Cogongrass: Research results from competition and herbicide studies

1. Cogongrass: Research results from competition and herbicide studies C. Ramsey, USDA-APHIS-PPQ-CPHST National Weed Management Lab Fort Collins, CO

2. Cogongrass history • Cogongrass – 1912 in Alabama • 1920’s – forage trials in Texas, Mississippi, Alabama, and Florida • Worldwide – 1 billion ac infested • 1979 – 19 counties MS • 2002 – 50 counties MS

3. Rhizome reserves • Biomass = 8.9 tons/ac = 2,000 g/m2 • Rhizomes are jointed • Rhizomes buried below 8 cm can not resprout • Rhizomes able to reproduce – 2 cm cutting

4. Defoliation and rhizome biomass • Defoliation – reduces total nonstructural carbohydrate reserves (TNC) • One mowing • reduced rhizome biomass by 22% • Second mowing • reduced rhizome biomass by 38% • Second disking • Reduced rhizome biomass by 66% Willard et al. (1997)

5. Aerial photos Oct. 2003 Nov. 2005

6. Field study descriptions • 2003 - Cogongrass competition loblolly pine • 2004 – Herbicide /adjuvant study • 2005 – Cogongrass – loblolly pine root drench study

7. Objectives for 2003 competition study • Competitive effects of cogongrass and native herbaceous vegetation on loblolly seedling growth and survival

8. Site Preparation • Loblolly pine plantation located in Pond Creek Unit – International Paper property • Harvested: 2000 • Site Preparation: October 15, 2002 • Planted: March 6-13, 2003 • Pine measured: • 10 MAP – 2003 • 20 MAP - 2004

9. Herbicides • Tank mix • Imazapyr (Chopper) - 0.84 kg ai ha-1 (48 fl oz/ac) • Triclopyr (Garlon 4) – 1.68 kg ai ha-1 (48 fl oz/ac) • Surfactant – Timberland 90 – 936.2 ml ha-1 (12 fl oz/ac) • Aerial application on Oct. 15, 2002

10. Vegetation condition • No site preparation in cogongrass • Cogongrass competition - CGC • Site preparation in cogongrass • Mixed vegetation competition - MVC • Site preparation in native vgt. • Native vegetation competition - NVC • Weed-free - WF

15. First year effects on pine biomass • Competitive effects of cogongrass, native vegetation, and no vegetation on loblolly pine biomass

18. Allelopathic root exudates • Cogongrass reduces corn yield by 80 – 100% (Udensi et al. 1999) • Liquid extracts – reduced rice germination by 11 – 15%, reduced rice height by 22% (Casini et al. 1998) • Italian ryegrass foliar biomass - 60 to 29% of untreated - residues 0.25 to 8% wt/wt

19. Allelopathy July 7, 2003 MVC plot April 28, 2003 MVC plot April 28, 2003

20. Loblolly height growth – 3 GSAP

21. Conclusions • Stem volume index • 2004 - WF > NVC > MVC > CGC • SVI – 98% reduction with cogongrass competition • Vegetation competition time lag • Pine diameter detected resource competition for four vegetation conditions

22. Pine restoration conclusions • 100% re-infestation of herbicide treated area by the end of second growing season • Pine establishment window too short for rapid canopy closure

23. 2004 Herbicide/adjuvant studyobjectives • Determine the effects and interactions of two herbicides and adjuvants on foliar control of cogongrass • Determine effects and interactions of herbicides and adjuvants on rhizome biomass over time

24. Study design • Four blocks • Outer plot - 5 x 5 m • Inner plot - 3 x 3 m • Spray date - Nov. 4-5, 2004

25. Site preparation • Cutover site - International Paper property • Harvested – July, 2000 • Site Preparation - June, 2001 • Velpar ULW – 5.3 kg/ha (4.7 lb/ac) • Planted – Jan. 2002 • Percent foliar cover and rhizome biomass • June, 2005 – 7 MAT • Nov., 2005 – 12 MAT

26. Herbicides • Study design – 2 x 2 x 2 x 3 = 24 trts • Imazapyr (Chopper) - 32 and 64 fl oz/ac • Gly Pro Plus (glyphosate) – 128 and 256 fl oz/ac • MSO conc – 0, 25, 50% v/v • Silwet L-77 – 0, 0.12% v/v • Stimupro – 0.7, 1.4, 2.1% v/v

27. Herbicide costs • Chopper • 32 fl oz/ac = $51/acre • 64 fl oz/ac = $102/acre • GlyPro Plus • 128 fl oz/ac = $19.61/ac • 256 fl oz/ac = $39.22/ac • MSO = 0, $49, $98/ac • Silwet L-77 = 0, $3/ac

28. November 6, 2004

29. Chopper vs GlyPro Plus – 12 MAT Chopper @ 1.12 - 25 - 0 GlyPro Plus @ 8.96 – 25 - 0

38. Conclusions • Foliar – 7 MAT • Chopper = GlyPro (8.9 kg ha-1) > Glypro Plus (4.4 kg ha-1) • Adjuvants • No effect at 7 MAT • Increased control at 12 MAT • Rhizomes – 7 MAT • Chopper – no effect • Adjuvants – no effect

39. Conclusions • 7 MAT sampling time – too soon to detect foliar or rhizome biomass effects • Rhizome sampling – 8 replications with screw type auger did not reduce variability • Improvements for sampling methods • Longer time frame – 12 or 24 MAT • Rhizomes – larger unit size – 20 x 20 x 20 cm

40. 2005 Loblolly pine root drench studyobjectives • Determine the effects of powdered charcoal and seaweed extracts on loblolly pine seedling growth and survival

41. Site preparation • Cutover site - International Paper property • Harvested – July, 2000 • Site Preparation - June, 2001 • Velpar ULW – 5.3 kg/ha (4.7 lb/ac) • Cogongrass application - Nov. 29, 2004 • Chopper – 1.12 kg/ha (64 fl oz/ac) • Planted – Jan. 2002 • Replanted on Feb. 9, 2005 - 2 MAT Chopper appl.

42. Root drenches • Factorial trt design – 3 x 4 = 12 trts • Gro-Safe charcoal – 0, 50, 100 g/l • Stimupro (seaweed extract) – 0, 4, 8, 12% (v/v) • Premixed in water for overnight • 1 liter sphagnum peat moss/pine seedling • 300 ml root drench/ seedling

43. June, 2005

47. Conclusions • Charcoal root drench • No effect on seedling survival • Trend to decrease survival • Stimupro • Negative effect on seedling survival

48. Conclusions • Peat moss – may have improved survival • Did not include a control for peat moss • Stimupro may have stimulated fine root growth • Increased root uptake • Increased seedling mortality • Test a larger “split peat moss plug”