Studies on biological control of powdery mildew in cucumber (Sphaerotheca fuliginea) and rose (S. pannosa) by means of mycoparasites

M.A. Verhaar

Research output: Thesisinternal PhD, WU


<p>Powdery mildew on rose ( <em>Sphaerotheca pannosa</em> ) and cucumber ( <em>Sphaerotheca fuliginea</em> ) are two serious diseases in glasshouses. Intensive control by fungicides is needed. The research presented here deals with biocontrol of powdery mildew on cucumber and rose by means of mycoparasites.</p><p>The mycoparasites <em>Ampelomyces quisqualis</em> , <em>Sporothrix rugulosa</em> and <em>Tilletiopsis minor</em> and <em>Verticillium lecanii</em> were tested on rose powdery mildew. <em>V. lecanii</em> produced the best results. For biocontrol at glasshouse scale an efficient production method of phialoconidia of <em>V. lecanii</em> was developed. In exploratory glasshouse experiments <em>V. lecanii</em> was superior to <em>S. rugulosa</em> in controlling cucumber mildew. Especially on a partially resistant cucumber cultivar biocontrol by <em>V. lecanii</em> showed prospect.</p><p>To identify characteristics for the selection of <em>V. lecanii</em> isolates with high potential for biocontrol under glasshouse conditions, effect of water limitation on 14 isolates was explored. Conidial germination, growth and sporulation were all clearly affected by humidity, but showed no correlation with mycoparasitic potential. The effect of timing the biocontrol treatment by <em>V. lecanii</em> was studied on rooted mildewed cucumber leaves. At high humidity early preventative and early curative treatments gave considerable reduction in mildewed leaf area. In semi-commercial glasshouse experiments our <em>V. lecanii</em> isolate, <em>A. quisqualis and Sporothrix flocculosa</em> were tested against cucumber powdery mildew.</p><em><p>A. quisqualis</em> did not control the disease. <em>V. lecanii</em> had only minor effects. <em>S. flocculosa</em> gave the best control. The failure of biocontrol by <em>V. lecanii</em> was attributed to low humidity in the glasshouse. Formulation of <em>V. lecanii</em> with arachid oil significantly reduced its humidity dependence. Possibilities for integrated control are combinations of partially resistant cultivars, formulation of <em>V. lecanii</em> and combination of <em>V. lecanii</em> with fungicides.</p>
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Zadoks, J.C., Promotor
  • Frinking, H.D., Promotor, External person
Award date23 Nov 1998
Place of PublicationS.l.
Print ISBNs9789054859321
Publication statusPublished - 1998


  • podosphaera fuliginea
  • podosphaera pannosa
  • plant pathogenic fungi
  • plant pathogens
  • plant diseases
  • cucumbers
  • roses
  • cucurbit vegetables
  • rosa
  • biological control agents
  • biological control
  • fungal antagonists
  • hyperparasitism


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