100

Crops

Top 7 Recommendations for Winter Wheat

Establishment ................................................................ 100

Plant Disease

Plant Disease Diagnostic Clinic (PDDC) Summary ..... 100

Vegetable Crop Update newsletter #17 ........................ 101

Insects and Mites

Wisconsin Pest Bulletin 8/15/13 ................................... 101

Top 7 Recommendations for Winter Wheat Establishment

Shawn Conley, UWEX Soybean and Small Grains

Specialist, John Gaska, Outreach Specialist

Top 7 winter wheat establishment recommendations:

1. Variety selection: please see the 2013 WI Winter

Wheat Performance Test

2. Plant new seed (don’t plant saved seed).

3. A fungicide seed treatment is recommended for

winter wheat in WI.

4. Wheat should be planted 1 inch deep.

5. The target seeding rate for wheat planted from

September 15th to October 1st is 1,300,000

to 1,600,000 seeds per acre.

6. The optimal seeding rate for wheat planted after

October 1st should be incrementally increased

as planting date is delayed to compensate for

reduced fall tillering.

7. Crop rotation matters.

To read the entire 5 page paper, see attached PDF

Plant Disease Diagnostic Clinic (PDDC) Update

Brian Hudelson, Ann Joy, Erin DeWinter and Joyce Wu, Plant

Disease Diagnostics Clinic

The PDDC receives samples of many plant and soil samples

from around the state. The following diseases/disorders have

been identified at the PDDC from August 10, 2013 through

August 16, 2013.

Plant/SampleType, Disease/Disorder, Pathogen, County

Field Crops

Corn, Northern Corn Leaf Spot, Bipolaris zeicola, Grant

Soybean, Charcoal Rot, Macrophomina phaseolina, Dane

Soybean, Dicamba Injury, None, Walworth

Soybean, Fusarium Root Rot, Fusarium sp., Trempealeau

Soybean, Soybean Cyst, Heterodera glycines, Trempealeau

Forage Crops

Alfalfa, Aphanomyces Root Rot, Aphanomyces euteiches,

Lafayette

Alfalfa, Crown Rot, Fusarium spp., Lafayette

Fruit Crops

Apple, Root/Crown Rot, Phytophthora sp., Pierce

Grape, Downy Mildew, Plasmopara viticola, Dane

Volume 20 Number 24 - - - University of Wisconsin Crop Manager - - - August 22, 2013

101

Follow us on

Grape, Powdery Mildew, Oidium sp., Dane

Raspberry, Root/Crown Rot, Pythium sp., Rhizoctonia sp.,

Fusarium sp., Cylindrocarpon sp., Lincoln and Rusk

Vegetables

Chard (Green), Cercospora Leaf Spot, Cercospora sp.,

Vernon

Chard (Red), Cercospora Leaf Spot, Cercospora sp., Vernon

Kale (Green), Alternaria Leaf Spot, Alternaria brassisicola,

Vernon

Kale (Green), Black Rot, Xanthomonas campestris pv.

campestris, Vernon

Okra, Alternaria Leaf Spot, Alternaria sp., Vernon

Pepper, Blossom End Rot, None, Vernon

Potato , Late Blight, Phytophthora infestans, Carroll (IL)

Tomato, Bacterial Speck, Pseudomonas syringae pv. tomato

Vernon

Tomato, Early Blight, Alternaria solani Vernon

Tomato, Late Blight, Phytophthora infestans Vernon

Tomato, Septoria Leaf Spot, Septoria lycopersici Vernon

Tomato, Sunscald, None, Sauk

Specialty Crops

Hop, Hop Latent Virus, Hop latent virus, Monroe

Soil

Soybean Soil, Soybean Cyst Nematode, Heterodera

glycines, Eau Claire, Walworth

For additional information on plant diseases and their

control, visit the PDDC website at pddc.wisc.edu.

Vegetable Crop Update newsletter #17

The 17th issue of the Vegetable Crop Update is now

available. Topics in the newsletter include:

▪ Late blight updates; DSVs (Disease Severity

Values)/Blitecast for late blight management

▪ PDays for early blight management

▪ Cucurbit downy mildew updates

▪ Onion downy mildew

▪ Release of N from ESN during cool, mid-summer

conditions

▪ Organic Potato Variety Trial meetings in ND and MN

Vegetable Crop Update 17, 8-20-13 is attached.

Wisconsin Pest Bulletin 8-15-13

Issue No. 16 of the Wisconsin Pest Bulletin is now available

at: http://datcpservices.wisconsin.gov/pb/index.jsp PRINT

THIS ISSUE

I N S I D E T H I S I S S U E

LOOKING AHEAD: Corn earworm migrants continue to

arrive

FORAGES & GRAINS: Counts of forage pests generally low

CORN: Annual rootworm survey shows minor population

declines in the south

SOYBEANS: Soybean aphid densities increase to moderate

levels in some fields

FRUITS: Second codling moth flight has peaked in most

orchards

VEGETABLES: Blossom end rot a problem for home

gardeners

NURSERY & FOREST: An assortment of oak galls noted this

week

DEGREE DAYS: Degree day accumulations through August

21, 2013

--------

Cool Bean AdvisorCool Bean AdvisorU N I V E R S I T Y O F W I S C O N S I N A G R O N O M Y , S O Y B E A N R E S E A R C H , U N I V E R S I T Y O F W I S C O N S I N - E X T E N S I O N

www.coolbean.info

Top 7 Recommendations for Winter Wheat Establishment in 2013 Shawn Conley, State Soybean and Small Grains Specialist

John Gaska, Outreach Specialist

Top 7 winter wheat establishment recommendations: 1. Variety selection: please see the 2013 WI Winter Wheat Performance Test 2. Plant new seed (don’t plant saved seed). 3. A fungicide seed treatment is recommended for winter wheat in WI. 4. Wheat should be planted 1 inch deep. 5. The target seeding rate for wheat planted from September 15th to October 1st is 1,300,000 to

1,600,000 seeds per acre. 6. The optimal seeding rate for wheat planted after October 1st should be incrementally increased as

planting date is delayed to compensate for reduced fall tillering. 7. Crop rotation matters.

Variety Selection

As with any crop, variety selection is the most important factor to consider in maximizing winter wheat yield and profitability. When choosing a winter wheat variety, several factors must be considered. These include winter survival, insect and disease resistance, lodging, test weight, and most importantly, yield. Since no variety is ideal for every location, it is important to understand the crop environment and pest complex that affects your specific region to maximize yield.

Yield is based on the genetic potential and environmental conditions in which the crop is grown. Therefore, by diversifying the genetic pool that is planted, a grower can hedge against crop failure. Select those varieties that perform well not only in your area, but across experimental sites and years. This will increase the likelihood that, given next year’s environment (which you cannot control), the variety you selected will perform well.

Test weight is also an important factor to consider when selecting a variety. The minimum test weight to be considered a U.S. #2 soft red winter wheat is 58 lb/bu. Wheat at lower test weights will be discounted. Both environment and pests may greatly affect test weight; therefore, selecting a variety that has a high test weight potential in your region is critical to maximizing economic gain.

Select a variety that has the specific insect and disease resistance characteristics that fits your needs. By selecting varieties with the appropriate level of resistance, crop yield loss may be either reduced or

www.coolbean.info

avoided without the need of pesticides. Careful management of resistant cultivars through crop and variety rotation, are required to ensure that these characteristics are not lost.

Plant height and lodging potential are also important varietal characteristics that may be affected by your cropping system. If the wheat crop is intended for grain only, it may be important to select a variety that is short in stature and has a low potential for lodging. This may decrease yield loss due to crop spoilage and harvest loss as well as increase harvesting rate. However, if the wheat crop is to be used as silage or is to be harvested as both grain and straw, then selecting a taller variety may be warranted.

For detailed information regarding winter wheat variety performance please visit www.coolbean.info for results of the 2013 WI Winter Wheat Performance Test.

Plant New Seed in 2013 To maximize wheat yields in 2013, it is imperative that growers plant certified or private

(professionally prepared) seed that is true to variety, clean, and has a high germination percentage (>85%).

Many wheat fields received a glyphosate application as a harvest-aid in 2013. Due NOT save seed from those fields as germination rate can be adversely affected.

If growers absolutely need to plant saved seed due to availability or other economic considerations, the following steps should be taken to increase the likelihood of establishing a legal and good wheat crop. Step One: Determine if you can legally plant the wheat seed you saved. Today, many private wheat varieties now come with statements which buyers sign at the time of purchase, stating that they understand they are not authorized to use the harvested grain for seed. Most current public winter wheat varieties are Plant Variety Protected (PVP) and though you may replant them on your own land, you do not have the right to trade/sell seed of those varieties to others for planting. Step Two: Once you have determined if you can legally plant the seed you saved, the next step is to clean the wheat seed. It is important that wheat seed be cleaned to remove small and damaged seeds and to eliminate weed seeds. Removing small and damaged seeds will not only aid in crop establishment, but will also provide a more uniform wheat seedling stand. Removing small and damaged seeds will also increase the thousand-kernel weight (TKW), which serves as a measure of seed quality. Wheat seed with TKW values greater than 30 grams tend to have increased fall tiller number and seedling vigor. Step Three: Perform a germination test. Germination tests can either be completed at home or by sending a sample to the Wisconsin Crop Improvement Association. A home test can be performed by counting out 4 sets of 100 seeds and placing each of them in a damp paper towel. Place the paper towel into a plastic bag to conserve moisture and store in a warm location out of direct sunlight. After five days, count the number of germinated seeds that have both an intact root and shoot. This will give the grower an estimate of % germination. It is important to choose random seeds throughout the entire seed lot and conduct at least 4 - 100 seed counts. If germination is below 85%, consider increasing the seeding rate to compensate; however, we would caution growers from seeding any wheat with a germination test below 80%. Step Four: Assess the need for a seed treatment. A number of fungicides and insecticides are labeled for use as seed treatments on winter wheat and are listed in Pest Management for Wisconsin Field Crops 2013 (UW-Extension A3646). Seed treatment fungicides protect germinating seed and young

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seedlings from seedborne and soilborne pathogens. Seed treatment fungicides will not improve germination of seed that has been injured by environmental factors and will not resurrect dead seed. Remember, seed treatment fungicides applied this fall will not protect against potential FHB infection next summer. If seed with scab must be used for planting, a seed treatment fungicide is a must. Seeding Depth Wheat should be planted ~1.0 inch deep depending upon soil moisture conditions. Wheat planted less than 0.5 inches deep may result in uneven germination due to seed exposure or dry soil conditions. Shallow planted wheat is also more susceptible to winterkill. Wheat planted more than 1.5 inches deep may result in death due to pre-mature leaf opening or poor tiller development and winter survival. Uniform seed placement and seeding depth are important in promoting crop health in the fall. Seeding rate and planting date The targeted fall stand for wheat planted from September 15th to October 1st is between 30 and 35 plants per square foot. This is about 22 seeds per foot in 7.5’ rows. To achieve this goal, the seeding rate for soft red winter wheat is between 1,300,000 and 1,600,000 viable seeds per acre (Table 1, 2). Depending upon varietal seed size, this equates to 74 to 119 pounds of seed per acre (Table 3). The optimal seeding rate for wheat planted after October 1st should be incrementally increased as planting date is delayed to compensate for reduced fall tillering (Table 1). Winter wheat and crop insurance (Information courtesy of Michele Austin, Director -Insurance Services; Badgerland Financial) The Wisconsin winter wheat final planting date varies by county, ranging from September 30th to October 10th. If the wheat is seeded after the county's final plant date (late planting period) the crop insurance guarantee is reduced by 1% per day for the first 10 days. If wheat is seeded after the late planting period, the crop insurance guarantee is reduced to 60% of the original guarantee. Special notes regarding the 2014 crop

The Trend Adjustment option is now available for some Wisconsin counties on Wheat. Talk to your crop insurance agent for more details.

Winter wheat coverage is not available in all Wisconsin counties. Air seeded (flown on by airplane) wheat is not insurable and no premium is charged. The final day to turn in a 2013 winter wheat claim is October 31st. The 2014 wheat price discovery on CBOT (using September '13 contract) will be determined as

follows (this price will be used for both yield protection and revenue protection plans of insurance):

The Projected Price tracks from August 15, 2013 - September 14, 2013 The Harvest price tracks from August 1, 2014 - August 31, 2014 There is a 200% maximum difference between the Base and Harvest Prices with no

downside limit.

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Table 1. Wisconsin seeding rate recommendations based on planting date. Wisconsin Winter Wheat Seeding Rate Recommendations Seeds/acre Seeds/sq ft Row Width (in)

Million 6 7 7.5 Seeds per foot row

0.4 9.2 5 5 6 0.5 11.5 6 7 7 0.6 13.8 7 8 9 0.7 16.1 8 9 10 0.8 18.4 9 11 11 0.9 20.7 10 12 13 Seeding Rate for Sept 1 to Sept 15 1.0 23.0 11 13 14 1.1 25.3 13 15 16 1.2 27.5 14 16 17 1.3 29.8 15 17 19 1.4 32.1 16 19 20 Seeding Rate for Sept 15 to Oct. 1 1.5 34.4 17 20 22 1.6 36.7 18 21 23 1.7 39.0 20 23 24 1.8 41.3 21 24 26 1.9 43.6 22 25 27 Seeding Rate for Oct. 1 to Oct 10 2.0 45.9 23 27 29 2.1 48.2 24 28 30 2.2 50.5 25 29 32 2.3 52.8 26 31 33 2.4 55.1 28 32 34 2.5 57.4 29 33 36

Table 2. Seeding rate impact on wheat yield. 2012/13 growing season.Seeding rate

(million seeds a-1) Grain yield (bu a-1)

1.25 86.5 1.50 86.5 1.75 89.8 2.00 89.7 2.25 89.5 2.50 89.6

LSD = 0.10 NS *Data pooled over environment (Janesville, Lancaster, Arlington, and Chilton. *No variety by seeding rate interaction (Sunburst, Pro260, P25R40)

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Table 3. Seed size and seeding rate conversion table. Seeds per acre (x 1 million)

Seeds/lb 1.0 1.2 1.4 1.6 1.8 2.0 2.2 Pounds of seed/acre

10000 100 120 140 160 180 200 220 11000 91 109 127 145 164 182 200 12000 83 100 117 133 150 167 183 13000 77 92 108 123 138 154 169 14000 71 86 100 114 129 143 157 15000 67 80 93 107 120 133 147 16000 63 75 88 100 113 125 138 17000 59 71 82 94 106 118 129

*This table is based on 100% germination. Adjust your seeding rate by the % germ printed on your bag tag. Crop Rotation: Yield data from our long term rotation experiment located at Arlington, WI indicated that wheat grain yield was greatest when following soybean (Table 3) (Lauer and Gaska, 2003-2006, unpublished). Yield of second year wheat (2003 column) was similar to wheat yields following corn for grain or silage. Third (2004), fourth (2005), and fifth (2006) year continuous wheat yields were dramatically lower than the other rotational systems. Our data suggests that growers should plant wheat after soybean first, then corn silage, corn for grain, and lastly wheat. Table 3. Winter wheat grain yield following winter wheat, soybean, corn for grain, and corn silage. Rotation 2003 2004 2005 2006 Average -------------Winter wheat grain yield bu a-1------------- Continuous Wheat 56.31 47.0 41.8 45.0 47.5 Corn-Soybean-Wheat 66.3 51.0 71.8 74.0 65.8 Soybean-Corn (grain)-Wheat 55.7 42.02 51.1 66.0 53.7 Soybean-Corn (silage)-Wheat 57.7 51.0 62.0 69.9 60.2 12003 marked the second year of the continuous wheat rotation treatment 2Poor stand establishment in the 2004 Soybean-Corn (grain)-Wheat rotation affected wheat yield. If growers choose to plant second year wheat, several management factors should be considered to reduce risk. First plant a different wheat variety in the second year that possesses excellent resistance to residue-borne diseases. Under no circumstances should growers consider planting bin-run seed in second year wheat. By planting a different variety with strong disease resistance characteristics you can reduce the likelihood of early disease pressure and significant yield loss. Growers should use a seed treatment in wheat following wheat. Be aware that seed treatments are not a cure all for all common diseases in continuous wheat systems (e.g. take-all). Growers should also consider increasing their seeding rate to 1.8 to 2.0 million seeds per acre in wheat following wheat systems. This will aid in stand establishment and increase the likelihood of a uniform stand going into the winter. Lastly, if using a no-till system, planting into a seedbed that is free of living volunteer wheat is important in reducing the incidence of Barley Yellow Dwarf Virus. Growers should consider a herbicide application to destroy any living volunteer wheat prior to planting to prevent a “green bridge” for the aphids that vector this virus.

Vegetable Disease Update – Amanda J. Gevens, Assistant Professor & Extension Vegetable

Plant Pathologist, UW-Madison, Dept. of Plant Pathology, 608-890-3072 (office), Email:

gevens@wisc.edu. Vegetable Path Webpage: http://www.plantpath.wisc.edu/wivegdis/

Late blight status in WI and the U.S.: We had a few new late blight samples this past week

– however – none from new counties. Table 1 includes further details. In the past week, KY,

MA, ME, NY, OH, PA, and Ontario Canada reported late blight on potato and/or tomato.

To date this production year, late blight has been reported in in FL, KY, LA, MA, MD, ME, MI,

NJ, NY, OH, OR, PA, TN, WI, WV, and Ontario Canada. The website:

http://www.usablight.org/ indicates location of positive reports of late blight in the U.S. and

provides further information on disease characteristics and management.

Table 1. Characterization of late blight from Wisconsin in 2013.

County Host Genotype Date of Confirmation

Adams potato US-23 28 Jun

Juneau potato US-23 29 Jun

Sauk tomato US-23 2 Jul

Dunn potato US-23 29 Jul

Portage potato US-8/US-23 29 Jul/6 Aug

Brown potato+tomato US-23 6 Aug

Langlade potato US-23 6 Aug

Racine tomato US-23 8 Aug

Waushara potato US-23 8 Aug

As a reminder, US-8 is resistant to mefenoxam/metalaxyl fungicides and is an A2 mating type;

US-23 is sensitive to mefenoxam/metalaxyl fungicides and is an A1 mating type.

In This Issue

Late blight updates; DSVs (Disease Severity Values)/Blitecast for late blight management

PDays for early blight management

Cucurbit downy mildew updates Onion downy mildew

Release of N from ESN during cool, mid-summer conditions

Organic Potato Variety Trial meetings in ND and MN

Calendar of Events

Aug 22 – UWEX-Langlade County Airport Research Station Field Day,

Antigo, WI

Vegetable Crop Update

A newsletter for commercial potato and vegetable growers prepared by the

University of Wisconsin-Madison vegetable research and extension specialists

No. 17 – August 20, 2013

A

B

C A B C

A

C

Current P-Day (Early Blight) and Severity Value (Late Blight) Accumulations P-Day of ≥ 300 indicates threshold for early blight risk and triggers preventative application of fungicide. DSV of

≥ 18 indicates threshold for late blight risk and triggers preventative application of fungicide. Red text in table

below indicates threshold has been met. NA indicates that information is not yet available as emergence has yet to

occur. http://www.plantpath.wisc.edu/wivegdis/contents_pages/pday_sevval_2013.html

Location Planted 50% Emergence P-Day

Cumulative (increase from

8/12)

DSV Cumulative (increase from

8/12)

Calculation Date

Antigo Area Early 5/13 6/4 547 (40) 50 (0) 8/19/13

Mid 5/22 6/17 470 (40) 42 (0) 8/19/13

Late 6/7 6/29 372 (40) 26 (6) 8/19/13

Grand Marsh Area

Early 4/15 5/10 674 (46) 270 (18) 8/19/13

Mid 5/1 5/21 639 (45) 270 (18) 8/19/13

Late 5/15 6/5 548 (45) 243 (18) 8/19/13

Hancock Area Early 4/20 5/15 749 (53) 86 (0) 8/19/13

Mid 5/5 5/23 688 (53) 84 (0) 8/19/13

Late 5/15 6/5 606 (53) 62 (0) 8/19/13

Plover Area Early 4/22 5/17 705 (88) 196 (27) 8/19/13

Mid 5/7 5/30 625 (88) 172 (27) 8/19/13

Late 5/24 6/5 583 (88) 163 (27) 8/19/13

DSVs and Late Blight: From in-potato-field weather stations here in Wisconsin, we have

exceeded initial threshold for Blitecast in all monitored locations. Accumulations of DSVs were

moderate to low in most sites. A 5 to 7-day fungicide program is appropriate at this time given

presence of pathogen in state. There is a chance of rain (~40%) for many areas of the state

tomorrow and later this week, with nights in the 50s (F) –weather which may promote late blight.

In order to help better understand the epidemic at hand, please submit samples to my lab or

work through your county agent and request that they send to me for genotyping. Even if a

sample has already been submitted from your county and determined to be US-23. All we need

to know is the county of sample origin. Identification of genotype at the county level would be

very helpful in improving our understanding of this epidemic and potential future risks. Lab

address is: Amanda Gevens, 1630 Linden Dr, Room 689, Plant Pathology Dept., University of

Wisconsin, Madison, WI 53706. Please send infected leaves in a slightly inflated ziplock bag

with no paper towel. Overnight shipping is best.

PDays and Early blight: P-Days have reached/surpassed the threshold of 300 in all plantings of

potato in WI. Fungicide applications for the management of early blight are recommended at

this time. Because of the dual risk of late and early blight, consider management options that

control against both diseases. Symptoms of early blight are advancing in lower and mid-plant

canopies throughout most of Wisconsin. In our early blight untreated control potato plots at the

Hancock Agricultural Research Station, we have roughly 60% disease severity at this time on

Russet Burbanks.

Cucurbit Downy Mildew: has been identified in Jefferson County Wisconsin in a commercial

field on melon and squash. No downy mildew has been observed, to date, on cucumber, or in

home gardens or our sentinel monitoring plots. In the past week, many states reported

cucurbit downy mildew including AL, GA, KY, MA, MI, NC, NJ, NY, PA, and WV. In

summary this year, AL, CT, DE, FL, GA, IN, KY, MD, MI, NC, NJ, NY, OH, PA, SC, TX, VA,

WV, and Ontario Canada have reported cucurbit downy mildew across multiple cucurbit hosts. I

will be keeping tabs on disease reports in the region and will provide updates in this newsletter.

No forecasted risk of movement of spores from states reporting detects to Wisconsin at this time.

Forecasts have the pathogen moving to the north and east of active sites at this time and we do

not have inoculum sources to our direct south or west. The website: http://cdm.ipmpipe.org/

offers up to date reports of cucurbit downy mildew and disease forecasting information.

Management information for cucurbit downy mildew can be found in UW Vegetable Crop

Updates – Disease Supplemental #8:

http://www.plantpath.wisc.edu/wivegdis/pdf/2013/Disease%20Supplement%208%20Aug%2013

%202013.pdf

Onion downy mildew has also been confirmed in a few areas of the state in the past week.

Onion Downy mildew can be very problematic in onion fields. This foliar disease is caused by a

fungus-like pathogen called Peronospora destructor. Infection is favored by temperatures less

than 72°F and high humidity and leaf wetness. The pathogen can overwinter in volunteer onion,

culls, and wild Allium weed species. Symptoms include pale or white elongated patches on

leaves that start off small and can elongate and produce a purple-gray sporulation which appears

“downy.” Leaves can bend over and eventually die due to severe downy mildew infection.

Please refer to picture below. This disease can impact bulb size, quality, and storability.

Management recommendations include practicing a 3+ year rotation to non-hosts such as small

grains and corn, eliminating culls and volunteers, avoiding dense planting, avoiding excess N

and overhead irrigation, and orienting rows parallel to prevailing wind to avoid prolonged leaf

wetness. Additionally, there are fungicides that can be effective for the management of onion

downy mildew. Effective fungicides for Downy mildew control include mancozeb (ie:

Dithane), azoxystrobin (Quadris, Amistar), pyraclostrobin (Cabrio), pyraclostrobin & boscalid

(Pristine), dimethomorph (Forum), mandipropamid (Revus), mefenoxam (Ridomil Gold),

phosetyl-aluminum (Aliette), fenamidone (Reason), and copper hydroxide (Kocide, Champ).

Although labeled for onion downy mildew, coppers and chlorothalonil are not very effective for

disease control, and coppers can be phytotoxic to onions. Please see the 2013 Wisconsin

Vegetable Production Guide A3422 for further details on application rates and specifications. If

you suspect you have Downy mildew in your onions, please get a sample and contact your

county agent, our disease diagnostic clinic, or myself for confirmation.

Downy mildew The 2013 A3422 Commercial Vegetable Production in

Wisconsin guide is available for purchase through the UW

Extension Learning Store website:

http://learningstore.uwex.edu/Commercial-Vegetable-

Production-in-Wisconsin2013-P540.aspx

A pdf of the document can be downloaded or is available at

the following direct link:

http://learningstore.uwex.edu/Assets/pdfs/A3422.pdf

Soil Science Update – Dr. Matt Ruark, Assistant Professor & Extension Soil Scientist, UW-

Madison, Dept. of Soil Science, 608-263-2889 (office), Email: mdruark@wisc.edu. Co-

authored by Mack Naber, Research Technician in Soil Science, UW-Madison.

Release of nitrogen from ESN during cool, mid-summer conditions: Questions have been

asked regarding if the unseasonably cool weather conditions occurring at the end of July would

have caused any issues with the performance of ESN. The release of nitrogen from ESN in Fig. 1

indicates that nitrogen release had stalled between 70 and 84 days after planting, which coincides

with a sharp decline in soil temperature. The release of N was determined by adding a known

amount of ESN to mesh bags and burying the bags in the potato hill. Every two weeks, a set of

mesh bags are collected and soil temperature was measured in the top 15 cm. The peak in the soil

temperature curve at day 40 coincided with canopy closure. For potato, it is expected that soil

temperatures will decline slightly and then remain steady until the canopy starts to sequence.

Total nitrogen release from ESN, based on previous experiments, was expected to have release

~90% of the nitrogen by day 80.

Looking at the prills pulled from the day 84 sample offers visual confirmation that some of the

nitrogen has not yet released. About a fourth of the day 84 ESN prills were hard and mostly full

of urea (Fig. 2). The difference between prills is visually striking. The empties, in the lower half

of the dish, are flat and desiccated. The ones at the top of the dish are round and smooth. This

would indicate even within the same soil environment, different prills are releasing N faster than

others.

Figure 1. Nitrogen

release from ESN and

soil temperature in a

Russet Burbank Potato

field. Error bars

represent standard

error

Figure 2. Picture of ESN prills in

mesh bag at 84 days after planting.

The top half of the circle contains

ESN prills full of urea, while the

bottom half contains empty ESN

coatings.

In a study tracking plant available nitrogen (PAN) in Russet Burbank Potato fields with and

without controlled-release fertilizer, ESN had slightly lower PAN concentrations in early June

compared to conventional fertilizer (Fig. 3). This would be expected, as ESN does not release as

much N into the soil environment at any one time. Measureable plant available nitrogen

decreased sharply following the heavy rainfall event on June 22 for both ESN and conventional

fertilizers. However, based on the measured release patterns of N from ESN, 30-40% of the N

remains protected in the polymer coating. It is also interesting to note that the conventional

managed field received multiple rescue applications of N, while the ESN field did not based on

petiole nitrate-N concentrations.

Organic Potato Meeting advertisements from Dr. Ruth Genger, UW-Department of Plant

Pathology

Potato variety trial field visits in Minnesota and North Dakota: Selecting varieties that are

adapted to your growing region, conditions and preferences can mean the difference between an

abundant, satisfying harvest or disappointment after lots of work and sweat! At two field visits in

Minnesota and North Dakota, Dr. Ruth Genger, from the University of Wisconsin-Madison, will

give an overview of 4 years of participatory variety selection on organic farms in the Upper

Midwest. We will view potato plots including varieties from Seed Savers Exchange, and talk

about opportunities to participate in potato variety selection in your farm or garden. Come join

us, and share your questions, experiences and ideas about potato production and variety

selection.

In Minnesota: Wednesday Aug 21, at Paradox Farm, 11643 State Hwy 78, Ashby, MN 56309.

Potluck lunch at 1:30 pm; variety trial tour, presentation and discussion from 3-4 pm.

Paradox Farm is located right off state highway 78, 10 miles south of Battle Lake and seven

miles north of Ashby. For more information: Sue Wika at paradoxhomestead@gmail.com or

218.747.2202

In North Dakota: Friday Aug 23, Dragonfly Garden, United Tribes Technical College, Bismarck,

ND. The Dragonfly Garden is located at the end of Burleigh Avenue, adjacent to the airport

fence-line. Time: TBA. For more information: Colette Wolf at cwolf@uttc.edu or 701.255.3285

ext. 1426

Figure 3. Plant available

nitrogen (which includes

both ammonium-N and

nitrate-N) in the top 6 inches

of a Russet Burbank Potato

hill before and after a large

rain event in fields fertilizer

with and without ESN.