Non-Peer ReviewedAscochyta rabiei control from aerial and ground application was assessed near Saskatoon in 2003 and 2004. Each year, a site of about 12 ha was seeded to kabuli (cv. CDC Xena) chickpeas. At the first sign of disease, applications of fungicide were commenced and maintained at approximately 10-day intervals. In 2003, four applications (two with Headline (pyraclostrobin), two with Lance (boscalid)) were conducted. In 2004, the last Lance application was not done. Aerial application was made using a Cessna AgTruck applying 37 L/ha using CP nozzles emitting a spray with a VMD of approximately 271 μm. Ground applications were conducted using a Melroe SpraCoupe applying 100 L/ha using XR8003 nozzles with a VMD of approximately 246 μm. Disease ratings were done throughout the season, and seed yields were
taken at crop maturity. Disease incidence progressed to 80 to 90% in the untreated plots, and fungicide application reduced disease incidence (to 20 to 30%) and increased seed yield in both years. Disease incidence and seed yield were not affected by application method in either season

Armstrong-Cho, C.

Banniza, S.

Caldwell, B.C.

Gan, Y.

Wolf, T.M.

English

eCommons@USASK

Comparison of ground and aerial application of fungicide for control of Ascochyta blight in chickpeas

University of Saskatchewan Research Archive

1Comparison of Ground and Aerial Application of Fungicide forControl of Ascochyta Blight in ChickpeasT.M. Wolf1, B.C. Caldwell1, C. Armstrong-Cho2, S. Banniza2, and Y. Gan31Agriculture & Agri-Food Canada, 107 Science Place, Saskatoon SK  S7N 0X22Crop Development Centre, University of Saskatchewan, Saskatoon SK  S7N 5A83Agriculture & Agri-Food Canada, Box 1030 Airport Road East, Swift Current SK  S9H 3X2Key Words: fungicide application, chickpeas, spray quality, water volumeAbstractAscochyta rabiei control from aerial and ground application was assessed near Saskatoon in2003 and 2004.  Each year, a site of about 12 ha was seeded to kabuli (cv. CDC Xena)chickpeas.  At the first sign of disease, applications of fungicide were commenced andmaintained at approximately 10-day intervals.  In 2003, four applications (two with Headline(pyraclostrobin), two with Lance (boscalid)) were conducted.  In 2004, the last Lance applicationwas not done.  Aerial application was made using a Cessna AgTruck applying 37 L/ha using CPnozzles emitting a spray with a VMD of approximately 271 µm.  Ground applications wereconducted using a Melroe SpraCoupe applying 100 L/ha using XR8003 nozzles with a VMD ofapproximately 246 µm.  Disease ratings were done throughout the season, and seed yields weretaken at crop maturity.  Disease incidence progressed to 80 to 90% in the untreated plots, andfungicide application reduced disease incidence (to 20 to 30%) and increased seed yield in bothyears.  Disease incidence and seed yield were not affected by application method in eitherseason.IntroductionFungicide application is an important disease management strategy for ascochyta blight (causedby Ascochyta rabiei) in chickpea due to the poor host resistance in available cultivars.Ascochyta blight, left untreated, can cause yield losses in excess of 90% in Saskatchewan, andappropriate timing and frequency of fungicide spray application is critical.  Producers wishing toapply fungicide are sometimes unsure which application method to use – aerial or ground.  Bothoffer potential advantages and disadvantages:  ground sprayers utilize greater water volumes, butleave tracks which can lower yield and spread disease.  Aircraft use lower water volumes but donot damage the crop and can cover more area in a timely fashion.  The relative importance ofthese characteristics is unknown.  Objectives of this study were to compare aerial and groundfungicide application on chickpea disease and seed yield.Materials and Methods:Chickpeas (certified CDC Xena, a unifoliate kabuli rated as having very poor ascochytaresistance) were seeded on May 15 (2003) and May 27 (2004) on 12-ha sites near Saskatoonwhich had been chem-fallow wheat stubble (2003) and spring wheat (2004) the previous year.Seed was treated with Crown and Apron and seeded at 190 kg/ha (35 seeds/m2) to a depth of 6.5cm using a Flexi-Coil air seeder with 22-cm row spacing.  The field was harrowed and rolledafter seeding.  Pursuit (70 mL/ha) and Post Ultra (0.32 L/ha) were applied for weed control in2both years.  The crop established evenly and weed populations (primarily prostrate pigweed andstinkweed) were low in 2003.  In 2004, sow thistle was the predominant weed.North89 m400 m356 mWheat WheatAerial applicationAerial applicationGround applicationGround applicationUntreated CheckUntreated CheckUntreated CheckFigure 1:  Field layout for trials.The site measured 400 m x 356 m (2003) and 400 m x 267 m (2004) and was divided into twoequal halves (replicates).  Each of three treatments was established in each half: untreated check,aerial, and ground application.  The aerial treatment consisted of four adjacent 15-m passes andthe ground application was five 13-m passes per replicate.  A control swath was left at either endof each replicate, but a sprayed buffer separated the control from a treatment to avoid diseasespread (Figure 1).In 2003, the crop was scouted at 5-day intervals for the presence of disease.  Initial disease levelsthrough June were very low and disease did not become visible until after the first major rainfallevent on July 6.  Headline (pyraclostrobin) was applied on July 11 and July 21 at 0.4 L/ha,followed by Lance (boscalid) on August 1 and 13-14 at 0.42 kg/ha.  Aerial and groundapplications were conducted at dusk with calm conditions.  Both were conducted within 1 h ofeach other except for the last application of Lance where the ground application followed thenext morning.In 2004, the crop was slow to establish due to cool temperatures, disease became prevalent earlyin the crop development, especially on the side of the field which bordered the 2003 trials.Headline was applied on July 12 and July 23, Lance was applied on August 2.In both years, aerial applications were done by Cessna Ag Truck applying 37 L/ha through 24CP-03 nozzles with the 0.125 flow orifice and 90º deflection, at a pressure of 234 kPa and 1923km/h airspeed.  At these settings, the spray had a volume median diameter (VMD) of 271 µmaccording to USDA atomization models.  Boom height was 3 to 4.5 m above ground (Figure 2).Figure 2:  Aerial and ground application of fungicide to chickpeas.Ground applications were done using a Melroe SpraCoupe 220 travelling 13 km/h, usingXR8003 nozzles operated at 275 kPa and a boom height of about 75 cm.  At these settings, theapplication volume was 100 L/ha, and the spray had a VMD of 246 µm (Figure 2).Disease symptoms became evident in early July in both years.  Ratings were conducted near thespraying dates using the 0-11 Horsfall-Barratt scale, converted to % infection.  Single plantswere rated at 64 (2003) and 60 (2004) locations in each treatment within each rep, for a totalnumber of 128 or 120 plants rated per treatment per rating date (except for the first rating, whereonly 24 plants per treatment were rated).  Ratings from the outside two passes of the aircraft ineach replicate were deleted since proper spray patterns were not expected at these edges.Figure 3:  Ascochyta blight symptoms on chickpea leaves.  Early infection (left); advancedinfection showing lesions with pycnidia (right).4In 2003, the crop matured in mid-August and Reglone was applied by ground sprayer travellingperpendicular to the treatments, on August 22.  In 2004, the crop failed to mature and wassprayed in a similar fashion with Roundup on September 20.The 2003 crop was harvested on September 3 using a Case 1688 combine with a 9-m flex header(Figure 4).  After removal of headlands, two 275 m long swaths were taken from each treatment,and the seed from each swath was weighed and sub-sampled for seed quality.  In the aerial plots,the central two spray swaths of each rep were sampled.  In the ground plots, two swaths weretaken with wheel tracks, and two without wheel tracks in each rep.  Wheel tracks were thenadjusted to a 90’ boom width for yield calculations.Figure 4:  2003 sprayer tracks (left) and combine operation (right).  Harvested seeds in insert.In 2004, harvest was impractical with the large combine due to the low seed yield and qualitywhich prevented accurate yield measurements.  On November 10, a Hege combine was used toharvest a single pass along the length of each sprayer swath for all treatments.  The grain wasbagged, dried, and weighed.All data were analyzed using analysis of variance (ANOVA) as a randomized complete blockdesign with two replicates.  Treatment effects were considered significant at p=0.05.Results and Discussion:Ascochyta was prevalent in both 2003 and 2004.  In 2003, disease incidence in the untreatedchickpea progressed from about 5% to about 66% from July 9 to July 31.  Disease incidence insprayed plots was significantly less, about 18 and 21% for the ground and aerial treatments,respectively on July 31.  A late flush of disease on new growth increased levels to 87% in theuntreated plots, and 28 to 41% in the ground and aerial plots, respectively, on August 14  (Figure5, left).In 2004, disease in the untreated plots steadily increased from 3% infection on July 14 to 99% onSept 14.  During this time, the treated aerial and ground plots increased from 4 to 18-20%,similar for both application methods (Figure 5, right).5Figure 5:  Ascochyta blight incidence on chickpeas throughout growing season.  2003 (left),2004 (right).Application methods generated visually different spray deposits on water sensitive cards (Figure6).  The ground application had greater overall coverage of the cards primarily due to the greaterwater volume used (100 L/ha vs. 37 L/ha).  Cards indicated that overall uniformity of the spraydeposit along the width of the boom was greater for the ground sprayer (data not shown).However, water sensitive cards provide an artificial collection surface that does not accuratelysimulate the complexity of a leaf surface or a multi-dimensional plant canopy.  These cardstherefore do not provide an assessment of leaf coverage, but are limited to a visual indication ofthe type of spray quality emitted by the application.Figure 6:  Spray deposit on water-sensitive paper for ground application at 100 L/ha (left) andaerial application at 37 L/ha (right).Fungicide application significantly increased seed yield in both years.  In 2003, yield averaged13 bu/acre for the unsprayed treatments, and 33 bu/acre where fungicides had been applied.Aerial treatments yielded 32.7 bu/acre, whereas ground treatments (track damage adjusted for90’ boom width) yielded 34.4 bu/acre.  This difference was not statistically significant (Table 1).Ground-sprayed areas without wheel tracks yielded 36.0 bu/acre, therefore yield loss due totracks was 1.6 bu/acre (Figure 7).Table 1:  Analysis of variance results for chickpea seed yield from aerial and groundapplications (ground with tracks adjusted for 90' boom), 2003.EffectdfEffectMSEffectdfErrorMSError F-value p-levelTreatment 1 5.89 1 1.41 4.18 0.290Replicate 1 12.10 1 1.41 8.58 0.209DateDisease incidence (%)020406080100July 14 July 28 Aug. 4 Aug. 12 Sept. 14CheckAerialGroundStd. Err.DateDisease incidence (%)020406080100July 9 July 22 July 31 Aug. 14CheckAerialGroundStd. Err.6Sprayer tracks reduced yield due to crop destruction, but they did not appear to spread diseasewithin the crop.  It is possible that application during evening hours before dew wetted thefoliage helped prevent disease spread.  The role of sprayer tracks requires further investigation.Figure 7:  Chickpea seed yield in plots treated with fungicide applied by air and ground.  2003(left), 2004 (right).Seed yield and quality were very poor in 2004 due to cool growing conditions and an early frost.In spite of this, results mirrored those from 2003:  fungicide applications significantly increasedyield, from 0.3 bu/acre in the untreated plots to 4.7 and 4.9 bu/acre in the ground and aerialtreatments, respectively.  Yield differences arising from application method were not statisticallysignificant.Seed quality analysis demonstrated no difference in chickpea grade between ground and aerialapplications.  Ascochyta rabiei was not detected on seed from any treatment in 2003.These results showed that both ground and aerial application of fungicide provided effectivecontrol of Ascochyta rabiei on chickpea.  Results from 2004 were compromised by a poorgrowing season, therefore further work may be necessary to confirm this outcome.  Nonetheless,the consistency of conclusions support recommending both methods to producers wishing toapply fungicides.Acknowledgements:We thank Roland Jenson (Cloud 9 Airspray) for conducting the aerial applications, MarkKuchuran and Dan Caldwell (BASF) for providing fungicide, herbicide, and overall support, JimKelley (Redhead Equipment) for providing harvesting equipment, Al Baraniuk (AAFC) forassisting with seeding and harvesting operations, and Curtis Sieben and Chris Gilchrist forplanning and implementing this trial.  Financial assistance was provided by the SaskatchewanPulse Growers (2003) and AAFC through the IFSP Initiative (2004).Two swaths per treatment, tracks 90'Chickpea yield (bu/acre)0510152025303540Aerial                   Groundno tracksGroundtracksUntreatedMean±Std. Dev.Chickpea yield (bu/acre)01234567Aerial Ground UntreatedMean±Std. Dev.

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Comparison of ground and aerial application of fungicide for control of Ascochyta blight in chickpeas

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