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