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Ecologically Based Managementof Salt Cedar
K. George BeckBioag Science & Pest Management
Colorado State University
References
• Sheley, R.L., T.J. Svejcar, & B.D. Maxwell. 1996. A theoretical framework for developing successional weed management strategies on rangeland. Weed Technology 10:766-773
• Sheley, R.L., S. Kedzie-Webb, & B.D. Maxwell. Integrated weed management on rangeland. in R.L. Sheley & J.K. Petroff, eds. Biology & Management of Noxious Rangeland Weeds p 57-68
Ecologically Based Weed Management
• Develop strategies based upon current understanding of succession– Recognizes plant communities dynamic– Use technology to enhance natural
processes & mechanisms that regulate vegetation change
– Direct weed infested communities on trajectory to more desirable community
Causes of Succession
• Site availability• Differential species availability• Differential species performance
• Successional weed management exploits these causes
Successional Weed Management Components
• Mgmt component:– Designed
disturbance– Controlled
colonization– Controlled species
performance
• Succession cause:– Site availability
– Differential species availability
– Differential species performance
Ecological Opportunities for
Weed Management
Controlledcolonization
Controlled performance
Designeddisturbance
Undesiredplant
community
Desiredplant
communityTime
Successional Weed Mgmt:
Treatment Examples
Bdlf herbicide Biocontrol Biocontrol
Cultivation Mowing Mowing
Non-selectiveherbicide
Seeding Early spr grazing
Flooding & draining Fertilization Fertilization
Grazing Grazing Sheep grazing
Burning Selective herbicide Selective herbicide
BurningPrevent wd intros
Reduce soil f ert.I rrigation
Designed Disturbance
ControlledColonization
Controlled spp Performance
Biological Control of Salt Cedar
• Several speakers to address this issue– biocontrol can be controlled
colonization and controlled species performance components of successional weed mgmt
Reference
• Brock, J.H. 1994. Tamarix spp. (Salt Cedar), an invasive exotic woody plant in arid and semi-arid riparian habitats in western USA. p.27-44 In L.C. de Waal, L.E. Child, P.M. Wade, and J.H. Brock, eds. Ecology and management of invasive riverside plants. John Wiley & sons, West Sussex, England.
Physical or Mechanical Control
• Fire:– not effective for controlling salt cedar
• readily resprouts from crown at rate of 3 to 4 M per year
– 20 A fire in UT summer 1975• 1 year later fire effects observable• but with surface of lush green salt cedar
regrowth over entire area• 1978 salt cedar fully recovered
Physical or Mechanical Control
• Fire:– UT research repeat burning
• during spring, summer, fall for 2 years• no effective control because of regrowth
from crowns
Physical or Mechanical Control
• Shredding, rollerchopping, chaining:– all designed to decrease canopy of
target species and ideally decrease plant density• fails to do so on salt cedar
Physical or Mechanical Control
• Grubbing:– cutting individual plants to a depth of
more than 20 cm deep also does not work well on salt cedar• regrowth evident following this technique
within 6 to 12 months
Physical or Mechanical Control
• Root plowing:– using horizontal blade more than 20 cm
deep controlled 40% of salt cedar in NM• must repeat operations to achieve greater
control
– In AZ, 1 M long ripper blades set 1 M apart & pulled with D9 crawler kept portion of Salt River nearly free of SC for 10 yr• must repeat at about 10 month intervals
Physical or Mechanical Control
• Flooding (Inundation):– inundation of established SC 24 to 36
months caused 99% control• flooding during growing season
– inundation also prevents seedling establishment
– established SC withstood• root crowns flooded for 98 days• total submersion for 70 days
Reference
• Duncan, K.W. and K.C. McDaniel. 1998. Saltcedar (Tamarix spp.) management with imazapyr. Weed Technology 12:337-344.
Chemical Control
• First chemicals used: – 2,4-D, 2,4,5-T, & silvex
• controlled topgrowth• regrowth always occurred
– 2,4,5-T & silvex banned 1983
Chemical Control
• Triclopyr (Garlon 3A): – used to treat individual plants– fairly effective– 1.5% solution v/v in 300 gallons total
spray solution per acre!!• Thorough coverage necessary• May best timing, August also good
Chemical Control
• Imazapyr (Arsenal):– Treating individual plants:
• 1% v/v solution in water sprayed to wet,but not to drip
– generally 90% control– best control in August or September (99%)– control less when sprayed in April or October
• an expensive treatment
Salt Cedar Mortality1% Solution Arsenal
0
20
40
60
80
100
120
May Jun Jul Aug Sep Oct
Individual plants treated
Chemical Control
• Imazapyr (Arsenal) + glyphosate (Roundup or Rodeo) individual plants:– often imazapyr & glyphosate tank-mixed
• decrease treatment expense
– 0.5 + 0.5% v/v solution + 0.25% NIS• controlled 95% of SC regardless of date of
application during growing season
– glyphosate at 2% v/v• only 32% control
Chemical Control• NMSU guidelines treating individual plants:
– young or regrowth SC < 4 M tall• easier to trt & better control
– trt areas root plowed, mowed, or cleared or where SC starting to invade
– trt areas < 160 trees/A– glyphosate+imazapyr 0.5 + 0.5% v/v + 0.25% nis
• comparable to 1% v/v imazapyr– spray foliage to wet, especially terminal ends of
branches– allow 2 full seasons before follow-up trts
Chemical Control
• “Broadcast” - carpet roller:– imazapyr + glyphosate 0.125 +
0.125% or imazapyr at 0.125% • controlled 85 & 92% of SC 2 YAT• mortality dropped to 32% when solution
decreased to 0.1 + 0.1%
– glyphosate alone 0.5%, 5% mortality– imazapyr alone 0.25%, 94% mortality
Chemical Control
• “Broadcast” - carpet roller:– good because only contacts target
vegetation• understory protected
– many plants went untreated• decreased with increased operator
experience
– treat only plants < 3 M tall
Chemical Control
• Aerial applications:– NMSU evaluated fixed wing
• 1993 & 1994; data 2 YAT• compared imazapyr at 0.75 lb ai/A to
mixtures of imazapyr and glyphosate• control ranged from 66% (imazapyr 0.75
lb) to 87% (0.5 + 0.5 lb imazapyr + glyphosate)
Fixed Wing Treatments Imazapyr & Glyphosate
0
20
40
60
80
100
1993
1994
Ima0.75
I+G0.25+0.5
I+G0.38+0.38
I+G0.38+0.5
I+G0.5+0.5
Data taken 2 YAT
Chemical Control
• Aerial applications:– aircraft fit with conventional raindrop
nozzles• delivered 7 gpa
– when changed to microaire nozzles at 3 gpa• control decreased 10 to 15%
– Upshot - higher gallonage important for coverage & to penetrate canopy
Chemical Control
• Aerial applications:– also found helicopter applications
caused highly variable control• 31-90% with no apparent rate response
– generally taller trees harder to control– trees with higher number of stems
harder to control
Tree Ht & Stem Number Influences Control
0
20
40
60
80
100
<3 M
3- 4 M
4- 5 M
5- 6 M
>6 M
Stem numbers1-4; 5-9; 10-19; >20
Tree ht
Reference
• Taylor, J.P. and K.C. McDaniel. 1998. Restoration of Saltcedar (Tamarix spp.)-infested floodplains on the Bosque del Apache National Wildlife Refuge. Weed Technology 12:345-352.
Ecologically Based SC Mgmt
• Designed disturbance:– root plowing– pile & burn
• Controlled colonization:– spot trt SC regrowth imazapyr or imazapyr
+ glyphosate individual trees• experience shows plowing, burning, spray better
than spray, chain or burn, spray• cost about 1/3 as much
– planted many native spp
Ecologically Based SC Mgmt
• Controlled species performance:– drip irrigation– ultimately mimic natural flooding by
controlled water manipulations• while stimulates SC recruitment, experience
shows that remains minor component of overall flora
Summary
• These are just examples– many treatment combinations that work
• Always:– know starting composition plant community;– know what composition trying to achieve;– thru designed disturbance, controlled
colonization, controlled species performance• put succession on trajectory to achieve desirable
plant community