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Fungicide treatments, applied in-furrow to undisturbed or cultivated soils, for control of rhizoctonia root rot of barley
Fungicide treatments, applied in-furrow to undisturbed or cultivated soils, for control of rhizoctonia root rot of barley P. J. Cotterill*
Department of Agriculture and Rural Affairs, Victoria 3400, Australia
Victorian Crops Research Institute, Horsham,
The effect of eight fungicides, applied in-furrow to undisturbed or cultivated soils, on rhizoctonia root rot and yield of barley (Hordeum vulgare) was investigated at six sites with differing soil type and disease risk in the north-west of Victoria, Australia. A single shallow cultivation on the day of sowing reduced disease severity at one site and increased grain yield at this and one other site, but at another site, grain yield was reduced in barley sown after cultivation. Five fungicides (flutriafol, tcbuconazolc, fenbuconazole, SN-539865 and diniconazole), coated on clay granules to give 400 g a.i. ha -I and applied to the drill row at sowing, generally reduced the severity of rhizoctonia root rot in direct-drilled plots; flutriafol, tebuconazole and diniconazole were effective when combined with soil cultivation, but only flutriafol, combined with cultivation, and fenbuconazole in undisturbed soil increased grain yields.
Keywords: Rhizoctonia root rot; barley; fungicides; in-furrow; cultivation
In Australia, barley (Hordeum vulgare L.) generally appears to be more susceptible to rhizoctonia root rot (caused by Rhizoctonia solani Kiihn) than wheat (Triticum aestivum L.) (MacNish, 1985a; Neate, 1989); barley, therefore, may not respond to cultural control measures as readily as wheat. Soil cultivation is currently regarded as the most effective control method in Australia, with several methods proving effective (Jarvis and Brennan, 1986; Rovira, 1986; de Boer and Kollmorgen, 1988). Cultivation is also effective in reducing rhizoctonia root rot of wheat in the USA (Weller et al., 1986; Pumphrey et al., 1987; Smiley, Wilkins and Klepper, 1990a). The calcareous sandy Ioams of the Mallee regions (which comprise much of the cereal-growing area of southern Australia) and other soil types, particularly the hard-setting red-brown earths, are not suited to constant conventional cultivation (Here, 1941; Roget, Neate and Rovira, 1989). Furthermore, cultivation is not always a wholly successful means of control (Cotterill, 1990a; Henry and Brown, 1991). Fungicides have been tested for control of rhizoctonia root rot of wheat in the USA (Smiley et al., 1990a, b), and in Australia (Cotterill, 1990b, 1991) both in the presence and absence of cultivation. Fungicide application to the drill row during the sowing operation has been used to control take-all ]caused by Gaeumannomyces graminis (Sacc.) von Arx & Olivier var. tritici Walker] of wheat
*Present address: Queensland Department of Primary Industries,
Queensland Wheat Research Institute, PO Box 2282, Toowoomba, Queensland 4350, Australia
in Australia (Ballinger and Kollmorgen, 1988) and such a technique could be beneficial in reducing yield losses due to rhizoctonia root rot in barley. The aims of this study were (a) to compare limited soil cultivation with direct-drilling and (b) to determine the efficacy of eight fungicides on clay granules drilled with the seed into cultivated or undisturbed soil, on the control of rhizoctonia root rot of barley at six sites of differing soil type and disease risk in north-west Victoria.
Materials and methods Fungicides
Eight fungicides were tested, namely flutriafol, tebuconazole, pencycuron, fenbuconazole (RH-7592), cyproconazole, flutolanil, SN-539865 and diniconazole (Cotterill, 1991). Clay granules ( - 1 mm diameter, Attapulgite, 100% absorbent granules, MallinaHoldings Ltd, Perth, Australia) were coated with each of the fungicides by thoroughly mixing batches of granules with an appropriate quantity of fungicide in a ball mill. This gave a concentration of 400 g a.i. ha `.-] when clay granules were applied to the field at a rate of 50 kg ha -~ . Field experiments Six sites of varying soil type, location and risk of rhizoctonia root rot (Cotterill, 1991) in north-west Victoria were chosen in 1988. Mean annual rainfall at the first four sites ranges between 425 and 456 mm and
0261-2194/93/04/0273-06 © 1993 Butterworth-Heinemann Ltd Crop Protection 1993 Volume 12 Number 4
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Control of rhizoctonia root rot in barley: P. J. Cotterill
at Walpeup and Woomelang is 342 mm. Soils at each site [according to the Northcote (1979) classification] are as follows:
Char#on: Dr 2.13, a clay loam A1 horizon with a pH of 6.0 to a depth of ~10 cm, no A2 horizon and an alkaline reaction trend to a medium clay at depth, Horsham: Ug 5.16, a friable self-mulching grey clay A horizon with a pH of 9.0 to - 1 0 cm underlain by a grey clay.
Comparisons were made, for the parameters discussed, at each site, and across all sites (severity of rhizoctonia root rot and grain yield only) between (a) nil fungicide, direct-drilled plots and nil fungicide, cultivated plots, (b) nil fungicide and the eight fungicide treatments in direct-drilled plots, (c) nil fungicide and the eight fungicide treatments in cultivated plots, and (d) nil fungicide, direct-drilled plots and combined treatments (fungicide-treated, cultivated plots).
Kaniva 1: Gn 5.43, a sandy clay A1 horizon with a pH of 5.5 to --5 cm, no A2 horizon evident and an
Statistical analyses
alkaline reaction trend to a medium clay.
A two-way analysis of variance was performed on the data from each site. For an overall fungicide treatment
Kaniva 2: Dr 2.13, as for Charlton except A1 horizon to - 7 cm.
Walpeup: Gn 2.13, a sandy loam A1 horizon with a pH of 6.5 to - 1 2 cm, no A2 horizon and an alkaline reaction trend to a light clay.
Woomelang: Gc 1.21, a sandy loam A1 horizon with a pH of 8.0 to - 1 0 cm, no A2 horizon and an alkaline reaction trend to a light clay.
Sites were prepared as described by Cotterill (1991) and sown in mid-May (Charlton, Waipeup and Woomelang) or the first week in June, 1989 (remainder). On the day of sowing, half of the plots at each site were cultivated to a depth of 6-7 cm using shares (10 cm wide) attached to the drill. Plots were then sown, using modified lucerne points, with 70 kg ha 1 barley (cv. Galleon), 80 kg ha-1 double superphosphate (17.5% P, 4.1% S) and 50 kg ha -1 clay granules either uncoated, or coated with fungicide. Seed was covered by dragging an upturned harrow behind the drill. During crop growth, diclofop methyl was applied to control ryegrass (Lolium rigidum Gaud.) and bromoxynil plus MCPA to control broad-leaved weeds (Cotterill, 1991). Plant emergence was measured using three quadrats (each representing two half-metre lengths of drill row per plot) at all sites, except Horsham, 3-5 weeks after sowing (Cotterill, 1991). At anthesis (growth stages 59~9; Zadoks, Chang and Konzak, 1974), barley plants were sampled from four randomly selected sections (30 cm) of drill row in each plot. Twenty plants were randomly selected from each plot sample and roots washed free of soil. Roots were rated for incidence (percentage plants infected), and severity (percentage roots infected per plant) of rhizoctonia root rot, on a 0-5 scale, where 0 = nil disease and 5 = maximum disease (Cotterill, 1991). Plants were also rated for incidence and, where appropriate, severity of take-all, using a 0-4 scale where 0 = nil disease and 4 = maximum disease (Cotterill, 1991). R. solani and G. graminis vat. tritici were isolated from barley plants to confirm that these were the causal agents of rhizoctonia root rot and take-all, respectively. At maturity, grain yield per plot (converted to kg ha 1) was determined. Plots were 15 m by six rows and the fungicide treatments were arranged in randomized complete blocks with three replications and three nil fungicide plots of each cultivation treatment per replicate,
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comparison within each cultivation treatment across all sites, the proportional reduction or increase in disease severity or yield over the nil fungicide treatments was calculated. For combined treatments (fungicide plus cultivation) the proportional change against the nil
fungicide, direct-drilled treatment was calculated. This was done by designating the mean value for the nil fungicide treatments at each site as 1.00, then calculating the proportional change of each treatment mean at each site. An analysis of variance was done on these data from all sites.
Results
Effect of cultivation treatments
At Kaniva sites 1 and 2, plant emergence was lower in nil fungicide plots that were direct-drilled than in those that were cultivated [5.96 compared with 10.07 plants m 1 drill row, 1.s.d. = 3.21 (all l.s.d, values are p = 0.05) and 8.96, compared with 14.45, l.s.d. = 3.15, respectively]. Incidence of rhizoctonia root rot on plants sampled from nil fungicide, direct-drilled plots at anthesis was 100, 10, 58, 47,100 and 100%, respectively, for the Charlton, Horsham, Kaniva 1, Kaniva 2, Walpeup and Woomelang sites. Tillage treatment did not affect disease incidence. Disease severity was not affected at any site either, with the exception of Kaniva 2 (Figure la). Take-all was recorded on plants at the Horsham, Kaniva 1, Kaniva 2 and Woomelang sites. Incidence (%) [and severity, (0-4)] for nil fungicide plots were 52% [2.25], 60% [1.32], 10% and 4%, respectively; no effects of tillage treatment were observed. Grain yields were greater from the nil fungicide, cultivated plots than from the nil fungicide, direct-drilled plots at both Kaniva sites; however, there was no difference in yield at Horsham, Walpeup or Woomelang. Charlton yields were greater in directdrilled plots (Figure lb). Effect of fungicides in direct-drilled plots Flutriafol reduced plant emergence in the direct-drilled plots at Charlton (from 10.7 to 8.0 plants m -I drill row, I.s.d. = 2.4). None of the fungicides reduced incidence of rhizoctonia root rot at any site, or severity at
Control of rhizoctonia root rot in barley: P. J. Cotterill 3.°[a
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ta~
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flutolanil and diniconazole increased incidence at Horsham (from 7.8 to 25.0 and 31.7°/,,, respectively, l.s.d. = 16.9). Few fungicide treatments reduced the severity of rhizoctonia root rot in cultivated plots, the exceptions being tebuconazole at Horsham, and flutriafol, fenbuconazole, flutolanil and diniconazole at Woomelang (Table 2). Only tebuconazole appeared to be generally effective (Table 3). Incidence of take-all was reduced by flutriafol and tebuconazole at Kaniva 1 (from 67 to 43 and 40%, respectively, l.s.d. = 23) and by flutriafol at Horsham (from 57 to 23%, 1.s.d. = 27), where diniconazole reduced take-all severity (from 2.46 to 1.38, l.s.d. = 0.78). At Charlton, flutriafol and fenbuconazole increased grain yield. No fungicide generally increased yield (Table 3).
.L
3
Effect of combined (fungicide plus cultivation) treatments
'~: ,z .~ c '~
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~
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__ Charlton Horsham Kaniva
Kaniva Walpeup W'lang
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2 Site Figure 1. Severity of rhizoctonia root rot (a) and grain yield (b) of barley either direct-drilled (B) into undisturbed soil or i n t o soil cultivated (D) once on the day of sowing, at six sites in north-west Victoria, Australia. Capped vertical lines represent I.s.d. (/9 = 0.05) Charlton, Horsham or Kaniva 1; however, all fungicides except diniconazole reduced severity at Kaniva 2, all but flutriafol and cyproconazole were effective at Woomelang, and at Walpeup only tebuconazole and SN-539865 were effective (Table 1). Generally, disease severity was reduced by flutriafol, tebuconazole, fenbuconazole, SN-539865 and diniconazole (Table 3). No fungicide treatment reduced incidence or severity of take-all at any of the infested sites, but fenbuconazole increased t a k e - a l l i n c i d e n c e ( f r o m l . 7 t o 1 3 . 3 % , l . s . d . = 9.0) at Woomelang. Grain yields were increased only by flutolanil at Woomelang and by fenbuconazole at Kaniva 1 (Table 1), although fenbuconazole appeared to be generally effective (Table 3). Effect of fungicides in cultivated plots Diniconazole increased plant emergence in cultivated plots at Kaniva 1 (from 6.0 to 11.9 plants m 1 drill row, I.s.d. = 4.6), but flutriafol reduced emergence (as it also did in direct-drilled plots) at Charlton (from 12.2 to 9.5, l.s.d. = 2.4), as did tebuconazole at Woomelang (12.7 to 8.2, l.s.d. = 4.1 ). Tebuconazole and pencycuron were the only fungicides to reduce the incidence of rhizoctonia root rot, and only at Kaniva 1 (from 69 to 42 and 37°/,,, respectively, I.s.d. = 25); however,
When fungicide treatments were combined with one cultivation on the day of sowing, they generally had no effect on emergence, except at Kaniva 1, where cultivation plus flutolanil or diniconazole increased emergence from 6.0 to 11.0 or 11.1 plants m i drill row, respectively (I.s.d. = 4.6). At Kaniva 2, cultivation plus pencycuron increased plant emergence from 9.0 to 14.7m -I (1.s.d. = 4.5), as did cultivation plus pencycuron or diniconazole at Woomelang (from 9.8 to 14.8 or 15.6 plants m 1, respectively). None of the combined treatmerits reduced plant emergence compared with the nil fungicide, direct-drilled control. Similarly, combined treatments had no effect on the incidence of rhizoctonia root rot; however, at Horsham, Kaniva 2, Walpeup and Woomelang, cultivation plus tebuconazole reduced severity of the disease (Table 2). Cultivation plus flutriafol or diniconazole reduced severity at Kaniva 2 and Woomelang; the combined SN-539865 treatment was effective at Kaniva 2 and Walpeup, as was the combined flutolanil treatment at Walpeup and Woomelang. The combined fenbuconazole and cyproconazole treatments were only effective at Woomelang and Kaniva 2, respectively. None of the combined treatments reduced either incidence or severity of take-all at any of the affected sites, but the SN-539865 plus cultivation treatment increased disease incidence from 47.8% in the nil fungicide, direct-drilled plots to 75.0% (I.s.d. = 27.1) at Horsham, and similarly at Kaniva 1, fenbuconazole plus cultivation increased incidence from 54.1 to 77.7% (I.s.d. = 22.7). Grain yields were improved only by the flutriafol and diniconazole combined treatments at Kaniva 1 and by the fenbuconazole plus cultivation treatment at Walpeup (Table 2), and flutriafol plus cultivation was the only combined treatment to increase yield consistently (Table 3).
Discussion In the nil fungicide plots at both Kaniva sites, cultivation on the day of sowing resulted in a higher grain yield
Crop Protection 1993 Volume 12 Number 4 275
Control of rhizoctonia root rot in barley: P. J. Cotterill Table 1. Severity (0-5) of rhizoctonia root rot and grain yield (kg ha-1) of barley following treatment with fungicide-coated clay granules (to deliver 400 g a.i. ha-1) direct-drilled with seed into undisturbed soil at six field sites in north-west Victoria Charlton Fungicide treatments Flutriafol Tebuconazole Pencycuron Fenbuconazole Cyproconazole Flutolanil SN-539865 Diniconazole
Horsham
Kaniva 1
Kaniva 2
Walpeup
Woomelang
Severity
Yield
Severity
Yield
Severity
Yield
Severity
Yield
Severity
Yield
Severity
Yield
2.28 2.32 2.17 2.45 2.60 2.32 2.20 2.15
1826 1972 1782 2425 1840 2045 2323 2381
1.00 0.67 1.00 1.00 1.00 1.00 0.67 1.00
953 1040 1112 895 1112 1112 1054 1069
1.14 1.19 1.44 1.11 1.18 1.49 1.35 1.18
1021 1219 1066 1965 *~ 655 975 1051 1005
1.00" 1.05" 1.09* I. I 1* 1.04* 1. I 1* 1.16" 1.20
2432 2735 2490 2979 2245 2691 2519 1785
2.12 1.87" 2.211 1.97 2. I 0 2.12 1.85" 1.97
11145 875 1155 1118 596 863 11170 1143
1.55 1.42" 1.38" 1.35* 1.65 1.43" 1.52" 1.31"
8511 765 1035 921 624 12115" 9117 921
"Asterisk (*) indicates disease severity rating lower (p = 0.05) or grain yield greater (p = 0.05) than nil control (see Figure 1)
Table 2. Severity (0-5) of rhizoctonia root rot and grain yield (kg ha-1) of barley following treatment with fungicide-coated granules (to deliver 400 g a.i. ha -1) drilled with seed into soil cultivated once on the day of sowing at six field sites in north-west Victoria Charlton Fungicide treatments Flutriafol Tebuconazole Peneycuron Fenbuconazole Cyproconazole Flutolanil SN-539865 Diniconazole
Horsham
Kaniva 1
Kaniva 2
Walpeup
Severity
Yield
Severity
Yield
Severity
Yield
Severity
Yield
Severity
Yield
2.02 2.117 2.45 2.32 2.40 2.47 2.43 2.37
2206*" 1884 1724 2293* 16811 2118 2133 2133
1.IXJ 0.33"* 1.00 1.00 0.811 1.00 1.00 0.67
1098 1098 1155 997 1141 1040 1127 1112
1.16 1.07 1.11 1.63 1.18 1.29 1.48 1.35
1432*" 1249 1127 914 945 1341 1173 1554t
.07* .10' .36 .29 .15t .23 .16' .08 t
29511 2936 3022 2634 2634 2735 2303 2677
1.98 1.80' 2.23 2.33 2.28 1.80 t 1.72 *t 1.97
1264 1094 9110 1415~ 535 1191 863 802
Woomelang Severity 1.42"* 1.47' 1.75 1.44*t 1.90 1.38"* 1.67 1.25*t
Yield 737 78(1 638 1035 765 765 921 879
"Disease severity rating lower (p = 0.05) or grain yield greater (p = 0.05) than nil cultivated plots (*) or nil direct-drilled plots (t) (see Figure 1)
Table 3. Effect of fungicide-coated a clay granules drilled with the seed into undisturbed soil or cultivated soil b on the severity c of rhizoctonia root rot and yield c of barley across six field sites in north-west Victoria in 1989
Disease severity DD C Combined
DD
Yield C Combined
Fungicide treatments Nil Flutriafol Tebuconazole Pencycuron Fenbuconazole Cyproconazole Flutolanil SN-539865 Diniconazole
1.00 0.89 0.83 0.92 0.89 0.94 0.95 0.86 0.89
1.00 0.95 0.80 1.07 1.09 1.02 1.00 1.04 0.92
1.00a 1t.86 0.75 0.98 1.00 11.94 0.92 0.96 0.85
1.00 1.00 1.03 1.08 1.06 1.01 1.13 0.93 1.31 1.08 0.85 0.84 1.13 1.04 1.12 0.98 1.09 1.02
1.00a 1.22 1.13 1.04 1.19 0.94 1.16 1.09 1.16
I.s.d.ep = 0.05
0.100 0.156
0.137
0.222 I).178
0.199
aFungicides were applied at 400 g a.i. ha t; ~uncultivatcd plots were sown by direct drilling (DD) and cultivated plots (C) received one cultivation on the day of sowing; 'values for disease severity ([I-51 and yield kg ha ') are proporti.... of the nil control treatment; avalucs arc means for nil fungicide, direct-drilled control plots; "least significant difference for comparisons between nil and fungicide treatments only
t h a n in t h o s e p l o t s w h e r e s e e d was d i r e c t - d r i l l e d . T h i s c o u l d h a v e o c c u r r e d b e c a u s e r h i z o c t o n i a r o o t rot was m o r e s e v e r e in t h e d i r e c t - d r i l l e d p l o t s (at t h e K a n i v a 2 site) a n d / o r b e c a u s e p l a n t e m e r g e n c e was g r e a t e r in c u l t i v a t e d p l o t s (at b o t h sites). It is u n l i k e l y t h a t r e d u c e d e m e r g e n c e in d i r e c t - d r i l l e d p l o t s was c a u s e d by r h i z o c t o n i a r o o t r o t , as o n l y t h e R. solani i s o l a t e s responsible for causing sharp eyespot have been i m p l i c a t e d ( B a n y e r , 1966). C e r t a i n l y , at K a n i v a 2 it is
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Crop Protection 1993 Volume 12 Number 4
possible that the disease was responsible f o r l o w e r yield in d i r e c t - d r i l l e d plots, because plant establishment alone should not have affected grain yields (Perry and J a r v i s , 1985). M o r e o v e r , at t h e C h a r l t o n site, w h i c h has t h e s a m e soil t y p e as t h e K a n i v a 2 site, yield was g r e a t e r in t h e d i r e c t - d r i l l e d r a t h e r t h a n t h e c u l t i v a t e d p l o t s , b u t t h e r e w e r e n o d i f f e r e n c e s r e c o r d e d for p l a n t e m e r g e n c e or disease levels between the two cultivation treatments. W h e n r o o t d i s e a s e o c c u r r e d in c o m b i n a t i o n w i t h soil s t r u c t u r a l p r o b l e m s in a h a r d - s e t t i n g r e d - b r o w n e a r t h ( s i m i l a r to t h e soils at C h a r l t o n a n d K a n i v a 2) in S o u t h A u s t r a l i a , d i r e c t - d r i l l e d b a r l e y ( s o w n using a s p e c i a l l y modified point) yielded better than barley sown following c u l t i v a t i o n ( R o g e t et al., 19891. A l t h o u g h t h e Charlton Chariton
a n d K a n i v a 2 sites h a v e s i m i l a r soils, t h e site r e q u i r e d an a p p l i c a t i o n o f g y p s u m to
i m p r o v e w a t e r p e n e t r a t i o n , w h e r e a s t h e K a n i v a 2 site ( w h i c h p r o d u c e d b e t t e r yields - a l t h o u g h o b v i o u s l y o t h e r f a c t o r s w e r e also i n v o l v e d ) did n o t r e q u i r e a g y p s u m a m e n d m e n t . It is p o s s i b l e , t h e r e f o r e , t h a t at C h a r l t o n , d e s p i t e t h e risk o f r h i z o c t o n i a r o o t r o t , d i r e c t - d r i l l i n g w a s m o r e b e n e f i c i a l to t h e c r o p t h a n c u l t i v a t i o n , in a m a n n e r s i m i l a r to t h a t r e p o r t e d by R o g e t et al. (1989). T h e i n c r e a s e d y i e l d o f b a r l e y in c u l t i v a t e d soil c o m p a r e d w i t h z e r o - t i l l soil at t h e r h i z o c t o n i a - p r o n e K a n i v a sites c o n f i r m s s i m i l a r results in b a r l e y ( M a c N i s h , 1985b; W e l l e r et al., 1 9 8 6 ) a n d in w h e a t ( J a r v i s a n d B r e n n a n , 1986; R o v i r a , 1986; W e l l e r et al., 1986; P u m p h r e y et al., 1987; d e B o e r a n d K o l l m o r g e n , 1988; S m i l e y e t a l . , 1990a). Five fungicides (flutriafol, tebuconazole, fenbucon-
Control of rhizoctonia root rot in barley: P. J. Cotterill
azole, SN-539865 and diniconazole) reduced rhizoctonia root rot in direct-drilled barley, but only f e n b u c o n a z o l e increased grain yields. The reduction in levels of rhizoctonia root rot observed at anthesis may have been insufficient to elicit a resultant yield increase or, alternatively, any reductions could have been too subtle for detection statistically. Barley m a y not respond as well as wheat to the application of the fungicides because it is possibly m o r e susceptible to the disease (MacNish, 1985a; Neate, 1989). In a similar study, diniconazole increased the yield of direct-drilled wheat at the Kaniva 2 site (Cotterill, 1991), whereas in this study the same treatment in barley resulted in a very poor yield, S m i l e y e t a l . ( 1 9 9 0 b ) r e p o r t e d t h a t f l u t o l a n i l , metalaxyl and tolclofos methyl were generally effective against rhizoctonia root rot in direct-drilled wheat, but ineffective in wheat sown following conventional cultivation. In the study described here, fungicides that reduced the severity of rhizoctonia root rot when c o m b i n e d with soil cultivation were generally no m o r e effective than when applied to undisturbed soil. This may be due to the fact that cultivation itself reduced the severity of disease to a level where fungicides were unable to have any further observable effect. Alternatively, cultivation could have reduced soil water retention, which may have affected fungicide efficacy, Several fungicides reduced the severity of rhizoctonia root rot at Kaniva 2, W a l p e u p and W o o m e l a n g , but if cultivation decreased soil water retention, hence reducing fungicide mobility (and therefore efficacy), then this effect was not apparent. Better soil structure at the above three sites c o m p a r e d with the Charlton site (which required an application of gypsum to improve water penetration) could explain why fungicides were generally effective at the three sites and ineffective at Charlton. It is evident that soil type may have a significant bearing upon the p e r f o r m a n c e of certain fungicides in cultivated or undisturbed plots: for
efficacy of each fungicide is heavily d e p e n d e n t on soil type and cultivation m e t h o d .
Acknowledgements The author is grateful to Miss L. M c L e a n , Miss B. Roberts, Mr G. Exell, Mr D. W a r d and staff of Malice Research Station, W a l p e u p for technical assistance, Dr G. Ford for soil classifications, cooperating farmers for provision of trial areas and Dr G. Wildermuth for c o m m e n t s on the manuscript. Funds for the investigations were provided by the W h e a t Research Council of Australia, B a y e r (Australia) Ltd, ICI (Australia) Pty Ltd, Shell Chemical (Australia) Pry Ltd and the Phosphate Cooperative C o m p a n y of Australia.
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and stubble retention on soil- and stubble-borne pathogens of wheat in Victoria - an overview. Plant Prof. Q. 3, 3--4
Henry, F. and Brown, J. (1991) Ccreal root diseasc survcy - 1990 results. Crop Prot. Bull. (Dept. Agric. Vie.)27,8-12 Hore, H, L. (1941) Soil drift control. J. Agric, Vic. 39, 357-365
example, at Kaniva 1, fenbuconazole was more effective in undisturbed soil, whereas at W a l p e u p it was more
Jarvis, R. J. and Brennan, R. F. (1986) Timing and intcnsity of surface cultivation and depth of cultivation affect rhizoctonia patch and whcat yield. Aust. J. Expl Agric. 26, 7(13-708
effective when c o m b i n e d with cultivation. Nevertheless, at Kaniva 1 the presence of take-all
MacNish, G. C. (1985a) Mapping rhizoctonia patch in consect,tivc cereal crops in Wcstcrn Australia. Plant Pathol. 34, 165-174
undoubtedly reduced yield in fenbuconazole-treated, cultivated plots because the fungicide did not control
MacNish,G. C. (1985b) Methods of reducing rhizoctonia patch of cereals in Western Australia. Plant Puthol. 34, 175-181
take-all or rhizoctonia root rot, but exacerbated both diseases. In direct-drilled plots, however, fenbuconazole doubled grain yield. The failure of fungicides to have any effect on barley yield at H o r s h a m could have been due to high levels of take-all at the site. A l t h o u g h flutriafol is used for take-all control (Ballinger and Kollmorgen, 1988), it failed to increase yields despite reducing incidence of the disease in cultivated plots. The only effective control measures that generally increased yields were fenbuconazole in undisturbed soil and flutriafol c o m b i n e d with cultivation. This study has identified two fungicides (flutriafol
Neate, S. M. (1989) A comparison of controllcd environment and field trials for detection of resistance in cereal cultivars to root rot caused by Rhizoctonia solani. Plant PathoL 38,494-5(11 Northeote, K.H. (1979) A Factual Key jor the Recognition oJ' Australian Soils, Rcllim Technical Publications, Adelaide Perry, M. W. and Jarvis, R. J. (1985)Depth of Sowing Cereals. Technote5/&5, Western Australian Department of Agriculture, Perth Pumphrey, F. V., Wilkins, D. E., l-lane, D. C. and Smiley, R. W. (1987) lnfluence of tillage and nitrogcn fertiliser on Rhizoctoniaroot rot (bare patch) of wintcr wheat. Plant Dis. 71, 125-127 Roget, D. K., Neate, S. M. and Rovira, A. D. (1989) Rcduction of root diseasc in direct-drilled cereals using a modified sowing point.
and f e n b u c o n a z o l e ) that show some potential for reducing rhizoctonia root rot and increasing grain yield of barley. None the less, it is quite evident that the
1989, p. 63, Australasian Plant Pathology Society, Brisbanc Rnvira, A.D. (1986) Influencc of crop rotation and tillagc on rhizoctonia barc patch of wheat. Phytopathology 76, 669-673
Abstr. 7th Australas. Plant Pathol. Soc. Conf , Brisbane, 3-7 July
Crop Protection 1993 Volume 12 Number 4
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Control of rhizoctonia root rot in barley: P. J. Cotterill Smiley, R. W., Wiikins, D. E. and Klepper, E. L. (1990a) Impact of fungicide treatments on rhizoctonia root rot, take-all, eyespot, and growth of winter wheat. Plant Dis, 74, 782-787 Smiley, R. W., Uddin, W., Ott, S. and Rhinhart, K. E. L. (1990b) Influence of flutolanil and tolclofos-methyl on root and culm diseases of winter wheat. Plant Dis. 74, 788-791 Weller, D. M., Cook, R. J., MaeNish, G., Bassett, E. N., Powelson, R. L. and Petersen, R. R. (1986) Rhizoctonia root rot of small grains
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Crop Protection 1993 Volume 12 Number 4
favoured by reduced tillage in the Pacific Northwest Plant Dis. 70, 70-73 Zadoks, J. C., Chang, T. T. and Konzak, C. F. (1974) A decimal code for the growth stages of cereals. Weed Res. 14, 415-421 Received 20 April 1992 Revised 4 December 1992 Accepted 7 December 1992
Department of Agriculture and Rural Affairs, Victoria 3400, Australia
Victorian Crops Research Institute, Horsham,
The effect of eight fungicides, applied in-furrow to undisturbed or cultivated soils, on rhizoctonia root rot and yield of barley (Hordeum vulgare) was investigated at six sites with differing soil type and disease risk in the north-west of Victoria, Australia. A single shallow cultivation on the day of sowing reduced disease severity at one site and increased grain yield at this and one other site, but at another site, grain yield was reduced in barley sown after cultivation. Five fungicides (flutriafol, tcbuconazolc, fenbuconazole, SN-539865 and diniconazole), coated on clay granules to give 400 g a.i. ha -I and applied to the drill row at sowing, generally reduced the severity of rhizoctonia root rot in direct-drilled plots; flutriafol, tebuconazole and diniconazole were effective when combined with soil cultivation, but only flutriafol, combined with cultivation, and fenbuconazole in undisturbed soil increased grain yields.
Keywords: Rhizoctonia root rot; barley; fungicides; in-furrow; cultivation
In Australia, barley (Hordeum vulgare L.) generally appears to be more susceptible to rhizoctonia root rot (caused by Rhizoctonia solani Kiihn) than wheat (Triticum aestivum L.) (MacNish, 1985a; Neate, 1989); barley, therefore, may not respond to cultural control measures as readily as wheat. Soil cultivation is currently regarded as the most effective control method in Australia, with several methods proving effective (Jarvis and Brennan, 1986; Rovira, 1986; de Boer and Kollmorgen, 1988). Cultivation is also effective in reducing rhizoctonia root rot of wheat in the USA (Weller et al., 1986; Pumphrey et al., 1987; Smiley, Wilkins and Klepper, 1990a). The calcareous sandy Ioams of the Mallee regions (which comprise much of the cereal-growing area of southern Australia) and other soil types, particularly the hard-setting red-brown earths, are not suited to constant conventional cultivation (Here, 1941; Roget, Neate and Rovira, 1989). Furthermore, cultivation is not always a wholly successful means of control (Cotterill, 1990a; Henry and Brown, 1991). Fungicides have been tested for control of rhizoctonia root rot of wheat in the USA (Smiley et al., 1990a, b), and in Australia (Cotterill, 1990b, 1991) both in the presence and absence of cultivation. Fungicide application to the drill row during the sowing operation has been used to control take-all ]caused by Gaeumannomyces graminis (Sacc.) von Arx & Olivier var. tritici Walker] of wheat
*Present address: Queensland Department of Primary Industries,
Queensland Wheat Research Institute, PO Box 2282, Toowoomba, Queensland 4350, Australia
in Australia (Ballinger and Kollmorgen, 1988) and such a technique could be beneficial in reducing yield losses due to rhizoctonia root rot in barley. The aims of this study were (a) to compare limited soil cultivation with direct-drilling and (b) to determine the efficacy of eight fungicides on clay granules drilled with the seed into cultivated or undisturbed soil, on the control of rhizoctonia root rot of barley at six sites of differing soil type and disease risk in north-west Victoria.
Materials and methods Fungicides
Eight fungicides were tested, namely flutriafol, tebuconazole, pencycuron, fenbuconazole (RH-7592), cyproconazole, flutolanil, SN-539865 and diniconazole (Cotterill, 1991). Clay granules ( - 1 mm diameter, Attapulgite, 100% absorbent granules, MallinaHoldings Ltd, Perth, Australia) were coated with each of the fungicides by thoroughly mixing batches of granules with an appropriate quantity of fungicide in a ball mill. This gave a concentration of 400 g a.i. ha `.-] when clay granules were applied to the field at a rate of 50 kg ha -~ . Field experiments Six sites of varying soil type, location and risk of rhizoctonia root rot (Cotterill, 1991) in north-west Victoria were chosen in 1988. Mean annual rainfall at the first four sites ranges between 425 and 456 mm and
0261-2194/93/04/0273-06 © 1993 Butterworth-Heinemann Ltd Crop Protection 1993 Volume 12 Number 4
273
Control of rhizoctonia root rot in barley: P. J. Cotterill
at Walpeup and Woomelang is 342 mm. Soils at each site [according to the Northcote (1979) classification] are as follows:
Char#on: Dr 2.13, a clay loam A1 horizon with a pH of 6.0 to a depth of ~10 cm, no A2 horizon and an alkaline reaction trend to a medium clay at depth, Horsham: Ug 5.16, a friable self-mulching grey clay A horizon with a pH of 9.0 to - 1 0 cm underlain by a grey clay.
Comparisons were made, for the parameters discussed, at each site, and across all sites (severity of rhizoctonia root rot and grain yield only) between (a) nil fungicide, direct-drilled plots and nil fungicide, cultivated plots, (b) nil fungicide and the eight fungicide treatments in direct-drilled plots, (c) nil fungicide and the eight fungicide treatments in cultivated plots, and (d) nil fungicide, direct-drilled plots and combined treatments (fungicide-treated, cultivated plots).
Kaniva 1: Gn 5.43, a sandy clay A1 horizon with a pH of 5.5 to --5 cm, no A2 horizon evident and an
Statistical analyses
alkaline reaction trend to a medium clay.
A two-way analysis of variance was performed on the data from each site. For an overall fungicide treatment
Kaniva 2: Dr 2.13, as for Charlton except A1 horizon to - 7 cm.
Walpeup: Gn 2.13, a sandy loam A1 horizon with a pH of 6.5 to - 1 2 cm, no A2 horizon and an alkaline reaction trend to a light clay.
Woomelang: Gc 1.21, a sandy loam A1 horizon with a pH of 8.0 to - 1 0 cm, no A2 horizon and an alkaline reaction trend to a light clay.
Sites were prepared as described by Cotterill (1991) and sown in mid-May (Charlton, Waipeup and Woomelang) or the first week in June, 1989 (remainder). On the day of sowing, half of the plots at each site were cultivated to a depth of 6-7 cm using shares (10 cm wide) attached to the drill. Plots were then sown, using modified lucerne points, with 70 kg ha 1 barley (cv. Galleon), 80 kg ha-1 double superphosphate (17.5% P, 4.1% S) and 50 kg ha -1 clay granules either uncoated, or coated with fungicide. Seed was covered by dragging an upturned harrow behind the drill. During crop growth, diclofop methyl was applied to control ryegrass (Lolium rigidum Gaud.) and bromoxynil plus MCPA to control broad-leaved weeds (Cotterill, 1991). Plant emergence was measured using three quadrats (each representing two half-metre lengths of drill row per plot) at all sites, except Horsham, 3-5 weeks after sowing (Cotterill, 1991). At anthesis (growth stages 59~9; Zadoks, Chang and Konzak, 1974), barley plants were sampled from four randomly selected sections (30 cm) of drill row in each plot. Twenty plants were randomly selected from each plot sample and roots washed free of soil. Roots were rated for incidence (percentage plants infected), and severity (percentage roots infected per plant) of rhizoctonia root rot, on a 0-5 scale, where 0 = nil disease and 5 = maximum disease (Cotterill, 1991). Plants were also rated for incidence and, where appropriate, severity of take-all, using a 0-4 scale where 0 = nil disease and 4 = maximum disease (Cotterill, 1991). R. solani and G. graminis vat. tritici were isolated from barley plants to confirm that these were the causal agents of rhizoctonia root rot and take-all, respectively. At maturity, grain yield per plot (converted to kg ha 1) was determined. Plots were 15 m by six rows and the fungicide treatments were arranged in randomized complete blocks with three replications and three nil fungicide plots of each cultivation treatment per replicate,
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comparison within each cultivation treatment across all sites, the proportional reduction or increase in disease severity or yield over the nil fungicide treatments was calculated. For combined treatments (fungicide plus cultivation) the proportional change against the nil
fungicide, direct-drilled treatment was calculated. This was done by designating the mean value for the nil fungicide treatments at each site as 1.00, then calculating the proportional change of each treatment mean at each site. An analysis of variance was done on these data from all sites.
Results
Effect of cultivation treatments
At Kaniva sites 1 and 2, plant emergence was lower in nil fungicide plots that were direct-drilled than in those that were cultivated [5.96 compared with 10.07 plants m 1 drill row, 1.s.d. = 3.21 (all l.s.d, values are p = 0.05) and 8.96, compared with 14.45, l.s.d. = 3.15, respectively]. Incidence of rhizoctonia root rot on plants sampled from nil fungicide, direct-drilled plots at anthesis was 100, 10, 58, 47,100 and 100%, respectively, for the Charlton, Horsham, Kaniva 1, Kaniva 2, Walpeup and Woomelang sites. Tillage treatment did not affect disease incidence. Disease severity was not affected at any site either, with the exception of Kaniva 2 (Figure la). Take-all was recorded on plants at the Horsham, Kaniva 1, Kaniva 2 and Woomelang sites. Incidence (%) [and severity, (0-4)] for nil fungicide plots were 52% [2.25], 60% [1.32], 10% and 4%, respectively; no effects of tillage treatment were observed. Grain yields were greater from the nil fungicide, cultivated plots than from the nil fungicide, direct-drilled plots at both Kaniva sites; however, there was no difference in yield at Horsham, Walpeup or Woomelang. Charlton yields were greater in directdrilled plots (Figure lb). Effect of fungicides in direct-drilled plots Flutriafol reduced plant emergence in the direct-drilled plots at Charlton (from 10.7 to 8.0 plants m -I drill row, I.s.d. = 2.4). None of the fungicides reduced incidence of rhizoctonia root rot at any site, or severity at
Control of rhizoctonia root rot in barley: P. J. Cotterill 3.°[a
/
2.5
]
]
ta~
& 2.0
1.5
>
T
I ______r--~. . . I
"~ L 1.0 :c 0.5 0
-
--
, b
-r
flutolanil and diniconazole increased incidence at Horsham (from 7.8 to 25.0 and 31.7°/,,, respectively, l.s.d. = 16.9). Few fungicide treatments reduced the severity of rhizoctonia root rot in cultivated plots, the exceptions being tebuconazole at Horsham, and flutriafol, fenbuconazole, flutolanil and diniconazole at Woomelang (Table 2). Only tebuconazole appeared to be generally effective (Table 3). Incidence of take-all was reduced by flutriafol and tebuconazole at Kaniva 1 (from 67 to 43 and 40%, respectively, l.s.d. = 23) and by flutriafol at Horsham (from 57 to 23%, 1.s.d. = 27), where diniconazole reduced take-all severity (from 2.46 to 1.38, l.s.d. = 0.78). At Charlton, flutriafol and fenbuconazole increased grain yield. No fungicide generally increased yield (Table 3).
.L
3
Effect of combined (fungicide plus cultivation) treatments
'~: ,z .~ c '~
2 ]~ H
~
0
~
__ Charlton Horsham Kaniva
Kaniva Walpeup W'lang
1
2 Site Figure 1. Severity of rhizoctonia root rot (a) and grain yield (b) of barley either direct-drilled (B) into undisturbed soil or i n t o soil cultivated (D) once on the day of sowing, at six sites in north-west Victoria, Australia. Capped vertical lines represent I.s.d. (/9 = 0.05) Charlton, Horsham or Kaniva 1; however, all fungicides except diniconazole reduced severity at Kaniva 2, all but flutriafol and cyproconazole were effective at Woomelang, and at Walpeup only tebuconazole and SN-539865 were effective (Table 1). Generally, disease severity was reduced by flutriafol, tebuconazole, fenbuconazole, SN-539865 and diniconazole (Table 3). No fungicide treatment reduced incidence or severity of take-all at any of the infested sites, but fenbuconazole increased t a k e - a l l i n c i d e n c e ( f r o m l . 7 t o 1 3 . 3 % , l . s . d . = 9.0) at Woomelang. Grain yields were increased only by flutolanil at Woomelang and by fenbuconazole at Kaniva 1 (Table 1), although fenbuconazole appeared to be generally effective (Table 3). Effect of fungicides in cultivated plots Diniconazole increased plant emergence in cultivated plots at Kaniva 1 (from 6.0 to 11.9 plants m 1 drill row, I.s.d. = 4.6), but flutriafol reduced emergence (as it also did in direct-drilled plots) at Charlton (from 12.2 to 9.5, l.s.d. = 2.4), as did tebuconazole at Woomelang (12.7 to 8.2, l.s.d. = 4.1 ). Tebuconazole and pencycuron were the only fungicides to reduce the incidence of rhizoctonia root rot, and only at Kaniva 1 (from 69 to 42 and 37°/,,, respectively, I.s.d. = 25); however,
When fungicide treatments were combined with one cultivation on the day of sowing, they generally had no effect on emergence, except at Kaniva 1, where cultivation plus flutolanil or diniconazole increased emergence from 6.0 to 11.0 or 11.1 plants m i drill row, respectively (I.s.d. = 4.6). At Kaniva 2, cultivation plus pencycuron increased plant emergence from 9.0 to 14.7m -I (1.s.d. = 4.5), as did cultivation plus pencycuron or diniconazole at Woomelang (from 9.8 to 14.8 or 15.6 plants m 1, respectively). None of the combined treatmerits reduced plant emergence compared with the nil fungicide, direct-drilled control. Similarly, combined treatments had no effect on the incidence of rhizoctonia root rot; however, at Horsham, Kaniva 2, Walpeup and Woomelang, cultivation plus tebuconazole reduced severity of the disease (Table 2). Cultivation plus flutriafol or diniconazole reduced severity at Kaniva 2 and Woomelang; the combined SN-539865 treatment was effective at Kaniva 2 and Walpeup, as was the combined flutolanil treatment at Walpeup and Woomelang. The combined fenbuconazole and cyproconazole treatments were only effective at Woomelang and Kaniva 2, respectively. None of the combined treatments reduced either incidence or severity of take-all at any of the affected sites, but the SN-539865 plus cultivation treatment increased disease incidence from 47.8% in the nil fungicide, direct-drilled plots to 75.0% (I.s.d. = 27.1) at Horsham, and similarly at Kaniva 1, fenbuconazole plus cultivation increased incidence from 54.1 to 77.7% (I.s.d. = 22.7). Grain yields were improved only by the flutriafol and diniconazole combined treatments at Kaniva 1 and by the fenbuconazole plus cultivation treatment at Walpeup (Table 2), and flutriafol plus cultivation was the only combined treatment to increase yield consistently (Table 3).
Discussion In the nil fungicide plots at both Kaniva sites, cultivation on the day of sowing resulted in a higher grain yield
Crop Protection 1993 Volume 12 Number 4 275
Control of rhizoctonia root rot in barley: P. J. Cotterill Table 1. Severity (0-5) of rhizoctonia root rot and grain yield (kg ha-1) of barley following treatment with fungicide-coated clay granules (to deliver 400 g a.i. ha-1) direct-drilled with seed into undisturbed soil at six field sites in north-west Victoria Charlton Fungicide treatments Flutriafol Tebuconazole Pencycuron Fenbuconazole Cyproconazole Flutolanil SN-539865 Diniconazole
Horsham
Kaniva 1
Kaniva 2
Walpeup
Woomelang
Severity
Yield
Severity
Yield
Severity
Yield
Severity
Yield
Severity
Yield
Severity
Yield
2.28 2.32 2.17 2.45 2.60 2.32 2.20 2.15
1826 1972 1782 2425 1840 2045 2323 2381
1.00 0.67 1.00 1.00 1.00 1.00 0.67 1.00
953 1040 1112 895 1112 1112 1054 1069
1.14 1.19 1.44 1.11 1.18 1.49 1.35 1.18
1021 1219 1066 1965 *~ 655 975 1051 1005
1.00" 1.05" 1.09* I. I 1* 1.04* 1. I 1* 1.16" 1.20
2432 2735 2490 2979 2245 2691 2519 1785
2.12 1.87" 2.211 1.97 2. I 0 2.12 1.85" 1.97
11145 875 1155 1118 596 863 11170 1143
1.55 1.42" 1.38" 1.35* 1.65 1.43" 1.52" 1.31"
8511 765 1035 921 624 12115" 9117 921
"Asterisk (*) indicates disease severity rating lower (p = 0.05) or grain yield greater (p = 0.05) than nil control (see Figure 1)
Table 2. Severity (0-5) of rhizoctonia root rot and grain yield (kg ha-1) of barley following treatment with fungicide-coated granules (to deliver 400 g a.i. ha -1) drilled with seed into soil cultivated once on the day of sowing at six field sites in north-west Victoria Charlton Fungicide treatments Flutriafol Tebuconazole Peneycuron Fenbuconazole Cyproconazole Flutolanil SN-539865 Diniconazole
Horsham
Kaniva 1
Kaniva 2
Walpeup
Severity
Yield
Severity
Yield
Severity
Yield
Severity
Yield
Severity
Yield
2.02 2.117 2.45 2.32 2.40 2.47 2.43 2.37
2206*" 1884 1724 2293* 16811 2118 2133 2133
1.IXJ 0.33"* 1.00 1.00 0.811 1.00 1.00 0.67
1098 1098 1155 997 1141 1040 1127 1112
1.16 1.07 1.11 1.63 1.18 1.29 1.48 1.35
1432*" 1249 1127 914 945 1341 1173 1554t
.07* .10' .36 .29 .15t .23 .16' .08 t
29511 2936 3022 2634 2634 2735 2303 2677
1.98 1.80' 2.23 2.33 2.28 1.80 t 1.72 *t 1.97
1264 1094 9110 1415~ 535 1191 863 802
Woomelang Severity 1.42"* 1.47' 1.75 1.44*t 1.90 1.38"* 1.67 1.25*t
Yield 737 78(1 638 1035 765 765 921 879
"Disease severity rating lower (p = 0.05) or grain yield greater (p = 0.05) than nil cultivated plots (*) or nil direct-drilled plots (t) (see Figure 1)
Table 3. Effect of fungicide-coated a clay granules drilled with the seed into undisturbed soil or cultivated soil b on the severity c of rhizoctonia root rot and yield c of barley across six field sites in north-west Victoria in 1989
Disease severity DD C Combined
DD
Yield C Combined
Fungicide treatments Nil Flutriafol Tebuconazole Pencycuron Fenbuconazole Cyproconazole Flutolanil SN-539865 Diniconazole
1.00 0.89 0.83 0.92 0.89 0.94 0.95 0.86 0.89
1.00 0.95 0.80 1.07 1.09 1.02 1.00 1.04 0.92
1.00a 1t.86 0.75 0.98 1.00 11.94 0.92 0.96 0.85
1.00 1.00 1.03 1.08 1.06 1.01 1.13 0.93 1.31 1.08 0.85 0.84 1.13 1.04 1.12 0.98 1.09 1.02
1.00a 1.22 1.13 1.04 1.19 0.94 1.16 1.09 1.16
I.s.d.ep = 0.05
0.100 0.156
0.137
0.222 I).178
0.199
aFungicides were applied at 400 g a.i. ha t; ~uncultivatcd plots were sown by direct drilling (DD) and cultivated plots (C) received one cultivation on the day of sowing; 'values for disease severity ([I-51 and yield kg ha ') are proporti.... of the nil control treatment; avalucs arc means for nil fungicide, direct-drilled control plots; "least significant difference for comparisons between nil and fungicide treatments only
t h a n in t h o s e p l o t s w h e r e s e e d was d i r e c t - d r i l l e d . T h i s c o u l d h a v e o c c u r r e d b e c a u s e r h i z o c t o n i a r o o t rot was m o r e s e v e r e in t h e d i r e c t - d r i l l e d p l o t s (at t h e K a n i v a 2 site) a n d / o r b e c a u s e p l a n t e m e r g e n c e was g r e a t e r in c u l t i v a t e d p l o t s (at b o t h sites). It is u n l i k e l y t h a t r e d u c e d e m e r g e n c e in d i r e c t - d r i l l e d p l o t s was c a u s e d by r h i z o c t o n i a r o o t r o t , as o n l y t h e R. solani i s o l a t e s responsible for causing sharp eyespot have been i m p l i c a t e d ( B a n y e r , 1966). C e r t a i n l y , at K a n i v a 2 it is
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Crop Protection 1993 Volume 12 Number 4
possible that the disease was responsible f o r l o w e r yield in d i r e c t - d r i l l e d plots, because plant establishment alone should not have affected grain yields (Perry and J a r v i s , 1985). M o r e o v e r , at t h e C h a r l t o n site, w h i c h has t h e s a m e soil t y p e as t h e K a n i v a 2 site, yield was g r e a t e r in t h e d i r e c t - d r i l l e d r a t h e r t h a n t h e c u l t i v a t e d p l o t s , b u t t h e r e w e r e n o d i f f e r e n c e s r e c o r d e d for p l a n t e m e r g e n c e or disease levels between the two cultivation treatments. W h e n r o o t d i s e a s e o c c u r r e d in c o m b i n a t i o n w i t h soil s t r u c t u r a l p r o b l e m s in a h a r d - s e t t i n g r e d - b r o w n e a r t h ( s i m i l a r to t h e soils at C h a r l t o n a n d K a n i v a 2) in S o u t h A u s t r a l i a , d i r e c t - d r i l l e d b a r l e y ( s o w n using a s p e c i a l l y modified point) yielded better than barley sown following c u l t i v a t i o n ( R o g e t et al., 19891. A l t h o u g h t h e Charlton Chariton
a n d K a n i v a 2 sites h a v e s i m i l a r soils, t h e site r e q u i r e d an a p p l i c a t i o n o f g y p s u m to
i m p r o v e w a t e r p e n e t r a t i o n , w h e r e a s t h e K a n i v a 2 site ( w h i c h p r o d u c e d b e t t e r yields - a l t h o u g h o b v i o u s l y o t h e r f a c t o r s w e r e also i n v o l v e d ) did n o t r e q u i r e a g y p s u m a m e n d m e n t . It is p o s s i b l e , t h e r e f o r e , t h a t at C h a r l t o n , d e s p i t e t h e risk o f r h i z o c t o n i a r o o t r o t , d i r e c t - d r i l l i n g w a s m o r e b e n e f i c i a l to t h e c r o p t h a n c u l t i v a t i o n , in a m a n n e r s i m i l a r to t h a t r e p o r t e d by R o g e t et al. (1989). T h e i n c r e a s e d y i e l d o f b a r l e y in c u l t i v a t e d soil c o m p a r e d w i t h z e r o - t i l l soil at t h e r h i z o c t o n i a - p r o n e K a n i v a sites c o n f i r m s s i m i l a r results in b a r l e y ( M a c N i s h , 1985b; W e l l e r et al., 1 9 8 6 ) a n d in w h e a t ( J a r v i s a n d B r e n n a n , 1986; R o v i r a , 1986; W e l l e r et al., 1986; P u m p h r e y et al., 1987; d e B o e r a n d K o l l m o r g e n , 1988; S m i l e y e t a l . , 1990a). Five fungicides (flutriafol, tebuconazole, fenbucon-
Control of rhizoctonia root rot in barley: P. J. Cotterill
azole, SN-539865 and diniconazole) reduced rhizoctonia root rot in direct-drilled barley, but only f e n b u c o n a z o l e increased grain yields. The reduction in levels of rhizoctonia root rot observed at anthesis may have been insufficient to elicit a resultant yield increase or, alternatively, any reductions could have been too subtle for detection statistically. Barley m a y not respond as well as wheat to the application of the fungicides because it is possibly m o r e susceptible to the disease (MacNish, 1985a; Neate, 1989). In a similar study, diniconazole increased the yield of direct-drilled wheat at the Kaniva 2 site (Cotterill, 1991), whereas in this study the same treatment in barley resulted in a very poor yield, S m i l e y e t a l . ( 1 9 9 0 b ) r e p o r t e d t h a t f l u t o l a n i l , metalaxyl and tolclofos methyl were generally effective against rhizoctonia root rot in direct-drilled wheat, but ineffective in wheat sown following conventional cultivation. In the study described here, fungicides that reduced the severity of rhizoctonia root rot when c o m b i n e d with soil cultivation were generally no m o r e effective than when applied to undisturbed soil. This may be due to the fact that cultivation itself reduced the severity of disease to a level where fungicides were unable to have any further observable effect. Alternatively, cultivation could have reduced soil water retention, which may have affected fungicide efficacy, Several fungicides reduced the severity of rhizoctonia root rot at Kaniva 2, W a l p e u p and W o o m e l a n g , but if cultivation decreased soil water retention, hence reducing fungicide mobility (and therefore efficacy), then this effect was not apparent. Better soil structure at the above three sites c o m p a r e d with the Charlton site (which required an application of gypsum to improve water penetration) could explain why fungicides were generally effective at the three sites and ineffective at Charlton. It is evident that soil type may have a significant bearing upon the p e r f o r m a n c e of certain fungicides in cultivated or undisturbed plots: for
efficacy of each fungicide is heavily d e p e n d e n t on soil type and cultivation m e t h o d .
Acknowledgements The author is grateful to Miss L. M c L e a n , Miss B. Roberts, Mr G. Exell, Mr D. W a r d and staff of Malice Research Station, W a l p e u p for technical assistance, Dr G. Ford for soil classifications, cooperating farmers for provision of trial areas and Dr G. Wildermuth for c o m m e n t s on the manuscript. Funds for the investigations were provided by the W h e a t Research Council of Australia, B a y e r (Australia) Ltd, ICI (Australia) Pty Ltd, Shell Chemical (Australia) Pry Ltd and the Phosphate Cooperative C o m p a n y of Australia.
References Ballinger,D.J. and Kollmorgen, J.F. (1988) Effect of triazole coated superphosphate, applied at sowing, on take-all and yield of wheat. Aust. J. Expl Agric. 28, 635438 Banyer, R. J. (1966) Ccreal root discases and thcir control. Part III. j. Agric. South Aust. 69,415-417 CotterilI, P.J.(1990a) AssessmentofyieldlosscausedbyRhizoctonia root rot in a barley crop sown following cultivation at Nhill, northwest Victoria. Australas. Plant Pathol. 19, 77-78 Cotterill, P. J. (1990b) Evaluation of fungicides, applied at seeding, against Rhizoctonia root rot of wheat. Tests of Agrochemicals and Cultivars (Ann. Appl. Biol. 116 Suppl.) No. 1I, pp. 48--49 Cotterill, P. J. (1991) Evaluation of in-furrow fungicide treatments to control rhizoctonia root rot of wheat. Crop Prot. 10, 473-478 de Boer, R. F. and Kollmorgen, J. F. (1988) Effects of cultivation
and stubble retention on soil- and stubble-borne pathogens of wheat in Victoria - an overview. Plant Prof. Q. 3, 3--4
Henry, F. and Brown, J. (1991) Ccreal root diseasc survcy - 1990 results. Crop Prot. Bull. (Dept. Agric. Vie.)27,8-12 Hore, H, L. (1941) Soil drift control. J. Agric, Vic. 39, 357-365
example, at Kaniva 1, fenbuconazole was more effective in undisturbed soil, whereas at W a l p e u p it was more
Jarvis, R. J. and Brennan, R. F. (1986) Timing and intcnsity of surface cultivation and depth of cultivation affect rhizoctonia patch and whcat yield. Aust. J. Expl Agric. 26, 7(13-708
effective when c o m b i n e d with cultivation. Nevertheless, at Kaniva 1 the presence of take-all
MacNish, G. C. (1985a) Mapping rhizoctonia patch in consect,tivc cereal crops in Wcstcrn Australia. Plant Pathol. 34, 165-174
undoubtedly reduced yield in fenbuconazole-treated, cultivated plots because the fungicide did not control
MacNish,G. C. (1985b) Methods of reducing rhizoctonia patch of cereals in Western Australia. Plant Puthol. 34, 175-181
take-all or rhizoctonia root rot, but exacerbated both diseases. In direct-drilled plots, however, fenbuconazole doubled grain yield. The failure of fungicides to have any effect on barley yield at H o r s h a m could have been due to high levels of take-all at the site. A l t h o u g h flutriafol is used for take-all control (Ballinger and Kollmorgen, 1988), it failed to increase yields despite reducing incidence of the disease in cultivated plots. The only effective control measures that generally increased yields were fenbuconazole in undisturbed soil and flutriafol c o m b i n e d with cultivation. This study has identified two fungicides (flutriafol
Neate, S. M. (1989) A comparison of controllcd environment and field trials for detection of resistance in cereal cultivars to root rot caused by Rhizoctonia solani. Plant PathoL 38,494-5(11 Northeote, K.H. (1979) A Factual Key jor the Recognition oJ' Australian Soils, Rcllim Technical Publications, Adelaide Perry, M. W. and Jarvis, R. J. (1985)Depth of Sowing Cereals. Technote5/&5, Western Australian Department of Agriculture, Perth Pumphrey, F. V., Wilkins, D. E., l-lane, D. C. and Smiley, R. W. (1987) lnfluence of tillage and nitrogcn fertiliser on Rhizoctoniaroot rot (bare patch) of wintcr wheat. Plant Dis. 71, 125-127 Roget, D. K., Neate, S. M. and Rovira, A. D. (1989) Rcduction of root diseasc in direct-drilled cereals using a modified sowing point.
and f e n b u c o n a z o l e ) that show some potential for reducing rhizoctonia root rot and increasing grain yield of barley. None the less, it is quite evident that the
1989, p. 63, Australasian Plant Pathology Society, Brisbanc Rnvira, A.D. (1986) Influencc of crop rotation and tillagc on rhizoctonia barc patch of wheat. Phytopathology 76, 669-673
Abstr. 7th Australas. Plant Pathol. Soc. Conf , Brisbane, 3-7 July
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Control of rhizoctonia root rot in barley: P. J. Cotterill Smiley, R. W., Wiikins, D. E. and Klepper, E. L. (1990a) Impact of fungicide treatments on rhizoctonia root rot, take-all, eyespot, and growth of winter wheat. Plant Dis, 74, 782-787 Smiley, R. W., Uddin, W., Ott, S. and Rhinhart, K. E. L. (1990b) Influence of flutolanil and tolclofos-methyl on root and culm diseases of winter wheat. Plant Dis. 74, 788-791 Weller, D. M., Cook, R. J., MaeNish, G., Bassett, E. N., Powelson, R. L. and Petersen, R. R. (1986) Rhizoctonia root rot of small grains
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favoured by reduced tillage in the Pacific Northwest Plant Dis. 70, 70-73 Zadoks, J. C., Chang, T. T. and Konzak, C. F. (1974) A decimal code for the growth stages of cereals. Weed Res. 14, 415-421 Received 20 April 1992 Revised 4 December 1992 Accepted 7 December 1992