Journal of Plant Diseases and Protection

, Volume 126, Issue 5, pp 429–436 | Cite as

Comparison of wetness sensors and the development of a new sensor for apple scab prognosis

  • Katja EhlertEmail author
  • Lin Himmelmann
  • Joachim Beinhorn
  • Andreas Kollar
Original Article


Apple scab prediction is based on the model of Mills which describes the risk of Venturia inaequalis infection using leaf wetness duration and air temperature data. The quality of prognosis relies on sensor quality. Six brands of commercially available leaf wetness sensors were compared at the Julius Kuehn-Institute (Germany) apple orchard from 2011 to 2013. Also a new wetness sensor was developed and optimized from 2009 to 2015 in cooperation with Thies Clima company. The Thies-wetness sensor was equipped with a glass–ceramic surface, an adjustable heating system to avoid dew and an adjustable cooling system to prolong wetness duration of sensor surface. Prototypes were tested in climate chamber before exposition in the orchard to achieve sensor settings with drying properties broadly similar to apple leaves. The market-ready prototype showed suitability for prognosis in field assays in primary seasons of 2015–2017 and maybe integrated into prognosis of apple scab without further modeling. The Thies-sensor was shown to be more reliable, uniform, sensitive and more suitable for forecasting than the purchased models.


Apple scab Wetness sensor Spore dissemination Prognosis 



We thank K. Piwowarczyk for technical assistance, F. M. Porsche for comments, A. Engelhardt for collection of leaves, and M. Ehlert and T. Ehlert for proof reading.


The project was supported by funds of the German Government’s Special Purpose Fund held at the Landwirtschaftliche Rentenbank.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflicts of interest.

Human and animal rights

This article does not contain any studies involving animals or human participants performed by any of the authors.

Declaration of authorship

All authors agree with this publication.


  1. Alt S, Kollar A (2010) Hydrodynamics of raindrop impact stimulate ascospore discharge of Venturia inaequalis. Fungal Biol 114:320–324. CrossRefPubMedGoogle Scholar
  2. Batzer JC, Gleason ML, Taylor SE, Koehler KJ, Monteiro JEBA (2008) Spatial heterogeneity of leaf wetness duration in apple trees and its influence on performance of a warning system for sooty blotch and flyspeck. Plant Dis 92:164–170. CrossRefPubMedGoogle Scholar
  3. Brook P (1966) The ascospore production season of Venturia inaequalis (Cke.) Wint., the apple black spot fungus. N Z J Agric Res 9:1064–1069CrossRefGoogle Scholar
  4. Brook P (1969a) Effects of light, temperature, and moisture on release of ascospores by Venturia inaequalis (Cke.) Wint. N Z J Agric Res 12:214–227. CrossRefGoogle Scholar
  5. Brook PJ (1969b) Stimulation of ascospore release in Venturia inaequalis by far red light. Nature 222:390–392CrossRefGoogle Scholar
  6. DeBary HA (1853) Untersuchungen über die Brandpilze und die durch sie verursachten Krankheiten der Pflanzen mit Rücksicht auf das Getreide und andere Nutzpflanzen. HabilitationGoogle Scholar
  7. Frey C, Keitt G (1925) Studies of spore dissemination of Venturia inaequalis (Cke.) Wint. in relation to seasonal development of apple scab. J Agric Res 30:529–540Google Scholar
  8. Gadoury DM, Seem RC, Stensvand A (1994) Ascospore discharge in Venturia inaequalis. Nor J Agric Sci Suppl 17:205–219Google Scholar
  9. Getz R (1992) Report on the measurement of leaf wetness, vol 38. World Meteorological Organisation, Agricultural Meteorology, GenfGoogle Scholar
  10. Hirst JM, Stedman OJ (1962) The epidemiology of apple scab (Venturia inaequalis (Cke.) Wint.). Ann Appl Biol 50:525–550. CrossRefGoogle Scholar
  11. Huber L, Gillespie TJ (1992) Modeling leaf wetness in relation to plant disease epidemiology. Annu Rev Phytopathol 30:553–577. CrossRefGoogle Scholar
  12. Jones AL (1986) Role of wet periods in predicting foliar diseases. In: Leonard KJ, Fry WE (eds) Plant disease epidemiology. MacMillan Publishing Company, New York, pp 87–100Google Scholar
  13. Keitt GW, Jones LK (1926) Studies of the epidemiology and control of apple scab. Wis Agric Exp Stn Res Bull 73:1–104Google Scholar
  14. Kohl R (1993) Untersuchungen zur Epidemiologie des Apfelschorfs (Venturia inaequalis (Cke.) Wint.)Google Scholar
  15. Kollar A (1997) Present research on the most important pathogen on apple, the apple scab fungus Venturia inaequalis. Plant Res Dev 46:88–96Google Scholar
  16. Kollar A (1998) A simple method to forecast the ascospore discharge of Venturia inaequalis. Z Pflanzenk Pflanzen 105:489–495Google Scholar
  17. MacHardy WE (1996) Apple scab. Biology, epidemiology and management. The American Phytopathological Society, St. PaulGoogle Scholar
  18. MacHardy WE, Gadoury DM (1986) Patterns of ascospore discharge by Venturia Inaequalis. Phytopathology 76:985–990CrossRefGoogle Scholar
  19. MacHardy WE, Gadoury DM (1989) A revision of Mills’ s criteria for predicting apple scab infection periods. Phytopathology 79:304–310CrossRefGoogle Scholar
  20. Madeira AC, Kim KS, Taylor SE, Gleason ML (2002) A simple cloud-based energy balance model to estimate dew. Agric For Meteorol 111:55–63. CrossRefGoogle Scholar
  21. Magarey RD, Seem RC, Weiss A, Gillespie TJ (2005) Estimating surface wetness on plants. In: Hatfield JL, Baker JM (eds) Micrometeorology in Agricultural Systems. American Society of Agronomy, MadisonGoogle Scholar
  22. Miller P, Waggoner P (1958) Dissemination of Venturia inaequalis ascospores. Phytopathology 48:416–419Google Scholar
  23. Mills WD (1944) Efficient use of sulfur dusts and sprays during rain to control apple scab Cornell Ext. Bulletin 630:2–4Google Scholar
  24. Moore M (1958) The release of ascospores of apple scab by dew. Plant Pathol 7:4–5CrossRefGoogle Scholar
  25. Roßberg D (2008) Neptun 2007—Obstbau Berichte aus dem Julius Kuehn-Archiv 147Google Scholar
  26. Roßberg D, Harzer U (2015) Erhebungen zur Anwendung von Pflanzenschutzmitteln im Apfelanbau. Journal für Kulturpflanzen 67:85–91Google Scholar
  27. Rossi V, Ponti I, Marinelli M, Giosue S, Bugiani R (2001) Environmental factors influencing the dispersal of Venturia inaequalis ascospores in the orchard air. J Phytopathol 149:11–19CrossRefGoogle Scholar
  28. Rowlandson T, Gleason M, Sentelhas P, Gillespie T, Thomas C, Hornbuckle B (2015) Reconsidering leaf wetness duration determination for plant disease management. Plant Dis 99:310–319. CrossRefPubMedGoogle Scholar
  29. Sentelhas PC, Gillespie TJ, Gleason ML, Monteiro JE, Helland ST (2004) Operational exposure of leaf wetness sensors. Agric For Meteorol 126:59–72CrossRefGoogle Scholar
  30. Sutton TB, Aldwinckle HS, Agnello AM, Walgenbach JF (2014) PART I: infectious diseases. In: Sutton TB, Aldwinckle HS, Agnello AM, Walgenbach JF (eds) Compendium of apple and pear diseases and pests, Second edn. Diseases and pests compendium series. The American Phytopathological Society, St. Paul, pp 8–116. CrossRefGoogle Scholar

Copyright information

© Deutsche Phytomedizinische Gesellschaft 2019

Authors and Affiliations

  1. 1.Federal Research Centre for Cultivated Plants, Institute for Plant Protection in Fruit Crops and ViticultureJulius Kuehn Institute (JKI)DossenheimGermany
  2. 2.University of Applied Sciences RapperswilRapperswilSwitzerland
  3. 3.Adolf Thies GmbH & Co. KGGoettingenGermany

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