effect of pesticide spray techniques on foliage coverage ... · vegimpact report 43– effect of...

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Herman de Putter, Witono Adiyoga, Tonny K. Moekasan and Laksminiwati Prabaningrum

vegIMPACT Report 43 September 2017

Effect of pesticide spray techniques on foliage coverage, pests and diseases, and

crop yield in Java, Indonesia

vegIMPACT Report 43– Effect of pesticide spray techniques on foliage cover, pests and diseases, and crop yield

vegIMPACT is a program financed by The Netherlands’ Government promoting improved vegetable production and marketing for small farmers in Indonesia, contributing to the food security status and private sector development in Indonesia. The program builds on the results of previous joint Indonesian-Dutch horticultural development cooperation projects and aligns with recent developments in the horticultural private sector and retail in Indonesia. The program activities (2012 – 2016) include the Development of Product Market Combinations, Strengthening the Potato Sector, Development of permanent Vegetable Production Systems, Knowledge Transfer and Occupational Health. Wageningen University & Research, The Netherlands: - Wageningen Plant Research, Lelystad - Wageningen Centre for Development Innovation (CDI), Wageningen - Wageningen Plant Research, Wageningen - Wageningen Economic Research, Den Haag

Wageningen University & Research Contact person: Huib Hengsdijk, [email protected] Indonesian Vegetable Research Institute (IVEGRI, Indonesia) Contact person: Witono Adigoya, [email protected] Fresh Dynamics (Indonesia) Contact person: Marcel Stallen, [email protected]

Website: www.vegIMPACT.com

© 2017 Wageningen University & Research, Wageningen Plant Research, P.O. Box 16, 6700 AA Wageningen, The Netherlands; T +31 (0)317 48 07 00; www.wur.nl/plant-research . Stichting Wageningen Research. All rights reserved. No part of this publication may be reproduced, stored in an automated database, or transmitted, in any form or by any means, whether electronically, mechanically, through photocopying, recording or otherwise, without the prior written consent of Stichting Wageningen Research. DLO is not liable for any adverse consequences resulting from the use of data from this publication.

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Effect of pesticide spray techniques on foliage coverage, pests and diseases, and

crop yield in Java, Indonesia

Herman de Putter, Witono Adiyoga, Tonny K. Moekasan and Laksminiwati Prabaningrum


Contents Abstract ........................................................................................................................................................ 5

1. Introduction .......................................................................................................................................... 6

2. Materials and methods ........................................................................................................................ 7

2.1 Applied pesticides ......................................................................................................................... 7

2.2 Locations ....................................................................................................................................... 8

2.3 Crop data ...................................................................................................................................... 8

2.4 Observations ................................................................................................................................. 8

2.4.1 Climate .................................................................................................................................. 8

2.4.2 Plant height ........................................................................................................................... 9

2.4.3 Crop coverage ....................................................................................................................... 9

2.4.4 Pest and disease observations and analysis ....................................................................... 10

2.4.5 Crop yields .......................................................................................................................... 10

2.4.6 Relationship crop yield and coverage ................................................................................. 11

2.4.7 Economic analyses .............................................................................................................. 11

3. Results ................................................................................................................................................ 12

3.1 Temperature ............................................................................................................................... 12

3.2 Crop development and water volumes ...................................................................................... 12

3.3 Observations of crop coverage with fluorescence and water sensitive paper .......................... 17

3.3.1 Cucumber ........................................................................................................................... 18

3.3.2 Potato ................................................................................................................................. 26

3.3.3 Shallot ................................................................................................................................. 32

3.4 Pest and disease observations ................................................................................................... 36

3.4.1 Cucumber ........................................................................................................................... 36

3.4.2 Potato ................................................................................................................................. 36

3.4.3 Shallot ................................................................................................................................. 41

3.5 Yields of cucumber, potato and shallot ...................................................................................... 42

3.6 Relationship between crop coverage and yield ......................................................................... 44

3.7 Economic analysis ....................................................................................................................... 44

4. Discussion and conclusions ................................................................................................................ 46

5. References .......................................................................................................................................... 48

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Abstract

In the dry season of 2015 a test with two pesticide spray volumes (low versus high-farmers’ practice) was carried out in shallot (Allium cepa var. aggregatum), potato (Solanum tuberosum) and cucumber (Cucumis sativus). The crops were weekly sprayed according a standard fungicide and insecticide spray programme.

At three moments in the growing season, crop coverage using both spray volumes was assessed with two different methods. A fluorescent spray solution was sprayed and water sensitive paper was placed in the crop at different positions in the crop, bottom, centre and top. After spraying leaf samples from the bottom, centre and top of the plant were taken to check on fluorescent coverage using a black light. Water sensitive papers were collected and the percentage of covered surface was determined. Pest and diseases in the crops were observed weekly.

Despite the lower coverage observed with the fluorescent and water sensitive paper, lower water volumes for spraying resulted in both shallot and potato in the same pest and disease pressure and yields as using the high(er) water volumes commonly applied by farmers.

In cucumber, a crop with more foliage than the other two crops, the measured coverage and yields were significantly lower using reduced spray volumes. However, pest and disease pressure was not different between the low and high spray volumes. Hence, yield differences could not be ascribed to better pest and disease control in the treatment with high spray volumes.

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1. Introduction

In Indonesia, vegetable farmers face a lot of pests and diseases often resulting in crop damage and low yields. In order to keep the crops free of pests and diseases, farmers mostly rely on the use of pesticides. In general, vegetable farms are relatively small and most farmers apply pesticides by using hand-operated or battery-operated knapsack sprayers with a single hollow or full cone nozzle. Farmers still perceive that pesticides are only providing full protection when all plant parts are thoroughly sprayed and wetted. High water volumes are applied resulting in undesired run-off of excessive spray solution. Simultaneously, because every plant part is targeted, the spray pattern is uneven and the distance between nozzle and plant becomes variable. As a result, some plant parts receive too much spray solution and other parts too little. A new generation of pesticides is actually more effective because these pesticides have a local systemic or residual mode of action to control pests and diseases. With a good spray schedule farmers should be able to keep the pest and disease pressure at low levels. An optimal coverage is still important, but it is not necessary to cover each plant part such as the underside of the leaves. In this report we describe the results of an experiment carried out in Java, Indonesia, using shallot, potato and cucumber to test different spray techniques on crop canopy cover, pest and disease pressure and crop yields. We compare the commonly used spray technique of farmers with an improved technique based on constant forward movement of the knapsack operator. The latter application techniques was further tested with a constant nozzle swing over the crop and a constant nozzle swing along the crop.

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2. Materials and methods

Two different spraying methods were tested in shallot, potato and cucumber: 1. Low water volumes and spraying at steady pace of the operator in combination with steady

movement of the nozzle over the crop at a fixed distance. With this method, more uniform spray distribution is achieved, but penetration of the spray solution in the crop is less but still sufficient to achieve a good control. This technique is indicated with ‘LV’ in the remainder of the report.

2. Farmers’ practice, i.e. intensive spraying with high water volumes and less steady uniform

movement of the operator and nozzle movement. This technique is indicated with ‘HV’ in the remainder of the report. Compared to LV this technique requires more labour when using the same equipment: Labour requirements increase linearly with the water volume applied at a given nozzle output. In addition, more water applied means also more refilling of the knapsack sprayer which can take up to 15 minutes when including walking time and measuring the right volumes of pesticides and water. For example, when spraying 400 l/ha water with a standard 17 litre spray tank 400 minutes for spraying is needed plus 400/17 litre times 15 minutes for filling up the tank resulting in about 760 minutes (12.7 h/ha). In case 800 l/ha is sprayed the total time needed is about 1520 minutes, twice as much.

The two spray techniques LV and HV were tested in shallot, potato and cucumber. Shallot has very erect leaves with a waxy structure with low adhesion to droplets, and low soil cover, potato has a much better soil cover and a more horizontal leave stand, while cucumber has larger leaves and more leave biomass than the other two crops. Per crop one spray operator carried out all the sprays with a standard knapsack sprayer fitted with a hollow cone nozzle. The experiment was laid out as a complete randomized block design with four blocks for all three crops. The data was analysed with Genstat.

2.1 Applied pesticides

A spraying programme was designed to control pests and diseases in the three tested crops (Table 2.1). In shallot, starting 12 days after planting, every five days one insecticide and every ten days one fungicide was applied. The insecticides were applied at one day and the fungicides at the other day when both needed to be sprayed. A total of 12 insecticide and five fungicide applications were applied in this way. In potato, starting on 28 July, 22 days after planting, one insecticide and one fungicide were applied as a mix every five days until the end of the growing season on 28 September. In total 14 sprays were applied. In cucumber, starting on August 5, one week after planting, a mix of one insecticide and one fungicide was applied every five days until the end of the growing season on November 8. In total 20 sprays were applied.

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Table 2.1. Applied doses, pesticide characteristics and costs of the pesticides used. Item Active ingredient Crop use Costs Unit

Spray labour (1 hr per 50 litre) all

Labour costs all 9000 IDR/hr

Agrimec 18 EC Abamectine 18 g/l Cucumber / Potato 850 IDR/ml

Daconil 75 WP Chlorothalonil 750 g/kg Cucumber / Potato 140 IDR/g

Endure 120 SC Spinetoram 120 g/l Cucumber / Potato 1570 IDR/ml

Destello 480 SC Thiodicarb 360 g/l + Triflumuron 120 g/l Shallot 220 IDR/ml

Delsene 50 WP Carbendazim 500 g/kg Shallot 130 IDR/g

Dithane 80 WP Mancozeb 800 g/kg Shallot 85 IDR/g

Ludo 310 EC Chlorfenapyr 310 g/l Shallot 495 IDR/ml

Starelle 660 SC Chlorpyrifos 600 g/l + Cypermethrin 60 g/l Shallot 200 IDR/ml

2.2 Locations

The experiment was carried out in three crops, i.e. shallot, potato and cucumber, each crop having different leaf densities. The test with shallot was located in the lowlands (10 m ASL) of Sumber lor, West Java. The location of the two other crops was in Lembang (1225 m ASL), West Java. The soil in Sumber lor is a heavy clay soil (fluvisol,) while the soil in Lembang is a loamy clay soil of volcanic origin (andosol).

2.3 Crop data

Cucumber (cv. Bandana) was planted on 28 July 2015. Planting distance was 30 x 60 cm. Plot size was 2.5 x 6 m containing 80 plants. Basal fertilization was carried out seven days before planting using 10 t/ha manure, 467 kg/ha NPK 15-15-15, 67 kg/ha Urea and 80 kg/ha KCl. Three weeks after planting a side application of 133 kg/ha Urea was applied. Total N-P2O5-K2O applied with chemical fertilizer in this way was 162, 70 and 188 kg/ha, respectively. Harvest took place every two days starting from September 13. Ten harvests were administered. Potato (cv. Granola) was planted on 6 July 2015 and harvested on 6 October 2015. Planting distance was 30 x 70 cm. Plot size was 2.6 x 6 m containing 80 plants. Basal fertilization was carried out two days before planting by applying 20 t/ha manure, 667 kg/ha NPK 15-15-15, 433 kg/ha SP-36 and 267 kg/ha KCl. Four weeks after planting a side application of 233 kg/ha Urea was applied. Total N-P2O5-K2O applied with chemical fertilizer in this way was 207, 256 and 260 kg/ha, respectively. Shallots (cv. Bima Curut) were planted on August 21, 2015. Plot size was 1.5 x 9 m large. Plant distance was 15 x 15 cm. Fertilizers were applied 2 days before planting at a rate of 533 kg/ha NPK 15-15-15, 59 kg/ha SP-36 and 37 kg/ha KCl. Ten and 30 days after planting side dressings of 185 kg/ha Urea and 407 kg/ha Ammonium Sulphate were applied, respectively. This resulted in total amounts N-P2O5-K2O of 250, 101 and 102 kg/ha, respectively. Harvest took place on October 13, 2015.

2.4 Observations

2.4.1 Climate

In Cirebon, temperature and rainfall data were collected from a local weather station. Cirebon is

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representative for the lowland conditions of Sumber lor. For the highland conditions no weather data have been recorded.

2.4.2 Plant height

The distance between soil surface and top of the crop was measured using a ruler every five days.

2.4.3 Crop coverage

Crop coverage has been approximated here by adding a fluorescent to the spray solution and the following two methods: 1) After spraying, leaves from different locations in the crop were collected and the percentage of leaf surface covered by the spray solution was determined with a black light, and 2) water sensitive paper that was placed before spraying at different locations in the crop was assessed visually and using image processing software after spraying. Both methods have been applied at three moments in the growing period (Table 2.2). Table 2.2. The three observation dates of the coverage of leaves and water sensitive paper with

pesticides after pesticide applications.

Date 1 Date 2 Date 3

Cucumber 24 August 8 September 21 September

Potato 6 August 24 August 7 September

Shallot 6 September 20 September 4 October

The crops were sprayed with water containing a 5% fluorescence solution. Before the spraying, water sensitive papers (strips of 2 x 5 cm) were placed at fixed positions in the crop (Fig. 2.1). The positions of water sensitive papers in potato and cucumber were located in the top, middle and bottom of the crop with one card per position placed facing upwards on a leaf and facing downward at the underside of a leaf. This resulted in six different positions, per position two cards were used resulting in 12 cards per plot per observation. In shallot water sensitive papers attached to plants according to position in the planting bed. Three leaves were collected from the left side of the bed, three from the middle and three from the right side of the bed. Water sensitive papers were attached to two plants per position. Papers were vertical in an upright position attached to the shallot leaves. After spraying the water sensitive papers were collected and the percentage coverage was rated visually and using the snap card app, a tool that calculates the percentage coverage of a water sensitive paper using a digital image-processing app (Nansen et al., 2015). After collecting the water sensitive papers, leaves were picked from the plants. Two leaves, other than the ones used for connecting the water sensitive papers, from the top, two leaves from middle and two leaves from the lower part of the plant were picked. Six positions times two leaf orientations giving 12 leaves per plot were harvested in this way. The collected leaves were visually inspected in a dark room using black light and percentage coverage of the upper- and underside of the leaves was rated.

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Figure 2.1. Water sensitive paper in Cucumber.

2.4.4 Pest and disease observations and analysis

Every five days pests and diseases were observed using leaf, plant or plot counting or rating. For most pests randomly ten plants per plot were selected, each observation date it could be different plants. Depending on the type of disease/pest per plant the presence of the pest or disease was (a) rated on a scale from 0 (not present) to 5 (heavy infestation), or (b) number of pest infestations were counted per plant, or (c) counting was done on one randomly selected leaf per selected plant. For some pests and diseases per experimental plot the percentage of attacked plants was calculated based on the total number of observed plants. AUDPC (area under the disease progress curve) (Madden et al. 2007) or AUPPC (area under the disease progress curve) for pests and diseases were calculated by the following formula:

Cumulative sum of the difference in observation score or figure between dates / 2 x number of days between observations. For example, on 11 November a disease rating of 10 was determined, on 16 November a disease rating of 24 and on 21 November a disease rating of 26. The AUDPC is then calculated as (10+20)/2 x (5 days) + (24+26)/2 x (5 days) = 15 x 5 + 25 x 5 = 200.

2.4.5 Crop yields

At harvest, the yields of cucumber, potato and shallot of the two spray treatments were graded and

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weighed (kg) and counted per grade. Grade A are the bigger tubers with 2-5 tubers per kg, B is 6-8 tubers per kg and Grade C has 10-12 tubers per kilogram. Grading was done visually on the field.

2.4.6 Relationship crop yield and coverage

The relationship between crop yields and crop coverage was analysed using simple linear regression analysis. For the analysis marketable yield of cucumber, total marketable (A+B+C) of potato and fresh, yield of shallot were used. Per crop, the relative yield was calculated as percentage of the maximum crop yield. The regression was calculated between the average fluorescent coverage percentage of all observations per crop, position and observation date, and the relative yield.

2.4.7 Economic analyses

First, the cost price of production was calculated based on the measured yield per treatment and cost for pesticides and labour to apply them. Pesticide prices were based on prevailing prices of pesticide products at the local agro supply shop and pesticide amounts were calculated based on actual use. We assume further that one person can spray 50 l spray solution per hour per hectare and labour costs are 9,000 IDR per hour. In general, farmers perceive that pesticides applied with higher water volumes result in higher yields, because low volume sprays do not cover the crop well, resulting in suboptimal pest and disease control and lower yields in the end. In the case that the HV treatment resulted in a higher yield, we calculated whether the financial gains of the extra yield was high enough to compensate the additional crop protection costs (pesticides and labour associated with the pesticide application).

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3. Results

3.1 Temperature

No precipitation was observed during the shallot experiment in Cirebon. Maximum daily temperature was about 40oC during the whole period from planting until harvest (Fig. 3.1). Minimum temperature was mostly about 25oC with some lower temperatures towards 20oC at the end of September.

Figure 3.1 Mean daily maximum and minimum temperature (oC) measured at Cirebon during the

experiment.

3.2 Crop development and water volumes

Cucumber plants of both treatments showed a similar grow in terms of plant height (Fig. 3.2) with a final height of approximately 100 cm.

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Figure 3.2 Development of cucumber plant height (cm) (average: p=0.88; LSDɑ = 0.05 = 3.1). Spray

technique 1= Low Volume, Spray technique 2= High Volume. Different spray techniques were associated with different water volumes (Table 3.1). On average, 440 l/ha per application was used with spray technique 1 (LV) and 611 l/ha per application with spray technique 2 (HV). The spray volumes applied with spray technique 1 (LV) were 11 to 41% lower than the volumes used with spray technique 2 (HV). Table 3.1 Used spray volumes and reduction in spray volume with spray technique 1 compared to

spray technique 2 in cucumber. Spraying date Spray technique 1 (LV) Spray technique 2 (HV) Reduction in spray volume (%)

5-8-2015 283 463 39

10-8-2015 378 448 16

15-8-2015 425 475 11

20-8-2015 425 525 19

25-8-2015 500 663 25

30-8-2015 463 663 30

4-9-2015 438 738 41

9-9-2015 438 688 36

14-9-2015 513 758 32

19-9-2015 488 668 27

23-9-2015 488 638 24

Average 440 611 28

p < 0.001

LSD ɑ=0.05 53.3

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In addition, the plant height development in potato was about the same for both treatments (Fig. 3.3). The crops of both treatments reached a height of approximately 45 cm early September after which the plant height decreased.

Figure 3.3 Development of potato plant height (cm) (average: p=0.69; LSDɑ = 0.05 = 1.0). Spray technique

1= Low Volume, Spray technique 2= High Volume. In potato, spray technique 1 (LV) used a significantly lower water volume than spray technique 2 (Table 3.2). On average, a volume of 452 l/ha was applied per spraying with LV and 570 l/ha with HV. The reduction in spray volume ranged from 8 to 37 % with an average of 21%. Measurements of spray volumes used in farmers’ practice in Pangalengan and Garut showed that potato farmers used on average more than 900 l/ha per application (De Putter et al., 2014; Pronk et al., 2017). Hence, with spray technique 2, resembling farmers’ practice, a significantly lower spraying volume (about 40%) was applied than actual farmers’ practice.

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Table 3.2 Used spray volumes and reduction in spray volume with spray technique 1 (LV) compared to spray technique 2 (HV) in potato. Low volume = LV; High volume = HV.

Spraying date Spray technique 1

(LV)

Spray technique 2

(HV)

Reduction in spray volume (%)

7-aug 350 413 15

12-aug 413 463 11

17-aug 420 555 24

22-aug 375 525 29

27-aug 438 688 36

1-sep 450 713 37

6-sep 490 538 9

11-sep 440 605 27

16-sep 538 588 9

21-sep 508 588 14

26-sep 550 600 8

Average 452 570 21

p < 0.001

LSD ɑ=0.05 36.8

In shallot, plant development in terms of the number of leaves per plant was similar for both treatments (Fig. 3.4). In total, about 5.5 leaves per plant were present at harvest.

Figure 3.4 Development of leaf number per plant of shallot (average: p=0.87; LSDɑ = 0.05 1.4). Spray

technique 1= Low Volume, Spray technique 2= High Volume.

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Compared to cucumber and potato, the number of pesticide applications in shallot was higher with 17 applications. Table 3.3 shows that the applied volume with the LV spray was significantly lower than with the HV spray in shallot. At the start of crop growth, differences in volume were absent or very low, but after mid-September, differences increased ranging from 9 to 43%. Measurements of spray volumes used by shallot farmers’ practice in 2014 and 2015 in Sumber lor, Cirebon region, showed average spray volumes of 700 l/ha. Hence, spray volumes with HV were still about 25% lower than actual farmers’ practice. Table 3.3 Used spray volumes and reduction in spray volume with spray technique 1 (LV) compared to

spray technique 2 (HV) in shallot. LV = Low Volume, HV = High Volume. Spraying date Spray technique 1 (LV) Spray technique 2 (HV) Reduction in

spray volume (%)

2-9-2015 463 463 0

6-9-2015 444 463 4

7-9-2015 556 556 0

9-9-2015 556 556 0

13-9-2015 463 550 16

14-9-2015 426 519 18

16-9-2015 481 528 9

20-9-2015 296 519 43

21-9-2015 417 546 24

23-9-2015 389 537 28

27-9-2015 472 552 14

28-9-2015 389 552 30

30-9-2015 435 552 21

4-10-2015 444 554 20

5-10-2015 435 537 19

7-10-2015 398 546 27

11-10-2015 444 552 20

Average 442 534 17

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3.3 Observations of crop coverage with fluorescence and water sensitive paper

Figure 3.5. Cover of water sensitive paper with Spray technique 1 (LV) in Cucumber on 24 August 2015

(Left column cards: upper side of leaves, Right column cards: underside of leaves; above four cards: top of crop, Middle 2 cards: middle of crop, Bottom 4 cards: lower parts of crop).

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Figure 3.6. Cover of water sensitive paper in cucumber with Spray technique 2 (HV) on 24 August 2015

(Left column cards: upper side, Right column cards: underside of leaves; above four cards: top of crop, Middle 2 cards: middle of crop, Bottom 4 cards: lower parts of crop).

3.3.1 Cucumber

The average leaf cover (percentage fluorescence surface) observed on 25 August was significantly higher with spray technique 2 (HV) than spray technique 1 (LV) (Table 3.4). Higher crop cover with HV occurred especially at the underside of the leaves and on the leaves observed at the bottom of the

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plants. Table 3.4 Fluorescence surface of cucumber leaves on 25 August 2015 (percentage of leaf surface

covered). LV = Low Volume, HV = High Volume. Leaf orientation Plant position Spray technique 1 (LV) Spray technique 2 (HV) Average

underside top 2 a 35 b 18

centre 1 a 31 b 16

bottom 0 a 14 a 7

average 1 27 14

upper side top 62 d 65 de 63

centre 60 cd 82 f 71

bottom 47 c 77 ef 62

average 56 74 65

average

29 51 40

Analyse p LSD ɑ=0.05

Spray technique * Leaf orientation * Plant position 0.015 15

Spray technique * Leaf orientation 0.22 9

Spray technique <0.001 6

Leaf orientation <0.001 6

Plant position 0.06 8

On 8 September, the leaf coverage with fluorescence was higher at the upper side of the leaves (Table 3.5). In general, the crop cover with spray HV was higher than with LV. Only at the top of the plant, the cover of the upper side of leaves was similar for both LV and HV.

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Table 3.5. Fluorescence surface of cucumber leaves on 8 September 2015 (percentage of leaf surface covered). LV = Low Volume, HV = High Volume.

Leaf orientation Plant position Spray technique 1 (LV) Spray technique 2 (HV) Average

underside top 1 a 25 b 13

centre 1 a 26 b 14

bottom 0 a 34 b 17

average 1 29 15

upper side top 63 d 54 cd 59

centre 58 c 78 e 68

bottom 51 c 95 f 73

average 58 76 67

average

29 52 41




Spray technique <.001 5

Leaf orientation <.001 5


Results of 23 September were similar to those of 25 August and 8 September (Table 3.6): A higher crop cover with HV, the upper side of the leaves showed a higher cover with fluorescence, and the top leaves showed higher crop cover than the bottom leaves. In cucumber, the crop cover ranged from 0 to 70% with LV and from 15 to 81% with HV.

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Table 3.6. Fluorescence on cucumber leaves on 23 September 2015 (percentage of leaf surface covered). LV = Low Volume, HV = High Volume.


underside top 5 ab 31 c 18

centre 1 a 15 b 8

down 0 a 15 b 7

average 2 20 11

upper side top 70 ef 61 e 66

centre 49 d 81 f 65

down 35 c 81 f 58

average 51 75 63

average

2 20 11


Spray technique * Leaf orientation * Plant position <0.001 11

Spray technique * Leaf orientation <0.001 6




Overall, spray technique 1 (LV) covered the underside of the leaves less at all three observation dates than spray technique 2 (HV) (Fig. 3.7). For the upper side of top leaves the coverage for both techniques is similar. At all other positions in the crop the coverage with spay technique 2 is higher. With LV spray, the top is relatively better covered than other crop parts. Over time, there is no clear decrease in coverage visible.

Figure 3.7. Fluorescence on cucumber leaves with the two spray techniques (Low volume = LV; High

volume = HV) (percentage of leaf surface covered).

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The second method was the use of water sensitive paper attached at different positions in the crop. The observation on 25 August showed that the percentage of surface covered with HV was higher than with LV (Table 3.7). In general, paper attached at the underside of leaves showed lower surface percentages than paper attached at the upper side. Table 3.7 Percentage surface covered of water sensitive paper attached to cucumber leaves on 25

August 2015 using snap card method. Low volume = LV; High volume = HV. Leaf orientation plant position Spray technique

1 (LV) Spray technique 2

(HV) Average

underside top 6 a 26 bc 16

centre 6 a 31 bcd 18

bottom 6 a 14 ab 10

average 6 24 15

upper side top 74 fg 47 de 60

centre 53 ef 73 fg 63

bottom 46 cde 81 g 63

average 58 67 62

average

32 45 39




Spray technique 0.003 8



On 8 September, the coverage of water sensitive papers attached facing down at the underside of the leaves showed no significant differences in coverage between the two spraying techniques (Table 3.8). Papers attached at the upper side of the leaves and facing upwards showed a slightly lower coverage with LV than with HV.

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Table 3.8. Percentage surface covered of water sensitive paper attached to cucumber leaves on 8 September 2015 using snap card method. Low volume = LV; High volume = HV.

Leaf orientation plant position Spray technique 1

(LV) Spray technique 2

(HV) Average

underside top 3 a 14 ab 8

centre 3 a 13 ab 8

down 3 a 11 ab 7

average underside

3 13 8

upper side top 69 f 41 cd 55

centre 47 de 52 ef 50

down 24 bc 47 de 35

average upper side

47 47 47

Average

25 30 27







On 21 September, water sensitive papers attached at the underside of leaves showed no differences in coverage between LV and HV (Table 3.9). Paper attached on the upper side showed some differences. For LV, the top leaves were better covered, but the lower bottom leaves were less covered as compared to HV.

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Table 3.9 Percent surface covered of water sensitive paper attached on cucumber leaves on 21 September 2015 using snap card method. Low volume = LV; High volume = HV.



(HV) Average

under side top 6 a 9 ab 7

centre 9 ab 6 a 8

down 3 a 3 a 3

average underside

6 6 6

upper side top 68 f 49 e 58

centre 38 de 32 cd 35

down 21 bc 42 de 31

average upper side

42 41 42

Average

24 23 24






Plant position <0.001 7

Differences between the spray techniques were very distinctive on 25 August. Especially on the upper side of the water sensitive paper at the bottom and upper side and underside at the centre of the plant coverage with HV was higher (Fig. 3.8). At these positions, a decrease in coverage over time was visible with HV.

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Figure 3.8. Percentage of surface covered of water sensitive paper attached on cucumber using snap

card method (Low volume = LV; High volume = HV).

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3.3.2 Potato

In potato, a higher percentage of fluorescence coverage was found at the upper side of leaves with HV (Table 3.10). Table 3.10 Fluorescence on potato leaves on 7 August 2015 (percentage of leaf surface covered). Low

volume = LV; High volume = HV. Leaf orientation Plant position Spray technique 1 (LV) Spray technique 2 (HV) Average

underside top 1 27 14

centre 2 17 9

bottom 0 14 7

average 1 a 19 b 10

upper side top 13 40 26

centre 14 49 32

down 16 58 37

average 14 b 49 c 32

average

8 34 21







On 16 August, water sensitive papers at the upper side of leaves showed higher coverage percentages than at the underside of leaves (Table 3.11). With HV, coverage was higher than with LV.

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Table 3.11 Fluorescence on potato leaves on 16 August 2015 (percentage of leaf surface covered). Low volume = LV; High volume = HV.



centre 1 13 7

down 1 17 9

average 2 a 18 b 10


centre 27 64 45

down 30 77 54

average 28 c 64 d 46

average

15 41 28







The observations on 3 September indicate that the coverage of the underside of the leaves with LV was significantly lower than with HV (Table 3.12). With HV, the upper side leaves were better covered, especially the leaves in the centre and bottom of the plant. Within both treatments, the top leaves were better covered with LV while the bottom leaves with HV were best covered. Average coverage of leaves observed on September 3 ranged between 4 and 47% for LV and 29 to 76% for HV.

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Table 3.12 Fluorescence on potato leaves on 3 September 2015 (percentage of leaf surface covered). Low volume = LV; High volume = HV.


underside top 10 a 38 cd 24

centre 6 a 30 bc 18

bottom 4 a 29 bc 16

average 7 32 19

upper side top 47 de 52 e 49

centre 37 bcd 76 f 56

bottom 24 b 75 f 49

average 36 68 52

average

21 50 36







In potato, HV showed a higher coverage of leaves then LV for all positions except for the upper side of the paper attached to the top of the plant (Fig. 3.9).

Figure 3.9. Fluorescence on potato leaves on 3 September 2015 with the two spraying techniques (Low

volume = LV; High volume = HV) (percentage of leaf surface covered). Observations on 7 August showed that HV resulted in a better coverage of water sensitive papers at the underside of the leaves positioned at the top of the plant and at the upper side of the paper in the

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bottom of the plant(Table 3.12). With LV, the upper side of the leaves at the top of the plant showed a significantly higher coverage than at the centre and at the bottom. The coverage at the bottom was significantly lower than the coverage of the centre leaves. With HV, no differences in coverage between positions were identified for the upper side. Overall, the coverage with HV was higher (48%) than with LV (34%). Table 3.12 Snapcard method observation of water sensitive paper attached on potato leaves on 7

August 2015 (percentage of surface covered). Low volume = LV; High volume = HV. Leaf orientation plant position Spray technique 1


(HV) Average

underside top 13 a 35 bc 24

centre 5 a 7 a 6

bottom 3 a 17 ab 10

average 7 20 13

upper side top 81 e 75 de 78

centre 62 d 77 de 70

bottom 39 c 73 de 56

average 61 75 68

average

34 48 41

p LSD ɑ=0.05





Plant position <0.001 9

On August 16, no differences between the treatments in coverage were observed at the underside of water sensitive papers (Table 3.13). Higher coverage with HV was observed at the upper side of the water sensitive paper. In general, water sensitive paper at the top of the plants showed higher coverage than those at the centre or bottom of the plants.

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Table 3.13 Snapcard method observation of water sensitive paper attached on potato leaves on 16 August 2015 (percentage of surface covered). Low volume = LV; High volume = HV.



(HV) Average


centre 4 7 6

bottom 4 3 3

average 4 a 10 a 7


centre 29 68 49

bottom 31 66 49

average 36 b 68 c 52

average

20 39 30







On September 3, the coverage of water sensitive papers ranged between 2 to 41% with LV and between 8 and 48% with HV. The average coverage of water sensitive papers attached at the underside of the leaves with LV was on average 3% (Table 3.14) and this was significantly lower than obtained with HV, especially at the top and centre leaves. With LV, the upper side of the water sensitive paper showed significant higher coverage than the underside of the leaves. With HV, the coverage of the upper side of the paper was on average higher than with LV for the centre and bottom positions. Contrary to LV, at the upper side, no significant differences in coverage of the upper side of the leave positions were observed with HV.

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Table 3.14 Snapcard method observation of water sensitive paper attached on potato leaves on 3 September 2015 (percentage of surface covered). Low volume = LV; High volume = HV.



(HV) Average

underside top 3 a 35 bcd 19

centre 4 a 19 abc 11

bottom 2 a 8 a 5

average 3 21 12

upper side top 41 cd 40 cd 40

centre 23 abc 48 d 36

bottom 16 ab 36 bcd 26

average 27 41 34

average

15 31 23







For the snap card method except for the upper side of water sensitive paper at the top, HV showed at all three observation dates a higher coverage than LV.

Figure 3.10. Snapcard method observation of water sensitive paper attached on potato leaves (Low

volume = LV; High volume = HV) (percentage of card surface covered). Low volume = LV; High volume = HV.

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3.3.3 Shallot

In shallot, coverage of leaves with fluorescence on 6 September showed no significant differences between spray techniques or between positions in the bed (Table 3.15). On average a coverage of about 40% was observed in both treatments On 20 September, the coverage of plants at the left side of the bed with HV showed a higher coverage than plants at the other positions or with LV (Table 3.15). On average, the coverage of plants was higher with HV, 69% versus 48% with LV. On 4 October, no significant differences in coverage were observed between both spray techniques (Table 3.15). Table 3.15 Fluorescence on shallot leaves (percentage of leaf surface covered) observed 4 and 20

September2015 and 4 October 2015. Low volume = LV; High volume = HV. Date Bed position Spray technique 1

(LV) Spray technique 2 (HV) Average

6-9-2015 left side 37 45 41

middle 49 40 45

right side 30 27 28

average (p=0.5)

40 37 38

20-9-2015 left side 43 a 82 b 62

(p=0.01) middle 46 a 53 a 50

right side 57 a 78 a 68

average (p=<0.001) 48 69 59

4-10-2015 left side 53 59 56

middle 54 54 54

right side 53 65 59

average (p=0.1)

54 59 56

Average

47 55 51

Coverage at the first observation was less than at the following dates (Fig. 3.11). Coverage for the two techniques were more or less the same. The leaves in the middle of a bed showed slightly less coverage than at the sides.

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Figure 3.11. Fluorescence on shallot leaves (Low volume = LV; High volume = HV) (percentage of leaf

surface covered). On September 6, the coverage of water sensitive papers at the middle of the bed with spray technique 1 was significantly higher than at the edges of the bed (Table 3.16). Compared to HV, coverage in the middle of the bed was better with LV, while coverage of leaves on the edges was the same using different spray techniques. Coverage was lower at the first observation date than at the two later observation dates. Overall, the crop coverage was the same between spray techniques. Table 3.16 Snapcard method observation of water sensitive paper attached on shallot leaves on 6

September 2015 (percentage of paper covered). Low volume = LV; High volume = HV. Bed position Spray technique 1


(HV) Average

left side 9 a 23 ab 16

middle 39 b 7 a 23

right side 14 a 17 a 16

average 21 16 18

Spray technique x Bed position: p = 0.007; LSD ɑ=0.05 = 21 Spray technique: p=0.4 On September 20, no differences between spray techniques were observed (Table 3.17). The coverage at the bed edges was higher than in the middle, but the differences were not significant.

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Table 3.17 Snapcard method observation of water sensitive paper attached on shallot leaves on 20 September 2015 (percentage of paper covered). Low volume = LV; High volume = HV.

Bed position Spray technique 1


(HV) Average

left side 38 41 39

middle 11 18 14

right side 27 37 32

average 25 32 28

Spray technique x Bed position: p = 0.9; LSD ɑ=0.05 = 22 Spray technique: p = 0.3 On October 4, no significant differences were observed in coverage between both spray techniques (Table 3.18). Table 3.18 Snapcard method observation of water sensitive paper attached on shallot leaves on 4

October 2015 (percentage of paper covered). Bed position Spray technique 1


(HV) Average

left side 39 33 36

middle 21 22 21

right side 25 38 31

average 28 31 30

Spray technique x Bed position: p = 0.2; LSD ɑ=0.05 = 15 Spray technique: p = 0.5 Except for LV on the first observation date, coverage of water sensitive paper attached on plants on the side of the bed was higher than the paper attached in the middle (Fig. 3.12). Coverage with HV did not differ much from LV at the other observation dates.

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Figure 3.12. Snapcard method observation of water sensitive paper attached on shallot leaves (Low

volume = LV; High volume = HV) (Percentage of card surface covered).

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3.4 Pest and disease observations

3.4.1 Cucumber

In cucumber, several pests and diseases were observed. The population of thrips for both spray techniques was quite similar (Fig. 3.13). The peak of thrips pressure was around 13 September.

Figure 3.13 Presence of thrips (# trips per leave) in cucumber during the growing season using two

spraying techniques, spray technique 1 = low volume, and spray technique 2 = high volume. Based on the observations for each pest and disease in cucumber, the AUDPC or AUPPC was calculated (Table 3.19). For all pests and diseases, no significant differences were identified between both spray techniques. Table 3.19 AUDPC or AUPPC per pest and disease in cucumber. Low volume = LV; High volume = HV. Pest or disease Spray

technique 1 (LV)

Spray technique 2

(HV)

Average p LSD

ɑ = 0.05

Thrips sp. (no./leaf) 35 30 32 0.1 9

Aphids sp. (no./leaf) 38 29 34 0.3 27

Spodoptera litura (no. / leaf) 3 3 3 0.9 6

Downy mildew (% plants) 42 11 26 0.2 64

Cercospora (% plants) 105 154 130 0.2 92

Alternaria (% plants) 175 152 164 0.2 49

3.4.2 Potato

Thrips in potato was observed in the period mid-August till mid-September (Fig. 3.14). Between spray techniques, no large differences in trips pressure were identified.

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Figure 3.14 Number of thrips per potato leaf during the growing season using two spraying techniques,

spray technique 1 = low volume, and spray technique 2 = high volume. A similar development of the thrips population was observed for the aphids, and also in the aphid population no differences were observed for both spray techniques (Fig. 3.15). Aphid population peaks were observed in early September and mid-September.

Figure 3.15 Number of aphids per potato leaf during the growing season using two spraying techniques,

spray technique 1 = low volume, and spray technique 2 = high volume. Potato tuber moth was observed in mid-August and early September (Fig. 3.16). Peaks in the tuber moth attack were identified at the same dates for both spray techniques. The percentages were also the same for both spray techniques.

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Figure 3.16 Percentage of potato plants with Phthorimaea opercullela (potato tuber moth) during the

growing season using two spraying techniques, spray technique 1 = low volume, and spray technique 2 = high volume.

White fly was present during the entire growing season of potato with three distinctive peaks at early August, early September and late September (Fig. 3.17). The development of the white fly population was not different among both spray techniques.

Figure 3.17 Percentage of potato plants with white fly during the growing season using two spraying

techniques, spray technique 1 = low volume, and spray technique 2 = high volume. Liriomyza was only found in the crop treated with spray technique 1 (LV). The percentage of plants with leaf miners peaked around August 4 and a showed smaller peak mid-September (Fig. 3.12).

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Figure 3.18 Percentage of potato plants of Liriomyza (leaf miner) in potato during the growing season

using two spraying techniques, spray technique 1 = low volume, and spray technique 2 = high volume.

Spodoptora litura showed a peak mid-August with LV and a peak early September for HV (Fig. 3.19). The percentage of plants with Spodoptora was largest with spray technique 1 (LV).

Figure 3.19 Percentage of potato plants with Spodoptora litura caterpillars during the growing season

using two spraying techniques, spray technique 1 = low volume, and spray technique 2 = high volume.

With both spray techniques, Epilachna sp. was observed in potato (Fig. 3.20). The first peak was in the third week of August and was similar for both spray techniques. The second peak was in the first week of September with a higher incidence of Epilachna with spray technique 2 (HV).

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Figure 3.20 Percentage of potato plants with of Epilachna sp. during the growing season using two

spraying techniques, spray technique 1 = low volume, and spray technique 2 = high volume. Alternaria was observed in the last week of September but its development did not show big differences between the spray techniques (Fig. 3.21).

Figure 3.21 Percentage of potato plants with Alternaria during the growing season using two spraying

techniques. Between spray techniques, no significant differences were identified in the calculation of AUDPCs or AUPPCs for each observed pest or disease (Table 3.20).

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Table 3.20 AUDPC or AUPPC per pest and disease in potato. Low volume = LV; High volume = HV. Pest or disease Spray

technique 1 (LV)

Spray technique 2

(HV)

Average p LSD

ɑ = 0.05

Thrips sp. (no./leaf) 105 92 98 0.5 53

Aphids sp. (no./leaf) 82 70 76 0.5 43

Phthorimaea operculella (no./plant) 24 22 23 0.5 10

P. operculella (% plants) 0 1 0 0.4 3

Bemisia tabaci (no./leaf) 118 112 115 0.6 31

Liriomyza sp. (% plants) 17 0 8 0.4 49

Epilachna sp. (% plants) 33 33 33 1 43

Spodoptera (% plants) 16 6 11 0.5 40

Phytophthora Infestans (% plants) 6 0 3 0.4 19

Alternaria (% plants) 589 477 532 0.5 480

Virus complex (% plants) 2 2 2 0.4 0.1

3.4.3 Shallot

In shallot, only Spodoptora exigua was present, and no other pests were observed. With both spray techniques, a peak in Spodoptera caterpillars was observed in the second week of September and after a decline, there was again steady increase in the number of caterpillars from the end of September (Fig. 3.22). Although there were some differences between both spray techniques the overall trend in Spodoptera pressure using both techniques was more or less the same.

Figure 3.22 Percentage of leaves with Spodoptera caterpillars in shallot. The calculation of AUPPCs for Spodoptera were done for different pest indicators of Spodoptera, i.e. the average number of egg packages per plot, average number of larva per plot, and damaged leaves (Table 3.21). No significant differences were observed between spray techniques except for the egg package AUPPC showing more egg packages with HV.

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Table 3.21 AUPPC of Spodopotera exigua observations in shallot. Low volume = LV; High volume = HV. pest indicator Spray

technique 1 (LV)

Spray technique 2

(HV)

Average p LSD

ɑ = 0.05

Spodoptera exigua egg package (no./plot)

4 7 6 0.02 2

Spodoptera exigua caterpillars (no./plot)

1 1 1 1 3

Spodoptera exigua affected leaves (%)

215 221 218 0.8 72

Leaves with Spodoptera exigua (% leaves)

496 486 491 0.9 187

3.5 Yields of cucumber, potato and shallot

On average, the marketable yield of cucumber was 2.4 t/ha higher with HV than with LV (Table 3.22). More fruits were attacked and damaged by fruit fly reducing the marketable yield with LV. However, the average cucumber weight was significantly higher using LV. Table 3.22 Yields and yield characteristics of cucumber using two pesticide-spraying techniques. Low

volume = LV; High volume = HV. parameter Spray

technique 1 (LV)

Spray technique 2 (HV)

Average p LSD

ɑ = 0.05

Marketable yield (t/ha) 18.3 20.7 19.5 0.01 1.3

Waste due to fruit fly damage (t/ha)

2.5 1.9 2.2 0.03 0.5

Marketable fruits (number) 183,667 209,833 196,750 0.008 13,316.7

Average fruit weight (g) 102.9 101.6 102.3 0.03 696.6

In potato, no significant differences in marketable yield or yield per class were observed (Table 3.23). Only the average tuber weights of Class A and Class B were significantly higher using HV.

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Table 3.23 Yields and yield characteristics of potato using two pesticide-spraying techniques. Low volume = LV; High volume = HV.

Spray

technique 1 (LV)

Spray technique 2

(HV)

Average p LSD

ɑ = 0.05

Marketable yield (t/ha 18.7 19.5 19.1 0.58 3.8

Yield Class A (t/ha) 4.8 4.9 4.9 0.93 2.5

Yield Class B (t/ha) 6.8 6.8 6.8 1.00 1.9

Yield Class C (t/ha) 7.1 7.7 7.4 0.44 2.3

Tubers with Rot % 0.6 0.0 0.3 0.10 0.8

Tubers with Insect damage (%) 4.8 4.0 4.4 0.50 3.3

Average tuber weight Class A (g) 136.3 167.6 152.0 0.01 19.4

Average tuber weight Class B (g) 30.0 85.6 57.8 0.03 43.2

Average tuber weight Class C (g) 32.0 31.6 31.8 0.89 9.1

The fresh yield of shallots was significantly higher with LV than with HV (Table 3.24). However, the yields of air-dried and cleaned shallots were not significantly different between the two spray techniques. Table 3.24 Yields of shallot using two pesticide-spraying techniques. Low volume = LV; High volume =

HV. Spray technique

1 (LV) Spray

technique 2 (HV)

Average p LSD

ɑ = 0.05

Yield (fresh) t/ha 34.3 31.9 33.1 0.054 2.4

Yield (air dried) t/ha 27.0 25.6 26.3 0.16 2.6

Yield (dried & cleaned) t/ha 23.9 23.1 23.5 0.18 1.4

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3.6 Relationship between crop coverage and yield

No clear relationship between crop coverage with pesticides and yield was observed (Fig. 3.23). The percentage of explained variance was low and in the case of fresh yield of shallot the relation between coverage and yield was even negative.

Figure 3.23 Relationship between average plant coverage with fluorescent during the growing season

and relative yield.

3.7 Economic analysis

Based on the yields and the costs for pesticides and labour for spraying a break-even price of the extra-generated yield for each spraying technique was calculated. Spray technique 1 (LV) differs from spray technique 2 (HV) because it applies less pesticides and needs less labour as the volume of spray solution is smaller. We used the yields as shown in Table 3.22-3.24 that showed that HV resulted in a significantly higher marketable cucumber yield, while LV resulted in a significantly higher fresh yield in shallot. No significant differences in potato yields were observed. For cucumber, pesticide costs were 4.8 million IDR per hectare with LV and 6.9 million IDR per hectare with HV (Table 3.24). The associated labour and pesticide costs for HV was 8.1 million IDR/ha, which was 2.4 million IDR/ha higher than LV. Considering a yield benefit of 2.3 ton/ha the break-even price for using HV is 1,015 IDR per kg cucumber. Hence, this is the minimum price for the extra yield that farmers require to cover the extra pesticide and labour costs. Any lower price makes LV from an economic perspective more attractive. The average market price of cucumber, which was about 4,400 IDR/kg, suggests that the HV treatment was interesting from an economic point of view. In potato, no significant difference in yield was present. Hence, the higher costs of HV are not covered by any yield increase making the LV option most interesting from an economic perspective. In shallot the yields obtained with HV were lower than with LV and thus any additional costs for pesticides and labour is not interesting from an economic perspective.

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Table 3.24 Yield, labour, cost and breakeven price of the two spray techniques used. Low volume = LV; High volume = HV.

calculation Cucumber Potato Shallot

Spray technique LV HV LV HV LV HV

(A) Marketable yield (t/ha) 18.3 20.7 18.7 19.5 34.3 31.9

(B) Pesticide costs (IDR x 1,000/ha) 4,848 6,893 5,310 6,780 2,099 2,555

(C) Total water volume applied during season (l/ha)

4,835 6,723 4,970 6,273 7,509 9,080

(D) Labour hours (hr/ha) C / 50 96.7 134.5 99.4 125.5 150.2 181.6

(E) Labour costs (IDR x 1,000/ha) D * 9000 870 1,210 895 1,129 1,352 1,634

(F) Total costs (IDR x 1,000/ha) B + E 5,718 8,103 6,205 7,910 3,451 4,190

(G) Cost price of spraying (IDR/kg) F/A 312 392 331 406 101 131

(H) Extra yield with HV (kg/ha) A2 - A1

2,349

- 2,339

(I) Extra costs with HV (IDR x 1,000/ha) F2 – F1

2,385

740

(J) Breakeven market price for additional yield (IDR/kg)

G / I

1,015

-

Producer price 4,424 2) 8,0001) 10,100 2)

Cucumber Potato Shallot

p LSDɑ = 0.05 p LSDɑ = 0.05 p LSDɑ = 0.05

Marketable yield (t/ha) 0.01 1.3 0.58 3.8 0.054 2.4

Pesticide costs (IDR x 1,000/ha) 0.002 615.6 0.030 1,204.0 n/a

water volume (l/ha) <0.001 403 0.027 1,028 n/a

Labour hours (hr/ha) <0.001 8.1 0.027 20.6 n/a

Labour costs (IDR x 1,000/ha) <0.001 72.5 0.027 185.1 n/a

Total costs (IDR x 1,000/ha) 0.002 686.8 0.030 1,388.8 n/a

n/a = not available 1) Average producer price in Central Java, 2014. Source: Statistik Harga Komoditas Pertanian Tahun 2015. Pusat

Data dan Sistem Informasi Pertanian Sekretariat Jenderal – KementerianPertanian 2) Average producer price in West Java, 2014. Source: Statistik Harga Komoditas Pertanian Tahun 2015. Pusat

Data dan Sistem Informasi Pertanian Sekretariat Jenderal – KementerianPertanian

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4. Discussion and conclusions

In this report the results are described of an experiment using three crops to assess the effect of two pesticide spraying techniques, i.e. a low spray volume (LV) and a high spray volume (HV), on crop coverage (with spray solution), occurrence of pest and diseases, and crop yield. Crop coverage was approximated using two methods after having sprayed the crop, i.e. the percentage cover of selected leaves from different locations in the crop and the percentage cover of water sensitive paper placed at different locations in the crop. Information from both methods provided insight in the lateral distribution of LV and HV spray treatments in the crop canopy and at the top and bottom of leaves. In general, for cucumber and potato, the crop coverage with LV was lower compared to HV. Lower crop coverage of LV as compared to HV was especially observed at the underside of the leaves and not so clear at the upper side where infection of most fungal diseases starts. In shallot differences between both spray techniques were small. No significant differences in pest and diseases were identified between LV and HV. Yield of cucumber was significantly higher with HV but it was also more costly because of higher inputs of pesticides and labour for spraying. Based on the calculated breakeven price of the yield benefit, a cucumber price of at least 1,013 IDR/ha would compensate for the higher costs of associated with HV. The average cucumber market price was around 4,400 IDR/kg in 2014 and therefore HV was in the experiment from an economic point of view an interesting option to be applied in cucumber. No significant differences in potato yield were observed between the two spray techniques. This means that the extra costs for higher spray volumes were not cost-effective. In shallot, HV also did not result in higher yield and only resulted in higher costs. Overall, there was no clear relationship between coverage and yield. Although a higher crop coverage was achieved in cucumber and potato with HV in all crops the pest and disease control was similar with both spray techniques. Yields of potato and shallot did not improve under HV. Only in cucumber, spraying with a higher water volume resulted in a higher yield. It is unclear what the mechanism is behind this yield increase as pest and disease pressure was hardly different between both spray techniques.

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5. References

De Putter, H., Gunadi, N., Uka, Wustman, R., Schepers, H., 2014. Economics and agronomics of Atlantic and Granola potato cultivation in the dry season of 2013 in West Java. vegIMPACT Internal report 10, Wageningen UR, The Netherlands.

Nansen, C., Ferguson, C., Moore, J., Groves, L., Emery, R., Garel, N., Hewitt, A., 2015. Optimizing pesticide spray coverage using a novel web and smartphone tool, SnapCard. Agronomy for Sustainable Development 35:1075–1085.

Pronk, A., Van den Brink, L., Gunadi, N., Komara, U., 2017. Economics and agronomics of Atlantic and Granola potato production in the dry season 2014 in West Java. vegIMPACT External Report 36. Wageningen UR, The Netherlands.

effect of pesticide spray techniques on foliage coverage ... · vegimpact report 43– effect of...

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