvest.




Balancing Weed Control and Crop Safety - Mark VanGessel, Extension Weed Specialist, mjv@udel.edu


Now that some of the corn fields are starting to dry out and sprayers can get back into the fields, it will be important to assess the need for postemergence sprays.  I am republishing the height restrictions for postemergence herbicides.  These height restrictions are due to potential crop injury.  Many fields have corn at a range of growth stages.  You will need to decide the appropriate measure on a field by field basis.


Broadcast applications refer to an over the top application and directed refers to use of special spray equipment to direct the spray and avoiding the spray coming in contact with the whorl of the corn.   When corn height and collar number are given, base decision on whichever feature is first attained.






Maximum corn size


broadcast:  6 collars or 20 in.

directed: 10 collars or 36 in.


broadcast: up to 8 collars

directed: when necessary


12 inches tall



more than ˝ pt/A:

     broadcast: 5 lvs or 8 in.

     directed: 36 inches tall

˝ pt/A or less:  36 inches tall


No restrictions listed


broadcast: min- 4 inches tall

     max- 20 in. tall or 6 collar

directed: pre-tassel




30 inches tall or 8 collars

2,4-D Amine

broadcast: 8 inches tall

directed: pre-tassel

2,4-D Ester

broadcast: 8 inches tall

directed: pre-tassel


directed only: 12 inches tall do not apply 3 weeks before tasseling

Harmony GT

1 - 4 collars or 12 inches tall


broadcast: 24 inches tall or 7 collars

directed: 20 to 36 inches tall


broadcast: 16” tall or V5

directed: 16-36” tall


broadcast: 48 inches tall

directed: when necessary


Poast Plus

broadcast: emergence to start of pollen shed

directed: when necessary (depending on corn canopy and weed ht.)


broadcast: 2- to 10-lf collars

directed: when necessary; when corn leaves interfere w/ spray

Roundup products

up to 30 inches or 8 collars


24 inches tall


up to 8 collars


until 68 days pre-harvest






2 collars or 6 inches tall

Basis Gold

5 collars or 12 inches tall

Celebrity Plus

broadcast: 4 to 24 inches tall


6 oz rate:  4 to 10 inches  tall

4 oz rate:  up to 24 in.  tall

directed:  4 oz up to 36 inches tall


broadcast: min- 4 in. tall

     max- 20 in. tall or 6 collar

directed: 20 to 30 inches tall

Field Master

do not apply to emerged corn

Hornet WDG

broadcast: 20 inches tall or 6 collars

directed: 20 to 36 inches tall


12 inches tall

Liberty ATZ

12 inches tall


broadcast: 12 inches tall

directed: 20 inches tall


broadcast:  5-lf stage or 8 inches tall


broadcast: min- 4 inches tall

     max- 20 in. tall or 6 collar

directed: 20 to 30 inches tall

Ready Master ATZ

emergence until 12 inches tall


broadcast: 8 inches tall

directed: 12 inches tall

        or if rate >2 pts


broadcast: 20 inches tall or 6 collars (min. 4 in. tall)

directed: 20 to 24 inches tall (before tassel emerg.) 


less than 20 inches or 6 collars


spike through 36 inches tall






Farm and Home Field Day Set for August 13


Take a day to enjoy summertime in the country at the University of Delaware’s Farm and Home Field Day, Wednesday, August 13.  Held from 8:30 a.m. until 1:30 p.m. on the grounds of the Research and Education Center, on 16483 County Seat Highway (U.S. Rt. 9) west of Georgetown, this annual event offers many fun-filled, educational activities, tours, interactive exhibits and demonstrations for homeowners and farmers alike.


Field tours by wagon will highlight agronomic and vegetable crops.  Farmers can consult with Extension specialists about the latest research and pest control strategies.


Visitors to Field Day can drop by the Master Gardener demonstration garden to view the wide array of plantings.  What began several years ago as a yearly one-day display for Farm and Home Field Day has blossomed into a large permanent exhibit for plants, including herbs, shade-loving plants, annual flowers, perennial ground covers, decorative grasses, a  problem garden, a bog garden, a children’s garden, and a container garden.


Children, parents, and caregivers will learn about keeping their young children safe during the summer months.  This year’s emphasis identifies risks associated with popular summer activities and the unfortunate escalating number of recreational and sport-related injuries.  This portion of the program will include many interactive exhibits and demonstrations plus costumed characters, children’s aerobics, face painting, finger printing, a petting zoo, and car seat check.  Local 4-H clubs will set up a petting zoo and food booths.  Consumer, environmental and commodity groups will staff informational booths in the Grove.  Carriage and pony rides will round out the morning’s activities.


Farm and Home Field Day is free and open to the public, and plenty of free parking is available.  Tickets for a traditional barbecued chicken luncheon at 12 noon can be purchased at the registration table for $6.00.


For more information, call Mark Isaacs at 302-856-1997 or Jay Windsor at 302-856-7303.






                 Weather Summary



Weeks of June 19 to June 26, 2003


0.29 inches: June 20

0.03 inches: June 21

0.03 inches: June 22

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

Air Temperature:

Highs Ranged from 93°F on June 25 to 73°F on June 22

Lows Ranged from 65°F on June 24 to 59°F on June 21

Soil Temperature:

73°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, 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.

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