Steve Poppe, Horticulture Scientist

Emily Hoover, Dept Head/Professor

Andy Petran and Jack Tillman, Graduate Students

Emily Tepe, Research Associate

Esther Jordan, Communications Specialist

University of Minnesota Day-neutral Low Tunnel

Strawberry Project

Background

• Strawberries are an important part of a healthy diet

• Short MN growing season

• Day-neutral cultivars available to extend strawberry harvest

• Use of organic production methods

• Funding provided by the North American Strawberry Growers Association (NASGA) and the

MN Dept. of Ag, MN Specialty Crop Block Grant

Long Term Impacts:

• Extend the harvest season and increase yields

• Aim to enhance profits

• Increase supply of locally produced organic strawberries

• Fruit available during a non-traditional time

Why Low Tunnels instead of High Tunnels

In high tunnels:

• Space not used efficiently due to strawberry plant stature

• Increased incidence of diseases and insects

• Wind and snow damage

• Temperature gradient high between inside and outside

2015-2016 Project Objectives

• Grow Albion day-neutral strawberry plants on a raised bed in an open field vs. in a low tunnel system

• Develop recommendations for nitrogen requirements

• Evaluate production, fruit quality, pest, weed and disease management throughout the season

• Educate and develop more strawberry growers in the upper Midwest region

2015 Summary: Morris Albion yield and berry weight

Treatment Fertility RateAverage Yield/Plant (lb)

Average Yield/Acre (lb)

Average Berry Weight (g)

Low Tunnel

0x 1 ab 18450 ab 11.4 ab

0.5x 0.75 c 13710 c 9.2 c

1x 0.82 bc 14991 bc 9.8 bc

1.5x 1.12 a 20446 a 11.9 a

1-0x 0.94 abc 17228 abc 10.5 abc

No Low Tunnel

0x 0.95 17278 10.1

0.5x 0.86 15687 10.1

1x 1 18414 10.3

1.5x 0.92 16828 9.7

1-0x 0.9 16467 9.4

2015 Summary: St. Paul Albion yield and berry weight

Treatment Fertility RateAverage Yield/Plant (lb)

Average Yield/Acre (lb)

Average Berry Weight (g)

Low Tunnel

0x 0.78 13263 10.1

0.5x 0.76 13933 10.9

1x 0.71 12991 8.8

1.5x 0.79 14393 10.7

1-0x 0.91 15493 9.6

No Low Tunnel

0x 0.55 b 9933 b 10.3

0.5x 0.79 ab 14330 ab 10.4

1x 0.61 ab 11081 ab 9.7

1.5x 0.61 ab 11164 ab 9.6

1-0x 0.85 a 15493 a 9.8

Harvest

• Strawberry flowers removed 3 times

• Removed strawberry runners 3 times during the growing season

• Typically, harvest begins around the 3rd or 4th week of July

• Picked fruit until mid October

A Noticeably Sweet Berry

• Brix is a measure of total soluble solids

• Albion has relatively high brix compared to other day-neutrals

• Our 2013 June-bearing variety trial had an average brix level of 7.7

• Brix content more influenced by harvest date than fertility of tunnel presence (St Paul)

Brix Content, St Paul 2015

8.20.15

LT

0x 6.45

0.5x 8.01

1x 7.15

1.5x 6.73

1-0x 6.63

PL

0x 6.96

0.5x 7.24

1x 7.31

1.5x 7.01

1-0x 6.45

9.10.15

LT

0x 5.40

0.5x 5.45

1x 5.75

1.5x 5.54

1-0x 5.55

PL

0x 5.11

0.5x 5.83

1x 5.68

1.5x 6.06

1-0x 5.88

10.19.15

LT

0x 10.68

0.5x 11.08

1x 10.51

1.5x 9.52

1-0x 10.33

PL

0x 10.33

0.5x 9.24

1x 10.89

1.5x 9.93

1-0x 10.92

Temperature and Humidity

• Temperature and humidity recorded in the low tunnel and non-low tunnel beds

• Data loggers suspended 12 inches above both beds

Temperature and Humidity

2013 2014 2015

Low tunnel Non-low tunnel

Low tunnel

Non-low tunnel

LowTunnel

Non-lowTunnel

Average temperature

71.3 F 68.2 F 64.6 F 63.6 F 67.3 F 66.2 F

Average relative humidity

82.4% 74.1% 78.2% 70.7% 81.7% 56.1%

Average due point

63.5 57.8 56.4 51.8 60.3 54.9

Variable costs

Total low tunnel

Treatmentper 100'

Fertilizer $70 $11.67

Pesticides $17 $2.78

Plants $125/1000 (w/o

shipping)

approx. 17,500

plants/acre$25.00

Irrigation - drip tape $13/acre $2.22

Mulch - Plastic (white on black) $112.00/9600’ of row $5.00

1.5 mil Clear Film Roll $176.00/1640” $11.00

Galvanized Steel Hoops placed

every 5” (Quantity: 20)$3.98 $79.60

Straw (for walkways) $56.00 $9.33

Hoops for beginning and end of

each row, anchor pipe, steel stakes

to anchor hoops and elastic bungee

53.44

Tractor Fuel (tillage, bed prep,

plastic laying)

approx. 1 gallon/hour

approx. 20 hours

per acre,

$3.50/gallon

$3.50

1 lb. plastic qt. containers

$0.05

approx. 1 lb per

plant & 200 plants

per 100' row

$10.00

Total costs (variable + fixed)$213.54

Expenses (labor not included)

Projected Profit

Projected profit based on 2015 data

Average total yield/plant 0.831 lbs

Estimated marketable yield/plant (15% loss) 0.706 lbs

Average marketable yield/100’ row 141.2 lbs

Average selling price/pound X $5.00

Gross profit/100’ row = $706.00

10 hrs labor to pick 100’ row x $9.50/hr - $95.00

Total costs (variable and fixed, from last slide) - $213.54

Net profit/100’ row = $397.46

1 acre (660’ x 66’) ≈ 72.6 100’ rows*

Net profit/acre $28,855.60

* 6’ row spacing

Low Tunnel Construction and Planting Steps- 2015

Materials needed:

• Bed shaper

• Mulch machine

• 4 foot wide, 1 mil white on black plastic mulch

• Drip tape irrigation

• Dormant day-neutral strawberry plants

Creating a Raised Bed

Creating a Raised Bed

• Once the bed is created, a 4 foot wide 1 mil white on black plastic mulch is placed on top of the bed

• The dry wheel puncher makes small holes in the plastic to act as a guide for proper plant spacing

Creating a Raised Bed

Planting

• Row spacing was 14 inches between rows, and 12 inches between plants in a staggered row

• Use a 1 inch x 12 inch wooden plant stake to transplant

• Place the blunt end of the wood plant stake at the tip of the roots and insert the transplant into the ground

Low Tunnel Support

Use pipe to anchor plastic hoop at the beginning and end of each row

Installing hoops and anchor stakes

Installing Tunnel Plastic

1.5 mil clear film roll

Securing Plastic Hoop with Elastic Bungee

Fertilizer Injector

• At grower sites, fertilizer applied through Ez-Flo injector

• Applied AgGrand 4-3-3 water soluble organic fertilizer through drip tape

Fertilizer Treatments

• Chilean Nitrate, organic

fertilizer, 16-0-0

• Perforated centrifuge tubes

‘planted’ in the soil next to

each plant

• Fertilizer solutions were

mixed for each treatment in

another centrifuge tube

• One ounce of solution is

poured into each perforated

tube beside each plant using

this funnel device

Spotted Wing Drosophila (SWD)

• Very few, if any, SWD were detected in our traps at the Morris or St. Paul sites in 2013, 2014, or 2015.

• Applied Oxidate (OMRI Approved) for control at 1 oz./1 gallon water on a weekly basis at the Morris site

Spotted Wing Drosophila Traps

• Clear plastic quart-size cup, with lid

• Drilled 3/16” holes around the cup • Wire handle inserted into the sides • Yellow sticky traps inside the lid • Trap cups monitored weekly • New bait each week

Recipe for SWD trap bait:• 12 fl oz water• 4 T sugar• 1 T active dry yeast• 1 T apple cider vinegar• 1-2 T whole wheat flour

Tarnished Plant Bug• Damage occurs when the insects use

their sucking mouthparts to “drink” the sugars out of developing fruit

• Results in distorted, cat-faced berries at maturity

• Pressure was noticeably higher in 2015 than in 2013-2014 leading to a reduction in total and marketable yields

• Present in both low tunnel and non-low tunnel treatments, however the damage was more severe in the non-low tunnel in early season at St. Paul

• At both sites a variety of organic insecticides were applied on a weekly basis

• Insecticides used were Mycotrol, Purespray Green, Pyganic and Oxidate

Strawberry Leaf Spot

• Infection is a continuous process with older lesions producing spores to infect young leaves during each season

• Spores are carried to new leaves by rain splash causing the disease cycle to begin again

• More prevalent on the non-low tunnel plant leaves versus the low tunnel

Strawberry Leaf Spot Control

• Most organic fungicides and biocontrol agents are not highly effective against overall disease complex on strawberry

• Products containing sulfur or copper have little or no activity against most leaf spot diseases

• In order to apply sufficient copper to obtain control, the potential for plant injury is probably unacceptable

• Emphasis for controlling these diseases should be placed on selection and use of disease resistant cultivars

New alternative disease control materials for strawberries.

• Messenger

• Oxidate

• Trilogy

• Trichodex

Many of these products have great potential but under moderate to high disease pressure effectiveness is uncertain.

Information taken from Organic Small Fruit Disease Management Guidelines-Ohio State University

Iron Chlorosis Issue

• Chlorosis in day-neutral cultivars due to high soil pH

• Yellow foliage indicates a lack of chlorophyll, the green pigment responsible for photosynthesis (sugar production) in plants

• This photo shows chlorosis on plants that are planted in a soil that measured 7.6 pH

• We have determined that these newer day-neutral cultivars will grow successfully in soils that have a pH of 7.3 or lower

Dubois Retractable Tunnel System Advantages

• No wind damage issues

• Faster/simpler to install as compared to our original system

• Less costly than original system

Concerns

• Slight tearing of hoop plastic

• Our original 4 mil thick plastic provided better heat retention in October

• Sides tend to roll down

What We Learned

• Skillful management required throughout entire growing season

• Fertility: Need 2nd year of data to make conclusions

• Multiple cultivars is better

• Faster installation of Dubois retractable tunnel system

• Insect and disease pressures posed significant challenges in 2015

… this has the potential as a real production system

Special thanks to Nourse Farms for donating strawberry plants for the 2015 trial season

Portola

University of Minnesota West Central Research and Outreach Center

Morris, MN

Steve Poppe

Horticulture Scientist

poppesr@morris.umn.edu

Andy Petran

Graduate Student

petra057@umn.edu

For more information visit our low tunnel blog

http://fruit.cfans.umn.eduAlbion