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Biological Calendars:Using Degree-Days and Plant Phenology to
Predict Pest Activity
Dan Herms
Department of EntomologyThe Ohio State University
Ohio Agricultural Research and Development CenterWooster
Landscapes and nurseries are diverse ecosystems
Objectives:
1. Degree-days2. Phenology and biological calendars3. OSU Phenology Garden Network4. National Phenology Network
Development rate of plants and insects is temperature dependent.
Daily temperature readings can be used to calculate growing degree-days, which is a measure of accumulated heat.
Degree - Day:
Amount of heat accumulated over a specified base temperature during a 24 hour day.
Base Temperature:
• Temperature above which degree-day accumulation is calculated.
• Ideally, the lower temperature threshold.
Lower Temperature Threshold:
Temperature below which no growth or development occurs in the species of interest.
Cumulative Degree - Days:
Number of degree-days accumulated during a specified time interval (i.e. since the beginning of the year).
Key Point:
Degree-days only have meaning if base temperature and starting date are specified.
Calculating Degree-Days
• Average method
• Modified average method
• Modified sine wave
70 + 40
2 =- 50 5 DD
Average Method:
DD = Avg Temp – Base Temp
Max = 70, Min = 40
Modified Average Method:
When minimum temperature drops below basetemperature, set minimum = base temp.
More accurate when minimum drops below base.
70 + 40
2
Modified Average Method:
=- 50 5 DD
70 + 50
2 =- 50 10 DD
Average Method:
Max = 70, Min = 40
Modified Sine Wave Method:
Limitations of Degree-Day Models:
• Insect response to temperature is not linear.
• Lower temperature threshold known for very few species.
• Measured temperatures not the same as those experienced by the pest.
• Degree-days are cumbersome to track.
Since plant development is temperature-dependent, phenological events of plants can also be used to track degree-days…
and predict pest development.
Phenology: The study of recurring biological events.
“The oldest science.”
Hypothesis: the flowering sequence of ornamental plants can be used as a biological calendar to predict pest activity and schedule pest management appointments.
The hypothesis was tested in Secrest Arboretum by monitoring over the past 7 years:
1. The phenology of 45 key arthropod pests of ornamental plants (e.g. egg hatch, adult emergence).
2. The flowering sequence of 75 taxa of woody ornamental plants.
First bloom: date first flower on the plant opens to reveal pistils and / or stamens.
Full bloom: date 95% of flowers have opened (e.g. 1 out of 20 buds remains closed).
Key Phenological Events
The flowering sequence of plants can be used as a biological calendar to track degree-days and schedule pest management appointments.
S. G
age, Michigan S
tate Univ. D.G. Nielsen, Ohio State Univ.
Phenological Sequence for Secrest Arboretum
Species Event Degree-Days
Red Maple first bloom 45Eastern Tent Caterpillar egg hatch 92Eastern Redbud first bloom 197Gypsy Moth egg hatch 203Snowdrift Crabapple first bloom 214Birch Leafminer adult emergence 231Common Lilac first bloom 238Pine Needle Scale egg hatch 301Vanhoutte Spirea first bloom 309Lilac Borer adult emergence 336Black Cherry first bloom 376Euonymus Scale egg hatch 463Black Locust first bloom 503Bronze Birch Borer adult emergence 519Mountain-laurel first bloom 565Juniper Scale egg hatch 579Littleleaf Linden first bloom 878Japanese Beetle adult emergence 966
Red maple, Acer rubrum
Corneliancherry Dogwood, Cornus mas
Star Magnolia, Magnolia stellata
Border Forsythia, Forsythia x intermedia
Eastern tent caterpillar egg hatch
Saucer Magnolia, Magnolia soulangiana
Bradford Callery Pear, Pyrus calleryana ‘Bradford’
European pine sawfly egg hatch
PJM Rhododendron, Rhododendron x ‘PJM’
Serviceberry, Amelanchier grandiflora
Spruce spider mite egg hatch
Redbud, Cercis canadensis
Gypsy moth egg hatch
Crabapple, Malus spp.
Common lilac, Syringa vulgaris
Pine needle scale egg hatch
When red buckeye (Aesculus pavia) blooms:
Hummingbirds return
Black cherry, Prunus serotina
Optimal timing for aerial Bt applicationsfor gypsy moth
Miss Kim Lilac, Syringa patula ‘ Miss Kim’
Oystershell scale egg hatch
Black locust, Robinia pseudoacacia
Bronze birch borer adult emergence
Littleleaf Linden, Tilia cordata
Egg hatch of soft scales
Key premise: phenological sequence remains constant from year-to-year.
http://www.oardc.ohio-state.edu/gdd
How accurate is a biological calendar developed in one region
when it is used in another?
We’ll soon find out.
The OSU Phenology Garden Network
Coordinators:
Denise Ellsworth Summit County Extension
Dan HermsOARDC
The concept: a state-wide network of identical gardens toquantify geographic patterns of phenological and climaticvariation across Ohio.
Objective: create a standardized biological calendar
Research: document short-term phenological and weather variation; long-term climate change.
Outreach: predict pest emergence / fine-tune timing recommendations.
Science Literacy: increase public awareness / involvement with “the world’s oldest science”.
Education: provide infrastructure for experimentation and demonstration projects.
The Biological Calendar
Species First Bloom (DD50)Star Magnolia 83Forsythia 86 PJM Rhododendron 147Koreanspice Viburnum 185Coralburst Crabapple 217Common Lilac 234Vanhoutte Spirea 309Redosier Dogwood 326Miss Kim Lilac 423Bush Cinquefoil 445 Red Prince Weigela 446Arrowwood Viburnum 534Bumald Spirea 624Elderberry 707Oakleaf Hydrangea 835Rose-of-Sharon 1347
Additional applications:
Butterfly garden and phenology (when do monarchs return?)
Bird / wildflower / mushroom phenology (when should I look for trilliums; hunt for morels?)
Weed phenology (forsythia and crabgrass?)
Frost-free dates (Vanhoutte Spirea?)
Planting dates (forsythia and radish; lilac and beans?)
Plant propagation (when to take cuttings?)
Others?
Protocols:
1. Monitor plants regularly to record date of first and full (95%) bloom, and number of cumulative degree-days.
2. Enter data promptly at website.
3. Record and share your experiences.
4. Be creative.
5. Have fun!
Cooperating Nurseries:
Cottage Gardens
Herman Losely & Son
Klyn Nurseries
Roemer Nursery
Studebaker Nurseries
Sunleaf Nursery
Willoway Nurseries
The National Phenology Network
www.npn.uwm.edu
Coordinator:
Dr. Mark Schwartz
University of Wisconsin Milwaukee
Facilitate collection and dissemination of plant phenological data across the US
Support research on interactions between plants and lower atmosphere, and long-term impacts of climate change.
National Phenology Network Mission
NPN: Lilac Observations
Syringa chinensis 'Red Rothomagensis'
Lilac Phenological Observations:
1. First leaf
2. 95% leaf
3. First bloom
4. Full bloom
5. End bloom
www.npn.uwm.edu
First Leaf
widest part of leaf past tips of brown
bud scales
Full Leaf
95% of buds open
First Bloom
at least 50% of flower clusters on the plant have
at least one open bud
at least 50% of flower clusters have all buds
open
Full Bloom
End of Bloom
95% of flowers have withered or dried and floral display has ended.
End of Talk
95% of attention spans have withered or dried and PowerPoint display has ended.
