Volume 14, Issue 8                                                                                  May 19, 2006

Soybean Rust Update



The recent rains and cool weather in Florida have produced favorable conditions for rust and as a result soybean rust was seen on kudzu this week in Gadsden County in the Florida panhandle. Rust development continues to be slow which is good for us, but that can change if the weather becomes more favorable for infection. Many soybean fields have been planted down South and to date no soybean rust has been detected on soybeans in sentinel plots or grower fields.


All the Delaware sentinel plots are emerged and the earliest planted plot has the first trifoliate leaves expanding. Growers are encouraged to keep up-to-date with recent developments by logging in to http://www.sbrusa.net for more information.

Bob Mulrooney





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



Continue to scout all melons for aphids, cucumber beetles, and spider mites. We have received the first reports of economic levels of spider mites in watermelons. The warm winter conditions and dry spring have been favorable for overwintering populations. The threshold for mites is 20-30% infested crowns with 1-2 mites per leaf. Acramite, Agri-Mek, Capture (bifenthrin), Danitol, Kelthane (phased out this year) and Oberon are all labeled on melons for spider mite control. It will be important to rotate chemistry to avoid the development of resistance.



In addition to adult Colorado potato beetles, be sure to watch for the first larvae. A treatment should be considered for adults when you find 25 beetles per 50 plants and defoliation has reached the 10% level. Once larvae are detected, the threshold is 4 small larvae per plant or 1.5 large larvae per plant. A corn borer spray may be needed 3-5 days after an increase in trap catches or when we reach 700-degree days (base 50). If you are scouting for infested terminals, the first treatment should be applied when 10% (fresh market) or 20-25 % (processing) of the terminals are infested. Since the first potato leafhoppers have migrated into the area, you should also begin scouting for leafhoppers.


Snap Beans

All seedling stage fields should be scouted for leafhopper and thrips activity. As a general guideline, 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.



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


Fungicide Update

The regional IR-4 Project headquartered at Rutgers University has just petitioned the EPA for several uses of thiophanate-methyl (Topsin M) including: use on caneberry (raspberries, blackberries, etc.), brassica leafy greens, mushrooms, mustard, sunflower, tuberous and corm veggies, tomato, and turnip greens. Some of the uses petitioned for are needed for Delaware growers in special situations. The use on mushrooms to control dry bubble has been satisfied by a section 18 registration, the rest had been discontinued and now will be restored. We will inform you when the labels are issued by EPA.


Potato Cyst Nematode Update

Surveys of the two regulated fields in Idaho where the nematode was found, all packaging facilities, and processing plants associated with the initial sample were completed the week ending May 5, 2006 - totaling 1,983 soil samples. All samples have been negative. Sampling began of the seed producing fields for these two infested fields and some 593 soil samples were taken, no results yet on that effort. Korea, Canada and Mexico are not receiving shipments of fresh potatoes from Idaho and Japan continues to ban all fresh potatoes from the US as a result of this find. See Issue 5 for more details of the discovery.



Potato Disease Advisory #4 - May 18, 2006


Disease Severity Value (DSV) Accumulation as of May 17, 2006 is as follows:

Location: Byfield Farms field east of Magnolia, DE. Greenrow: April 23


Remember that 18 DSVs is the threshold to begin a spray program





Daily DSV

Total DSV

Spray Recs


P days*

4/23- 4/30





4/30- 5/10































Recent rains and cool weather have provided enough high humidity to begin to accumulate DSVs again after the dry spell. The threat of late blight from seed infection is low, but more of a potential problem than last year. Remember that these values are for potatoes that would have about 50% emergence and made a row that you can see on or before April 23.


Growers who do not want to rely only on the DSV calculations for scheduling fungicide applications for late blight should apply at least 1-2 sprays of mancozeb (Dithane, Manzate, Pencozeb, Manex II) or Bravo (chlorothalonil) before plants canopy down the row. Late blight has not been a problem here in Delaware for many years and unless you have seed from an unknown source, the risk of late blight is very low. See 2006 Vegetable Crops Recommendations for more fungicide choices.


* P days- We use the predictive model WISDOM to determine the first fungicide application for prevention of early blight as well. The model predicts the first seasonal rise in the number of spores of the early blight fungus based on the accumulation of 300 physiological days (a type of degree-day unit, referred to as P-days) from green row. To date, 171 P-days have accumulated at the site near Magnolia. Once 300 P-days have accumulated, the first fungicide for early blight control should be applied. This usually occurs when rows are touching.



Spinach White Rust Kate Everts; Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu


In Issue 5 of the Weekly Crop Update, several fungicides were listed that are registered for, and effective on, white rust. The rate of Cabrio listed in that article was 12 to 16 oz/A. That rate range is correct for the leaf spots, such as anthracnose and Cercospora leaf spot. However, white rust can be managed with a lower rate of 8 to 12 oz/A. Additional information is available on the Cabrio label.



Agronomic Crops


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



Since the first potato leafhoppers have migrated into the area, you should check all fields for leafhoppers within one week of cutting. Be sure to sample all spring planted fields since they are very susceptible to damage. Once the damage is found, yield loss has already occurred. The treatment thresholds are 20 per 100 sweeps on alfalfa 3 inches or less in height, 50 per 100 sweeps in 4-6 inch tall alfalfa and 100 per 100 sweeps in 7-11 inch tall alfalfa.


Field Corn

We are starting to hear reports of cutworm damage on corn. Be sure to sample all fields through the 5-leaf stage for damage. As a general guideline, a treatment should be considered in 1-2 leaf stage corn if you find 3 % cut plants or 10% leaf feeding. If cutworms are feeding below the soil surface, it will be important to treat as late in the day as possible, direct sprays to the base of the plants and use at least 30 gallons of water per acre. You should also sample no-till fields for true armyworms, especially where a grass cover or volunteer small grains were burned down at planting. As a general guideline, a treatment may be needed for armyworms if 25% of the plants are infested with larvae less than one inch long.



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



Disease issues continue to be very minimal on wheat. The recent rains may cause some late season diseases to occur but nothing has been seen yet. The risk of head blight or scab is present, but we will have to wait and see. This past week has been powdery mildew weather but levels are still very low. No fungicides are labeled for application to wheat past the flowering stage.



Horseweed (Marestail) ControlMark VanGessel, Extension Weed Specialist; mjv@udel.edu


No-till soybean fields that have not been treated yet pose a difficult situation. 2,4-D at 1 pt/A will have very little effect on the taller horseweed plants. ALS-inhibiting herbicides such as FirstRate are not particularly good on these taller plants. The best option available is Canopy SP because of the high rates of Classic (a component of Canopy). This is not a good option to use every year, but it is a good choice if you have not treated your fields yet. If Canopy SP does not fit into your herbicide program, two applications of Gramoxone Enteon will be needed to control/suppress these large weeds.



Hot Weather and Volatility with Dicamba and 2,4-DMark VanGessel, Extension Weed Specialist; mjv@udel.edu


Common sense is critical for spraying dicamba and 2,4-D. It is very critical to avoid sensitive plants (vegetables, ornamentals, trees, etc.). Both of these products are volatile and prone to move from the treated areas as vapors. Spraying postemergence herbicides in early planted corn or burndown in no-till fields that have not been treated yet may require additional consideration because of the temperature. Furthermore, many of the vegetables and fruits have been planted and they are often very sensitive to these herbicides. It is not recommended to spray dicamba or 2,4-D when the temperature is expected to be 85 degrees or hotter; or spray late in the day when temperatures drop below 85. A number of pre-mixes have dicamba (active ingredient in Banvel and Clarity) including, Distinct, Celebrity Plus, Marksman, Yukon, and NorthStar so the temperature consideration applies to them as well.



Postemergence Pokeweed ControlMark VanGessel, Extension Weed Specialist; mjv@udel.edu


A few questions have come in about controlling common pokeweed postemergence in field corn. We had a trial last summer with tall pokeweed (sprayed in late June) and had results similar to a study conducted at Southern Illinois University. Dicamba [Banvel, Clarity, Sterling]; Distinct; NorthStar, and Callisto were the best treatments for conventional corn hybrids. Glyphosate was also effective if Roundup Ready corn was planted. Our trial did not include Lightning, but the SIU trial reported good control with Lightning with Clearfield corn. For soybeans, glyphosate is the best option. In non-Roundup Ready soybeans, Synchrony was fair (but requires STS-soybeans) or FirstRate which was only fair in the SIU trial.



Corn Height Restrictions for Postemergence HerbicidesMark VanGessel, Extension Weed Specialist; mjv@udel.edu


Corn herbicides need to be applied at the correct timing to avoid crop injury. Applications after this time can result in crop injury and possibly yield reduction. Refer to the table on page 4 for the corn height restrictions for common corn herbicides. “Broadcast” applications refer to an over the top application and “directed” refers to use of special spray equipment that directs the spray so that the spray does not come in contact with the whorl of the corn. When corn height and collar number are given, you’re your decision on whichever feature is first attained. This table also includes information on rainfastness. Rainfastness is the number of hours needed between time of application and rainfall or irrigation to ensure sufficient absorption in the plant.





interval (hr)

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




16 oz/A: 5 leaves or 8 inches

8 oz/A or less: 36 inches tall or 15 days pre-tassel



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

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 inches tall or V5

directed: 16-36 inches tall



broadcast: 48 inches tall

directed: when necessary



broadcast: 2- to 10 collars

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

Roundup products


up to 30 inches or 8 collars on Roundup Ready Corn

Roundup WeatherMax on “Roundup Ready Corn 2”


broadcast: up to 30 inches or 8 collars

recommended directed: 24 to 30 inches

directed: 30 to 48 inches



up to 8 collars






2 collars or 6 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

4 oz directed up to 36 in. tall



broadcast: 12 in. or 4 collar

directed: 12 to 36 inches or 4 to 8 collar



broadcast: min- 4 in. tall; max- 20 in. tall or 6 collar

directed: 20 to 30 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



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

up to 6 collars

Steadfast ATZ


up to 12 inches or 6 collars



spike through 36 inches tall



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


Commodity Market Recap

Last week's USDA's May 12th supply/demand report was termed blockbuster by one highly respected private analyst. As expected, commodity prices did move higher over this past week, both the corn and wheat futures markets forged ahead in an explosive manner. Now the question becomes what, if anything, are grain marketers to do about it?


Other questions have entered into the picture overnight. They include a 200 point decline in the Dow at yesterday's close and a slackening in metal and energy futures prices. How are these factors going to impact commodity prices in the week(s) ahead?


Dry weather forecast in the Southern Plains has brought a new round of speculative buying to the wheat market taking both new crop hard red winter (HRW) and soft red winter (SRW) wheat to new life of contract highs. In turn, corn and wheat prices have garnered support from the buying in the wheat pits. Corn has also benefited from continuing strong export demand with another week under our belts termed bullish to corn futures prices.


Export Sales Bullish for Corn and Soybeans

U.S. corn exports were reported at a whopping 60.6 million bushels (mb), 44 percent over the four week average, and well above pre-report expectations. Only 21.1 mb were needed this week to stay on pace with USDA's revised annual projection of 2.025 billion bushels. Corn export totals were the largest since early February.


U.S. soybean exports, reported at 12.2 mb were 51 percent above the prior four-week average, in the middle of trade guesses, and nearly triple the 4.3 mb needed this week to stay on pace with USDA's 900 mb annual projection. Soybean sales were well above average which may come as somewhat of a surprise to commodity traders who generally expect a slowdown in U.S. exports this time of year. This level may only be temporary until Brazilian farmers begin selling their new crop soybeans.


U.S. wheat exports reported at 3.6 mb were termed bearish. Wheat exports were 50 percent below the four-week average. The old-crop sales number was well below the 13.4 mb needed this week to stay on pace to meet USDA's revised annual projection. An additional 6.8 mb in sales were reported for the new marketing year, which begins June 1.


All export sales reported are for the week ending May 11th.


Marketing Strategy

Locally, corn marketers have been advised to be at least 30% forward priced for new crop corn. Due to expected increases in the demand for corn, for both ethanol production and export, and the likelihood that China and Argentina will have less corn for export, it is advisable to remain at the 30% contracted level for new crop corn. The current rally in the corn market should be used to bring new crop corn sales to the 30% level. Advancing new crop soybean sales are also not advised at this point in time.


It is advisable to advance new crop wheat sales, previously sitting at the 50% level of expected production. Wheat sellers should consider advancing both new crop '06 wheat sales and '07 wheat sales. Both contracts made new life of contract highs in yesterday's bidding (5/17/06). It may be necessary to consider taking a Hedge to Arrive (HTA) contract in the event that new crop basis levels are too weak. The HTA will lock the current futures price allowing the seller to assign or affix basis later.





Pea Twilight Meeting

Tuesday June 13, 2006     6:00 p.m.

Carvel Research and Education Center

Georgetown, DE


Meeting will include a tour of the late pea variety trial and updates on current pea research projects followed by refreshments.


For more information contact:

Emmalea Ernest or Ed Kee at (302) 856-7303.




Pesticide Safety Training and Testing for Pesticide Applicators Certification

June 6 & 7, 2006

Del Tech Terry Campus, Dover, DE

Room 427 Corporate Training Center


June 6th is training – 8:30 a.m. – 4:30 p.m.  Training continues the morning of June 7th, from 8:30 a.m. – noon.  The exam starts at 1:00 p.m. on June 7th.


Be sure to bring your Workbook! You don’t have to register for training, but you must register for the exam.  Call DDA (302-698-4500) one week in advance to register for the exam. All the exams are closed book!! Bring your calculator for the calibration questions.


For more information go to:




Weather Summary


Week of May 11 to May 17, 2006

Readings Taken from Midnight to Midnight



0.49 inch on May 11

0.04 inch on May 12

0.05 inch on May 14

0.10 inch on May 15

0.20 inch on May 16


Air Temperature:

Highs Ranged from 74°F on May 17 to 60°F on May 14.

Lows Ranged from 55°F on May 13 to 49°F on May 17.


Soil Temperature:

65°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.