Volume 10, Issue 3                                                                                                     April 12, 2002


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



The first planted potatoes have emerged from the ground so be sure to watch for Colorado potato beetle adults. Overwintering conditions have been very favorable for beetle survival.  In fields where Admire, Platinum or Tops MZ Gaucho were not used at planting, foliar insecticides will not be needed until you find 25 beetles per 50 plants and defoliation has reached the 10% level.


Sweet Corn.

As soon as the first plants emerge, be sure to look for cutworm feeding damage. Since black cutworm egg laying has just begun, we should not see cutting from this species until early May. However, another cutworm species, the variegated cutworm, is often present in early-planted fields. In general, this species is the first cutworm causing damage to early-planted sweet corn. Regardless of the species, a cutworm treatment should be applied if you find 10% leaf feeding or 3% cut plants in one-two leaf stage corn. Ambush, Asana, Pounce, or Warrior will provide effective control. Fields should be treated early in the morning or early evening when cutworms are close to the soil surface to achieve the best control.



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


Spinach Diseases.

Stemphylium leaf spot and Cladosporium leaf spot of spinach are present on Delmarva.  Symptoms of the two diseases are small (up to 0.5 cm) tan to brown leaf spots that can appear similar to chemical damage.  Cladosporium leaf spot will produce tan conidiophores and conidia (fruiting structures) under moist conditions.  Stemphylium leaf spot lesions appear papery and lack obvious fungal growth.  Both diseases will be more severe in low areas of the field where leaf wetness duration is greater.  Quadris can be applied at 6.2 to 15.4 fl. oz./A for control.  In our 2000 research trial at University of Maryland LESREC in Salisbury, Stemphylium leaf spot control was achieved with the lower (6.2 fl. oz.) Quadris rate.



Reflex Receives Section 18 Exemption for Snap Beans in Delaware - Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu


EPA has granted a Section 18 for the use of Reflex to control broadleaf weeds in Snap Beans.  Reflex is effective on certain morningglory species and other broadleaf weeds.  Check the label for details.


Field Crops

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



Economic levels of alfalfa weevil continue to be found in fields throughout the state. Although a general threshold of 50% of the tips infested can be used, it is more effective to base treatment decisions on the number of larvae per stem.  Before alfalfa is 12 inches tall, the threshold is 0.7 per stem. Once alfalfa reaches 12 inches tall, the treatment threshold is one per stem.


Field Corn.

Although cutworm moth activity continues to increase, we have not seen a peak in moth activity. As indicated in the last newsletter, trap catches only provide an indication of areas of potential cutworm outbreaks. In areas with significant trap counts, you should begin to see cutting when 300 base-50 degree-days have accumulated since peak moth flights. Current trap catches can be found at www.udel.edu/IPM/traps/currentbcwtrap.html


Small Grains.

If temperatures remain warm, we should see our first cereal leaf beetle egg hatch by next week. We are also starting to see an increase in true armyworm moth catches. A cumulative count of 200 moths for the month of April indicates the potential for a true armyworm outbreak. Weather factors have been favorable for survival of overwintering armyworms so you should begin checking fields for armyworms by the last week in April. Currently, the highest trap catches have been found in the Harrington and Rising Sun areas. We are also starting to hear reports from Virginia of aphid activity in barley. Once heads emerge, a treatment may be needed if you find 20-25 aphids per head. You should also watch for beneficial insect activity since a ratio of one beneficial to every 50 aphids can help keep populations under control. Remember, Warrior and Mustang are not labeled for barley. If threshold levels of aphids are found in barley, Lannate, Malathion or Penncap-M should be used.




The following information was prepared by Galen Dively, University of Maryland: Reports are coming in from all over the state of Maryland describing yellowed or brown patches in orchardgrass, often circular in shape and quite extensive throughout fields. Upon examination, plants are severely stunted and actually appear to be dead above-ground but the root systems and crowns are still alive in most cases.  So far, three causal agents have been identified including white grubs, winter grain mites and aphids. In some fields, aphids have been detected in affected fields but the low numbers present and absence of signs of past aphid activity suggest that they probably are not the major cause. In other locations (as well as in Virginia), greenbug aphid populations have been high.  In Anne Arundel County, several fields have been diagnosed by Dave Myers who reports finding high numbers of grubs, mainly Japanese beetle, and some wireworms in the root zone beneath affected plants with roots heavily pruned back. Grubs are common insects in orchardgrass, as well as other perennial pasture or hay fields, which have been in production for several years or more.  These fields are usually able to tolerate or compensate for root feeding under normal weather conditions.  However, the mild dry fall and winter have stressed orchardgrass and thus exacerbated the impact of the root injury.  Furthermore, mild temperatures and lack of frozen soil have probably allowed grubs to remain higher in the soil profile and thus have probably been feeding throughout the winter.  Normally they migrate deeper in the soil to escape freezing temperatures and remain inactive until spring.  It is also suspected that dry soil conditions may have favored grub survival by reducing the incidence of fungal pathogens and other diseases that normally take their toll on the overwintering stages.


Other affected orchardgrass fields reported in central Maryland have few grubs associated with the damaged areas and no evidence of root pruning. Many of these fields are infested with winter grain mites, which is a sporadic pest of wheat, turfgrass, and forage grass, particularly in the western U.S.  Interestingly, this same mite was reported in a number of wheat fields in eastern Virginia back in early February, and the injury symptoms were similar to the circular dead areas that are now showing up in  orchardgrass.  The scientific name of this mite is Penthaleus major. It is larger and moves around much faster than spider mites. They are 1/32- to 1/16-inch long, have 8 legs (6 in the first stage), and a dark bluish black body with red orange legs and a reddish patch on their upper side.  Like other mites, they use their piercing-sucking mouthparts to feed on the sap of their host plants. They feed primarily at night and hide around the base of the plant during the day.  Thus, they can easily be overlooked when scouting fields during the day.  Feeding on leaves causes yellowing, leaf tips to turn brown, and stunted plants with a silvery-gray appearance. Damage resulting from a heavy infestation is similar to winter-kill. In the northeast and mid-Atlantic area, these mites seldom cause sufficient damage to be of concern.  However, the unusual weather conditions during the past fall and winter have apparently favored their survival and development.  Other causal factors, such as plant diseases, have not been ruled out, and it may turn out that a combination of pest organisms and plant conditions are responsible for the orchardgrass problems.  In any case, it is important to check damaged areas in affected fields to try to link the injury to a particular pest or pests. If either grubs or winter grain mites are the culprits, there are unfortunately few options available to effectively manage these pests.  Only Sevin and malathion (both of which have several formulations) are registered for orchardgrass, but these chemicals have poor efficacy against grubs and furthermore cannot be applied in any effective way to control insects in the soil.  Malathion (25% WP) at the 1 lb. rate per acre is recommended in some western states to control winter grain mites in wheat, so this may be the only product that can be used to control mites on orchardgrass. However, before chemical control is used, keep in mind that the recent rains may help to alleviate plant stress and allow the damaged areas to green-up.  Also, each orchardgrass field needs to be evaluated on a case by case basis, because it appears that there is no one causal factor involved.  And it may not be wise to apply chemical controls against a pest that has not been directly linked to the injury symptoms or determined that it will cause further damage if not controlled.

Winter grain mite

(Penthaleus major)



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


Sluggish Commodity Markets Offer Limited Opportunities


Chicago Board of Trade new crop bids for corn, soybeans, and wheat have declined slightly since last week's report. It is possible to see a modest recovery this next week due to, among other things, the market being oversold. Additionally, at some point commodity traders will have to bid prices higher in order to book sales. For example, new crop corn prices may equate to a harvest delivery price of anywhere between $2.21 to $2.31 per bushel on the Eastern Shore (11 to 21 cents over the $2.10 loan rate). However, new crop corn basis offerings in the corn belt are likely to be currently offered at 20 to 30 under the Dec (equating a harvest delivery price of only $1.91 to $2.01 per bushel). Corn belt farmers are not likely to be booking new crop sales, at this point in time. Eastern Shore farmers are urged to consider using basis contracts on the corn and soybeans that are to be delivered at harvest, with new crop corn and soybean basis offerings being bid at 10 over the Dec for corn and 20 under the Nov for soybeans (Seaford delivery). The current basis offerings are running about average as compared to the past five marketing years.


The situation in the Middle East and the war on terrorism continues to cast uncertainty over all of the markets, and some could argue that uncertainty is not price positive.  There are currently a few bright spots. World corn stocks are currently forecast at just 2 million tones above the record low world carryout recorded in 1995. Weekly soybean exports for the week ending April 5th were exceptionally strong and corn planting in the Delta/Tennesse Valley is now running behind the yield-losing time frame, due to wet weather. The recently harvested Texas wheat crop is way below last years output and below USDA forecasts. Rains have been more than ample in the corn belt and in some areas it will be the end of April before planting begins. In the recent past, corn planting in the corn belt has gotten underway by April 1.  Perhaps it is time for commodity prices to rally!




Early Season Corn Planting - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu


Some growers may just be anxious to get started, others have time constrains that require early planting, while others may be trying for the late summer early corn market.  In any case, here are a few tips to help speed corn emergence, improve uniformity of emergence, and all round just improve stand uniformity that will help maximize corn yield potential.


Ø         Tillage operations that loosen and aerate at least the top few inches of soil will help dry the surface soil, and that means it will warm up much faster.  Warmer soil means faster and more uniform germination and this improves yield potential.


Ø            Be certain your planting equipment is working well, especially with respect to depth bands or however seeding depth is controlled.  Well maintained planting units will also improve seed spacing and this improves yields.


Ø            If your depth control is good, try seeding only 1.25 to 1.5 inches deep since the surface inch or two of soil warms up fastest.  Be aware that other problems can occur with shallow planting such as bird damage and rapid desiccation of the germinating zone.


Ø         Use a starter fertilizer since early root growth will be limited if cool weather persists.  Place the starter two inches to the side and below the seed to allow the seedling roots to intercept the band.  Did you know that phosphorus moves by diffusion an average distance of 0.01 inches and potash moves diffuses only 0.1 inches?  From that you can see that if the roots are not growing rapidly because of cool soil temperatures, early season nutrient uptake can be very limited unless a band is placed near the seedling.


Ø      Provide enough nitrogen to carry the seedling until sidedress time.  The number of rows per ear is set very early in the growth cycle of corn, usually by the fifth or sixth leaf stage.


Ø    Be sure compaction or some other factor will not inhibit deep rooting by the corn plants.  A strong, healthy root system is a key component of top yields.


Ø    For the early markets, early maturing hybrids will be the obvious choice, but otherwise choose full-season hybrids to make the maximum use of the longer growing season with early planted corn.




Agronomic Tips for 2002 - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu


Have you been wondering how to survive current low commodity prices?  The obvious answers of minimizing your costs and maximizing the selling price of the crop are not the complete answer.  In some cases, you may have to spend money to either save or make money in the long run.  There are some agronomic actions you can take to improve your yield potential and gross income with minimal out of pocket cost.


With the above normal rainfall two years ago and good rainfall in some areas last year, are any of your fields at risk for compaction problems?  Do you have vegetables in your rotation that might lead to extra vehicle traffic on your fields?  If so, you should check the fields for compaction.  An easy, inexpensive way to do that is to get a wire flag and use it to push into the soil at a number of locations across the field.  If there’s compaction,  you’ll quickly identify it and without having to use fancier and much more expensive soil penetrometers that measure the force needed to penetrate soil layers.


Did you study the available variety/hybrid performance data and choose a variety or hybrid that is widely adapted or did you limit yourself to only one particular brand?  With today’s prices for grain, your selection of seed to plant should be based on performance, not brand loyalty or new variety hype.


Do you have soybean fields that just don’t perform as well as you would expect, especially in droughty years?  A soil test analyzed for Soybean Cyst Nematode (SCN) can answer the question of why.  SCN often is the cause of declining yields or fields that perform under expectations.  With the use of SCN-resistant varieties and crop rotation you can help control this pest and improve yields with little expense.


Plant your most productive fields first.  Make sure that those fields with the best chance of good yields will be planted early enough to maximize yield potential.  If weather delays, equipment problems, or other unforeseen delays put you off schedule, you can decide at the end of the planting window whether to even plant the less productive fields which often don’t produce enough to break even in good years.


For corn, plant by May 1 for optimum yields.  Corn planted after May 10 will have lower yield potential.  Plant corn hybrids from several maturity groups to spread your pollination and grain fill periods to reduce the chances that a short dry or hot spell at the wrong time will reduce your yield by a large amount.


For full-season soybeans, early planting is very important.  Group IV and V varieties should be planted in early May (use a fungicide seed treatment if the soil is cold and wet) to maximize yields.  Group III beans should be planted in mid-May for best yield.  For double-crop beans, the earlier they are planted the better the yield potential in all maturity groups.


Fertilize for realistic yield goals not for wished-for yield levels.  Use your soil test results as a guide.  Look at the trends in soil test results from year-to-year.  Are nutrient levels going up, down, or staying the same?  Are they in the high to excessive level now?  If nutrient levels are staying the same (and are high or better) or the level is going up, consider reducing the amount of that nutrient you plan to apply this year.  Similar to pasture and hay fields, high yields the last two years in many areas have lead to increased potassium (K) deficiency symptoms on corn and beans.  Check your most recent soil test trends to be sure you have enough K in the soil.  Stresses (drought, insect, disease, etc.) can be better tolerated by crops well supplied with K.


During the season, scout for insect, disease, and nutritional problems.  If you have a history of soil insects reducing stands, scout for soil insects and make your treatment decisions based on the appropriate economic threshold.  During the season, either scout fields or have your fields scouted by a professional so you can monitor pests levels and use economic threshold levels to determine when it pays to treat.


If you use manure on your fields, the pre-sidedress nitrogen test (PSNT) can help you estimate if there is enough nitrogen available for maximum economic yields or how much more needs to be applied as sidedress nitrogen or by fertigation.  For irrigated corn, leaf tissue analysis or the leaf chlorophyll meter can be effective ways to manage nitrogen fertilization.


Lastly, begin as soon as possible to increase the organic matter inputs into your fields.  Soils high in organic matter hold more nutrients, hold more water, have better tilth, and offer many more benefits.  Whenever you’re not growing a crop for harvest, use the opportunity to grow green manure cover crops.




Reminders On Acetachlor Use Restrictions - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu


Acetachlor is a preemergence herbicide for corn that controls annual grasses and some broadleaf weeds.  It is in the following products: Harness, Harness Extra, Degree, Degree Extra, Topnotch, and Fultime.  There are restrictions that are important in our area.  The restrictions pertain to groundwater quality.  The restrictions are based on depth of groundwater within one month of planting and the combination of soil type and organic matter.  Do not apply acetachlor if the groundwater depth is 30 feet and you have sands with less than 3% organic matter, or loamy sands with less than 2% organic matter, or sandy loam with less than 1% organic matter.




New Corn Products for 2002 - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu


Callisto 4SC (Syngenta) is a new active ingredient called mesotrione, with a new site of action.  It is a pigment inhibitor and causes sensitive plants to turn white.  It can be used either soil-applied or postemergence, but due to costs postemergence has the best fit in our area.  Soil-applied rates are 5.0 to 7.7 fl oz/A and postemergence rates are 3 fl oz/A.  It is most effective with a little atrazine (0.5 lbs/A or 1 pt/A atrazine).  There is excellent crop safety, up to 30-inch corn or 8 collars (whichever is most restrictive).  There are numerous broadleaf weeds listed as controlled on the label, with large crabgrass as the only grass species listed.  Replant is 4 months to small grains and 18 months for most other crops.  There are precautions for use with Counter and Lorsban, refer to the label.



Define 60DF (Aventis/Bayer) is the single active ingredient of flufenacet (which is contained in Axiom and Domain).  Define is similar to Dual, Micro-Tech, Harness, Frontier, etc., and provides preemergence control of many annual grasses.  Define, as a single ingredient has not been in our trials in past years, so we have little experience with this product.


Harmony GT 75DF (DuPont) is a new, more concentrated formulation of Pinnacle 25DF, and its use rate is much less than Pinnacle.  Harmony GT is used at one-twelfth of an ounce per acre.  It can be applied to 2 to 6 leaf corn (up to 12 inches tall).  Harmony GT provides excellent control of lambsquarters and pigweed (including triazine resistant).  In “Clarity-sensitive areas”, it can be a good alternative.  There are precautions on the label about use with Counter due to crop injury (see label).


Hornet (Dow AgroSciences) has been reformulated as Hornet 68.5WDG instead of Hornet 85.6WG.  It is a pre-packaged mixture of Stinger and Python.  The new use rates for Hornet WDG will be 2 to 6 oz/A.


Option 35WDG (Aventis) is a new postemergence herbicide from the same class of herbicides as Accent, Beacon, and Permit (ALS-inhibiting herbicides).  Use rate is 1.5 to 1.75 oz/A.  Application timing is emergence to 16 inches or V-5 stage, whichever is more restrictive.  The label recommends methylated or ethylated seed oil plus nitrogen fertilizer for additives.  There are numerous grasses and broadleaves listed as controlled on the label.  Corn can be replanted 7 days after application, soybeans 14 days, and all other crops can be planted 60 days after application.  There are precautions about use for corn previously treated with Counter or Lorsban, refer to label.


Outlook 6EC (BASF) contains dimethenamid-p which is the more active isomer of dimethenamid (Frontier, Guardsman, and LeadOff).  Since it is more active, the use rates will be lower by approximately 55%.  Outlook controls the same weed spectrum as Frontier; providing good control of annual grasses, some broadleaves and nutsedge.  Outlook is available as a pre-packaged mixture with atrazine and called Guardsman Max.


Steadfast 75WDG (DuPont) is a pre-packaged mixture of Matrix and Accent, or another way to think of it is Basis Gold without atrazine.  It is a postemergence herbicide with a use rate of 0.75 oz/A.  At this use rate there is 0.75 oz/A Matrix plus 0.5 oz/A Accent.  There are precautions with organophosphate insecticides, refer to label.





Agricultural Fact –


The United States average yield for corn has gone from 27 bushels/acre in 1900 to 121 in 1997.  Soybeans have risen from 16.1 bu./A in 1930 to 36.5 in 1997.  Potatoes from 57 cwt/A in 1900 to 325 in 1997. 




                        Weather Summary

Weeks of April 6 to April 10, 2002



0.29 inches: April 10


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


Air Temperature:

Highs Ranged from 77°F on April 9 to 47°F on April 6.

Lows Ranged from 59°F on April 9 to 25°F on April 7.


Soil Temperature:

55°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, John C. Nye, 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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