controlling liverworts r kasten dumroese, usda forest service, southern research station kent...
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Controlling Liverworts
R Kasten Dumroese, USDA Forest Service, Southern Research Station
Kent Eggleston, USDA Forest Service, Coeur d’Alene Nursery
Anthony S Davis, UI Center for Forest Nursery and Seedling Research
David Barcel, Chemtura Crop Protection
Background Demand for whitebark pine seedlings for reforestation is high
Difficult to obtain large quantities of seeds
Difficult to germinate seeds
Slow growing species requires two full growing seasons to reach target specs
Important to maximize seed-to-seedling ratios
Liverworts invade during second growing season; reduce seedling survival and growth unless removed – hand weeding only effective treatment
Hand weeding increases costs about 17%
Keeping second season whitebark pine seedlings clean maximizes growth needed for stock quality prior to shipping.
Methods
Two Montana seed sources: Gardiner District on the Gallatin NF Glacier National Park
SuperCells-98/tray-10cu.in.
Second growing season
Liverwort intensities qualitatively assessed Low = removed by hand 1 mo before (Glacier) Medium = removed by hand 2 mo before (Glacier) High = rampant, never removed (Gardiner)
Liverwort Intensity
Low Medium High
Pe
rce
nta
ge
of
Tra
y S
urf
ace
Co
vere
d
0
25
50
75
100
Initial Liverwort Intensities Qualitative assessment
Low = liverwort removed 1 mo earlier; starting to re-invade Medium = liverwort removed 2 mo earlier High = rampant liverwort; never removed
Liverwort at high intensity was about 3 cm (1.25 in) thick
Method-Treatments Treatment 1. Gentry (a fine powder; 26% 2-amino-3-chloro-1,4-
naphthoquinone) mixed at a rate of 0.14 g in 100 ml of water and applied with a hand sprayer evenly across the block. Equivalent to manufacturers lowest suggested label rate (1 oz per gallon of water applied at 1 quart per 100 sq ft).
Treatment 2. 0.28 g Gentry / 100 ml
Treatment 3. 0.42 g Gentry / 100 ml
Treatment 4. 0.56 g Gentry / 100 ml. Equivalent to manufacturer’s highest suggested label rate (2 oz per gallon of water applied at 2 quarts per 100 sq ft).
Treatment 5. TerraCyte, a fine powder (34% sodium carbonate peroxyhydrate), applied at the label rate of 15 lb per 1000 sq ft (13.6 g per block of seedlings) after wetting the crop to improve adherence of the chemical to plant tissue. We used a series of #30 and #40 standard soil sieves to ensure even distribution of the chemical across the block (well, sorta).
Treatment 6. Control. Application of 100 ml plain water with the hand sprayer.
Methods-Applications Each tray of SuperCells (98 plants)
was a replicate
3 replicates
Each batch of chemical made and applied independently to avoid pseudo-replication
Applied 29 March 2007
Efficacy measured 12 April 2007
Liverwort Intensity
Low Medium High
Live
rwor
t Mor
talit
y (%
)
0
20
40
60
80
100 0.14 g/100 ml0.28 0.420.56TerraCyte
Liverwort Mortality
Qualitative assessment At low and medium liverwort intensities, all rates of Gentry were effective At high liverwort intensities, only two highest rates of Gentry were effective
TerraCyte was effective with low intensities of liverwort; less effective at the medium and high intensities—may be a function of application technique rather than efficacy.
Phytotoxicity
No phytotoxicity observed with Gentry Also applied operationally to Douglas-fir and ponderosa pine in the same
greenhouse
Phytotoxicity observed with TerraCyte Poor distribution of powder across tray Poor distribution caused necrotic tissue; in worst cases, seedling mortality For operational use, would need a better application method
Summary – Management Implications Use when liverworts are just becoming established—lowest rates
work fine
If liverwort intensity is “high” then higher rates are necessary—follow-up application a few days later will probably be needed to kill remaining liverworts
No observed phytotoxicity on actively growing whitebark pine, ponderosa pine, or Douglas-fir (Kas also had good success with spot applications under wild ginger). (Kent had good success on willow, kinnikinnik, western larch)
Gentry submitted by Chemtura for registration with US Environmental Protection Agency—decision expected by January 2008.
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