Rep oduaed by the Forest Service, U.S. Department of
. Agriculture,
foY' offiaiaZ use, from Western Forestry
and Conservation Association 'WESTERN FOREST NURSERY
COUNCIL PROGEEDINGS 1968.
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REPELLE TS_EFFECTS ON SOILS,' TREES , . AND TREE STORl}.gE
by
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Prin ipal Plant Physiolo ist
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P o1fio No thwest Forest and R ge Experiment.
'Sta ion
.' Forest Servioe, U S. Department of Agrioul urf ,
. Portla.nd ,- O r egon '
N$ A.
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INTRODUCTION
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In. the ml,q,f:l.fties, a few forast tree nUrseries sU::rtkci' for the' fi'r t time
. to spray. ri\lr;;ery s o k nth' ohemioal
repellents to prot¢of plant d sefild.1ings·
t o
from nl.mals. , S1noethat 'time,'.this practice has peen grefj.£fy exPanded, and
today, most nurseries use,' epellen chemicals to some e;rl.ent
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. At present, TMI'D '(tetramethylthiu am dis fide) and ZI '(rz;:i, 'o dimethyl...
d,ithiqoarpall)a;�e... oyolohe�l. artrj,ne) are the ,only available e'pell,e:hts "'" Beqause
c:>f their v:it.al rolE! in; f rest regenera.ta.on and in .order. to bea.'bl , t'o Use, them
mo e etfe9 t4vely a.n<;lsa.t'ely, it is . essential to have a. bas b un,der tandJ.ng of
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the
effect
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REPELLENT EFFECTS
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On nursery soils.--Mechanical spray equipment caus'es 'addition of variable
amounts of the spray formulation to seedbed soil. The proportion varies ac­
cording to the tree species sprayed, age of seedlings, and stocking of beds.
Normally, about 25 p rcent of the repellent reaches the soil, but the amount
may reach 70 percent
or more on poorly stocked beds and when true firs are
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sprayed.
Recently, persistence of TMTD and its effect on activity of soil micro­
flora in general and nitrifying micro-organisms in particular were investi­
gated in soil
1lL±he
bs.te!! -a..l'ld-tJH�-(k-eeley---nur-s-e-l'-i-es­-Hl-Wes-'&e-rl'l >lsi3i'l'ing­
ton <!!). Results of this study showed that TMrD was b,roken down in both soils:
rate of breakdown depended on initial concentration of the chemical and action
of soil micro-organisms. In addition, TMTD strongly inhibited respiration and
nitrification, but these effects were only temporary since the micro-organisms
recevered in time as TMrD was broken down in the soils.
Stability and effects of ZIP
soil have not been investigated. ' It is
suspected, however, that the ZIP, which resembles TMTD chemically, would de­
compose in soil in a UlB.nner similar to that of TMrD, but with the liberation
of zinc. Amounts of zinc equivalent to those which could be released from one
ZIP application were not harmful to Douglas-fir in Webster soil (!). In addi­
tion, it dees not seem likely that zinc from ZIP could, all be released at the
same time or that repeated applications of ZIP could cause buildup of zinc in
the soil to toxic levels under present rotation regimes of forest tree nurser­
ies. However, it i ·advisab;I.e to determine effects"'of 'ZIP ,in individual nurs­
ery soUs before the treatment QalJ'l be ,llf d silf� y..•
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On trees.--Effects of T}ITD and the zinc compound (without the other in­
. 0.1' he r p 1ient fOJ;'mu1at on ) on se:e
(t plants. hav
een investi­
gredients
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seedl1 gs (g), mod1f1es normal
gated. TMTD inhib1ts
su . va.l of Doug as-f1r
development.!3Xld ,; shap ,of mycorJ:'hi, a,e of Monterey :pins . (z) " . and. ciecreases photo­
synthesis of sc,>
' me,.iowe.r plants (J), •. . The zinc qe>mpound has"little effect on
germirlation and root' d.evelopw
. nt ot: ;radisa: and benefits root development of
Douglas-fir (g).
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However, when these chemi als, are! '\ls,ed as repellents, they are applied to
the shoots and may reach the rootsinB:nio,imts and' formulations differen:t from
, ,";"Y1entioned repo:rts. AJr-ldel"these. conditioils:; there a.re
tr?SE,3 ',l�r d,,;in tl:l �95)ve
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a:f.p;:, l?-' Ml ' e era ';W,e indioa ing:serious!,u.n esirable ' effects:�i:C'T.MI'rrancf : .:
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Z!P repellent forrinU.at1on , therefors,·: ar El'oonsl.del'edlll onphytotoxl.C to· forest
tree se;e'chiil s,ey p he aPplied at, rates much.higher than' thosere'conuriended.
(Unpublished datav'on file at the Forestry Sciences Laboratory, Olympia, .Wash.),
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en outpla ting is'd layed by,,'.ad:V'ersewea:th t'bF·dt er
c.ondi :t p n :'· pe ent..:treated s edlings Jl).u,st ·be stol:\ed in the'c61q i}lx: tI ' e 4ed.
:
ecently t. ,gr
A- B.l1d ,repelle pyo(: M.l'D,..'breated :2-..0: IDouglas fir(s
-: 'eSdI:ing's were
investiga:teda:f'ter' fl orag , at<35°F.:for 21' days : (:5,):..>Results ofthl:s fuve ti­
gation showed that for beth fall (October) and spring (April) treatments, sur­
vival, height growth, needle appearance, and date of bud bUrst of TMTD-treated
seedlings were only slightly different f:rom those of untreated trees
However,
cold storage caused a high loss of Tl D from the treated seedlings and conse­
quently much reduction in their repellency. Possible reduction of seedlings'
repellency, therefore, would be the only reason against cold storage of TMTD
seedlings.
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There is no information on the effeot of cold storage on T D-treated
eedlings of species other than Douglas-fir or on ZIP-treated trees of any
speoies. In these oas s. effeots of OQ1 storage would probably be similar to
those reported for Douglas-fir sinoe all oonifers have waxy needles and because
ZIP and TMTD are chemically related and their formulations contain the same ad­
hesive. However, researoh shoUld be carried out to positively evaluate storage
effects in ea h case.
�USIONS
Under normal nursery oonditions, spraying dormant planting stock.with
repellents at the reoommended rates appears to be safe for both nursery soils
and trees. Jim.Le3ffi , _additionaL .!'es-Ela.J:'.ch -i - -l'leedeQ.- -tG-: -(-1-}de:tel"tlrl-ne -per-si*enee
and effects of ZIP in different nursery soils; (2) evaluate effects of cold
storage on ZIP-treated seedlings; (3) reduce loss of repellent from treated
seedlin gs af,ter cold stora'ge; and (4) develop new spray eqUipment to minimize
loss of repellent to nursery soils.
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,LITERATURE CITED
1. Anderson, Rarry vi.
1967. Zino rodent repellents also improve
root growth of DQuglas-fir seedlings, but {dgher levels cause
mortality. Tree Planters' Notes 18:14-17
2. Du;ffieid, John H. and Rex P. Eide. 1962. Application of rabbit
epellent to coniferous· planting stock in the Pacific Northwest.
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J. Forest. 60 :l09.. 11 .
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3. Lindahl, p. E. B.j!;rn. 1961. Inhibition of growth and photo..
synthesis in submerged plants with tetramethylthiuram disulphide
and sodium dimethldithiocarbamate and revers l of this inhibition
of Photosynthesis. Nature 191:51.. 53.
4. Radwan, M. A. 1965. Pe:rsistenc.e and effect of TMrD on soil respira­
tion and nitrification in two nursery soils. Forest Sci. 11:152-159. 5.
.
' 11J'. E. Dodge and H. S. 1rlard. 1967.
Effect of storage
on subsequent growth and repellency of Douglas-fir. seedlings sprayed
with TMTD. Tree Pl nters' Notes 18:10-13.
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6. Shea, Keith R •. · 196i. F:l.eld survivai of thiram-treated Douglas-fir
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seed. Weyerhaeuser Co. Forest. Res. Note 38, 8 pp.
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7. Wilde, S. A. and D. J. Persidsky. 1956. Effect of biocides on
development of ectotrophic mycorrhizae in Monterey pine seedlings
Soil Sci,. Soc·. Amer. Proc. 20:107-110.
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