Volume 14, Issue 4                                                                       April 21, 2006

Soybean Rust Update



Scouting for soybean rust continues on kudzu patches from Florida northward through Georgia and Alabama, and westward to Texas. Many of the soybean sentinel plots have been planted in the most southern states with some soybeans emerging and observations for rust taken in Texas. Currently, there are no reports of rust on newly planted soybean in 2006. The forecast for the Southern states continues to be dry and warm, not very conducive for soybean rust infections at the present time.


Bob Mulrooney





Vegetable Crop Diseases

Bob Mulrooney; Extension Plant Pathologist; bobmul@udel.edu


The following article, written by Dr. Andy Wyendandt, Extension Vegetable Plant Pathologist, Rutgers University and reproduced here with his permission, is the first of three parts on understanding fungicide groups and the importance of understanding the new FRAC groupings. FRAC stands for the Fungicide Resistance Action Committee. FRAC is a Specialist Technical Group of CropLife International (which is a chemical industry group). For more info their website is http://www.frac.info/frac/index.htm. The purpose of FRAC is to provide fungicide resistance management guidelines to prolong the effectiveness of "at risk" fungicides and to limit crop losses should resistance occur.


The main aims of FRAC are to:

Ø      Identify existing and potential resistance problems.

Ø      Collate information and distribute it to those involved with fungicide research, distribution, registration and use.

Ø      Provide guidelines and advice on the use of fungicides to reduce the risk of resistance developing, and to manage it should it occur.

Ø      Recommend procedures for use in fungicide resistance studies.

Ø      Stimulate open liaison and collaboration with universities, government agencies, advisors, extension workers, distributors and farmers.


Growers guide to understanding protectant fungicides (FRAC Groups M1 – M9)

Protectant (contact) fungicides, such as the inorganics (copper, FRAC group M1) and sulfur (M2), the dithiocarbamates (maneb, mancozeb, thiram, M3) and chloronitriles (chlorothalonil, M5) belong to FRAC (fungicide) groupings which have a low chance for fungicide resistance to develop. Protectant fungicides typically have broad spectrum in controlling many different pathogens. Why wouldn’t fungi develop resistance to protectant fungicides? Protectant fungicides are used all the time, often in a weekly manner throughout much of the growing season. The answer, quite simply is in their modes-of-action (MOA). Protectant fungicides have MOAs that affect (i.e. prevent) fungal development in different manners. In inorganic compounds, sulfur (M1) prevents fungal growth (i.e. spore germination) by disrupting electron transport in the mitochondria. Coppers (M2), on the other hand, cause non-specific denaturation of proteins. Chlorothalonil (M5) inactivates amino acids, proteins and enzymes by combining with thiol (sulfur) groups. In all cases, a protectant fungicide’s chemistry disrupts fungal growth and development either non-specifically or in multiple manners. Because of this, there is a low chance for fungi to develop resistance to them. Protectant fungicides are contact fungicides, meaning they must be present on the leaf surface prior to the arrival of the fungus and must then come into direct contact with the fungus. Protectant fungicides can be redistributed on the leaf surface with rainfall or overhead irrigation, but can also be washed off by too much of either! Remember that with protectant fungicides, any new growth is unprotected until the next protectant fungicide is applied, in other words, protectant fungicides do not have systemic or translaminar activity like some of the newer chemistries. Protectant fungicides are often tank-mixed with fungicides with higher chances for fungal resistance development. Protectant fungicides used in this manner will help slow (or reduce the chances for) resistance development. In any case, it’s best to always follow the label and tank mix protectants with higher risk fungicides when suggested or required to do so.



Agronomic Crops


Agronomic Crop Diseases

Bob Mulrooney; Extension Plant Pathologist; bobmul@udel.edu


Wheat and Barley

The dry weather has been very unfavorable for the development of diseases and little if anything has been detected so far. As mentioned before, weekly scouting should begin at jointing (GS 6). We did get a report that stripe rust was present in some areas of Georgia, so if we should get enough rain to favor infection, we may see stripe rust again in 2006.



If the continued dry weather persists into the planting season or soon after, susceptible soybean varieties are at risk to soybean cyst nematode. Under Delaware conditions the worst damage from SCN is seen as stunting (occasionally plant death) and eventually yield loss when we have dry weather early in the season during the vulnerable stages of early root development. Susceptible soybeans, high SCN numbers, and dry weather are a combination that can result in serious stunting and yield loss. Early soil sampling for SCN can avoid this loss. It is still not too late to check for soybean cyst nematode. Soil test bags with the submission form can be purchased at the Extension offices. If you have a fax machine and need results quickly, test results can be sent via FAX if you provide the number on the Nematode Assay Information Sheet. This information sheet can be found on the web as well at the Plant Clinic Website http://ag.udel.edu/extension/pdc/index.htm .



Weed Control in Pastures and AlfalfaMark VanGessel, Extension Weed Specialist; mjv@udel.edu


If you have not done so yet, be sure to examine your hay, pasture, and alfalfa fields for weed infestations. Earlier applications are much more effective than later ones, as weeds get larger and start to produce seeds. For grass hayfields or pastures, weed control options include dicamba (Banvel or Clarity), 2,4-D, Overdrive, Crossbow, or Cimarron. Cimarron and Crossbow provide residual control, while the other products do not.


For pure alfalfa fields, Buctril, 2,4-DB, Pursuit or Raptor are labeled. Pursuit and Raptor will provide both postemergence control as well as residual control. For mixed stand of legumes and grasses, Pursuit is an option.


Be sure to read the label and follow all precautions concerning grazing and haying restrictions as well as overseeding and re-seeding restrictions.



Water is Needed to “Activate” Soil-Applied HerbicidesMark VanGessel, Extension Weed Specialist; mjv@udel.edu


Herbicides applied to the soil surface require rainfall or irrigation to move them into the soil where the plants will absorb them. The amount of water need to “activate” these herbicides depends on the water solubility of the herbicide and moisture content of the soil. Most soil-applied herbicides require 0.5 to 0.75 inches to be moved in the soil if the soil is “dry” (less water if the soil is moist). Princep requires 0.75 to 1.0 inches of water to become “activated”. If you have irrigation and your corn herbicides have been applied but you have not received at least 0.5 inches of water, you should consider applying that amount with your system. This is one situation where spending a little money now could save money later. For instance, if your residual grass herbicide is not moved into the soil and grass control is poor, you are looking at a postemergence application of Steadfast or Option. And control of crabgrass with postemergence herbicides is only fair. Spending the money to irrigate and activate the herbicides could save a high herbicide bill later.


Solubility is measured in parts per million (ppm) as how many milliliters of the herbicide will dissolve in 1 liter of water. The less soluble the herbicide, the more moisture (rain or irrigation) needed to incorporate (activate) the herbicide. The relative moisture to activate the herbicide is a guideline for rainfall or irrigation needed within a short time after application to move the herbicide into the root zone. Amount of moisture needed also depends on the soil moisture level at time of application.


Herbicides, their solubility, and relative moisture required for their activation



Solubility1 (ppm)

Relative moisture required to activate2










Dual II Magnum / Cinch



Harness / Degree



Lasso / Micro-Tech









Prowl / other pendimethalin formulations






Premixes and Their Components

Bicep II Magnum / Cinch ATZ

Dual II Magnum (or Cinch), Atrazine

Bicep Lite II Magnum

Dual II Magnum, Atrazine


Micro-Tech, Atrazine

Field Master

Harness, Atrazine, Roundup

Fultime / Keystone

Topnotch, Atrazine

Guardsman Max

Outlook, Atrazine

Harness Xtra / Degree Xtra

Harness (or Degree), Atrazine

Lumax / Lexar

Dual II Magnum, Callisto, Atrazine

1 in unbuffered distilled water

2 Relative moisture ranges from little (+) to high amount of moisture (++++). ppm <100= ++++; 100-250= +++; 250-500 ppm= ++; >500= +

NOTE: “++++” does not need 4X the moisture as “+”; it is used to demonstrate herbicides with more +’s need more moisture for incorporation (activation).



Scout Alfalfa Fields Now for Alfalfa WeevilRichard Taylor, Extension Agronomist; rtaylor@udel.edu and Cory Whaley, Sussex County Agricultural Agent; whaley@udel.edu


In the past week, several reports have come in about alfalfa fields that have been severely infested with alfalfa weevil. The fields in question have been in the early growth phase (less than 12 inches of growth) and have had other stress factors present such as weeds (chickweed, predominately) or drought stress. Growers are concerned because they are not sure if the yield potential is there to warrant an insecticide application. Unless the grower is planning to plow under the field after the first harvest, the risk of permanent injury to the stand and long-term yield reductions certainly will justify pesticide application to control the pest. Also in all cases, alfalfa fields are not anywhere near full bud in all locations I have examined. An early harvest can be an effective control strategy since it can help control the pest. However, early harvest before full bud when defoliation has occurred is not an option since the alfalfa plants will not have replaced the root energy reserves that are needed to support regrowth following cutting.


The following information on alfalfa weevil comes from our IPM field crops web site. Go to http://www.udel.edu/IPM/facts/awfactsheet.htm for all the information including pesticide options.


“Larvae feed on the tips of plants and on leaves, resulting in a skeletonized plant. Severe damage causes the leaves to turn gray and appear "frosted". This insect is primarily a pest of the first cutting; but, when high populations are present just before the first cutting, regrowth of the second cutting may also be damaged. Larval damage results in reduced yield and quality of the first cutting and, when severe, the damage can also result in season-long yield loss and reduce the life of the stand. If alfalfa is less than 12 inches tall when the weevil population peaks, fewer than 2 larvae per stem can defoliate a crop. In comparison, alfalfa greater than 18 inches tall can tolerate significantly higher populations. If fields are monitored routinely and sprayed only when economic levels are present, natural enemies may be able to suppress weevil populations below an economic level.


“Begin sampling in late March and continue on a weekly basis until the first cutting. Fields should also be checked within one week of the first cutting for damage to the regrowth. During the first visit, examine 5-10 stems for damage and larvae. A full stem sample is not needed until damage or larvae are found on the plants. If leaf feeding is present, randomly collect 60 stems from throughout the field. Grasp stems at the base and place each stem upside down in a bucket. After collecting the stems, separate them into 3 or 4 bundles and beat them against the inside of the bucket to dislodge larvae from the stems. Count and record all larvae found per 60 stems. Measure 10 of the 60 stems and record the average stem height. Also, note if buds or flowers are present to determine the percentage of plants in the bud or flower stage.


“The following thresholds can be used as a guideline to make an alfalfa weevil control decision:


Threshold guidelines for alfalfa weevil larvae based on alfalfa stem height.

Average Stem Height (inches)

No. Weevil Larvae per Stem












“More precise decisions can be made by using the tables in Pest Management Recommendations for Field Crops (Bulletin 237).



“If alfalfa is in the full-bud stage and economic levels are present, early harvest is an alternative to spraying. If harvest is not possible within 3 days and populations are increasing, use a short residual insecticide. After the first cutting is removed from a field, examine the stubble for larvae. A stubble treatment will be needed if you find 2 or more larvae per stem and the population levels remain steady.”


Even though the current dry weather may reduce yield potential for each cutting this year, the effects on stand longevity from severe defoliation make it essential that the insects be controlled.



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



U.S. corn exports for the week ending April 13th were reported at 43.4 million bushels, more than double the 21.5 million bushels needed to stay on pace to meet USDA's projected 1.95 billion bushel mark. Soybean exports were reported at 7.1 million bushels, with 5 million bushels needed this week to stay on pace to meet USDA's 900 million bushel export projection. Soybean exports are expected to slacken this time of year well into the summer. U.S wheat exports reported at 7.7 million bushels were slightly below the 11.9 million bushels needed to stay on pace with USDA's 1.015 billion bushel projection.


Crop Ratings

U.S. winter wheat crop ratings remain poor in 32% of the country, compared to just 6 percent rated poor or very poor at the same time a year ago. Thirty-nine percent of the crop is rated good to excellent, as compared to 69% a year ago. Simultaneously, the winter wheat crop is maturing faster than normal with 9 percent now headed, 3 points ahead of last year. It is important to note that a warning also comes with the wheat crop ratings. In other years very poor early April ratings, have resulted in record or near record wheat crops. Currently new crop wheat futures at the CBOT are trading at $3.67 per bushel and July '07 wheat futures are trading at $4.23 per bushel.


Planting Progress

Weekly crop planting progress reports are just now starting. Commodity traders will be watching to see if planting progress keeps pace with the historical average. There is some preliminary concern that spring planting progress may be slowed due to weather, particularly in the Northern Plains.


Marketing Strategy

New crop corn futures are currently trading at $2.72 per bushel; new crop soybeans at $6.07 per bushel; new crop wheat at $3.67 per bushel. Dec '07 corn futures are trading at $2.90 per bushel; Nov '07 soybean futures are trading at $6.32; and July '07 wheat futures are trading at $4.23 per bushel. New crop basis levels are currently being offered at 10 over Dec for new crop corn; 10 under Nov for new crop soybeans; and 30 under July for new crop wheat. For technical assistance on making grain marketing decisions contact Carl German.





Strawberry Twilight Meeting

Tuesday May 16, 2006     6:00 – 8:00 p.m.

Wye Research and Education Center


Featured speakers this year are:

Dr. Bill Turechek, USDA Fruit Pathologist

Dr. Jerry Brust, UM Entomologist

Mr. Michael Embrey, UM Apiary Specialist


There will be a tour of high tunnel production and field plots, followed by light refreshments.


For more information contact Michael Newell at

(410) 827-7388.




Weather Summary


Week of April 13 to April 19, 2006

Readings Taken from Midnight to Midnight



0.06 inch: April 17


Air Temperature:

Highs Ranged from 83°F on April 15 to 56°F on April 17.

Lows Ranged from 58°F on April 15 to 36°F on April 18.


Soil Temperature:

61°F average.

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


The Weekly Crop Update is available online at



Weekly Crop Update is compiled and edited by Emmalea Ernest, 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. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Delaware Cooperative Extension, University of Delaware. It is the policy of the Delaware Cooperative Extension System that no person shall be subjected to discrimination on the grounds of race, color, sex, disability, age or national origin.