reduced fungicide use on a new australian peanut cultivar, highly resistant to the late leaf spot...

Reduced fungicide use on a new Australian peanut cultivar,highly resistant to the late leaf spot and rust pathogens

Lisa A. Kelly & Malcolm J. Ryley & Peter R. Trevorrow &

Jeffrey R. Tatnell & Charles Nastasi & Yash Chauhan

Received: 20 April 2011 /Accepted: 6 March 2012 /Published online: 27 April 2012# Australasian Plant Pathology Society Inc. 2012

Abstract Rust (caused by Puccinia arachidis) and late leafspot (LLS, caused by Mycosphaerella berkeleyi) can causesignificant yield losses in Australian peanut crops. Untilrecently, all commercial peanut varieties were highly sus-ceptible to these pathogens, but the new Australian cultivarSutherland has significantly higher levels of resistance thanthe older cultivars. Field trials were conducted at two sites inQueensland to (a) confirm the improved resistance of cv.Sutherland over another commercial cultivar, Menzies, (b)study the effects of timing of first spray, spray interval andcultivar on disease severity and yield, and (c) develop asuitable fungicide management program for cv. Sutherland.In the 2006 and 2007 trials, rust and LLS developed slowerand had lower final disease ratings and AUDPC values onunsprayed plots of cv. Sutherland than on cv. Menzies. Thetiming of the first spray is critical in managing both rust andlate leaf spot, with the results demonstrating that the firstfungicide spray on cv. Sutherland should be applied as soonas rust and LLS are first seen on cv. Menzies. In most trialsspray intervals of 14 days or 21 days were suitable toeffectively control rust and LLS. In years with low disease

pressure, few, if any, fungicide applications will be neededto manage the diseases, but in other years up to four spraysmay be necessary.

Keywords Peanut . Groundnut . Puccinia arachidis .

Mycosphaerella berkeleyi . Fungicide management .

Cultivar resistance

Introduction

In Australia, peanut (Arachis hypogaea) is a minor but highvalue crop, with approximately 40,000 t produced annuallyfrom 15,000 ha (Wright et al. 2010). Ninety (90) percent ofthe crop is grown in Queensland, either under irrigation incentral and southern Queensland or under rain-grown condi-tions in north Queensland, in sugarcane farming systems alongthe central Queensland coast and in the Burnett region (Wrightet al. 2010). In New South Wales peanuts are grown along thenorthern coast, on the NewEngland Tableland, and atWeeWaa(−30.2318, 149.4346) (Wright et al. 2010). There are smallerproduction areas in the Ord River Irrigation Area, WesternAustralia (−15.2019, 128.20039) and near Katherine, NorthernTerritory (−14.46676, 132.26677) (Wright et al. 2010).

Rust (caused byPuccinia arachidis) and late leaf spot (LLS,caused by Mycosphaerella berkeleyi) can cause significantyield losses in peanut crops in Australia (Wright et al. 2010).Puccinia arachidis produces orange pustules (uredinia) on thelower surfaces of leaves that rupture, exposing masses ofreddish-brown urediniospores (Subrahmanyam et al. 1985;McDonald et al. 1998). Infected leaves quickly become ne-crotic, resulting in large yield losses particularly when the cropis also attacked by other leaf spot pathogens (Mehan et al.1994). Temperatures between 20 and 28°C, high relative hu-midity and leaf wetness have been reported to favour infection

L. A. Kelly :M. J. Ryley (*)Department of Employment,Economic Development and Innovation,PO Box 102, Toowoomba, Qld 4350, Australiae-mail: [email protected]

P. R. Trevorrow : C. NastasiDepartment of Employment,Economic Development and Innovation,PO Box 1054, Mareeba, Qld 4880, Australia

J. R. Tatnell :Y. ChauhanDepartment of Employment, Economic Development andInnovation, J. Bjelke Petersen Research Station,PO Box 23, Kingaroy, Qld 4610, Australia

Australasian Plant Pathol. (2012) 41:359–373DOI 10.1007/s13313-012-0132-8

and disease development (Mallaiah and Rao 1979; Savary etal. 1988; McDonald et al. 1998). In Queensland, rust is moreprevalent in southern coastal regions where the warm, wetweather encourages infection and disease development. Lossesdue to rust are difficult to quantify because other diseases areoften present, but yield losses of up to 70 % have beenattributed to rust alone in overseas research (Harrison 1973;Subrahmanyam et al. 1984; Subrahmanyam et al. 1985).

Late leaf spot is characterised by small, semi circular-circular, dark brown-black lesions often surrounded by ayellow halo (Mulder and Holliday 1974; McDonald et al.1998). The pathogen also causes lesions on petioles, stemsand pegs (McDonald et al. 1998). Lesions become necrotic,leading to premature defoliation and pod drop. Late leaf spotcan cause complete defoliation and up to 70 % yield loss(Nutter and Shokes 1995). Temperatures between 18 and30°C, accompanied with leaf wetness periods of 20 h or moreare ideal for leaf spot infection and disease development(McDonald et al. 1998). In Australia, late leaf spot is morecommon on the Atherton Tableland in northern Queensland,which is cooler than other Australian peanut-growing regions.

Until recently, all peanut varieties grown in Australiawere highly susceptible to the late leaf spot and rust patho-gens. A range of protectant (FRAC groups M3 and M5) andsystemic (FRAC group 3) foliar-applied fungicides are usedin rotation to manage the diseases. The current recommen-dation is to apply a fungicide 4–5 weeks after planting andcontinue on a 10 to 14 day schedule until 14 days prior todigging, with the result that up to eight sprays are oftenapplied to a crop (Wright et al. 2010). The use of fungicidesto manage rust and leaf spot diseases worldwide is expen-sive, so breeding for resistance is a key strategy in reducingyield losses due to these diseases (Subrahmanyam et al.1985). The mechanisms of resistance to P. arachidis includean increase in the time between inoculation and pustuleeruption, and reductions in infection frequency, lesion di-ameter and sporulation index, resulting in “slow rusting”(Mehan et al. 1994; Subrahmanyam et al. 1983; Wynne etal. 1991). Resistance to the LLS pathogen is attributed toincreased incubation and latent periods, and a reduction inthe number of lesions per unit area of leaf surface, defolia-tion, and sporulation (Nevill 1981).

Recently, the Australian National Peanut ImprovementProgram released a new cultivar, Sutherland, which has highlevels of resistance to the rust and leaf spot pathogens (Wright2008). It is a cross between D45-p37-102, a high oleic foliardisease-resistant genotype and B155–6L103, a normal oleicgenotype with good foliar disease resistance and some resis-tance to Cylindrocladium crotalariae, the causal agent ofcylindrocladium black rot. The improved resistance of cv.Sutherland to the major foliar pathogens raised the possibilitythat fewer fungicide sprays would be required to effectivelymanage them. A reduction in the number of fungicide sprays

would have benefits to growers through an improvement inprofit margins and to the environment by reducing off-targetimpacts on terrestrial, soil and water biota.

In this study we report on the results of field trials thatwere conducted at two sites with contrasting climates, oneon the Atherton Tablelands and the other at Bundaberg,southern Queensland to (a) confirm the improved resistanceof cv. Sutherland over another commercial cultivar, Men-zies, (b) study the influences of timing of first spray, sprayinterval and cultivar on disease severity and yield, and (c)develop a suitable fungicide management program for thenewly released, resistant cultivar, Sutherland. In the first2 years, both cv. Menzies and cv. Sutherland were includedin the trials at both sites to gather data on the relativeresistance of the two cultivars and to assess the efficacy ofdifferent spray schedules, but in the last 2 years the efficacyof different treatments was assessed only on cv. Sutherland.

Methods

Field trial information

Field trials were conducted each year from 2006 to 2009 at theDepartment of Employment, Economic Development andInnovation (DEEDI) research stations at Bundaberg[−24.8502, 152.4017; approx. 50 m Above Sea Level(ASL)] in south-eastern Queensland and at Kairi(−17.21823,145.56502; 697 m ASL) on the Atherton Tablelands in north-ern Queensland. At Bundaberg [Bundaberg Airport, Bureauof Meteorology (BOM) station 039128] the long-term meanannual rainfall is 1033.7 mm with 60 % falling betweenDecember and April inclusive; the long-term mean monthlymaximum temperature range over this period is 27.4–29.4°Cand the corresponding range for mean monthly minimumtemperature is 17.5–20.6°C. At Kairi Research Station(BOM station 031034) the corresponding values are1285.1 mm with 80 % falling between December and April,maximum temperatures 24.8–28.9°C and minimum temper-atures 16.8–18.5°C (BOM 2011). A randomised completeblock design was used for all field trials. There were twoguard rows of the rust and LLS-susceptible cv. Menziesbetween each plot and one bordering the plots at each sideof the trials. None of the trials were inoculated with either P.arachidis or M. berkeleyi.

Prior to planting, the Bundaberg trial sites were treated withthe 480 g L−1 trifluralin herbicides Treflan 480 (Dow Agro-sciences) (2006–2008) or Trilogy (Farmoz) (2009), applied at1.5 L product ha−1. Thirty one (31) days after planting the2006 trial was sprayed with the post-emergence 224 g L−1

acifluorfen herbicide Blazer (United Phosphorus Ltd.) at 2.0 Lproduct ha−1 mixed with the surfactant Shirwet 600. The 2009Kairi trial received four separate herbicide applications;

360 L.A. Kelly et al.

prometryn (Prometryn 500 g L−1, Farmoz) was applied at 2 Lproduct ha−1 before emergence while imazapic (Flame 240 gL−1, Crop Care Australasia) at 400 mL product ha−1, a mixtureof bentazon (Basagran 480 g L−1, BASF SE), acifluorfen(Blazer 224 g L−1, United Phosphorus Ltd.) and 2,4-DB(Buttress 500 g L−1, Nufarm Australia Ltd.) at a ratio of1:1:1 L product ha−1, and haloxyfop (Verdict 520 g L−1,Dow Agrosciences) were applied at 4, 9 and 11 weeks afterplanting (WAP) respectively.

The fungicide spray treatments and timing of applicationsare presented in Tables 1 and 2, and in the followingsections.

Field trials 1 & 2, Bundaberg research station, 2006 & 2007

The cultivars Menzies and Sutherland were planted on 13December 2005 (Field trial 1) and 14 December 2006 (Field

trial 2) in plots consisting of 2×9.5 m long rows, 0.9 mapart. There were six treatments for each variety, replicatedthree times. Treatments were an unsprayed control (T1);fungicide applications starting at 5 WAP (early), then ateither 14 day (T2) or 21 day (T3) intervals, resulting in sixor four sprays respectively; fungicide applications starting at9 WAP (late), then at either 14 day (T4) or 21 day (T5)intervals, resulting in four or three sprays respectively; and afungicide application with a total of four sprays starting at 5WAP (early), then at 14 day intervals, with the final spray at11 WAP (early finish) (T6) (Table 1). The timing of the firstspray reflects the practice of many Australian peanutgrowers who apply fungicides before rust and/or late leafspot are observed. Barrack 720® (720 g chlorothalonil L−1,CropCare Australasia) (2006 trial) and Bravo Weather Stik®(720 g chlorothalonil L−1, Syngenta Australia) (2007 trial)were applied at 1.8 L product ha−1 in all fungicide treatments.

Table 1 Fungicide spray schedules for trials at DEEDI Bundaberg Research Station between 2006 and 2009

Year Treatmenta Week of fungicide application (WAP) Total sprays

5 6 7 8 9 10 11 12 13 14 15 16 17

2006 Unsprayed (T1) 0

Early start, 14 day interval (T2) ✓ ✓ ✓ ✓ ✓ ✓ 6

Early start, 21 day interval (T3) ✓ ✓ ✓ ✓ 4

Late start, 14 day interval (T4) ✓ ✓ ✓ ✓ 4

Late start, 21 day interval (T5) ✓ ✓ ✓ 3

Early start & finish, 14 day interval (T6) ✓ ✓ ✓ ✓ 4


Early start, 14 day interval (T2) ✓ ✓ ✓ ✓ ✓ ✓ 6

Early start, 21 day interval (T3) ✓ ✓ ✓ ✓ 4

Late start, 14 day interval (T4) ✓ ✓ ✓ ✓ 4

Late start, 21 day interval (T5) ✓ ✓ ✓ 3

Early start & finish, 14 day interval (T6) ✓ ✓ ✓ ✓ 4


Full spray, 7 or 14 day intervals (T2) ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ 8

First sign + 10 days, Amistar Xtra® (T3) ✓ 1

First sign + 10 days (T4) ✓ 1

First sign + 10 days, 14 day interval (T5) ✓ ✓ ✓ 3

First sign + 10 days, 21 day interval (T6) ✓ ✓ 2


Full spray, 14 day interval (T2) ✓ ✓ ✓ ✓ ✓ ✓ ✓ 7

First sign (T3) ✓ 1

First sign, 14 day interval (T4) ✓ ✓ 2

First sign, 21 day interval (T5) ✓ ✓ ✓ 3

First sign, 14 day interval (T6) ✓ ✓ ✓ ✓ 4

First sign, then at rating 3 (T7) ✓ ✓ 2

APSIM model, 21 day interval (T8) ✓ ✓ ✓ ✓ 4

a Barrack 720® (720 g chlorothalonil L−1 , CropCare Australasia) (2006 trial) or Bravo Weather Stik® (720 chlorothalonil g L−1 , SyngentaAustralia) (2007, 2008, 2009 trials) were applied at 1.8 L product ha−1 to all treatments unless otherwise indicated; Amistar Xtra® (80 gcyproconazole L−1 + 200 g azoxystrobin L−1 ; Syngenta Australia) was applied at 0.75 L product ha−1 in treatment 3 in the 2008 trial

Reduced fungicide use on a new Australian peanut cultivar 361

Tab

le2

Fun

gicide

sprayschedu

lesfortrialsat

DEEDIKairiResearchStatio

nbetween20

06and20

09

Year

Treatmenta

Weekof

fung

icideapplication(W

AP)

Total

sprays

45

67

89

1011

1213

1415

1617

1819

20

2006

Unsprayed

(T1)

0

Early

start,14

dayinterval

(T2)

✓✓

✓✓

✓✓

✓✓

8

Early

start,14

,21

or28

dayinterval

(T3)

✓✓

✓✓

✓✓

6

Latestart,14

dayinterval

(T4)

✓✓

✓✓

✓✓

6

Latestart,21

dayinterval

(T5)

✓✓

✓✓

4

Early

start&

finish,14

dayinterval

(T6)

✓✓

✓✓

✓✓

6

2007

Unsprayed

(T1)

0

Early

start,14

or21

dayinterval

(T2)

✓✓

✓✓

✓✓

✓✓

8

Early

start,21

or28

dayinterval

(T3)

✓✓

✓✓

✓✓

6

Latestart,14

dayinterval

(T4)

✓✓

✓✓

✓✓

6

Latestart,21

dayinterval

(T5)

✓✓

✓✓

4

Early

start&

finish,14

or21

dayinterval

(T6)

✓✓

✓✓

✓✓

6

2008

Unsprayed

(T1)

0

Fullspray,7,

14or

21dayintervals(T2)

✓✓

✓✓

✓✓

✓7

Firstsign

+10

days

firstAmistarXtra®

,then

21dayintervals(T3)

✓✓

✓3

Firstsign

+10

days

(T4)

✓1

Firstsign

+10

days,14

dayor

21dayintervals(T5)

✓✓

✓✓

4

Firstsign

+10

days,21

or28

dayintervals(T6)

✓✓

✓3

2009

Unsprayed

(T1)

0

Fullspray,7,

14or

21dayintervals(T2)

✓✓

✓✓

✓✓

✓✓

✓9

Firstsign

(T3)

✓1

Firstsign

,14

dayinterval

(T4)

✓✓

2

Firstsign

,21

dayintervals(T5)

✓✓

✓3

Firstsign

,14

dayintervals(T6)

✓✓

✓✓

4

Firstsign

,then

atratin

g3(T7)

✓✓

2

Fullspray,7or

14dayintervals,lastAmistarXtra®

(T8)

✓✓

✓✓

✓✓

✓✓

8

Fullspray,7,

14or

21dayintervals,lastAmistarXtra®

(T9)

✓✓

✓✓

✓✓

✓✓

✓9

aBayer

Chlorothalonil5

00SC®(500

gchlorothalon

ilL−1,B

ayerCropS

cience

Australia),was

appliedat1.6–2.6Lprod

uctin20

06and20

07trialsandin

2008

and20

09Sipcam

PacificEcho®

(500

chlorothalon

ilL−1,Sipcam

Pacific

Australia)was

appliedat

2.6Lha

−1un

less

otherw

iseindicated;

AmistarXtra®

(80gcyprocon

azoleL−1

+20

0gazox

ystrob

inL−1;Syn

gentaAustralia)was

appliedat

0.75

Lprod

uctha

−1in

treatm

ent3in

the20

08trial


The fungicides were applied using 110–02 DG nozzles intwin caps at 400 kPa on a tractor-mounted boom in 464 Lwater ha−1, or 110–15 Albuz tapered fan nozzles at 300 kPaon a handheld pressurised boom in 120 L water ha−1. Inboth trials rust severity was assessed every 14±2 days fromthe first sign of infection up until 128 (2006 trial) and131 days after planting (DAP) (2007 trial) respectively.The severity of LLS was assessed only in the 2006 trial,because the severity was low (rating <3) in unsprayed plots.Details of the rating scales are detailed in a later section.Plots were harvested 136 DAP in the 2006 trial and 134DAP in 2007 and NIS yield determined using the methodsdescribed below. The insecticide Lannate® (225 gmethomyl L−1) was applied at 1.5 L product ha−1.to all plots62 DAP in the 2007 trial.

Field trials 3 & 4, Kairi research station, 2006 & 2007

The cultivars Menzies and Sutherland were planted on 19December 2005 (Field trial 3) and 8 December 2006 (Fieldtrial 4) in plots consisting of either 2×6 m (2006 trial) or 2×8 m rows (2007 trial), 0.9 m apart. The same six treatmentsused in the Bundaberg Field trials 1 and 2 were repeated atthe Kairi Research Station (Table 2), each replicated threetimes. However, the early stray treatments commenced 4WAP and there were different spray intervals in some treat-ments (Table 2). Bayer Chlorothalonil 500SC® (500 gchlorothalonil L−1, Bayer CropScience Australia) was ap-plied at 1.6–2.6 L product in 300 L water ha−1 usingATR80RE Albuz cone nozzles on a tractor-mounted boomin 300 L water ha−1. The fungicide rate depended on diseaseseverity in the untreated plots, reflecting the practice ofsome commercial peanut growers in northern Queenslandwho apply lower rates of fungicide early in season. In bothtrials the severity of rust and LLS was assessed once, 107DAP (2006 trial) and 108 (2007 trial) DAP. The trials wereharvested 147 DAP and 161 DAP, respectively and NISyields determined.

Field trial 5, Bundaberg research station, 2008

The cv. Sutherland was planted on 11 December 2007 inplots consisting of 2×12 m long rows, 0.9 m apart. The sixtreatments, replicated four times were an unsprayed control(T1); a full spray schedule with the first spray 5 WAP thenothers at either 7 or 14 day intervals (T2), a total of eightsprays; a single spray of Amistar Xtra® (80 g cyproconazoleL−1 + 200 g azoxystrobin L−1; Syngenta Australia) appliedat 0.75 L product ha−1 10 days after the first sign of rustinfection on the susceptible cultivar Menzies (T3); one sprayof Bravo Weather Stik® 10 days after the first sign of rustinfection on the cultivar Menzies (T4); as T4, but includinga spray of Bravo Weather Stik® at either 14 day (T5) or

21 day (T6) intervals after the initial spray (Table 1). Intreatments T2, T4, T5 and T6 Bravo Weather Stik® wasapplied at 1.8 L product ha−1. The fungicides were appliedusing the same methods as those described for field trials 1and 2. Rust severity was assessed every 14±2 days from thefirst sign of infection up until 127 DAP. Plots were har-vested 134 DAP and NIS yield determined. All plots weresprayed with Lannate at 1.5 L product ha−1 at 27 DAP.

Field trial 6, Kairi research station, 2008

The cv. Sutherland was planted in plots of 2×5 m rows, 1 mapart, on 17 December 2007. The same six treatmentsapplied in Field trial 5 at Bundaberg were repeated at theKairi Research Station, except that treatment 3 (T3) includ-ed two additional sprays of the Sipcam Pacific Echo® (500chlorothalonil L−1, Sipcam Pacific Australia) applied at14 days and 35 days after the initial spray of Amistar Xtra®(Table 2). Each treatment was replicated six times. In alltreatments, Sipcam Pacific Echo® was applied at 2.6 Lproduct in 300 L water ha−1using ATR80RE Albuz conenozzles on a tractor-mounted boom. In treatment T3, Amis-tar Xtra® was applied at 750 mL product in 300 L waterha−1 using the same equipment that was used to apply thechlorothalonil sprays. Late leaf spot was assessed 112 DAPand plots were harvested 35 days later.


The cv. Sutherland was planted on 11 December 2008 in 2×10 m rows, 0.9 m apart. There were eight treatments withfour replicates. The treatments were an unsprayed control(T1); a full spray schedule commencing at 5 WAP andcontinuing at 14 day intervals until harvest, for a total ofseven sprays (T2); one spray applied at the first sign of rustin the Menzies guard rows (T3); as T3 then another sprayeither 14 days (T4) or 21 days (T5) later, a total of two orthree sprays respectively; as T3 followed by three sprays at14 day intervals (T6) (total of four sprays ); as T3 and asecond spray once the disease severity reached a rating of 3on the modified 1–10 pictorial scale (Subrahmanyam et al.1995) (T7) (total two sprays); first fungicide applicationapplied at a date based on a model that predicted rustincidence using an APSIM model (McCown et al. 1996)followed by applications every 21 days (T8), for a total offour sprays (Table 1). The equations for the APSIM modelwere essentially those described by Butler and Jadhav(1991) and were incorporated in the manager module ofthe APSIM model (Butler and Jadhav 1991). The modelwas run in conjunction with the APSIM peanut module(Robertson et al. 2002) using climatic data collected fromthe BOM station at the BSES Limited research station,opposite the DEEDI Bundaberg research station. The


parameters for model prediction were based on critical tem-perature values for rust and early and late leaf spot, asdescribed by Wadia and Butler (1994), as well as leaf wetnessand rainfall values, using themethod described by Norman andCampbell (1983). Rust severity was rated every 14±2 daysfrom the first sign of the disease until 133 DAP and plots wereharvested 140 DAP. The insecticides Bacillus thuringiensissubsp. Kurstaki, Strain HD-1 (DiPel DF 780 g ha−1, ValentBioSciences) and nucleopolyhedrovirus (Vivus Gold375 mL ha−1, Ag Biotech Australia) were applied to allplots 85 DAP.


On 11 December 2008 cv. Sutherland was planted in 2×6 mrows, 1 m apart. There were nine treatments replicated fourtimes. The timing and intervals of treatments T1–T6 werethe same as the equivalent treatments in the 2009 Bundabergtrial. The other treatments were one spray applied at the firstsign of disease in the cv. Menzies guard rows then a secondspray once the disease severity reached a rating of 3 on themodified 0–9 scale (T7); a full Sipcam Pacific Echo® sprayregime commencing at the first sign of leaf spot on cv.Menzies, with an additional spray of Amistar Xtra® appliedat flowering (8 WAP) (total eight sprays) (T8); and a fullysprayed Sipcam Pacific Echo® treatment commencing 5WAP, plus an application of Amistar Xtra® at flowering (8WAP) (T9), totalling nine sprays (Table 2). Sipcam PacificEcho® and Amistar Xtra were applied at 2.6 L product and750 mL product respectively in 300 L water ha−1 using theequipment described above for the fungicide applications atKairi in previous trials. Late leaf spot was assessed every 7–21 days from the first sign of the disease until 147 DAP.Plots were harvested 154 DAS and NIS yield determined.

Disease severity and area under the disease progress curve

In the Bundaberg trials, rust severity was rated using a 1–10scale modified from Subrahmanyam et al. (1995), in which1 0 no disease, 9 0 almost all leaves are withered and stemsare bare (Subrahmanyam et al. 1995), and 10 0 dead plants.Rust severity was visually assessed at 10 arbitrarily selectedsites in the datum rows of each plot and the mean ratingcalculated. In 2006 only, LLS severity was determined ineach plot in a similar manner, using a 1–10 scale modifiedfrom Subrahmanyam et al. (1995), in which 1 0 no diseaseand 9 0 almost all leaves are defoliated and stems are bare(Subrahmanyam et al. 1995), and 10 0 dead plants. In the2006, 2007 and 2008 trials at Kairi, LLS severity wasassessed using a modification of the scale outlined above,where 0 0 no disease and 9 0 dead plants. Rust was notassessed at Kairi in any year because severity levels, even inthe unsprayed control plots, were low (ratings <2).

The Area Under the Disease Progress Curve (AUDPC)was calculated for rust in each treatment in the four Bunda-berg trials, and for LLS in the 2006 Bundaberg trial and2009 Kairi trial using the following formula –

AUDPC ¼ni¼1

Σ Xi þ Xiþ1ð Þ=2½ � tiþ1 � t1½ �

Where xi and xi+1 are the proportion of leaf area infectedat the ith and ith +1 observations respectively, ti and ti+1 arethe time (days) at the ith and ith +1 observations respective-ly and n is the total number of observations.

Nut in shell yield

At maturity all plants in each plot were mechanically cut, pulledand inverted by hand. When pods had reached 18–20 % mois-ture content (MC) the plants were mechanically threshed andthe pods were artificially dried to less than 12 % MC. Extrane-ous material was removed from the harvested pods by the useof a mechanical pre-cleaner and hand sorting and the podsweighed to determine the Nut-in-shell (NIS) yields of each plot.

Statistical analyses

In all trials, analyses of variance using least significantdifferences (GenStat 12th Edition, Lawes Agricultural Trust,Rothamsted Experimental Station) were conducted to deter-mine if differences in disease severity, AUDPC, and nut-in-shell yield between treatments were statistically significant.Unless otherwise stated, all references to statistically signif-icant differences are at P≤0.05. AUDPC values for the 2006and 2007 Bundaberg trial data were log transformed be-cause residual values showed an unequal variance.

Results

Field trials 1 & 2, Bundaberg DEEDI research station, 2006& 2007

Disease development

In the 2006 trial, LLS and rust were first observed on bothcultivars 12 weeks after planting (WAP), when all treat-ments had already received one (T5; late start, 21 day inter-val, 3 sprays) to four (T2 - early start, 14 day interval, 6sprays, and T6 - early start and finish, 14 day interval, 4sprays) sprays. In 2007, rust was first observed on cv.Sutherland 8–9 WAP, by which time two sprays had beenapplied to the early start treatments T2, T3 (early start,21 day interval, 4 sprays) and T6 (Table 1). Thereafter, inboth years rust severity in the unsprayed Sutherland treat-ment (T1) increased gradually (Figs. 1 and 2), but at a much


slower rate than that in the cv. Menzies unsprayed treatment.In 2006, in all sprayed treatments of both cultivars rustdeveloped at a slower rate than that of the unsprayed treat-ment up until 14 WAP. Between 14 and 16 WAP, rustdeveloped at a similar or slower rate than the unsprayedtreatments in the respective cultivars, except for the cv.Sutherland T3 and T5 (late start, 21 day interval, 3 sprays)treatments. After 16 weeks, rust developed at a similar orslower rate than that of the unsprayed treatments except forthe cv. Menzies T6 treatment. In 2007, in the sprayed treat-ments of both cultivars rust developed at a slower rate thanin the unsprayed plots throughout the trial.

In the 2006 trial, LLS in sprayed treatments of bothcultivars developed at a slower or similar rate to those of

the corresponding unsprayed treatments, except for the T6treatments on both varieties in which the rust developedfaster than in the unsprayed plots 16–18 weeks after plant-ing (Fig. 3).

AUDPC

In both trials all of the sprayed cv. Sutherland treatments hadsignificantly lower AUDPC values for rust than the un-sprayed cv. Sutherland treatment and all of cv. Menziestreatments (Table 3). The AUDPC value of the unsprayedcv. Sutherland treatment was significantly lower than thecorresponding values of all cv. Menzies treatments exceptthat of T2 in 2006, and T2 and T6 in 2007. In both years, allfungicide treatments in cv. Menzies had significantly lower

1

2

3

4

5

6

7

8

9

10

12 13 14 15 16 17 18

Weeks after planting

Ru

st s

ever

ity (1

-10)

A

1

2

3

4

5

6

7

8

9

10

12 13 14 15 16 17 18


Ru

st s

ever

ity (1

- 10)

B

Fig. 1 Development of rust in unsprayed, 0 s (T1)(Black triangle);early start and finish, 14 d interval, 4 s (T6)(White triangle); early start,21 d interval, 4 s (T3)(White square); late start, 21 d interval, 3 s (T5)(White circle); late start, 14 d interval, 4 s (T4)(Black diamond); andearly start, 14 d interval, 6 s (T2)(Black square) fungicide treatmentson (a) cv. Menzies and (b) cv. Sutherland at Bundaberg in 2006. Earlyor late start 0 first spray applied either 5 or 9 weeks after plantingrespectively; 0 s, 3 s, 4 s, 6 s 0 0, 3, 4 or 6 sprays of a chlorothalonilfungicide. Refer to Table 1 for spray schedules and fungicide details.Lsd bars P00.05

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Fig. 2 Development of rust in unsprayed, 0 s (T1)(Black triangle); latestart, 21 d interval, 3 s (T5)(White circle), early start and finish, 14dinterval, 4 s (T6)(White triangle): early start, 21 d interval, 4 s (T3)(Whitesquare), late start, 14 d interval (T4)(Black diamond), and early start, 14 dinterval (T2)(Black square) fungicide treatments on (a) cv. Menzies and(b) cv. Sutherland at Bundaberg in 2007. Early or late start 0 first sprayapplied either 5 or 9 weeks after planting respectively; 0 s, 3 s, 4 s, 6 s 0 0,3, 4 or 6 sprays of a chlorothalonil fungicide. Refer to Table 1 for sprayschedules and fungicide details. Lsd bars P00.05


AUDPC values than that of the unsprayed cv. Menziestreatment except for T5 in 2007, with the best treatment(T2) having a significantly lower transformed AUDPC val-ue than all other fungicide treatments.

For LLS in cv. Sutherland, all of the fungicide treatmentsexcept T5 had significantly lower values of AUDPC thanthat of the unsprayed treatment (T1). The values of AUDPCfor the best treatments, T2, T3 and T6, were not significant-ly different from each other. For cv. Menzies, all fungicidetreatments had significantly lower AUDPC values than thatof the unsprayed treatment. The AUDPC values of the bestfungicide treatments on cv. Menzies (T2 and T6) did notdiffer significantly from those of treatments T3 and T4 (latestart, 14 day interval, 4 sprays) on cv. Sutherland (Table 3).

Final rust and LLS severity

In both trials, for cv. Sutherland the final mean rustseverity values (and for LLS severity in 2006) in allfungicide treatments were significantly lower than thatthose of the unsprayed treatment (T1). In 2006 therewere no significant differences between the sprayedtreatments, while in 2007 treatments T2 and T4 hadsignificantly lower rust severity values than the otherfungicide treatments except T3. In 2006, the final rustseverity values of the best treatments (T2, T3, T4) oncv. Menzies were not significantly different to eachother or from the cv. Sutherland unsprayed treatment.In 2007, the best cv. Menzies treatment (T2) had sig-nificantly lower rust severity than all other cv. Menziestreatments, and was not significantly different to thoseof the cv. Sutherland T5 and T6 treatments (Table 5). In2006, the final LLS severity value of the best treatment(T2) on cv. Sutherland was significantly less than thoseof all other Sutherland treatments except for that of T4.For cv. Menzies, the final LLS severity value on T2was significantly lower than those of all other cv. Men-zies treatments except T3, and than that of the Suther-land unsprayed treatment (Table 3).

NIS yield

For cv. Sutherland, in 2006 there were no significant differ-ences in NIS yields between any treatment, while in 2007only the late start 14 day interval treatment (T4) had asignificantly higher NIS yield than the unsprayed treatment,but differences in yield between the cv. Sutherland fungicidetreatments were not statistically significant. For cv. Menziesin both years, all fungicide treatments significantly im-proved the NIS yield over the unsprayed treatment. In2006, the yield of the best Menzies treatment (T2) did notdiffer significantly from the NIS yields of any cv. Sutherlandtreatment, and only two treatments (T5, T6) had yieldslower than that of the unsprayed cv. Sutherland treatment(T1). In 2007 the NIS yield of all the cv. Menzies spraytreatments except T5 were not significantly different fromthose of any of the sprayed cv. Sutherland treatments(Table 3).

Weather conditions

In 2007, a total of 254.7 mm of rain fell on 25 daysduring the trial, nine of which were between 9 and 11WAP. The daily minimum temperature ranged from 15to 25.5°C (mean 20.6°C) and the daily maximum tem-perature from 26 to 35°C (mean 30°C). The minimumtemperatures fell steadily from 13 WAP to the end ofthe trial.

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Fig. 3 Development of late leaf spot in unsprayed, 0 s (T1)(Blacktriangle); early start and finish, 4 s (T6)(White triangle); late start, 21 dinterval, 3 s (T5)(White circle), early start, 21 d interval, 4 s (T3)(Whitesquare); late start, 14 d interval, 4 s (T4)(Black diamond); and earlystart, 14 d interval, 6 s (T2)(Black square) fungicide treatments on (a)cv. Menzies and (b) cv. Sutherland at Bundaberg in 2006. Early or latestart 0 first spray applied either 5 or 9 weeks after planting resepc-tively; 0 s, 3 s, 4 s, 6 s 0 0, 3, 4 or 6 sprays of a chlorothalonilfungicide. Refer to Table 1 for spray schedules and fungicide details.Lsd bars P00.05


Field trials 3 & 4, Kairi research station, 2006 & 2007

Final LLS severity

In both years, final LLS severity ratings in all cv. Sutherlandtreatments were significantly lower than those of all cv. Men-zies treatments and were not significantly different from eachother. All cv. Menzies fungicide treatments except the earlystart, 14/21/28 day interval, 6 spray treatment (T3) had signif-icantly lower LLS values than that of the unsprayed treatment(T1). There were no significant differences in LLS valuesbetween the other fungicide treatments (Table 4). In 2007,only treatments T2 (early start, 14/21 day interval, 6 spray),T4 (late start, 14 day interval, 6 spray) and T6 (early start andfinish, 14/21 day interval, 6 spray) significantly reduced LLScompared to the unsprayed treatment (Table 6).

NIS yield

In 2006 for cv. Sutherland, treatments T2, T3 and T5 (latestart, 21 day interval, 4 sprays) had significantly higher NISyields than the unsprayed cv. Sutherland treatment (T1), butthere were no significant differences in this parameter be-tween any of the fungicide treatments. In 2007, for the samecultivar only treatments T5 and T6 had significantly higherNIS yields that that of the unsprayed treatment and therewas no significant difference between them or with T2 andT3. In 2006, the NIS yield of the best fungicide treatment on

Menzies (T4) was not significantly different to those of thecv. Sutherland T1 (unsprayed), T4, T5, and T6 treatments.In both years for cv. Menzies, treatments T2, T4 and T6 hadsignificantly higher NIS yields than that of the unsprayed cv.Menzies treatment (T1) and differences between NIS yieldsfor these three treatments were not significantly differentfrom each other (Table 4).


Disease development

Rust was first observed on the bordering plots of cv. Menziesapproximately 7 WAP and was not seen in unsprayed plots ofcv. Sutherland until 9 WAP, by which time T2 (full spray, 7/14 day interval, 8 sprays) had received three sprays and allother sprayed treatments had received one spray (Table 1).Rust severity increased rapidly in the unsprayed treatment(T1) from 12 WAP onwards (Fig. 4). The slowest rate of rustdevelopment was in the full spray schedule (T2), followed bythe 14 day schedule commencing 10 days after the first sign ofrust on cv. Menzies (T5; 3 sprays), with all other treatmentshaving a faster rate of rust development than that of T5 (Fig. 4).

AUDPC and final rust severity

All fungicide sprays significantly reduced AUDPC com-pared to the unsprayed treatment. The AUDPC value of

Table 3 Effects of different fungicide treatments on Area Under the Disease Progress Curve (AUDPC), final disease severity for rust and late leafspot (LLS), and on nut-in-shell yield (NIS yield) on cv. Menzies and cv. Sutherland at Bundaberg in 2006 and 2007

Variety & Treatmenta AUDPCb Final severityc (1–10) NIS yield(t/ha)

Rust (2006) Rust (2007) LLS (2006) Rust (2006) Rust (2007) LLS (2006) 2006 2007

Sutherland early start, 21 d, 4 s (T3) 78.81a 104.06ab 69.27abc 2.67 2.07 1.77 6.77 4.79

Sutherland late start, 14 d, 4 s (T4) 72.24a 106.06ab 78.85bcd 2.00 2.03 1.47 6.67 5.81

Sutherland unsprayed, 0 s (T1) 99.78b 150.81d 97.69e 3.73 4.37 3.17 6.52 4.36

Sutherland early start, 14 d, 6 s (T2) 68.92a 95.49a 60.19a 2.00 2.00 1.07 6.47 5.38

Sutherland early start & finish, 14 d, 4 s (T6) 75.19a 105.64ab 68.10ab 3.00 2.77 2.33 6.34 5.00

Menzies early start, 14 d, 6 s (T2) 114.09bc 124.46c 79.30bcd 3.67 2.93 2.00 6.27 5.60

Sutherland late start, 21 d, 3 s (T5) 80.64a 114.66bc 88.60de 2.07 2.87 2.00 6.13 4.73

Menzies late start, 14 d, 4 s (T4) 145.47de 200.34e 120.23f 3.90 4.30 2.67 5.88 5.65

Menzies early start, 21 d, 4 s (T3) 129.93cde 190.95e 90.38de 4.40 4.67 2.33 5.84 4.96

Menzies late start, 21 d, 3 s (T5) 151.71e 241.05f 127.58f 4.73 6.37 3.50 5.75 4.24

Menzies early start & finish, 14 d, 4 s (T6) 122.73 cd 144.32d 80.08 cd 5.00 4.03 3.07 4.93 5.67

Menzies unsprayed, 0 s (T1) 223.18f 355.31f 149.87 g 8.67 9.57 5.00 3.55 0.87

lsd (P00.05) 1.17 0.73 0.58 0.69 1.25

a early start or late start 0 first spray applied either 5 or 9 weeks after planting respectively; 14 d, 21 d 0 14 day or 21 day spray intervals; 0 s, 3 s, 4 s,6 s 0 0, 3, 4 or 6 sprays of a chlorothalonil fungicide respectively; refer to Table 1 for spray schedules and fungicide details in both yearsb Backtransformed values followed by different letters represent statistically significant (P00.05) differences between the corresponding logtransformed valuesc Final severities of rust and LLS were assessed 128 days after planting in 2006, and for only rust 131 days after planting in 2007


the full spray schedule (T2) was significantly lower than thecorresponding values of all other treatments, with T5 havingthe next lowest value and being significantly lower thanthose of T3 (one spray of Amistar Xtra at first sign+10 days), T4 (one spray of Bravo WeatherStik) at first sign

+10 days) and T6 (first sign +10 days, 21 day interval, 2sprays). Differences in AUDPC between these last threetreatments were not statistically significant. The final rustseverity ratings followed a similar trend to that of AUDPCvalues with T2 <T5 <T6 <T4 <T3 <T1, all differences beingstatistically significant (P00.05) (Table 5).

Table 4 Effects of different fungicide treatments on final disease severity for late leaf spot (LLS) and on nut-in-shell yield (NIS yield) on cv.Menzies and cv. Sutherland at Kairi in 2006 and 2007

Variety & Treatmenta Final severityb (0–9) NIS yield (t/ha)

2006 2007 2006 2007

Sutherland early start, 14 d, 8 s (T2) 2.00 2.33 3.48 4.09

Sutherland early start, 14, 21 or 28 d, 6 s (T3) 2.00 3.00 3.31 4.54

Sutherland late start, 21 d, 4 s (T5) 2.00 2.00 3.06 5.00

Sutherland late start, 14 d, 6 s (T4) 2.00 2.33 2.98 3.45

Sutherland early start & finish, 14 d, 6 s (T6) 2.00 2.67 2.93 5.41

Menzies late start, 14 d, 6 s (T4) 4.00 5.00 2.32 3.07

Sutherland unsprayed, 0 s (T1) 2.33 2.67 2.20 3.14

Menzies early start & finish, 14 d, 6 s (T6) 4.33 4.00 2.09 3.94

Menzies early start, 14 d, 8 s (T2) 4.67 4.33 1.95 3.80

Menzies late start, 21d, 4 s (T5) 4.67 5.67 0.98 1.77

Menzies early start, 14, 21 or 28 d, 6 s (T3) 6.00 6.00 0.93 2.38

Menzies unsprayed, 0 s (T1) 6.00 6.67 0.35 1.03

lsd (P00.05) 0.74 1.04 0.84 1.74

a early start or late start 0 first spray applied either 4 or 8 weeks after planting respectively; 14 d, 21 d, 28 d 0 14 day, 21 day or 28 day sprayintervals; 0 s, 4 s, 6 s, 8 s 0 0, 4, 6 or 8 sprays of a chlorothalonil fungicide respectively; refer to Table 2 for spray schedules and fungicide details inboth yearsb Final severity of LLS was assessed 107 and 108 days after planting in 2006 and 2007 respectively

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Fig. 4 Development of rust in unsprayed, 0 s (T1)(Black triangle);Amistar Xtra, first sign of rust + 10 d, 1 s (T3)(White square); first signof rust + 10 days, 1 s (T4)(Black diamond), first sign of rust + 10 d,21 d interval, 2 s (T6)(White triangle); first sign of rust + 10 d, 14 dinterval, 3 s (T5)(White circle); and full spray, first spray 5 WAP, 7 or14 d interval, 8 s (T2)(Black square) fungicide treatments on rustdevelopment on Sutherland in the 2008 Bundaberg trial. First sprayin T3–T6 applied 9 weeks after planting; 0 s, 1 s, 2 s, 3 s, 8 s 0 0, 1, 2, 3or 8 sprays of a chlorothalonil fungicide, except in T3. Refer to Table 1for spray schedules and fungicide details. Lsd bars P00.05

Table 5 Effects of different fungicide treatments on Area Under theDisease Progress Curve (AUDPC) and final disease severity for rustand on nut-in-shell (NIS) yield on cv. Sutherland at Bundaberg in 2008

Treatmenta AUDPC Final severityb

(1–10)NIS yield(t/ha)

Full spray, 5 WAP, 7 or14 d, 8 s (T2)

120.8 3.05 6.12

First sign + 10 days,9 WAP, 14 d, 3 s (T5)

177.8 4.2 4.96

First sign + 10 days,9 WAP, 21 d, 2 s (T6)

228.7 6.23 4.16

First sign + 10 days,9 WAP, 1 s (T4)

240.3 6.97 3.97

Amistar Xtra, 9 WAP,1 s (T3)

243.1 7.23 3.76

Unsprayed, 0 s (T1) 278.6 8 3.16

lsd (P00.05) 15.06 0.54 0.50

a 5 WAP and 9 WAP 0 first spray applied 5 or 9 (first sign rust + 10 d)weeks after planting; 7 d, 14 d, 21 d 0 7, 14 or 21 day spray intervals;0 s, 1 s, 2 s, 3 s, 8 s 0 0, 1, 2, 3 or 8 sprays of a chlorothalonil fungicideexcept in T3; refer to Table 2 for spray schedules and fungicide detailsb Final severity of rust was assessed 127 days after planting


NIS yield

Final rust severity and AUDPC was reflected in NIS yield,with increasing rust severity and AUDPC resulting in lowerNIS yield. The statistical relationships in NIS yield betweentreatments were identical to those of AUDPC outlinedabove. The NIS yield of the full spray schedule (T2) wassignificantly greater than the coreesponding values of allother treatments, followed by T5, then T3, T4 and T6 withthe NIS yields of the last three not being significantlydifferent from each other. All fungicide treatments signifi-cantly increased yield over that of the unsprayed treatment(Table 5).

Weather conditions

The total rainfall during the trial period was 590.5 mmon 37 days, most occurring prior to 10 WAP. The meandaily maximum and minimum daily temperatures rangedfrom 22 to 34.5°C (mean 28.6°C) and 15–24.5°C (mean20.2°C) respectively, gradually decreasing from 10 WAPonwards.


Final LLS severity

The final LLS severity in the full spray treatment (T2 -7/14/21 day interval, 7 sprays) was significantly lowerthan the LLS severity values of all other treatments(Table 8). All spray treatments except T4 (one sprayat first sign +10 days) had significantly lower final LLSseverity ratings than the unsprayed treatment (T1). Thefinal LLS values of T3 (one spray at first sign +10 daysof Amistar Xtra, then 2 sprays of Sipcam Pacific Echoat 21 day intervals), T5 (first sign +10 days, 14/21 dayinterval, 4 sprays) and T6 (first sign +10 days, 21/28 day interval, 3 sprays) were not significantly differ-ent from each other (Table 6).

NIS yield

The highest NIS yield was in T3 but there were no signif-icant differences in NIS yield between any of the treatments(Table 6).


Disease development

Rust was first seen on the cv. Menzies border rows at8 WAP, when treatments T2 (full spray, 14 day interval, 7sprays) and T8 (APSIM model, 21 day interval, 4 sprays) on

cv. Sutherland had received their first fungicide applications(Table 1). Rust was first observed on plants in unsprayed cv.Sutherland plots 14 WAP, at which point all fungicide treat-ments had received one to five sprays, depending on thetreatment. Rust developed more rapidly in the unsprayedtreatment (T1) and in the single spray at first sign of rust(T3) than the other treatments. For treatment 7 (first signthen rating 3, 2 sprays) rust developed rapidly 14–15 WAP,then again at 17–19 WAP. Rust development was similar inall other treatments between 14 and 17 WAP, with rust in T4(first sign, 14 day interval, 2 sprays), developing rapidlyafter 17 WAP. The slowest rates of development were in thefully sprayed treatment (T2) and the first sign, 14 day inter-val, 4 spray treatment (T6) (Fig. 5).

AUDPC and final rust severity

All fungicide treatments significantly reduced AUDPCand final rust severity compared to the correspondingvalues in the unsprayed treatment, except for the onespray treatment (T3). The full spray schedule (T2) had asignificantly lower AUDPC and final rust severity val-ues than those of all other treatments except for that ofT6 (Table 7).

NIS yield

All fungicide treatments except T3 and T7 had significantlyhigher NIS yields than that of the unsprayed treatment (T1).Treatments T2, T5 (first sign, 21 day interval, 3 sprays), T6,and T8 had significantly higher NIS yields than the

Table 6 Effects of different fungicide treatments on final diseaseseverity for late leaf spot (LLS) and on nut-in-shell yield (NIS yield)on cv. Sutherland at Kairi in 2008

Treatmenta Final severityb


Amistar Xtra, 11 WAP, 21 d, 3 s (T3) 2.17 5.07

Full spray, 8 WAP, 7 d, 14 d, or 21 d,7 s (T2)

1.17 4.72

First sign + 10 days, 12 WAP, 14 d or21 d, 4 s (T5)

2.46 4.66

Unsprayed, 0 s (T1) 3.17 4.57

First sign + 10 days, 12 WAP, 21 d or28 d, 3 s (T6)

2.29 4.55

First sign + 10 days, 12 WAP, 1 s (T4) 2.88 4.45

lsd (P00.05) 0.46 0.83

a 8 WAP, 11 WAP, 12 WAP 0 first spray applied 8, 11 or 12 (first signLLS + 10 d) weeks after planting; 7 d, 14 d, 21 d, 28 d 0 7, 14, 21 or28 day spray intervals; 0 s, 1 s, 3 s, 4 s, 7 s 0 1, 3, 4 or 7 sprays of achlorothalonil fungicide except in T3 in which the first spray wasAmistar Xtra (cypronconazole + azoxystrobin); refer to Table 2 forspray schedules and fungicide detailsb Final severity of LLS was assessed 112 days after planting


corresponding values of the other treatments, although NISyields for T2, T5 and T6 were not significantly different to

T4 (Table 7). NIS yields for T4 and T7 were not signifi-cantly different from each other (Table 7).

Weather conditions

During the trial, rain fell on 43 days, with a total of615.1 mm. The daily minimum temperature was 16–26.5°C(mean 21.3°C) and the corresponding maximum tempera-tures were 24.5–33.5°C (mean 29.4°C).


Disease development

LLS was first detected in border rows of cv. Menzies at 9WAP, at which point treatments T2 (full spray, 7/14/21 dayinterval, 9 sprays) and T9 (full spray with final AmistarXtra; 9 sprays) had received 2 sprays and all other fungicidetreatments one spray (Table 2). LLS developed rapidly inthe unsprayed treatment (T1) from 12 WAP onwards(Fig. 6). The LLS values for all treatments at 12 WAP weresimilar, but LLS developed at various rates from that timeonwards. The slowest rates of development were in fullspray treatments, T2, T8 (full spray, 7/ 14 day interval thenAmistar Xtra, total 8 sprays) and T9 and although LLSprogressed at different rates in the remaining treatments,

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Fig. 5 Development of rust in first sign of rust, 1 s (T3) (Whitesquare); unsprayed, 0 s (T1)(Black triangle); first sign of rust thenspray at rating 3, 2 s (T7) (Black circle); first sign of rust, 14 d interval,2 s (T4)(Black diamond); first sign of rust, 21 d interval, 3 s (T5)(White circle); first spray on APSIM model (7 weeks after planting),21 d interval, 4 s (T8)(White diamond); first sign of rust, 14 d interval,4 s (T6)(White triangle); and full spray, first spray 5 WAP, 14 dintervals, 7 s (T2)(Black square) fungicide treatments on rust develop-ment on Sutherland in the 2009 Bundaberg trial. First spray in T3–T7applied 8 weeks after planting, 0 s, 1 s, 2 s, 3 s, 4 s, 7 s 0 0, 1, 2, 3, 4 or7 sprays of a chlorothalonil fungicide. Refer to Table 1 for sprayschedules and fungicide details. Lsd bars P00.05

Table 7 Effects of different fungicide treatments on Area Under theDisease Progress Curve (AUDPC) and final disease severity for rustand on nut-in-shell yield (NIS yield) on cv. Sutherland at Bundaberg in2009

Treatmenta AUDPC Finalseverityb

(1–10)

NISyield(t/ha)

APSIM model, 7 WAP, 21d, 4 s(T8)

79.62 2.88 6.31

First sign, 8 WAP, 14d, 4 s (T6) 73.67 2.30 6.29


Full spray, 5 WAP, 14d, 7 s (T2) 65.71 2.15 6.16


First sign + rating 3, 8 WAP,56d, 2 s (T7)

113.92 4.83 5.20

Unsprayed,0 s (T1) 132.04 6.13 4.68

First sign, 8 WAP, 1 s (T3) 132.47 6.18 4.66

lsd (P00.05) 12 0.67 0.70

a 5 WAP, 7 WAP, 8 WAP 0 first spray applied 5, 7 or 8 (first sign rust)weeks after planting; 14 d, 21 d, 56 d 0 14, 21 or 56 day sprayintervals; 0 s, 1 s, 2 s, 3 s, 4 s, 7 s 0 0, 1, 2, 3, 4 or 7 sprays of achlorothalonil fungicide; refer to Table 1 for spray schedules andfungicide detailsb Final severity of rust was assessed 133 days after planting

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Fig. 6 Influences of unsprayed, 0 s (T1)(Black triangle); spray at firstsign of late leaf spot (LLS), 14 d interval, 2 s (T4)(Black diamond); firstsign of LLS, 21 d interval, 3 s (T5)(White circle); first sign of LLS, 1 s(T3) (White square); first sign of LLS, 14 d interval, 3 s (T6)(Whitetriangle); first sign of LLS then rating 3, 2 s (T7)(X); full spray, firstspray 4 WAP, 14 d intervals, 9 s (T2)(Black square); full spray, first signLLS, 7 or 14 d intervals + 1 spray Amistar Xtra, 8 s (T8)(White diamond);full spray, first spray 5WAP, 7 or 14d intervals + 1 spray Amistar Xtra, 9 s(T9)(Black circle) fungicide treatments on leaf spot development onSutherland in the 2009 Kairi trial. First spray in T3–T8 applied 8 weeksafter planting; 0 s, 1 s, 2 s, 3 s, 4 s, 8 s, 9 s 0 0, 1, 2, 3, 4, 8 or 9 sprays of achlorothalonil fungicide, except in T8 and T9. Refer to Table 2 for sprayschedules and fungicide details. Lsd bars P00.05


their final LLS severity values were similar to that of theunsprayed treatment (Fig. 6).

AUDPC and final LLS severity

For both AUDPC and final LLS severity, treatments T2, T8and T9 had significantly lower values than correspondingvalues for all other treatments. There were no significantdifferences in both AUDPC and final LLS severity betweenthese three treatments. For the other six treatments therewere no significant differences between them in final LLSseverity, but there were for AUDPC with all treatmentshaving significantly lower AUDPC values than the un-sprayed treatment (T1). The best of these treatments (T6 -first sign, 14 day interval, 4 sprays) had an AUDPC valuewhich was not significantly different from those of T5 (firstsign, 21 day interval, 3 sprays) and T7 (first sign then rating3, 2 sprays) (Table 8).

Nut-in-shell yield

All fungicide treatments had significantly higher NIS yieldsthan that of the unsprayed treatment (T1) (Table 8). The

highest NIS yield was in T2, but it was not significantlydifferent to those of treatments T5, T8 and T9. The next besttreatment, T6, had a NIS yield which was not significantlydifferent from those of T5, T8 or T9 (Table 8).

Discussion

Trials conducted in 2006 and 2007 have demonstrated theimproved disease resistance of cv. Sutherland to the rust andlate leaf spot pathogens over that of cv. Menzies. In the 2006and 2007 trials at Bundaberg the final mean severity valuesfor rust in unsprayed cv. Sutherland plots ranged from 3.37to 4.37 while the corresponding values for cv. Menzies were8.67–9.57. Similarly, the severity values for LLS on cv.Sutherland at Kairi in 2006 and 2007 were 2.33–2.67, whilethe corresponding values for cv. Menzies were 6.00–6.67. Inthese four trials, the NIS yields of 18 of the 20 Sutherlandfungicide treatments were greater than those of thecorresponding treatments for Menzies; in eight of thesetreatments the differences were statistically significant. Al-so, rust and LLS became evident on cv. Menzies earlier thanon cv. Sutherland and progressed more slowly throughoutthe season, demonstrating cv. Sutherland’s ‘slow rusting’resistance (Mehan et al. 1994; Subrahmanyam et al. 1983;Wynne et al. 1991). Final disease severity and yields in thebest performing cv. Menzies fungicide treatments were ei-ther significantly lower or statistically similar to the un-sprayed cv. Sutherland treatment (T1) in each of these trials.

The results also demonstrate that the rust and LLS patho-gens can be effectively managed in the newly releasedresistant cv. Sutherland with fewer fungicide applicationsthan the up to eight sprays needed to manage foliar diseasesin the susceptible cv. Menzies. In the 2006 field trials, thebest Menzies treatment (T2 and T4, respectively), whichboth received a total of six sprays, had yields that were notsignificantly different to that of the unsprayed Sutherlandtreatment (T1). In those and both 2007 trials, three or morefungicide sprays on cv. Menzies were required to obtain asimilar yield to that of unsprayed cv. Sutherland. In yearsless conducive for disease development, such as in the 2006Bundaberg and the 2008 Kairi trials, there was no benefit inyield by applying a fungicide to control rust or LLS in cv.Sutherland. In other years, when conditions are more con-ducive to the development of rust and LLS, the applicationof one or more sprays of a chlorothalonil fungicide orcyproconazole + azoxystrobin fungicide will be needed tosignificantly improve the NIS yield of cv. Sutherland com-pared to unsprayed crops. The results of the 2006 and 2007trials indicate that only four fungicide sprays would beneeded to effectively manage P. arachidis and M. berkeleyion cv. Sutherland, compared to six sprays on cv. Menzies.Experience in commercial crops of cv. Sutherland, where

Table 8 Effects of different fungicide treatments on Area Under theDisease Progress Curve (AUDPC) and final disease severity for lateleaf spot (LLS) and on nut-in-shell yield (NIS yield) on cv. Sutherlandat Kairi in 2009

Treatment a AUDPC Final severityb


Full spray, 5 WAP, 7d, 14 d or21 d, 9 s (T2)

221 4.38 3.35

Full spray + Amistar Xtra,5 WAP, 7 d, 14 d or 21 d,9 s (T9)

205 3.81 3.15

First sign, 8 WAP, 21 d,3 s (T5)

307 7.63 3.06

First sign + Amistar Xtra,8 WAP, 7 d or 14 d,8 s (T8)

207 4.00 3.09


306 7.19 2.73


333 7.63 2.47

first sign + rating 3, 8 WAP,56 d, 2 s (T7)

325 7.19 2.44

First sign, 8 WAP, 1 s (T3) 249 7.31 2.05

Unsprayed, 0 s (T1) 416 7.88 1.27

lsd (P00.05) 50 0.73 0.45

a 5 WAP, 8 WAP 0 first spray 5 or 8 (first sign LLS) weeks afterplanting; 7 d, 14 d, 21 d, 56 d 0 7, 14, 21 or 56 day spray interval; 0 s,1 s, 2 s, 3 s, 4 s, 8 s, 9 s 0 0, 1, 2, 3, 4, 8 or 9 sprays of a chlorothalonilfungicide except in T8 and T9 in which the last spray was Amistar Xtra(cypronconazole + azoxystrobin); refer to Table 2 for spray schedulesand fungicide detailsb Final severity of rust was assessed 147 days after planting


fewer fungicides sprays are required to manage these patho-gens on cv. Sutherland than cv. Menzies, corroborates ourfindings.

The timing of the initial fungicide application is critical inmanaging both rust and LLS on peanut crops (Shokes et al.1982). For cv. Sutherland, there was no advantage in applyingone or more fungicide sprays before the diseases were ob-served in plots of unsprayed cv. Menzies. For example, in the2007 Bundaberg trial, there was no significant difference inNIS yield between the early start 14 day interval treatment(T2; 6 sprays) which commenced at 5WAP, 3–4 weeks beforerust was first seen on cv. Menzies, and the corresponding latestart treatment in which the first spray was applied when rustwas first seen, 9 WAP (T4; 4 sprays). There was a similarfinding for LLS on cv. Sutherland in the 2007 Kairi trial,where the two extra sprays applied before the disease wasobserved did not significantly increase NIS yield. The 2009Bundaberg and Kairi trials demonstrate that rust and LLS canbe effectively managed if a spray regime commences whenthe disease is first observed in unsprayed cv. Menzies, irre-spective of the subsequent spray interval; in these trials onlythree sprays of a chlorothalonil fungicide at 21 day intervalswere required for effective disease control, producing NISyields not significantly different to treatments that receivedmore sprays. In the 2009 Bundaberg trial the rust predictionmodel incorporated into the APSIM peanut module predictedthat the first spray should be applied 7 WAP, a week earlierthan rust was first observed on cv. Menzies. The NIS yield ofthis treatment (3 sprays at 21 day intervals) did not differsignificantly from that of a similar treatment which started at8 WAP. The model therefore provides a potential way ofpredicting the appearance of P. arachidis on a foliar disease-resistant variety, and its applicability to commercial situationsneeds further investigation.

Results from the 2008 Bundaberg trial suggest that delay-ing the time of application of the first protectant fungicidespray by 10 days has a deleterious influence on the level ofrust control and consequently on NIS yield. A similar studyby Shokes et al. (1982) on the fungicide management ofpeanut leaf spot diseases in Florida (USA), found that thelevel of leaf defoliation at harvest increased as the time ofapplication of the first chlorothalonil spray was delayedfrom 34 to 118 days after planting, and losses in yieldoccurred when initiation dates were later than 72 days afterplanting. Another study in Georgia (USA), found that yieldsonly decreased when initial fungicide sprays were delayeduntil 60–70 days after planting, and that applying fungicidesprior to 60 days after planting did not result in higher yields(Culbreath et al. 2006).

In commercial crops of foliar disease-susceptible peanutvarieties such as cv. Menzies in Australia, fungicide sprayintervals of 14 days are common. In our 2006 and 2007trials at both sites, the NIS yields of the 14 day interval

fungicide treatments in cv. Menzies were significantlyhigher than the yield of the corresponding 21 interval treat-ment starting at the same time in three of eight combina-tions; in the other combinations there were no significantdifferences in NIS yield. However there is evidence fromour results that the improved resistance of cv. Sutherlandmay enable the fungicide spray interval to be longer than14 days. In all trials except the 2008 Bundaberg trial, theNIS yields of cv. Sutherland in 14 day spray intervals wasnot significantly different to corresponding 21 day intervaltreatment with the same start date. However, in most instan-ces the 14 day interval treatments had higher NIS yields thanthe 21 day interval treatments. In the 2008 Bundaberg trial,the 14 day interval treatment had significantly higher NISyield than the 21 day treatment.

Chlorothalonil, a protectant fungicide, is highly effica-cious in the management of both rust and LLS on peanuts( Subrahmanyam and McDonald 1983; Vaishnav et al.1991; Culbreath et al. 1995; Kishore and Pande 2005;Sunkad et al. 2005) and the results of our trials supportthese overseas reports. Improvement in yield in sprayedtreatments relative to unsprayed treatments was up to164 % for Sutherland (Kairi 2009), and up to 550 % forcv. Menzies (Bundaberg 2007). A range of systemic fun-gicides including cyproconazole, tebuconazole and azox-ystrobin + cyproconazole is also efficacious in themanagement for foliar diseases on peanuts in Australia(Wright et al. 2010) and overseas. The only direct com-parison between chlorothalonil and a systemic fungicidecan be made in treatments T2 and T9 in the 2009 Kairitrial where the last of nine sprays of chlorothalonil (T2)was replaced with a spray of azoxystrobin + cyprocona-zole (Amistar Xtra) (T2). There were no significant differ-ences in NIS yield between these treatments. The use ofcyproconazole has been reported to be effective in con-trolling both rust and LLS in Tifton, USA and India(Adiver et al. 1995; Rideout et al. 2002).

Although the combination of improved resistance of cv.Sutherland and targeted fungicide applications will effec-tively manage P. arachidis and M. berkeleyi in Australia,they need to be combined with other management practicesto provide an integrated disease management package. Suchpractices include crop rotation, careful paddock selection toavoid close proximity to paddocks where foliar disease-susceptible varieties are, or have been grown in the past,and destruction of peanut volunteers (Jackson and Bell1969; Mallaiah and Rao 1979; McDonald et al. 1985;McDonald et al. 1998; Rao et al. 1993).

Acknowledgment The authors thank the Grains Research and De-velopment Corporation for funding this research, staff at BundabergResearch Station and Kairi Research Stations for technical assistanceand Ms Carole Wright and Ms Susan Fletcher for biometrics support.


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http://www.bom.gov.au/climate/?averages

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http://dx.doi.org/10.1094/PHP-2006-0214-01-RS

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http://www.pca.com.au/pdfs/growing-peanuts/productionguide.pdf

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reduced fungicide use on a new australian peanut cultivar, highly resistant to the late leaf spot...

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