Galea, V. J.

MacManus, G. P. V.

O'Brien, R. G.

University of Queensland eSpace

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1997
Programme and Summ aries
Monday 29 September - Thursday 2 October
Rendezvous Observation City Hotel,
Pe rth, Weste rn Australia
OILBASED ADJIryANTS IMPROVE FI]NGICIDE ACTIVIIY AGAINST DOWNY MILDEW IN GLASSHOUSE
GROWN ONION SEEDLINGS
G.P.V. Mac ManusA, V.J. GaleaA and R.G. o'BrienB .
oUniversity 
of Queensland, Gatton College, Qld 4345. BQueensland Departnent of Primary Industries, Qld 4068
INIRODUCTION
The poretration and translocation of sytemic
fimgicides can be enhanced by adjuvants which may
disrupt the wax and cr.rticular layers. The development of
the crystalline structure of epicrtricular waxes on
successive leaves in onions makes spray retention more
difficult (1). Enhanced activity with lipid adjuvants is
usually associated with improved foliar penetration (2).
MATERIAIJ AND METEODS
Seven treatments using six different adjuvants were
applied as both pre. and post- inoculation sprays to onion
seedlings in a replicated glasshouse pot trial. Pr+
inoculation fimgicide sprays were applied a.m. on 28.8.96
and all pots inoculated p.m. with a metalaxyl-sensitive
isolate ofPeronospors destructor (4xl0a conidia/L, 80%
germination on water agar) in distilled water. Post-
rnoculation fimgicide treatments were applied 48 h later.
Plants were enclosed in hi$ humidity containers
ovemight ther kept in a glasshouse for 13 days; retumed
to high humidity then rated for disease severity (o/o laf
area afected) and % plants showing sporulation the next
day. (Acrobatt lvIZ: 9oglkg dimethomorph + 600g/kg
mancozeb, Top Wetr :100o/o organic wetting age,nt,
Tween 8d :Polyoryethylen{20) Sorbitan mono-oleate,
Synertrolo Or13 :832gtL emulsifiable vegetable oil, Nu
Filn5 :9049& Di-l-Menthene and DC-Tron6 :839glL
pdrolerrm oil).
RESIILTS
All the pre.inoculation frmgicide treatme,uts
sipificantly reduced disease severity (P:0.001) and
completely srrypressed sporulation (Table l), uftich is
highly desirable in disease management of onion downy
mildew The onlv treatments that maintained the same
level of inhifllsry effect on diseaseprogress urten applied
post-infection were Acrobato l\A with Synertrol,
Codacide and DC-Tron.
Acrobato lvIZ atone gave rmsatisfactory control wtrich
would suggest that there may be limited rrytake and
translocation with this formulation as a post-infectional
treabnent. Additional research to determine the
effective,ness of dimethomorph and mancozeb, as separate
components, would provide firther insight into the
activity of the combined formulation.
The oil-based adjuvants,namely, Synertrol, Codacide
and DC-Tron obviously enhanced the penetration and
translocation of this systemic firngicide. Testing these
adjuvants under field conditons is recommended.
ACKNOWLEDGEMENTS
Frmded by Horticultural Research & Development
Corporation and. Queensland Fruit & Vegetable Growers
REFERENCES
I. Verity, J., Walker, A and Dre,nnan, D.S.H. (1981).
Aspects of selective phytotoxicity of methazole. I.
Measure,ments of species response, spray retention
and leaf snrface characteristics.ll/eed Res earch 21.
243-253.
2. Stock, D. and Davies, L. E. (1994). Foliar poretration
of agrochenricals: limitations imposed by formulation
type and some interactions with adjuvants. 1n
'Interactions Betweeir Adjuvants, Agrochemicals and
Target Organisms. @ds P.J. Holloway, R Rees and D.
Stock) pp. 27-49. (Springer-Verlag: Berlin).
Table 1. The effect of spray adjuvants on the efficacy of Acrobaf ldZ (2glL) aspre- and post- infectional treatments to control
onion downy mildew in yourgplants.
Treatment Leaf area atrected (%)
Pre-inoculation Post-inoculation
% ofplants showing sporulation
Preinoculation Postinoculation
I. Acrobat%Z
2. AcrobatoMZ + Top Wetl (0.2 nLIL)
3. AcrobatoMZ + Tween 802 (0.2 mLlL)
4. Acrobat\4z + Synertrol Oil3 (3 mL/L)
5. AcrobatoMZ + Codacidea (3 mLlL)
6. Acrobat\4z + Nu Filmr (0.3 mLlL)
7. AcrobatfuZ + DC-Tron6 (20 nLIL\
8. Unsprayed control
7.25 ab
4.04 a
2.25 a
4.63 a
2.75 a
2.38 a
7.38 ab
34.50 de
28.38 cd
31.46 d
29.75 d
17.13 b
10.50 ab
24.42 cd
9.50 sb
43.79 e# 67.r4 d
3l.72bc
43.60 c
36.63 c
15.76 ab
14.86 ab
63.17 d
7.82 a
87.43 e
0a
0a
0a
0a
0a
0a
0a
LSD (P:0.05) (rr.72) (17.61)(P:0.00r) (20.36) (30.47)
# Treatment means followed by the same letter are not significantly diferent, using Fisher's LSD test.
t7


Oil-based adjuvants improve fungicide activity against downy mildew in glasshouse grown onion seedlings

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Oil-based adjuvants improve fungicide activity against downy mildew in glasshouse grown onion seedlings

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