Biological control of powdery mildew in greenhouse produced cucumber
an evaluation of two microbiological control agents
Powdery mildewCucumberGolovinomyces cichoracearumPodosphaera xanthiiBiological controlAmpelomyces quisqualisPythium oligandrum
Powdery mildew is a serious problem in both field and greenhouse cucumber production and
can cause serious infection and radically reduced yields. Today, powdery mildew is the main
disease in greenhouse produced cucumber.
Disease control should preferably be both efficient and environmentally friendly, which is not
easy to achieve at all times. Alternatives to chemical control of powdery mildews are biological
control, physical control, non-fungicide control and cultivation of resistant or tolerant varieties.
Biological control can be described as the suppression of damaging activities inflicted
of a harmful organism by one or more other organisms, which are called antagonists or natural
enemies. In Sweden, there are currently no registered biological control products available
to control cucumber powdery mildew.
The aim of this study was to investigate the effect of two biological control products in order
to evaluate their ability to prevent or reduce powdery mildew infection to an acceptable level
in greenhouse produced cucumber. In the experiments, different application regimes were also
studied. The active organisms in both tested products are fungi. In one of the products the
active organism was Ampelomyces quisqualis and in the other Pythium oligandrum. The fungal
species causing the powdery mildew in the experiments was characterized.
The present report consists of a literature study, an experimental part and a microscope study.
Trials were performed in a greenhouse at a conventional cucumber grower?s site at
Sånnagården, Kvidinge, and in a chamber in one of the greenhouses at the Swedish University
of Agricultural Sciences, Alnarp.
In this study, some of the biocontrol treatments could prevent and reduce powdery mildew
attacks to an acceptable level in greenhouse produced cucumber. The effect of using the
biocontrol agents prophylactically was significantly better with P. oligandrum compared to
the untreated control but not with A. quisqualis. The effect of using A. quisqualis with an application
interval of fourteen days was significantly better compared to a seven days application
interval. For P. oligandrum, there was no difference between the two application intervals.
The fungus causing the powdery mildew symptoms in this experimental study was most
probably Golovinomyces cichoracearum.