Volume 11, Issue 25                                                                                                   September 12, 2003



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



We can still find economic levels of DBM and cabbage looper in fall cabbage fields. The treatment threshold is 5% of the plants infested. If both species are present, Avaunt (3.5 oz/acre), a Bt, Proclaim (3 oz/acre),or  Spintor (4-5 oz per acre) will provide control. If cabbage looper is the predominant species, a pyrethroid, Intrepid  (8 oz/a) or Confirm (8 oz/acre) will also provide control.


Lima Beans.

Continue to scout fields for corn earworm. In some cases, 2 applications may be needed for earworm control. A treatment is recommended for corn earworm if you find one worm per 6 foot of row.



Continue to spray peppers on a 5-7 day schedule for beet armyworm, corn borer, corn earworm, and fall armyworm. Aphid populations have also increased, especially in fields were a continuous pyrethroid program was used. Lannate, Assail, Actara, Fulfill or Provado will provide aphid control.


Snap Beans.

Sprays are still needed at the bud and pin stages on processing snap beans for corn borer control. A corn earworm material will also be needed at the pin spray for corn earworm.  After the pin spray, sprays will be needed on a 5-6 day schedule until harvest. Since this can change quickly, be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in processing snap beans  (http://www.udel.edu/IPM/traps/latestblt.html and our link to http://www.udel.edu/IPM/thresh/snapbeanecbthresh.html).  As soon as pin pods are present, fresh market beans should be sprayed on a 5 to 7-day schedule.



The first webworms have been found in recently emerged spinach. Be sure to watch for both webworms and beet armyworms and apply controls when worms are small and before they have moved deep into the hearts of the plants. Also, remember that both insects can produce webbing on the plants. Confirm, Intrepid or Spintor will be needed for beet armyworm control. If webworms are the predominant species,  Ambush, Pounce, Confirm (6-8 oz/acre), Intrepid (8-10 oz) or Spintor (4-8 oz/acre) should be used. Generally, at least 2 applications are needed to achieve control of webworms and beet armyworm.


Sweet Corn.

Fresh market silking sweet corn should be sprayed on a 2-3 day schedule throughout the state. Be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in fresh market sweet corn (http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/silkspraythresh.html ) .



UD IPM Black Light and Pheromone Trap Counts

Average Number of Moths per Night: September 5 to September 9, 2003

Trap Location

European Corn Borer

Black Light

Corn Earworm

Black Light

Corn Earworm

Pheromone Trap

Kent County












Killens Pond




Little Creek








Rising Sun








Sussex County





























* Numbers can change quickly. For the most recent trap counts, access the website at (http://www.udel.edu/IPM/traps/latestblt.html) or call 1-800-345-7544 (in-state); 1-302-831-8851 (out-of-state). Counts are updated on Tuesday and Friday.




Vegetable Crop Diseases Bob Mulrooney Extension Plant Pathologist; bobmul@udel.edu


Lima Beans.

Lima bean pod rot, caused by Phytophthora capsici, was diagnosed this week affecting a large area. The fungus had infected pods high in the canopy, which was also observed in 2001. It will infect pods on the ground, initially, then spreads in the canopy after last weeks favorable weather.


Sweet Corn.

Late sweet corn is being infected with several problems as mentioned last week. Common rust, Southern corn leaf blight continue to be the most common diseases identified. One field was diagnosed with root rot causing some stunting and yield reductions. Fusarium and Phoma were two fungi identified with that root rot.




Field Crops


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



Corn earworm populations continue to be low in fields throughout the state. The cooler weather has resulted in a decrease in corn earworm moth catches; however, double-crop beans are still attractive to egg laying moths. Fields with flat pods or seeds just beginning to enlarge are at the most risk. Ames Herbert from VA indicated last week in his newsletter that "these fields should be scouted until moths stop flying, or pods become mature. Most of the full season crop is at or near the point where fields are no longer attractive to moths.  Basically, once seeds are full sized and pods toughen up, they are no longer at risk. "  A combination of rainy weather, cool evenings and warm days, can result in populations crashing from disease organisms, so be sure to watch for diseased worms before making a treatment decision. In addition, as we move into September corn earworm will begin to enter their diapausing (overwintering) stage so do not treat too quickly. The treatment threshold for podworms is 3 per 25 sweeps in narrow fields and 5 per 25 sweeps in wide row fields (20-inches are greater). The following materials will provide corn earworm control in soybeans: Ambush, Baythroid, Asana, Mustang MAX, Pounce, Warrior (all pyrethroids) Steward, or Larvin.


Small Grains.

Although we have not seen widespread Hessian fly problems for a few years, a number of research plots in the region as well as some fields in Virginia did experience significant lodging this past spring. In most cases, this was the result of spring infestations. Plants attacked in the spring have shortened and weakened stems that may eventually break just above the first or second node, causing plants to lodge near harvest. Since the fly survives as puparia ("flax seeds") in wheat stubble through the summer, you should still consider this pest as you make plans to plant small grains.  In some cases, infested fields were planted after the fly free date. This traditional method of control is based on delaying planting until after flies have emerged.  Warm fall weather conditions can extend fly emergence and egg laying beyond the fly-free dates, but these dates should still be used as a guideline for planting. Since we rarely see plants stunted in the fall, we still feel that most of the damage we see is occurring from spring infestations. Plants attacked in the fall at the one-leaf stage may be killed outright. Wheat attacked later in the fall will be severely stunted, with the first tillers killed and plant growth delayed. Plants infested in the fall can easily be recognized by their darker than normal bluish coloration and leaves with unusually broad blades. A combination of strategies should be used to reduce problems from Hessian fly:

(1)   Be sure to completely plow under infested wheat stubble to prevent flies from emerging;

(2)    Avoid planting wheat into last season's wheat stubble, especially if it was infested with Hessian fly;

(3)    Avoid planting wheat next to last season's wheat fields - the most serious infestations can occur when wheat is early planted into wheat stubble or into fields next to wheat stubble;

(4)   Eliminate volunteer wheat before planting to prevent early egg laying;

(5)   Do not use wheat as a fall cover crop near fields with infestations;

(6)   When possible, plant after the fly free date (Oct 3 – New Castle County; Oct 8 – Kent County; Oct 10 – Sussex County) ;   and 

(7)   Plant resistant varieties – You should look for varieties that have resistance to Biotype L.  Although some of these varieties may not be appropriate for Delaware, the following is a list of varieties from North Carolina that have exhibited good resistance to Biotype-L : P 26R12, P 26R38, P 26R61, Roane, USG 3350, and USG 3430. 


As far as chemical control, most of the recent data with seed treatments and foliar insecticides has come from North Carolina where populations have been heavier and fall infestations more widespread in recent years. These chemical strategies are designed to control infestations at planting and will not last to control spring infestations. Earlier work in Maryland did not show an economic benefit from using seed treatments for Hessian fly management since most of our infestations occur in the spring.




Field Crop Diseases Bob Mulrooney Extension Plant Pathologist; bobmul@udel.edu


Field Corn.

Gray leafspot, anthracnose and common rust are increasing since last week on late planted corn. If corn is dented, there is no economical benefit from applying any fungicides at this time. Be sure to check fields for stalk rots by pinching stalks close to the ground. If stalks crush easily between your thumb and forefinger, schedule that field for early harvest to prevent losing it to a wind storm.




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


September Soybean Production Estimate Shocks Grain Trade.

USDA now estimates U.S. soybean production at 2.643 billion bushels, 219 million bushels less than the August production forecast. The soybean production forecast was 114 million bushels less than the average pre-report trade guestimate of 2.757 billion bushels. Ending stocks for U.S. soybeans are now placed at 135 million bushels, 85 million bushels less than the month ago estimate. The soybean market is currently trading anywhere from 16 to 20 cents per bushel higher as the lower production and ending stock numbers are being bid into prices.


World ending stocks for soybeans are now forecast at 34.77 million metric tons, 4.21 MMT less than the August estimate and slightly less than last year. The reduction is believed to stem largely from the reduction in the U.S. production estimate.


U.S. Corn.

U.S. corn production, estimated at 9.944 billion bushels, was above the pre-report average trade forecast of 9.8 billion bushels and 120 million bushels less than USDA's August estimate. Ending stocks for U.S. corn now placed at 1.064 billion bushels, above the average pre-report estimate of 990 million bushels, are also 120 million bushels less than the August forecast. Although the corn production estimate was initially viewed as disappointing by commodity speculators, it is likely to see some spillover effect from the soybean trading pit.


World corn ending stocks forecast at 74.30 MMT, are well below the August estimate of 78.76 MMT and last year's carry in of 98.10 MMT. World coarse grain ending stocks, now forecast at 106.41 MMT, is well below the August

estimate of 111.74 MMT and last year's carry in of 142.06 MMT.    


Market Strategy.

Short crops have long tails, meaning that prices typically peak just prior to, during, or shortly after harvest. Just when prices peak depends upon what happens to the production forecast from the September estimate to the actual harvest. If the production forecast declines further then commodity prices will peak later. It wouldn't be surprising to see commodity traders taking into account the reduction in this week's crop condition report for both corn and soybeans, if not by the end of this week then sometime next week. The reason being that the realization will set in that this week's decline was not reflected in the September crop report.  The current jump in soybean prices should be used to bring new crop soybean sales to the 50% level of expected production.



Frost Damage in Soybeans - Richard W. Taylor, Extension Agronomist, rtaylor@udel.edu


The extended and late planting window for both full-season and double-crop beans could mean that some acreage is at risk for damage by an early frost.  Generally, this can occur if beans are still green and the moisture is greater than 18 to 20 percent.


The actual impact of frost depends on the air temperature, the duration of the temperature and soybean growth stage.  The critical temperatures are similar to those for corn (see article on Frost Damage in Corn in this issue).  From observations in the past, growth state is really an important component for soybeans.  Beans that are close to maturity seem to be more sensitive to even a light frost that will often cause the plants to drop all their leaves.  Less mature beans (those still not showing leaf yellowing ahead of maturity) seem to tolerate lower temperatures without visual leaf damage.  It may be that damage still occurs on a physiological basis especially for sugar transport, color change, and grain dry down.


Frost damage can affect soybeans in similar ways to corn (see article on corn in this issue).  For harvest efficiency, combine beans by driving slower and keeping the head as close to the ground as possible.  Shattering can become a problem for early maturing varieties.


What are the characteristics to look for to identify frost damaged soybeans?

  Small, elongated beans

  Green beans

  Slower field dry-down

  Lower oil quality (especially if green beans are present) and reduced oil extraction

  Meal can have from 0.5 to 2 percentage points more residual oil in it

  Moisture will be higher by 1 to 2 percentage points

  Level of free fatty acids is increased and this can lead to rancidity in the beans

  Shelf life of the oil and meal will be reduced


What can be done about frost damaged soybean?  It should be dried at a temperature below 120˚F to 130˚F and stored only when the grain moisture is between 10 and 12 percent.  If beans are stored, they should be aerated more often to dry and cool them and as an added benefit this can reduce the amount of green color in the beans and improve marketability.  Unlike corn, frosted beans sold directly from the field often bring a lower price due to the market’s reaction to green beans.  Storing beans for a period of time often can improve the price if the beans are cleaned to remove the wetter weed seeds, trash, and plant parts before storage.




Fertility Management on Small Grains - Richard W. Taylor, Extension Agronomist, rtaylor@udel.edu


The continuation of above normal rainfall has implications for small grain fertility management this fall.  Soil nitrate nitrogen (N) levels are likely to be lower than we usually expect especially following dryland or irrigated corn since both crops have had adequate moisture to fully use soil N and rains have likely leached unused N out of the upper soil layers.  To counter this, I would suggest adding about 30 lbs N/A ahead of your small grains.  If the ground is worked, lightly incorporate the N in the very top surface layer so it will be available for uptake by small grains.


Another aspect to consider is the likelihood that sulfur (S) also has been leached out of the surface soil layer.  For this reason, some if not all of the 30 lbs N/A should be supplied as ammonium sulfate ((NH4)2SO4).  Another advantage, in certain situations, to using (NH4)2SO4 is the acidifying effect this form of fertilizer has on the soil.  These situations include fields planted to barley with soil pH above 6.0 to 6.2 and fields planted to wheat with soil pH above 6.2 to 6.6 and low native manganese (Mn) levels.  If (NH4)2SO4 is applied to the surface or incorporated in the top few inches of soil, the acidifying effect can raise the level of available Mn in the soil so that Mn deficiency is not as much a concern.  However, in areas such as south and west of Dover, where native Mn levels are very low and frequent problems with Mn deficiency occur, growers should also monitor the small grain seedlings carefully for Mn deficiency symptoms and apply foliar Mn when symptoms first occur.  Soil applications of Mn also can be used, but are generally more expensive because much higher rates of Mn are needed.


This past spring on sandy soils we did see some cases of magnesium (Mg) deficiency.  In fields that are very sandy and the pH is on the acidic end of the scale, growers should consider taking a soil sample this fall to check on Mg availability and soil pH in general.  In a number of fields, the frequent leaching rains required multiple application of N fertilizer to maintain corn growth.  Also adequate rainfall and some heat during the month of July and August resulted in the mineralization of soil organic matter and this process also acidified the soil.  Last spring the application of Mg as Epson salts or K-Po-Mag (potassium magnesium phosphate) helped reduce the damage of low soil Mg levels so keep these sources in mind in case the problem develops again next spring.




Frost Damage in Corn - Richard W. Taylor, Extension Agronomist, rtaylor@udel.edu


The extended and late planting window for corn (some is just now reaching the point of pollination) this past spring could mean that some corn acreage is at risk for damage by an early frost.


The actual impact of frost depends on the air temperature, the duration of the temperature and the growth stage of the corn.  For corn, a temperature of 32˚ F for a period of 4 to 5 hours, 28˚ F for less than an hour, or 26˚ F for only a few minutes can result in injury.  If the corn is still immature, there will be an increase in yield loss, grain breakage, grain moisture content, a decrease in grain test weight, and a slower dry down rate.  If the corn is near maturity or black layer, frost can loosen the husks and actually increase the dry-down rate, but yields may be unaffected depending on how close to maturity the corn is.  For silage corn, yield loss can occur at all stages due to the loss of leaf tissue, but there also can be an increased risk of nitrate toxicity especially where late nitrogen or manure applications or manure mineralization occur.


Frost damage can affect corn in five ways: yield, moisture, quality (test weight, color, cracking, and protein content), harvest efficiency, and drying costs.  Yield often is reduced if frost occurs before black layer (physiological maturity) and early frosts interfere with the movement of carbohydrate (sugars) to the grain from the leaves and stems.


 Frost usually results in a high plant moisture content and slower dry-down time although that varies with the growth stage of the corn.  Generally, corn grain moisture will be higher requiring growers to artificially dry corn.  Be aware that frost damaged corn often gives inaccurate moisture meter readings.


The low test weight and increase in broken grain and fines in the grain can result in more dockage when delivering and selling frost damage grain. 


Reduced harvest efficiency is caused by a possible increase in lodging for frost damaged corn.  Also, harvest losses due to wet cobs, smaller ears, and ears that do not thresh as clean will reduce harvest efficiency.  Be sure to match your chains and cylinder speed for your ground speed when harvesting since you may need to drive slower during harvest.


What are the characteristics to look for to identify frost damaged corn?

  Small, misshapen, soft kernels

  Pithy corn—undeveloped starch structure

  Test weight will be progressively lower, often <52 lb/bu in severely damaged corn

  High breakage susceptibility—more fines in stored grain

  Kernels may be dry on the surface, but the actual moisture can be 1 to 2 percentage points above moisture tester readings

  An increased risk of mold and mycotoxins [aflatoxin, fumonisin and vomitoxin (also known as DON or Deoxynivalenol)]

  Variable amino acid levels

  Lower digestibility

  Variable protein content (<8 percent protein if test weight is <52 lb/bu)


What can be done about frost damaged corn?  It should be dried at a temperature below 160˚ F and stored only when the grain moisture is below 14 percent.  If the grain is stored, it should be screened to remove the excess fines.  The grain will have a storage or half-life about half that of normal, undamaged corn.  The grain should be aerated frequently and should be marketed as early as possible often right out of the field.  If test weight has been reduced, the corn will be less valuable as a feed (about 2 to 5 percent lower than unfrosted corn on a per pound basis).  Ruminant animals and swine are less sensitive to the effect of lower test weight corn.




Pole Lima Bean Demonstration Open House


Date: Thursday, September 18, 2003

Location: New Delaware State University Farm near Smyrna (˝mile east of Rt. 13 on Smyrna-Leipsic Road)

Time: Anytime from 4:30 – Dusk


There will be 10 varieties of pole lima beans, both small and large seeded types, including some locally collected heirlooms.


For more information, contact Gordon Johnson at 302-730-4000 or Maggie Moor at 302-587-6426.





                            Weather Summary



Weeks of September 5 to September 10, 2003 *



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

Air Temperature:

Highs Ranged from 80°F on September 7 to 71°F on September 10.

Lows Ranged from 65°F on September 9 to 52°F on September 10.

Soil Temperature:

71°F average for the week.

(Soil temperature taken at a 2 inch depth, under sod)

* Data taken from Warrington Farm Weather Station. 


Web Address for the U of D Research & Education Center:



Compiled and Edited By:

Tracy Wootten

Sussex County Extension Educator - Horticulture







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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