Dennis Martin's 2020 OTRD Presentation

1. Effect of Mowing Timing and
Frequency on Green
Antelopehorn Milkweed in
Oklahoma Highway Right-of-Way
Dennis Martin, PhD
Professor, Turf & Vegetation
Management Specialist

3. Research conducted under Task 4 of 4 as part
of Joint ODOT-OSU Item 2157: Roadside
Vegetation Management Research Project
during 2016-2019.
Training & Implementation under Task 1 & 3 of
Joint ODOT-OSU Item 2156: RVM Training &
Consultation
Funding for this task was from ODOT SP&R as
well as wages and in-kind matched with OSU
Horticulture & Landscape Architecture and
OSU Integrative Biology Departments

4. Purpose
• To conduct research that generates knowledge that
contributes to an ever developing strategy for
management of non-clear zone right-of-way areas
• Integration of new and existing knowledge into
management programs that 1) promote a
functional and affordably managed vegetation
community consistent with soil stabilization, safety
and beautification goals and that 2) promote
monarch, pollinator and invertebrate habitat

6. MILKWEED
SPECIES
Image shows green antelopehornmilkweed
in flower.

7. Winter monarch butterfly surface area
count in Mexico from 1994 - 2019

8. Monarch eggs on milkweed
-Eggs hatch in ~3 to 5 days

9. Monarchcaterpillars at 1st instarlarvalstage
-There will be 5 instar larval stages with a shedding of skin
between each stage – 10 to 14 days in larval stage in total

10. Fifth instar of monarchlarvae

11. Chrysalis stage – pupation from larval
to adult stage takes 10 to 14 days

12. The evening prior to emergence, the chrysalis
turns clear and the features of the butterfly
become visible

13. Butterfly emerging (eclosure) from chrysalis –
generally they emerge in early to mid morning but
occasionally in early afternoon.

17. • In 2016 ODOT staff began a program aimed at
reducing mowing of areas outside of the
clear/safety zone (except when and where
necessary) until July in order to reduce mowing
maintenance costs and to protect milkweed and
nectaring plants for the benefit of monarch
butterflies and other pollinators.
• ODOT Chief Engineer Mr. Casey Shell along with
leaders of six other state DOTs, signed a
memorandum of understanding unofficially naming
I-35 the Monarch Highway in 2016

19. Management of the clear/safety zone doesn’t have to change. The focus for pollinator
habitat is on the area outside of the clear/safety zone

20. From 1993 ODOT Mowing Manual

22. Objectives
• To investigate right-of-way mowing
timing/frequency events* on the presence of
emerged milkweed in Oklahoma
• *in non-clear zone roadside areas
• Provide training and consultation to ODOT field
managers to assist them integrating findings of the
work into existing ODOT RVM Programs

23. Mowing regimetreatments
• 1) non-mowed
• 2) mowed four times per year (traditional = week
prior to Memorial Day, 4th of July, Labor Day and
late fall)
• 3) mowed in mid-July only
• 4) mowed in mid-July and late fall only
• 5) mowed in late fall only
• 6) mowed in mid-June [added in 2018] and late fall
only

24. Rangeof milkweed plot sites 2015 - 2020

25. Dennis Martin,
Principle Investigator

28. It’s especially important to leave
milkweed and habitat in place when
eggs, larvae or chrysalii are present!

31. Poorly timedmowingof monarch andpollinator
habitat has catastrophic consequences

32. A few September/October
nectaring options

33. Findings are highly variable depending upon weather conditions each year.
During a drought, both milkweed abundance and nectaring plant abundance are drastically
and negatively affected.
During a drought and with greatly reduced milkweednumbers, monarcheggs and larvae
found on Oklahoma roadsidesthroughout the growing season are greatly reduced.
Poorlytimed mowing during peak egg laying in April or May would result in mow-down
of milkweed plants and destruction of monarch eggs and larvae and reduces available
nectaring plants.
Mowing in July only or July and after growing season does help regenerate milkweed plants
if soil moisture is properin mid and late summerBUT it reduces nectaring plants in
mid-summerand late summer.
When soil moisture is adequate - In high quality habitat with milkweeds and nectaring
plants, not mowing duringApril – October allows for normal milkweedavailability in spring,
BUT reduces milkweed availabilityin late summerbut increases availabilityof a range of
nectaring plants throughout the growingseason.
Summary of Findings

34. 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
traditional mid-July non-mowed
#BloomingForbSpecies
Treatment
early June
mid July
early Sept
2017 Blooming nectaring plants per 11 sq. m as a function of survey date and mowing
timing

35. Mean percent (± SE) of milkweed plants remaining in subplots in June (A) and August
(B) 2019 relative to the number of milkweed plants present in each subplot in May.
0
5
10
15
20
PercentMilkweedRemaining Treatment
A B

36. Number of monarch eggs and instars collected across eight sites that were identified
following contour mowing from late August through September 2017. The total number of
green antelopehornmilkweed (A. viridis) plantswithin sites that were checked for monarchs is
indicatedabovethe dates. The decline in plantsover time reflects plant senescence.

37. Implementation

38. OKMP3

39. Okies for Monarchs BMP Guides

40. Management of the clear/safety zone doesn’t have to change. The focus for pollinator
habitat is on the area outside of the clear/safety zone

41. Recommendationsfor non-clearzone areas
• Johnsongrass is not high quality habitat and when left unmowed
and seeding outside the clear zone it threatens degradation of
additional areas – it needs to be controlled
• Some areas outside clear zone are not suitable monarch habitat
either due to low density of nectaring plants or milkweed – these
areas are options for replanting with a diverse plant community
• In high quality habitat create two types of regimes:
• Regime 1 - To maximize milkweed regrowth in late
July/August/September, there must be good soil moisture AND
regrowth is aided by July mowing – but this reduces July nectaring
plants and late summer nectaring plants
• Regime 2 – No mowing from April 1 – November 1 (or post freeze)
• When feasible, move the late/summer or fall clean up mowing of
non-clear zone areas to at least October 15th and its better if
placed after frost

42. WiperTechnology
• Strategically place a herbicide by wiping onto taller
target weeds that have foliage above the foliage
layer of the desired plant material to be preserved.

46. Acknowledgements
• Project 2156 and 2157 funding from the FHWA and ODOT
• Appreciation of SP&R ODOT Personnel
• ODOT Division 4 – Perry, OK Personnel
• Dr. Kristen Baum, OSU
• Dr. Dwayne Elmore, OSU
• Amanda Alexander, Kait Taylor, Vonceil Harmon, ODOT
• Present and former students/staff of Dr. Kristen Baum’s Lab:
Michael Caballero, Teri Cocke, Emily Geest, Ashley Knoch,
Alex Webb.
• Present and former staff of Dennis Martin’s Lab: Lydia
Calhoun, Andrea Connally, David Gerken, Clayton Hurst,
Caroline Nelson, Jimmie Underwood

47. Contact:
Dennis Martin
Oklahoma State University
Phone:405.744.5419
Email:dennis.martin@okstate.edu