Ecologically Based Management of Salt Cedar K George

Ecologically Based Management of Salt Cedar K. George Beck Bioag 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 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 performance

Ecological Opportunities for Weed Management Designed disturbance Undesired plant community Desired plant community Time Controlled colonization Controlled performance

Successional Weed Mgmt: Treatment Examples Designed Disturbance Controlled Colonization 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 D 9 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. Mc. Daniel. 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 3 A): – 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 Mortality 1% Solution Arsenal May Jun Individual plants treated Jul Aug Sep Oct

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 Ima 0. 75 I+G I+G 0. 25+0. 5 0. 38+0. 5 I+G 0. 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 Tree ht Stem numbers 1 -4; 5 -9; 10 -19; >20

Reference • Taylor, J. P. and K. C. Mc. Daniel. 1998. Restoration of Saltcedar (Tamarix spp. )-infested floodplains on the Bosque del Apache National Wildlife Refuge. Weed Technology 12: 345352.

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