Algae (and similar weeds) Control and
Products Comparison
Chris Marble
University of Florida/IFAS
Mid-Florida Research and Education Center
What are algae?
• Primitive plants, lack true roots, leaves and stems but
contain chlorophyll
• Very diverse group of simple plants
• Microscopic to giant kelp (over 100 ft. in length)
• Most grow by photosynthesis, some can grow in the dark
using sugar or starch for energy
• Many forms and colors
• Green film on almost any surface
Photo credit: The Royal Horticultural Society
Where does it come from?
• Cells and spores are found virtually everywhere
• Irrigation water is most common source
• Especially if from surface water (pond) or shallow well
• Dust from outdoor growing media
• Primarily reproduce vegetatively by single cell
division or sexually via zoospores (mobile spores)
How it starts
• First seen as a slight green haze on plant media or
other surface
• Grows thicker and can develop a black color
• When water is reduced, thick black layer becomes
hydrophobic
Image credit: Premiere Tech Horticulture: pthorticulture.com
What problems does it cause?
• Causes buildups on the inside walls of pipes
• Doesn’t reduce crop growth (directly) but…
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•
•
•
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Slow gas exchange in growing media (slows root growth)
Attracts fungus gnats, flies, other insects and pests
Safety hazard (slippery)
Reduces light when on glass greenhouses
Can reduce amount of water and nutrients that reach
plant roots
• Aesthetic damage
What problems does it cause?
http://blogs.plos.org/thestudentblog/files/2013/09/eutrophication.gif
http://en.wikipedia.org/wiki/Algal_bloom
Nostoc spp. (aka ground boogers)
• Classified as a cyanobacterium inhibits terrestrial and aquatic
sites
• Green, globby, slimy
• Forms a coating over its surface
• Tolerates drought (some species
found in desert environments into
Artic regions)
• Resumes growth when water is
reintroduced
• Chemical resistant
Oregon State is researching control methods. See
“Nasty Nostoc” by Heather Stoven and Jennifer
Parke (Oregon State University Extension) for more
information.
http://c.ymcdn.com/sites/www.oan.org/resource/r
esmgr/Digger2/Digger_201406_Nostoc.pdf.
Nostoc spp.
• Conduct photosynthesis
• Nitrogen fixation
• Actually used to improve nutrient deficient soils in some crops
Michigan State University has also researched control methods.
Visit:
http://msue.anr.msu.edu/news/nursery_growers_should_watch_for
_blue_green_algae_in_container_growing_area.
Photo Credit: Thomas A. Dudek, Michigan State University Extension
Nostoc spp.
• Very slippery when wet
• Grow on compacted soils, container ground pads,
driveways, walkways, gravel, etc.
• Typically not in growing media
• Little is known on factors leading to its occurrence in
nurseries
Nostoc spp.
• Favored by high pH soils (8 or above)
• Favored by high phosphorus content
• Via runoff or from soil concentrations
• Needs moisture
http://en.wikipedia.org/wiki/Nostoc_commune
Moss
• Small flowerless plants, typically grow in
dense green clumps or mats
• Soft, tuft-like feel
• Non-vascular (no xylem or phloem)
• Can’t transport nutrients
• Spread by spores (sexually) and asexually
(vegetatively) through fragmentation
"Taiwan 2009 JinGuaShi Historic Gold Mine Moss
Covered Retaining Wall FRD 8940" by Fred Hsu on
en.wikipedia
Liverwort
• Green, mat-forming non-vascular plant
• Spreads by spores (spread by air currents)
• Asexual reproduction occurs through small clonal fragments
call “gemmae” which form in cups
• Spread by splashing irrigation water, etc.
Liverwort Problems
• Extremely fast grower, spreads quickly throughout
greenhouses, shadehouses, etc.
• Prevents water/nutrients from reaching plant roots
• Much more competitive for water/nutrients
Common Denominators
• All of these weeds prefer….
• Moist environments
• Moderate to low light levels (under
plant canopies)
• Humid environments
• Most like high nutrient levels
• Usually worse on slower crops
• Exception is liverwort
Emma Lookabaugh, Bugwood.org
Cultural Control Practices
• Reduce excessive moisture from improper irrigation
practices
• Avoid overwatering slow growing plants or plants
early in production cycle
• Ensure media surface dries between irrigations
Matthew Chappell, University of Georgia, Bugwood.org
Determine Distribution Uniformity
• Place straight sides cups or
rain gauges on a grid
pattern in area
• Run irrigation as usual
• After cycle, record water in
each cup
• Each cup should have
about the same amount
Tennessee Master Nursery Program: Irrigation Module 1 of 2
Quick Method of Checking Distribution
Step 1: Catch Can Readings (mm):
25
15
20
10
15
20
25
28
22
18
17
10
14
7
18
19
14
12
9
18
16
15
23
13
22
Order can results from smallest to
largest reading:
7, 9, 10, 10, 12, 13, 14, 14, 15, 15, 15,
16, 17, 18, 18, 18, 19, 20, 20, 22, 22,
23, 25, 25, 28
Step 2: Take the lowest 25% can
readings (in this example lowest 6
readings) and find the average. In
this case, the average is 10.2.
Then, find the average for all cans.
The average for all 25 readings is
17.0.
Step 3: Calculate DU with equation:
DU = (avg. low 25% cans )/(avg. all cans)
DU = 10.2/17.0 = 0.6 or 60%
Cultural Control Practices
• Keep site clean of plant debris, spilled substrates, weeds
• Wipe down tools, benches, etc. with disinfectant
• Increase horizontal airflow
Fertilizer Management
• Ensure you are not over-fertilizing your crops
• Avoid excessive leaching of nutrients
• Fertilizer placement:
• Topdressing is the best method to INCREASE growth of
liverwort and other primitive weeds (James Altland,
USDA-ARS Wooster, OH)
• Dibbling dramatically improves weed control, but…
• Some crops sensitive to dibble
Media management
• Substrates that favor algae, liverwort, moss growth:
• Peatmoss, choir, compost, sawdust, fine bark
• Substrates that reduce growth:
• Coarse bark, pumice, perlite, vermiculite, etc. (James
Altland, USDA-ARS, Wooster, OH)
Algae (and similar weeds) Chemical
Controls and Products Comparisons
Chemical Controls
• What do all of these weeds have in common?
Photo credit: The Royal Horticultural Society
MossBuster.com
No/limited vascular systems
Chemical Controls
• Most systemic herbicides will have very little effect
• RoundUp, etc.
• What products are effective?
• Typically Contact Herbicides
• Specialty products
Reward® (Diquat)
• Fast-acting; visible results in
24-36 hrs.
• Only affects part of the plant
contacted
• Need complete coverage
• Needs a surfactant
• Use beneath benches and on
floors
• REI: 24 hrs.
Scythe® (pelargonic acid)
• Begins working within hours
• Only controls green vegetation
• Does not injure mature, nongreen woody stems
• Uniform coverage is needed
• Can be used in the greenhouse
• REI: 24 hrs
Axxe®/Racer™ (ammonium nonanoate)
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Contact, fast-acting; burndown in 1 to 2 hours
Only controls green vegetation
Can be used in and around all crops as directed application
OMRI (organic) listed
Good control of mosses and liverworts
REI 24 hours
Acetic Acid Products
• Have been shown to be very effective for liverwort
and some algae (Altland, 2009)
• Only use products labeled as herbicides
• REI typically 48 hrs.
Green-Shield, Physan 20, KleenGrow
(Quaternary ammonium)
• Labeled for fungal, bacterial, and algae
• Apply to floors, walls, benches, tools, pots, flats
• Physan 20 labeled for use on seeds, cut flowers, and
plants
• Read labels closely
• Contact with organic matter will deactivate
• Pre-clean all surfaces before use (dislodge any organic
matter)
ZeroTol 2.0
(Hydroden dioxide + Peroxyacetic Acid)
• Fungicide, bactericide, algaecide
• Labeled for use on ornamental plants and turf
• Can be used on bedding plants, woodies, roses,
poinsettia, ornamentals, trees, turf, bulbs, etc.
• All surfaces should be wet before application
• Can be used on benches, pots, floors, equipment
• Do not store and reuse the spray
• REI 1 hour
GreenClean Pro, TerraCyte
(Sodium Carbonate Peroxyhydrate)
• Granular algaecide
• Must be activated with water
• Apply to wet surfaces or water soon after application
• Can be used in ponds, lakes, etc.
• Undiluted granules will burn ornamentals; rinse off of
foliage
• Repeated applications likely needed
• REI of 4 hour
Moss Control
• Quicksilver T&O (carfentrazone)
• Labeled for control of moss (Silvery thread moss) in
turfgrass
• Also controls black medic, henbit, FL pusley, pigweed,
and other broadleaf weeds
• Symptoms appear in 24 hrs. or less
Liverwort Efficacy Trials
Liverwort coverage/growth stage at time of treatment.
• Products applied to liverwort and azaleas (OTT) twice (8 weeks apart)
• Avenger AG (d-limonene or citrus oil)
• Bryophyter (Oregano oil)
• Racer (ammonium nonanoate)
• Received either no irrigation or 0.25 in. immediately after treatment
• Yes = irrigated; No = no irrigation
Liverwort Efficacy – 1 week after treatment
Avenger Ag – 14% Yes
Avenger Ag – 14% No
Avenger Ag – 28% Yes
Oregano oil – 1% Yes
Oregano oil – 1% No
Oregano oil – 2% Yes
Racer – 3% Yes
Racer – 3% No
Racer– 6% Yes
Non-treated
Avenger Ag – 28% No
Oregano oil – 2% No
Racer – 6% No
Liverwort Efficacy – 8 WAT
Non-treated
1)14% YES 2)14% NO 3)28% YES 4)28% NO
Avenger Ag
1)1% YES 2)1% NO
3)2% YES
Oregano oil
4)2% NO
1)3% YES
2)3% NO
3)6% YES 4)6% NO
Racer
Liverwort Efficacy – 8 weeks after
second treatment (8 WAT2)
Non-treated
1)14% YES 2)14% NO 3)28% YES 4)28% NO
Avenger Ag
1)1% YES 2)1% NO
3)2% YES
Oregano oil
4)2% NO
1)3% YES
2)3% NO
Racer
3)6% YES 4)6% NO
Azalea Tolerance – 4 WAT
Non-treated
1)14% YES 2)14% NO 3)28% YES 4)28% NO
Avenger Ag
1)1% YES 2)1% NO
3)2% YES
Oregano oil
4)2% NO
1)3% YES
2)3% NO
3)6% YES 4)6% NO
Racer
Azalea Tolerance – 4 WAT2
Non-treated
1)14% YES 2)14% NO 3)28% YES 4)28% NO
Avenger Ag
1)1% YES 2)1% NO
3)2% YES
Oregano oil
4)2% NO
1)3% YES
2)3% NO
3)6% YES 4)6% NO
Racer
Other Trials
Bryophyter 1.0%
Tower 1.5 lbs aia
Bryophyter 2.0%
Tower 3.0 lbs aia
Champ 5.5 lbs/100 gal
Champ 11.0 lbs/ 100 gal
SureGuard 0.375 lbs aia
SureGuard 0.75 lbs aia
Control
140 Days after treatment
Nostoc efficacy trials
• Herbicides:
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Reward
Axxe
Marengo
GreenShield
Zerotol
TerraCyte
Copper sulfate
Control
Nostoc Health Rating (0 – 10)
10
9
8
7
6
5
4
3
2
1
0
1 WAT
4 WAT
Other effective methods:
• Solarization (empty greenhouse)
• Flame control
• Mulching (coarse materials)
• Preemergents
• Flumioxazin (Broadstar, SureGuard)
• Oxadiazon (Ronstar)
• Oxyfluorfen + oryzalin (Rout 3G)
Bottom Line
• Focus on cultural practices
• Control these weeds from the source
• Start early!
• Repeated applications will be needed
QUESTIONS