Volume 14, Issue 1                                                                       March 24, 2006

 

The Weekly Schedule Begins on April 7th

 

Issue 1 of the Weekly Crop Update is a sample of the information you will receive each week with a subscription or access via the internet. The newsletter is designed to provide subscribers with the latest information on disease and insect problems as they develop, timely weed control information, crop progress reports, and other topics related to agronomic and vegetable crop production in Delaware. University of Delaware Extension Specialists and Agents provide information for the newsletter.

 

The weekly issues will begin on April 7th and continue through September 15th. The Weekly Crop Update is posted on the web, and sent to mail and fax subscribers each Friday. As in past years, the cost of mail or fax subscription is $30. You can subscribe by returning the form at the back of this issue.

 

Crop Update is also available for free online at the following address:

http://www.rec.udel.edu/TopLevel/Publicat.htm

For those of you who access the newsletter via the internet we offer to send a weekly email reminder which will let you know when the WCU has been posted online, provide a link directly to the current issue, and give you a taste of the headlines. If you would like to receive the email reminder or if you experience problems during the season with the online WCU please contact me at emmalea@udel.edu or (302)-856-7303.

 

Emmalea Ernest

Soybean Rust Update

 

Many growers and fieldpersons have taken advantage of meetings over the winter that have addressed Asian soybean rust. The Sussex County Agronomic Crop Session on March 23 at 6 PM will be another opportunity to be updated on ASR. It is important to keep informed as the season progresses. We will again attempt to keep you updated this season by including information on soybean rust in Weekly Crop Update.

 

Scouting for soybean rust continues on kudzu patches from Florida northward through Georgia and Alabama, and westward to Texas. Scouts in southwest Alabama found a number of kudzu patches with new growth but no rust. Reports from Florida indicate that kudzu is greening in the panhandle and some rust has been found. The confirmed reports of counties with rust on kudzu in 2006 include five in Alabama, eleven in Florida, four in Georgia, and one in Texas. However most of these were frosted after detection so the number of active sites may be less at this point in time. Many of these detections on kudzu are being destroyed in hope of reducing initial spore numbers. In Florida the freeze line remains unchanged from near Tarpon Springs, Leesburg, Ocala, to Daytona Beach so any detections south of this line will still be active. In short, we were looking at more rust entering this season than last, but the frost within the last several weeks has changed that and we are about where we were at this time last year.

 

Our soybean rust website still has the lists of fungicides that are labeled and all the section 18 registrations from last year are still active for 2006. This information can be found at http://ag.udel.edu/extension/pdc/soybeanrustResources.htm . The website to bookmark and check regularly is the USDA site http://www.sbrusa.net/.

 

Bob Mulrooney

 

 

Vegetables

 

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

 

Admire Pro (Bayer) - This new formulation of imidacloprid will be in the marketplace in 2006. It contains 4.6 lbs of active of ingredient per gallon. Please be sure to check the label for use rates and restrictions (http://www.cdms.net/ldat/ld74S007.pdf)

 

Venom 70SG (Valent) - This new neonicotinoid, containing the active ingredient dinotefuran, is now labeled for use on cucurbits, fruiting vegetables, head and stem brassica, leafy vegetables and potatoes. Please see the label for use rates and restrictions. (http://www.cdms.net/ldat/ld76N001.pdf)

 

Tomatoes - Please note that Actara is not labeled on tomatoes. It is incorrectly listed under tomatoes in the Commercial Vegetable Production Recommendations, Extension Bulletin 137.

 

 

Vegetable Crop Fungicide Update –

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

 

There have been several new additions to the fungicide arsenal this past year including Reason from Bayer Crop Science and Ranman from FMC. Reason (fenamidone) is a new Group 11 fungicide labeled for use on tomatoes and potatoes for early blight and late blight with good activity against early blight. It is also labeled for cucurbits and would be an alternative for Alternaria leafblight on cantaloupes and watermelon. I would not expect activity against downy mildew on pickles although it is labeled for downy mildew as well. Ranman (cyazofamid) is new chemistry and is in fungicide group 21 all by itself. It is an excellent fungicide for the control of the oomycete fungi such as late blight and downy mildew. It is currently labeled for late blight on potato and tomato, and downy mildew on cucurbits.

Forum replaces Acrobat as the new formulation of the fungicide dimethomorph from BASF. Forum is a 4.18 lbs/gal SC formulation replacing the Acrobat wettable powder formulation. The labeled crops are the same.

 

 

Knowing Your FRAC Groupings for Fungicide Resistance Management – Bob Mulrooney; Extension Plant Pathologist; bobmul@udel.edu

 

FRAC, or the Fungicide Resistance Action Committee, was developed to help provide fungicide resistance management guidelines for ‘at or high risk’ fungicides. At or high risk fungicides have a high probability for fungi to develop resistance to because of their mode-of-action (MOA). Fungicides with chemistries that have a specific target site of activity against fungal pathogens, unfortunately, have a high risk for losing efficacy.

 

Also, fungicides with similar chemistries and similar MOAs may also allow fungi to develop cross-resistance. This is where a fungus that develops resistance to one fungicide in the FRAC group may also develop resistance to other fungicides in the group, even if those other fungicides haven’t been used. With the recent flux of new fungicide chemistries on the market great lengths have been taken to reduce the risk of fungicide resistance development. There are currently 42 numbered FRAC groupings and 4 lettered groups. As new fungicides with new MOAs are released on the market new numbered groups will be added to the list. Fortunately, for most vegetable crops many of the most commonly used fungicides fall into a few of these groupings. Most notably, the multi-sites (M) or low risk fungicide groupings include M1 and M2 (inorganics such as sulfur and copper); M3( Maneb, Mancozeb); and M5 (chlorothalonils such as Bravo, Guide, Equus).  Higher risk groups include Group 3 (triazoles, such as Nova), Group 4 (mefenoxams, such as Ridomil), and Group 11 (strobilurins, such as Amistar, Flint, Cabrio) to name a few.

 

Knowing which fungicides are in which grouping will have an impact on spray schedules, disease control, and resistance management. Protectant fungicides, such as those in the M FRAC groupings, have a low risk for fungicide resistance development and have less stringent restrictions. However, for those chemicals with a higher risk of fungicide resistance development the product labels are more stringent and labels should be followed precisely. Labels often require that high-risk fungicides be tank mixed with protectant fungicides to reduce the chances for fungicide resistance development. In general, tank mixing high-risk fungicides with protectant fungicides is always a good resistance management strategy. For example, the strobilurin fungicides in FRAC group 11 should not be sprayed consecutively. Such that, if Amistar (azoxystrobin, 11) is sprayed one week, it should not be followed the next week with another Group 11 compound such as Flint (trifloxystrobin, 11) or Cabrio (pyraclostrobin, 11) or a compound containing a Group 11 fungicide (Pristine, pyraclostrobin + boscalid, 11 + 7).

 

If this sounds confusing, it is, but a simple way to remember what to use next in fungicide rotation is to use a labeled fungicide with a different number or letter. FRAC groupings have been added to the fungicide table at the beginning of each crop section in the 2006 Recommendations Guide to help growers learn what fungicides belong to what FRAC groups and to help them chose fungicides for use in rotations. A complete list of fungicides and FRAC groups can be found in Table E-8 on pages E28 and E29 in the Recommendations Guide. Efforts in learning and using new chemistries with new modes of action along with knowing their FRAC grouping will ultimately pay off in the long run by reducing the chances for fungicide resistance development.

Adapted from Rutgers Plant & Pest Advisory, Veg Crops Edition, March 8, 2006 written by Andy Wyendandt, Extension Vegetable Plant Pathologist.

  

 

Winter Temperature Index for Predicting Stewart’s Wilt in Delaware Sweet Corn, 1996-2006 Bob Mulrooney; Extension Plant Pathologist; bobmul@udel.edu

 

Average monthly temperatures in °F at Georgetown, DE. REC. 1996-2006

 

2005-

06  

2004-05

2003- 04

2002-03

2001-

02

2000-01

1999-00

1998-99

1997-98

1996-97

December

36.2

38.9

38.6

36.7

43.2

31.2

40.3

41.3

39.3

42.0

January

43.0

34.9

29.5

28.9

40.0

33.8

33.9

39.5

42.6

35.0

February

37.4

36.7

35.2

33.8

39.9

38.8

39.7

38.7

40.6

41.5

INDEX

116.6

110.5

103.3

99.4

123.1

103.8

113.9

119.5

122.5

118.5

 

Average monthly temperatures in °F at Newark, DE Experiment Station. 1996-2006.

 

2005-

06

2004-05

2003- 04

2002-03

2001-

02

2000-01

1999-00

1998-99

1997-98

1996-97

December

34.0

35.5

34.0

33.5

43.3

31.1

39.1

41.0

38.4

40.9

January

39.5

31.0

26.4

27.1

39.6

31.5

32.6

34.8

40.9

33.2

February

34.5

34.2

33.1

29.5

40.1

38.4

37.8

38.0

40.6

40.3

INDEX

108.0

100.7

93.5

90.1

123.0

101.0

109.5

113.8

119.9

114.2

 

Severity Index: < 90, usually absent; 90-100, intermediate; >100, usually severe.

The index is used to predict overwintering flea beetle populations that vector the Stewart’s wilt bacterium, Pantoea stewartii.

Flea Beetle Population Predictions for 2006

 

Newark:  108.0 = Severe– Avg. monthly temp (Dec, Jan, Feb) -- 36.0 °F

Georgetown:  116.6 = Severe - Avg. monthly temp -- 38.8 °F

 

For processing and fresh market growers this means that if you are planting susceptible or moderately susceptible hybrids that flea beetle control is very important. A number of strategies are available including seed treatments, granular insecticides at planting and/or foliar applied insecticides after emergence. More on this in the next issue.

 

 

Agronomic Crops

 

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

 

Soybeans - EPA has approved the use of Orthene 97 on soybeans. The supplemental federal label can be obtaining at the following site:

http://www.cdms.net/ldat/ld2AQ011.pdf

 

Field Corn Soil Insect Management – The decision to use preventive treatments should be based on field history, sampling for the insects, and crop rotation. The following is a brief review of conditions favoring soil insects in field corn as well as observations from the 2005 season:

 

  I. Corn Rootworm (Larval Control): Since rootworms are generally a problem in continuous corn, rotating out of corn should be considered for corn rootworm larvae management. However, if you plan to plant continuous corn, control options include either a soil insecticide, a commercially applied seed treatment of either Cruiser (high rate) or Poncho 1250, or a transgenic corn hybrid with resistance to rootworm larvae

 

As far as seed treatments, reports from the Mid-West and areas in PA with heavy rootworm pressure state that “when rootworm densities and root injury have been moderate, seed treatments have provided acceptable protection of the roots. However, when rootworm densities have been high and root injury has been moderately high to severe, insecticidal seed treatments have not provided consistently acceptable control of corn rootworm larvae.”

 

  II. Wireworms: High soil organic matter, sod covers, and heavy grass weed pressure the previous season all favor wireworm populations. Fields having a combination of high organic matter and heavy grass weed pressure are the most susceptible to damage. Commercially applied seed treatments i.e. Cruiser (thiamethoxam) and Poncho (clothianidin) have generally provided good wireworm control. NOTE – Labels for Cruiser and Poncho state seed and seedling protection.

 

  III. Grubs: In general, grubs are favored by a number of factors including planting into soybean stubble, old sod, hay, pasture, or set-aside acreage. Cruiser and Poncho are labeled against white grubs. Although these two chemicals can work against moderate grub populations, in 2005, we did see poor control with both products in commercial fields under high Asiatic garden beetle pressure. If populations are high, you may still need to consider a soil insecticide. NOTE – Labels for Cruiser and Poncho state seed and seedling protection.

 

  IV. Black Cutworm: This insect is favored by late planting, broadleaf weed growth (especially chickweed) present before planting, poorly drained field conditions and reduced tillage. Rescue treatments can be applied for this soil insect if you are able to scout fields twice a week once leaf feeding is detected. Pheromone traps placed in the field by mid-March can be used to determine when to look for cut plants. Look for pheromone trap counts in future reports. At this point, we have not caught any moths in the traps. If you are unable to scout and you have conditions favoring cutworms, one of the following preventive approaches can be considered: (1) a soil insecticide labeled for cutworm control applied as a t-band, or (2) a commercially applied seed treatment insecticide, or (3) a tank mix of an insecticide with a pre-emergent herbicide or (4) a Herculex corn hybrid.

 

The seed applied treatments, Cruiser and Poncho, are systemic so larvae must feed to be affected. The Cruiser label only states cutworm suppression. The Poncho label says it will provide early season protection of seedlings against injury. In the Delaware/Maryland area, we are mainly dealing with populations that lay eggs early on weeds or, in some cases, an overwintering population so we generally find larger larvae (1/2 inch and greater) present in fields at planting time. After our field experiences in 2004 and 2005, we still feel that seed applied treatments may not provide economic cutworm control under our conditions, especially if economic levels of larger larvae are present at planting. Fields should still be scouted and a rescue treatment applied if necessary.

 

 

Control the Horseweed (or Marestail) in No-Till Soybeans When It’s Small – Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

 

The presence of glyphosate-resistant horseweed has made no-till soybean burndown programs more challenging. (Glyphosate is the active ingredient in Roundup and Touchdown). This species is not a problem in tilled fields (because it emerges before the tillage is completed, so tillage kills it) or in corn (because atrazine is pretty effective on it). Rather the problem has only been showing up in no-till soybean fields where glyphosate alone has been used for burndown control prior to planting. The presence of glyphosate-resistant horseweed is so wide-spread and it moves so easily with the wind, you have to assume that the horseweed plants in your field are resistant and not rely on glyphosate to control them.

 

What to use??  A program based on a plant-growth regulator herbicide (2,4-D or dicamba).  Glyphosate will not kill the resistant biotypes.  Paraquat often will not effectively control all the plants and it often requires two applications for good control (and two applications is not a sound resistance-management strategy).  There is concern about excessive use of ALS-inhibiting herbicides such as Amplify, FirstRate, Canopy EX, or Synchrony XP that could lead to additional resistance.  That leaves 2,4-D or dicamba.  Dicamba is the active ingredient in Banvel and Clarity.  The pint rate of 2,4-D ester is only marginal on horseweed (particularly when the plants are 4 inches or taller).  A quart rate of 2,4-D ester is needed to consistently control this species.  For most formulations, a quart rate (assuming 4 lb ai/gallon formulation) requires a period of 30 days from time of application until soybeans can be planted.  There are a few formulations available that require only 15 days between the quart application rate and planting soybeans.  So this treatment should be made as early as possible due to controlling small weeds and allowing the time interval prior to planting. 

 

For dicamba, there are some differences between Banvel and Clarity labels. Banvel is labeled for 8 to 16 oz/A, and requires a 30-day interval between application and planting soybeans.  Clarity use rates are 4 to 16 oz/A.  The interval between Clarity application and soybean planting is defined by a total accumulation of 1 inch of rain followed by 14 days.  Averaged over the past 20 year weather records, this is a 26 day period, but it can be longer.

 

There are a number of weed species not controlled by 2,4-D or dicamba.  These products should be tankmixed with a non-selective herbicide such as paraquat or glyphosate.  (Paraquat is the active ingredient in Gramoxone Max and other formulations are available).  Since most of the no-till soybeans will be planted with Roundup Ready soybeans, paraquat would be a better choice from a resistance management standpoint.

 

Additional flush of weeds is possible with this early application, so a tankmixture with a residual herbicide (such as Boundary, Sencor, Valor, Canopy) may eliminate the need for an additional application of paraquat at planting.

 

 

New Weed Control Guides are Available – And They’re Free – Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

 

Available from your county extension office are two weed management guides for assistance in weed control in corn and soybeans. There is a separate guide for soybeans and corn. The first half of each guide deals with soil-applied herbicides and the second half is for postemergence herbicides. These guides have pre-mixes and what is in the pre-mix, expanded weed control tables, information on application timing, comments for each of the herbicides, and much more. Contact your county extension office for these free guides. Or find them at the UD-REC website: http://www.rec.udel.edu/weed_sci/WeedPublicat.htm

 

 

Small Grain Weed Control – Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

 

It is time to consider your weed control for the small grain crop. Fields that were no-tilled or where chickweed emerged shortly after planting in the fall are fields to check first for spring treatment. If you have wild garlic or Canada thistle the time of application should be delayed since you need to spray these weeds when they have fully emerged. Coverage is important for these species. If weed pressure from winter annuals is great, it may not be possible to get control of the winter annuals and perennials with one application. In that case two applications may be required. You can mix your Harmony Extra with nitrogen. If spraying Harmony Extra with nitrogen, be sure to pre-mix it in water first. If using nitrogen as your carrier, no need for a surfactant unless wild garlic is over 8 inches tall. If applying Harmony Extra in nitrogen diluted with water, use a non-ionic surfactant at ½ to 1 pint/100 gallons of solution. If applying it in water use non-ionic surfactant at 1 qt/100 gallons.

 

Grass control in small grains is still challenging, even with a few new products. Hoelon is the only product labeled for grass control in barley, and it will only control annual ryegrass before it is more than 2 tillers. For winter wheat, Osprey is also available from Bayer. Fall will be a better time for Osprey applications, but it will control annual ryegrass in the early spring. Osprey can not be applied with nitrogen carrier and the Osprey application and nitrogen application must be made 21 days apart. Spray solution can not be any more than 15% nitrogen. Osprey has activity on small annual bluegrass. Large annual bluegrass control will be better with Maverick than with Osprey. However, Maverick requires that STS soybeans be used for double-cropping and does not allow for rotation to vegetables.

 

Have you considered resistance management with your small grains? Most of the small grains get treated only with Harmony GT or Harmony Extra, which contains two ALS-inhibiting herbicides (same type of herbicides as Pursuit, Accent, Classic, etc). Many weeds have developed resistance to herbicides that have this mode of action.  Consider how often a field is planted to small grains and how often it gets treated with Harmony Extra. If this rotation is short, 3 years or less, consider tankmixing another herbicide with Harmony Extra to minimize the risk of developing herbicide resistant weeds.

 

Finally, the following are the timing limitations for small grain herbicides. The timing restrictions are based on crop safety.

 

2,4-D - up to jointing stage (pre-jointing)

Banvel/Clarity - up to jointing stage (pre-jointing)

Buctril - up to boot stage

Harmony Extra or Harmony GT - up to flag stage (pre-flag leaf)

 

 

Precautions for Herbicide Use with Nitrogen Applications to Small Grains – Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

 

It is common to add herbicides when nitrogen is applied to small grains and small grain-legume mixtures. These precautions are from manufacturer’s label:

 

Harmony Extra or Harmony GT- slurry in water first and may result in temporary crop yellowing. If liquid nitrogen is less than 50% of the spray mix, then include a surfactant. For 2,4-D it varies with the formulation. The ester formulation can be mixed directly with nitrogen, but labels recommend good agitation. Amine formulation of 2,4-D should be mixed with 3 to 5 parts of water before adding it to the nitrogen solution. Buctril label cautions about potential leaf burn when mixed with liquid fertilizer, but leaves emerging after application are not affected. For MCPA, it varies some with the manufacturer. The ester formulation should not be applied with liquid nitrogen. The amine formulation varies, ranging from no mention of liquid nitrogen to application is allowed. Osprey restricts applications to no less than 3 weeks after a nitrogen application. Maverick cautions about possible leaf burn and reduced growth and states that weed control is more consistent when applied with water as the carrier.

 

 

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

 

Weather Becomes Dominant Factor in Commodity Markets