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%

Second season whitebark pine seedlings are very susceptible to liverwort and moss competition

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

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75

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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

Low Medium High

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

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)

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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.

Hand weeded 2 mo earlier

Control – high intensity

Hand weeded 1 mo earlier

Gentry (0.42 g)

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.

Out-takes