1. Ecologically Based Management of Salt Cedar K. George Beck Bioag Science & Pest Management Colorado State University

2. 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

3. 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

4. Causes of Succession Site availability Differential species availability Differential species performance Successional weed management exploits these causes

5. Successional Weed Management Components Mgmt component: –Designed disturbance –Controlled colonization –Controlled species performance Succession cause: –Site availability –Differential species availability –Differential species performance

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

7. Successional Weed Mgmt: Treatment Examples Designed Disturbance Controlled Colonization Controlled spp Performance

8. 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

9. 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.

10. 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

11. Physical or Mechanical Control Fire: –UT research repeat burning during spring, summer, fall for 2 years no effective control because of regrowth from crowns

12. 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

13. 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

14. 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

15. 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

16. Reference Duncan, K.W. and K.C. McDaniel. 1998. Saltcedar (Tamarix spp.) management with imazapyr. Weed Technology 12:337-344.

17. 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

18. 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

19. 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

20. Salt Cedar Mortality 1% Solution Arsenal May JunJulAugSepOct Individual plants treated

21. 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

22. 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

23. 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

24. 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

25. 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)

26. Fixed Wing Treatments Imazapyr & Glyphosate Ima 0.75 I+G 0.25+0.5 I+G 0.38+0.38 I+G 0.38+0.5 I+G 0.5+0.5 Data taken 2 YAT

27. 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

28. 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

29. Tree Ht & Stem Number Influences Control Stem numbers 1-4; 5-9; 10-19; >20 Tree ht

30. 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.

31. 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

32. 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

33. 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