50
▲Growing Knowledge
An ongoing series provided by Oregon State University in partnership with OAN
Treating irrigation waterThese water treatment methods can be effective at eliminating damaging water molds in nurseries
42
▲
cutting rots, and Phytophthora species, which cause root rot, shoot dieback and foliar blight on a wide range of nursery plants.
Unless recycled water is disinfested before reuse, irrigation water may become an effective delivery system for these plant pathogens.
Water sourcesExtensive sampling in nurseries
indicates that surface water sources such as rivers, ponds, and reservoirs for storing runoff water are almost always contaminated with Phytophthora and Pythium species and should be disin-fested before use in irrigation.
Only water from municipal sources and well water are free of these plant pathogens. You should assume that recirculated water is contaminated and disinfest it on a routine basis, or you can test your water at frequent (month-ly) intervals and treat only if needed.
PARK
E
By Jennifer Parke and Paul FisherNursery and greenhouse growers
commonly capture runoff water and reuse it for irrigation. This conserves water and prevents the escape of nutri-ents and pesticides into waterways.
However, reservoirs also pro-vide a habitat for waterborne plant pathogens. The most serious of these are the water molds, which look like fungi but require water to complete their life cycles.
The most common water molds are Pythium species, which cause damping-off of seedlings and stem
Water storage ponds, such as this one located at Fisher Farms in Gaston, Ore., are common to the nursery industry. It's important that nurseries treat recovered water before using it again for irrigation.
FEBRUARY 2012 ▲ DIGGER 41
▲ TREATInG IRRIGATIon
Testing your water for Pythium and Phytophthora
You can test for the presence of Pythium and Phytophthora by baiting water with rhododendron leaves for seven days and then testing the leaves with field diagnostic ELISA kits. Details for baiting water samples are avail-able here: http://www.aphis.usda.gov/plant_health/plant_pest_info/pram/downloads/rCNPv1/rncp-appendix7.pdf
ELISA kits use monoclonal or poly-clonal antibodies to detect the patho-gens, the same technology used in home pregnancy kits. Kits are available as dipsticks such as the ImmunoStrip® (Agdia®), or as lateral flow devices such as the Alert LF™ (Neogen Europe Ltd.).
Note that currently available ELISA tests for Phytophthora cross-react with several Pythium species, potentially leading to false positives. For this rea-son, the ELISA tests are best used to rule out the presence of Phytophthora species. If the Phytophthora test is positive, further testing by a university extension plant pathology lab is advised to make sure that Phytophthora ramo-rum is not present.
Water disinfestation methods Several methods are available for
effectively disinfesting irrigation water. These methods are summarized in a two-page table available for down-
A nursery technician prepares a leaf bait for an ELISA test to determine the presence of Phytophthora and Pythium pathogens in irrigation water.
PARK
E
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load from the Oregon Association of Nurseries website at www.bit.ly/oansystems. A summary of research on efficacy tests for different treatment technologies to control waterborne pathogens is available at www.watered-ucationalliance.org by selecting “grower tools” and “waterborne solutions.”
Water treatment systems differ in installation costs, operating costs, mode of action, space requirements, water volume treated, worker safety, and envi-ronmental concerns. No single system is best for all nurseries. A combination of filtration with chemical or ecological treatments is often needed.
Suspended solids (such as soil and organic matter) in the water reduce the effectiveness of disinfestation treatments. Total suspended solids should ideally be less than 20 mg/L. Higher amounts of suspended solids increase the risk of plugging emitters that can interfere with water disinfestation treatments.
For example, chlorine is deactivated by organic materials in the water. Pre-filtration is usually required to remove these materials (remnants of potting media, algae and plant debris) from the water. Effective UV treatment of water to kill waterborne pathogens also requires the water to be clear. For these reasons, filtration is often the initial step in various water treatment systems.
Water chemistry also affects the effectiveness of several disinfestation treatments. For example, the sanitiz-ing activity of chlorine is strongly dependent on pH. For water amended with either calcium hypochlorite or sodium hypochlorite, the optimal pH range is 6.0-7.5. Above pH 7.5, the chlorine would be in the form of hypochlorite, a weak sanitizer. Below pH 7.5, chlorine would be in the form of hypochlorous acid and is 20 to 30 times as effective as hypochlorite.
Copper ionization or copper sul-fate is also more effective below pH 7. If electrical conductivity EC is low (<0.20 mS/cm) then it may be necessary
44
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FEBRUARY 2012 ▲ DIGGER 43
▲ TREATInG IRRIGATIon
to increase the electrode surface area when ionizing copper.
Runoff source and placement of the pump inlet in the reservoir
A recent study in a Virginia nursery showed that baiting of Phytophthora species declined with increasing dis-tance from the source of water run-off into the reservoir. This suggests that the irrigation pump inlet should be placed as far away as possible from the source of runoff.
Bait colonization tended to be greatest when baits were at the water surface or near the bottom of the res-ervoir, suggesting that placement of the pump inlet at half the depth of the res-ervoir would result in the least uptake of Phytophthora.
The study can be downloaded
at http://onlinelibrary.wiley.com/doi/10.1111/j.1439-0434.2011.01831.x/full.
Types of water treatmentThe various water treatment sys-
tems disinfest water by different modes of action:
Oxidizing agents react with chemical groups on organic matter, changing the chemical structure of this material. Organic matter includes peat, algae, bacteria, plant debris, and pathogens. Pathogens are killed after exposure to the oxidizing agent if it is present at a certain concentration and duration. The oxidizing agent, however, can be depleted by organic matter in the water. That is why water should be pre-filtered before it is treated with oxidizing agents. Oxidizing agents also react with iron and other met-als. Oxidizing agents include bromine, chlorine gas, sodium hypochlorite, calcium hypochlorite, chlorine dioxide, ozone, and activated peroxygen.
Ultraviolet (UV) radiation involves exposure of the water in tubu-lar chambers to UV light, which kills living cells (including pathogens) by disrupting their DNA. Particulates in the water disperse the light, reducing the effectiveness of UV radiation. Pre-filtration of the water is necessary.
Copper ionization is the release of copper ions into the water result-ing from an electrical charge passed between copper plates. Copper ions are toxic to most pathogens and plants, but the levels used to treat water are well below those which cause phytotoxicity. Copper is also sometimes delivered as a dissolved salt, such as copper sulfate.
Heat treatment is another method of disinfesting water, but it is energy intensive and therefore too costly for treating large volumes. A temperature of 203°F for 30 seconds is sufficient to kill most plant pathogens.
Slow sand filtration is a low technology approach for disinfesting water that has been extremely effective in eliminating Phytophthora from recir-culating water in commercial nurseries in
Learn more
An excellent source for learning more about water treatment methods is the educational resource section of the Water Education Alliance for Horticulture website (www.watereducationalliance.org). The Alliance is a collaborative program between the University of Florida, other researchers and industry partners, that educates growers about water quality and conservation. At the website growers can find key articles and videos about water treatment technologies and monitoring, interactive grower tools and current and previous newsletters. You can also register for upcoming webinars and workshops.
44 FEBRUARY 2012 ▲ DIGGER
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GER
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NATIVE NURSERY LLC
‘Roots to grow on’Phone: 541-757-6520 Fax: 541-738-2607 www.sevenoaksnativenursery.com
- Over 300 species grown from seed- Hard to find natives - Drought tolerant, high elevation- Quaking Aspen specialists - Highest Quality bareroot seedlings- Containers from 4”-25 gallon
Germany www.plantmanagementnet-work.org/pub/php/research/2008/recy-cle. A biofilm crust, or Schmutzdecke, develops on the surface of the sand filter. While this layer is important for the functioning of the filter, it must be maintained or the filter can become clogged. Slow sand filtration may not be rapid enough to supply the volume of water during periods of peak demand, requiring filtration and then storage of the clean water in a reservoir.
SummaryGrowers can minimize their risk
of exposure to plant diseases and reduce pesticide use by ensuring that their irrigation water is free of Pythium and Phytophthora species. Several different disinfestation meth-ods, including high technology and low technology solutions, are avail-able for use by greenhouse and nurs-ery operations of all sizes.
DisclaimerChemical names and trade names are
included as a convenience to the reader. Their use in this publication does not imply endorsement, nor discrimination against similar products or services not mentioned. Individuals who use chemi-cals are responsible for ensuring that the intended use complies with current regu-lations and conforms to the product label. Be sure to obtain current information about usage and examine a current prod-uct label before applying any chemical. For assistance, contact your state pesticide regulating authority.
Dr. Jennifer Parke is an associate pro-fessor (senior research) at Oregon State University in Corvallis where she con-ducts research on Phytophthora species in nurseries. She can be reached at [email protected]. Dr. Paul Fisher is an associate pro-fessor and extension specialist in the Environmental Horticulture Department at the University of Florida in Gainesville. He can be reached at [email protected].
Your contribution today helps prepare the nursery industry leaders of tomorrow. OREGON
NURSERIESFOUNDATION
The ONF is a nonprofit 503(c)3 corporation. Donations may be tax-deductible; consult a qualified tax attorney or accountant.
Contact the Oregon Association of Nurseries for more information503.682.5089 or 800.342.6401
FEBRUARY 2012 ▲ DIGGER 45
60 SAFE PROCUREMENT AND PRODUCTION MANUAL
Tabl
e 8.
3.2b
— A
sum
mar
y of
tre
atm
ent
opti
ons
for
wat
erbo
rne
path
ogen
s in
nur
sery
and
gre
enho
use
irri
gati
on s
yste
ms
(Pag
e 1
of 2
)
Trea
tmen
tAc
tive
ingr
edie
ntRe
adily
so
lubl
eIn
ject
ion
met
hod
How
It W
orks
Usua
l ran
ge in
co
ncen
trat
ion1
Not
es
Brom
ine
Ex
ampl
e:
Agrib
rom
™
1-Br
omo-
3-ch
loro
-5,
5-di
met
hyl-2
,4-
imad
azol
idin
edio
neNo
Tabl
ets o
r gra
nule
s are
pla
ced
in a
cont
aine
r w
ith w
ater
. The
supe
rnat
ant s
olut
ion
is in
ject
ed in
to th
e irr
igat
ion
wat
er.
Oxid
izing
age
nts
liste
d in
this
tabl
e in
tera
ct w
ith re
activ
e ch
emica
l gro
ups o
n or
gani
c mat
ter. T
he
oxid
atio
n of
org
anic
mat
ter r
esul
ts in
a
chan
ge in
the
chem
ical s
truct
ure
of th
e or
gani
c m
atte
r, and
dea
th o
f th
e pa
thog
en. T
he
oxid
izing
age
nt it
self
is al
so “
used
up”
du
ring
sani
tatio
n be
caus
e th
e ag
ent
chan
ges c
hem
ical
form
as i
t rea
cts w
ith
orga
nic m
atte
r. Pl
ant
path
ogen
s var
y in
th
eir s
usce
ptib
ility
to
the
agen
ts li
sted
in
this
tabl
e. So
me
plan
t pat
hoge
ns a
nd
type
s of r
esist
ant
inoc
ulum
stru
ctur
es
may
requ
ire h
ighe
r ra
tes o
f oxi
dizin
g ag
ents
and
/or
expo
sure
tim
es
than
thos
e lis
ted.
Th
e m
ater
ial b
eing
ox
idize
d ca
n in
clude
pa
thog
ens,
peat
, an
d fe
rtiliz
er sa
lts.
Beca
use
all o
rgan
ic m
atte
r in
the
wat
er
will
abs
orb
and
depl
ete
oxid
izers,
go
od p
re-fi
ltrat
ion
is es
sent
ial.
5–35
ppm
bro
min
e
Beca
use
of lo
w so
lubi
lity,
som
e tim
e is
requ
ired
for
the
undi
ssol
ved
tabl
ets o
r gra
nule
s to
repl
enish
the
brom
ine
in th
e st
ock
solu
tion.
Diffi
cult
to m
aint
ain
a co
nsta
nt co
ncen
tratio
n of
bro
min
e ov
er th
e co
urse
of
the
day,
espe
cially
with
hig
h flo
w ra
tes.
Req
uire
s a
spec
ial i
njec
tor r
esist
ant t
o co
rrosiv
e ch
emica
ls.
Chlo
rine
gas
Cl2
Yes
Chlo
rine
gas i
s bub
bled
thro
ugh
the
wat
er, w
here
it co
mbi
nes w
ith th
e w
ater
to fo
rm h
ypoc
hlor
ous a
cid
(HOC
l) an
d hy
droc
hlor
ic ac
id (H
Cl).
0.5–
2 pp
m fr
ee ch
lorin
e.
Hy
poch
lorit
e is
a w
eak
acid
an
d ca
n be
foun
d in
solu
tion
in tw
o di
ffere
nt fo
rm: O
Cl- a
nd
HOCl
.
Beca
use
the
HOCl
form
is
muc
h m
ore
effe
ctiv
e at
disi
nfec
ting
than
the
OCl-
form
, the
wat
er p
H sh
ould
be
cont
rolle
d, a
s sa
nitiz
ing
reac
tions
tend
to
be sl
ower
at h
ighe
r pH.
Haza
rdou
s gas
requ
ires s
pecia
l equ
ipm
ent,
vent
ilatio
n, a
nd h
andl
ing.
As w
ith a
ll ch
lorin
e ap
plica
tion
met
hods
, hig
her t
han
reco
mm
ende
d co
ncen
tratio
ns ca
n be
toxi
c to
plan
ts.
Sodi
um
Hypo
chlo
rite
NaOC
lYe
sLiq
uid
NaOC
l sol
utio
ns
(5–1
5 pe
rcen
t chl
orin
e) a
re in
ject
ed
dire
ctly
into
irrig
atio
n w
ater
.
Requ
ires a
spec
ial i
njec
tor t
hat i
s res
istan
t to
very
co
rrosiv
e ch
emica
ls an
d ha
s a v
ery
high
inje
ctio
n ra
tio. H
as a
lim
ited
shel
f life
. War
m te
mpe
ratu
res a
nd
sunl
ight
spee
d up
bre
akdo
wn.
Nev
er co
mbi
ne w
ith
ferti
lizer
s or o
ther
chem
icals
cont
aini
ng a
mm
oniu
m.
Calc
ium
Hy
poch
lorit
eCa
(OCl
)2Ye
s
Gran
ules
may
be
diss
olve
d in
wat
er,
or ta
blet
s can
be
erod
ed in
a fl
ow-
thro
ugh
feed
er fo
r mor
e au
tom
atic
chlo
rinat
ion,
at c
hlor
ine
conc
entra
tions
up
to 1
0,00
0 pp
m, d
epen
ding
on
the
feed
er a
nd o
pera
ting
cond
ition
s.
Calci
um h
ypoc
hlor
ite so
lutio
ns o
f up
to
appr
oxim
atel
y 21
per
cent
can
be p
repa
red,
but
du
e to
the
pres
ence
of i
nsol
uble
mat
eria
ls su
ch a
s ca
lcium
carb
onat
e so
lutio
ns o
f abo
ve 2
00 p
pm te
nd
to b
e clo
udy.
Sedi
men
t for
ms w
ith v
ery
conc
entra
ted
solu
tions
. At l
ess t
han
100
ppm
ava
ilabl
e ch
lorin
e th
ere
shou
ld b
e no
app
aren
t clo
udin
ess o
r sed
imen
t.
Chlo
rine
Dio
xide
Ex
ampl
es:
Ultra
-Shi
eld™
, Se
lect
rocid
e™
ClO2
Yes
Dry
pack
et o
r tab
lets
pla
ced
in w
ater
, Cl
O2 sol
utio
n ge
nera
ted
in st
ock
tank
.
Inje
cted
into
irrig
atio
n lin
es.
Cont
inuo
us in
ject
ion
of
resid
ual c
once
ntra
tion
of
0.25
ppm
or l
ess.
Twice
a y
ear
shoc
k tre
atm
ent a
t 20
to 5
0 pp
m d
epen
ding
on
prod
uct.
Stoc
k so
lutio
n sh
ould
be
used
with
in 1
5 da
ys to
min
imize
loss
due
to v
olat
iliza
tion.
M
axim
um st
ock
conc
entra
tion
of 5
00 o
r 3,
000
ppm
dep
endi
ng o
n pr
oduc
t.
Ozo
neO3
No
An e
lect
rical
arc
is u
sed
to
prod
uce
the
ozon
e fro
m b
ottle
d or
at
mos
pher
ic ox
ygen
. The
ozo
ne is
th
en b
ubbl
ed th
roug
h th
e w
ater
.
Resid
ual e
ffect
from
reac
tion
prod
ucts
(per
oxid
es,
orga
nic r
adica
ls).
Brea
ks u
p bi
ofilm
. 10
gram
s/hr/m
³.
Requ
ires p
rofe
ssio
nal d
esig
n ba
sed
on w
ater
an
alys
is. P
rope
r des
ign
prev
ents
ozo
ne fr
om e
scap
ing
into
the
atm
osph
ere
in h
azar
dous
conc
entra
tions
.
Activ
ated
Pe
roxy
gen
Ex
ampl
es:
Zero
Tol™
, San
iDat
e™
Hydr
ogen
dio
xide
/hy
drog
en p
erox
ide
(H2 O
2 ) an
d Pe
roxy
acet
ic ac
id/p
erac
etic
acid
(C
H3 COO
-OH)
Yes
A st
abili
zed
H2 O2 a
nd p
erac
etic/
pero
xyac
etic
acid
solu
tion
that
is in
ject
ed d
irect
ly in
to
irrig
atio
n w
ater
. Pe
roxy
acet
ic ac
id is
a
mor
e ef
fect
ive
bioc
ide
than
H2 O
2 alo
ne.
27 to
540
ppm
H2 O
2Re
quire
s a sp
ecia
l inj
ecto
r tha
t is r
esist
ant t
o ve
ry
corro
sive
chem
icals
and
has a
ver
y hi
gh in
ject
ion
ratio
, or t
he m
ater
ial m
ust b
e di
lute
d be
fore
inje
ctio
n.
CHAPTER 8: PLANT PRODUCTION: WATER MANAGEMENT 61
Tabl
e 8.
3.2b
— A
sum
mar
y of
tre
atm
ent
opti
ons
for
wat
erbo
rne
path
ogen
s in
nur
sery
and
gre
enho
use
irri
gati
on s
yste
ms
(Pag
e 2
of 2
)
Trea
tmen
tAc
tive
ingr
edie
ntRe
adily
sol
uble
Inje
ctio
n m
etho
dHo
w it
wor
ksUs
ual r
ange
in
conc
entr
atio
n1N
otes
Ultra
viol
et
(UV)
radi
atio
nN/
A
Wat
er is
exp
osed
to h
igh
dose
s of
UV li
ght i
n tu
bula
r cha
mbe
rs. M
ost
com
mon
are
low
pre
ssur
e m
ercu
ry
vapo
r lam
ps w
ith a
wav
e le
ngth
of
254
nm
, clo
se to
the
optim
um
rang
e fo
r kill
ing
path
ogen
s.
UV ra
diat
ion
disr
upts
the
gene
tic m
ater
ial i
n th
e ce
ll,
effe
ctiv
ely
killi
ng it
. Dos
e, ex
posu
re ti
me
and
turb
idity
de
term
ine
effe
ctiv
enes
s.
250
mJ/c
m2 e
limin
ates
mos
t pa
thog
ens.
No re
sidua
l ef
fect
on
path
ogen
s do
wns
tream
of t
reat
men
t.
The
effe
ctiv
enes
s of t
he la
mp
decr
ease
s w
ith a
ge. A
ny p
artic
ulat
e m
atte
r in
the
wat
er w
ill d
isper
se th
e lig
ht, m
akin
g th
e ap
plica
tion
of U
V ra
diat
ion
less
ef
fect
ive.
Good
pre
-filtr
atio
n is
esse
ntia
l. Of
ten
used
with
oth
er d
isinf
ectin
g m
ater
ial t
o ge
t som
e re
sidua
l effe
ct.
Copp
er
ioni
zatio
nCu
++Ye
sAn
ele
ctric
al ch
arge
is p
asse
d be
twee
n co
pper
bar
s or p
late
s, re
leas
ing
copp
er io
ns in
to th
e w
ater
.
Copp
er io
ns a
re a
toxi
n to
m
ost p
atho
gens
, inc
ludi
ng
Pyth
ium
, Phy
toph
thor
a,
Xant
hom
onas
, and
alg
ae.
Rece
nt a
dvan
ces i
n co
ntro
ls pr
oduc
e co
nsist
ent c
oppe
r le
vels
and
relia
ble
resu
lts.
0.5
to 1
ppm
Cu
for p
atho
gens
. 1
to 2
ppm
for a
lgae
and
bio
film
.
Less
effe
ctiv
e if
wat
er p
H is
abov
e 7.
5.
Choo
se a
syst
em w
hich
act
ivel
y co
ntro
ls co
pper
out
put a
ccor
ding
to fl
ow a
nd
EC. A
pplie
d co
pper
conc
entra
tions
are
w
ithin
U.S.
drin
king
wat
er st
anda
rds
and
a fra
ctio
n of
pla
nt to
xicit
y le
vels.
Heat
tre
atm
ent/
past
euriz
atio
nN/
AW
ater
is h
eate
d to
spec
ific
tem
pera
ture
, and
was
te h
eat i
s re
cove
red
to p
re-h
eat i
ncom
ing
wat
er.
Path
ogen
resis
tanc
e to
hea
t var
ies.
Effe
ct
larg
ely
inde
pend
ent
of w
ater
qua
lity.
An e
xam
ple
treat
men
t is
203
F fo
r 30
seco
nds.
No
resid
ual e
ffect
on
path
ogen
s do
wns
tream
of t
reat
men
t.
High
ene
rgy
use
mak
es it
exp
ensiv
e fo
r lar
ge fl
ow. T
o pr
even
t sca
ling
of
heat
exc
hang
ers f
rom
har
d w
ater
, pH
need
s to
be re
duce
d to
4.5
, the
n ra
ised
agai
n as
nee
ded
for i
rriga
tion.
Bes
t for
lo
w-fl
ow, h
igh-
sani
tatio
n ap
plica
tions
.
Slow
sand
fil
tratio
nN/
A
Wat
er m
oves
pas
sivel
y th
roug
h sa
nd
bed
that
supp
orts
a b
iolo
gica
lly
activ
e la
yer (
Schm
utzd
ecke
or
biofi
lm cr
ust)
on th
e fil
ter s
urfa
ce.
Clea
n, fi
ltere
d w
ater
is st
ored
in
a co
vere
d re
serv
oir u
ntil
use.
Sand
filtr
atio
n w
orks
thro
ugh
a co
mbi
natio
n of
phy
sical
rem
oval
of
parti
cles a
nd b
iolo
gica
l act
ivity
of t
he
biofi
lm cr
ust.
Effe
ctiv
e at
elim
inat
ing
Phyt
opht
hora
spp.
from
wat
er.
An e
xam
ple
rate
of
filtra
tion
is 30
-90
m3 /h
r. A
filte
r bed
are
a of
260
m2
and
1 m
dee
p ca
n yie
ld
appr
oxim
atel
y 40
,000
m
3 filte
red
wat
er/m
o.
Whi
le th
e bi
ofilm
crus
t or S
chm
utzd
ecke
is im
porta
nt fo
r the
fu
nctio
ning
of t
he fi
lter, i
t mus
t be
mai
ntai
ned
by p
erio
dic r
akin
g or
the
filte
r can
bec
ome
clogg
ed. S
low
sand
filtr
atio
n m
ay n
ot
be ra
pid
enou
gh to
supp
ly th
e vo
lum
e of
wat
er d
urin
g pe
riods
of
peak
irrig
atio
n de
man
d. S
pace
lim
itatio
ns m
ay a
lso li
mit
the
size
of th
e sa
nd fi
lter a
nd th
e vo
lum
e of
wat
er th
at ca
n be
trea
ted.
Not
es1.
De
sired
conc
entra
tion
depe
nds o
n th
e ap
plica
tion
(e.g
. sho
ck tr
eatm
ent v
ersu
s con
tinuo
us tr
eatm
ent o
f clea
n w
ater,
and
the
spec
ific p
atho
gens
targ
eted
). S
ee p
rodu
ct la
bel a
nd m
anuf
actu
rer’s
instr
uctio
ns fo
r you
r app
licat
ion.
2.
All t
he m
etho
ds m
entio
ned
abov
e ar
e no
n-sp
ecifi
c and
will
reac
t with
any
type
of o
rgan
ic m
atte
r, whe
ther
it is
a p
atho
gen,
alg
ae, o
r a p
artic
le of
pea
t. In
all c
ases
, the
clea
ner t
he w
ater
is b
efor
e th
e ap
plica
tion,
the
mor
e ef
fecti
ve th
e di
sinfe
ction
m
etho
d is
at re
mov
ing
path
ogen
s.3.
Br
omine
, chlo
rine p
rodu
cts, o
zone
, per
oxya
cetic
acid
, and
hyd
roge
n pe
roxid
e are
stro
ng o
xidizi
ng a
gent
s. M
etal
micr
onut
rient
s (co
pper,
iron
, man
gane
se, a
nd zi
nc) a
re ea
sily o
xidize
d (p
artic
ularly
iron
). It
is lik
ely th
at lo
ng-te
rm ex
posu
re (g
reat
er th
an 2
0 m
inute
s) of
met
al m
icron
utrie
nts t
o th
ese o
xidizi
ng a
gent
s will
decre
ase t
heir
solub
ility.
Chela
ted
micr
onut
rient
s sho
uld b
e only
sligh
tly le
ss a
ffecte
d th
an su
lfate
s.4.
Ul
travio
let ra
diat
ion
is a
phot
o-ox
idizi
ng a
gent
. Res
earc
h by
Cor
nell U
nive
rsity
on
phot
o-ox
idat
ion
of ir
on in
ferti
lizer
solu
tions
indi
cate
s tha
t the
gre
ater
the
light
exp
osur
e, th
e les
s iro
n th
at w
ill re
mai
n in
solu
tion.
5.
Quat
erna
ry a
mm
oniu
m co
mpo
unds
such
as G
reen
-Shi
eld®, P
hysa
n 20
™, o
r Tria
thlo
n™ a
re lis
ted
for d
isinf
ectio
n of
wal
kway
s, be
nche
s, to
ols,
flats,
etc
., bu
t are
not
for u
se w
ith ir
rigat
ion
wat
er.6.
Liq
uid
hydr
ogen
per
oxid
e/hy
drog
en d
ioxid
e (H
2O2)
solu
tions
(35–
50 p
erce
nt H
2O2)
are
not E
PA-re
giste
red
for w
ater
trea
tmen
t in
gree
nhou
ses,
and
are
less e
ffect
ive a
nd st
able
com
pare
d w
ith re
giste
red
activ
ated
per
oxyg
en p
rodu
cts.
Chem
ical n
ames
and
trad
e na
mes
are
inclu
ded
in th
is pu
blica
tion
as a
conv
enien
ce to
the
read
er. Th
e us
e of
bra
nd n
ames
and
any
men
tion
or lis
ting
of co
mm
ercia
l pro
duct
s or s
ervic
es in
this
publ
icatio
n do
es n
ot im
ply n
dorse
men
t, no
r di
scrim
inat
ion
agai
nst s
imila
r pro
duct
s or s
ervic
es n
ot m
entio
ned.
Indi
vidua
ls w
ho u
se ch
emica
ls ar
e re
spon
sible
for e
nsur
ing
that
the
inte
nded
use
com
plies
with
curre
nt re
gula
tions
and
conf
orm
s to
the
prod
uct l
abel.
Be
sure
to o
btai
n cu
rrent
in
form
atio
n ab
out u
sage
and
exa
min
e a
curre
nt p
rodu
ct la
bel b
efor
e ap
plyin
g an
y che
mica
l. For
ass
istan
ce, c
onta
ct yo
ur st
ate
pesti
cide
regu
latin
g au
thor
ity.
Tabl
e m
odifi
ed b
y J. P
arke
, Ore
gon
Stat
e Un
iversi
ty, w
ith p
erm
issio
n fro
m F
isher,
P. (e
d.) 2
009.
Wat
er Tr
eatm
ent f
or P
atho
gens
and
Alg
ae.W
ater
Edu
catio
n Al
lianc
e fo
r Hor
ticul
ture
. 57
pp.