Cucumber powdery mildew

Last changed: 06 December 2023

Development of non-chemical greenhouse control methods in collaboration with growers

Project responsible: Erland Liljeroth, the Department of Plant Protection Biology, SLU Alnarp.  

Project members: Laura Grenville-Briggs and Mira Rur, both at the Department of Plant Protection Biology, SLU Alnarp, and Margareta Hökeberg, Centre for Biological Control (CBC), SLU Uppsala.

We have during recent years investigated the effect of a number of biocontrol agents, and biopesticides based on plant extracts or inorganic compounds. These alternative products were screened in medium-scale greenhouse experiments and their effect was compared with the fungicide regime. We found that ’Sakalia’ (based on extract of Reynoutria sachaliensis) combined with a wetting agent based on Yuccah schidigera provided efficient control of CPM. Some of the other products, e.g. silicon also had a significant effect.

The aim of this project is to develop efficient integrated plant protection strategies against CPM for Swedish greenhouse cucumber production in collaboration with growers.

Since the plant extract based product was very effective against CPM in research greenhouse trials our hypothesis is that it will give significant protection also in full-scale commercial greenhouses. We also hypothize that integrated use of biopesticides against CPM can make organic production of cucumber economically sustainable.


The most widely grown greenhouse crop in Sweden is cucumber. However, the organic production of cucumber is limited, mainly due to cucurbit powdery mildew disease (CPM), which causes severe yield losses. It is very difficult to control CPM without fungicides and control has been increasingly more difficult also in conventional cultivation due to development of fungicide resistance.

There are no biopesticides or biological control agents available in Sweden against CPM. Only two fungicides are currently registered for use against CPM in conventional production in Sweden. However, fungicide resistance has been reported in CPM populations and conventional growers are currently left to depend on only one fungicide and cultural practices as control measures against CPM. Organic growers rely on climate control, partially resistant cultivars, proper hygiene and sanitation measures only. Therefore, there is a great need for the development of alternative methods for the control of CPM both for organic and conventional cucumber production.


Erland Liljeroth, Professor and External Collaboration Specialist
Department of Plant Protection Biology, SLU, +46 40 41 55 67