Charles Merfield
Head of the Future Farming Centre of the Biological Husbandry Unit (BHU)
Permanent Agriculture and Horticulture Science and Extension
Lincoln University
PO Box 113
Lincoln 7646
New Zealand

Mesh crop covers: effect on reducing foliar blight on potatoes ?

Researchers from the Biological Husbandry Unit of Lincoln University in New Zealand - a member of TIPI* - are keen to find overseas collaborators interested in studying the blight effect of mesh crop covers.

Foliage covered abd uncovered

Green foliage on left was covered with mesh, while blackened foliage on right was uncovered. Photo: Charles Merfield, BHU


Research in New Zealand over the last two years has unexpectedly found that mesh crop covers for pest control, have the additional effect of reducing foliar blight on potatoes (potentially both Alternaria and Phytophthora).

The research originally focused on using crop covers to control the introduced psyllid Bactericera cockerelli, (called the Tomato Potato Psyllid (TPP) in New Zealand).  However, the first seasons ‘exploratory’ trial found that the mesh (a glasshouse quarantine) dramatically reduced blight levels - see photo.

A second years trial, using both the glasshouse quarantine mesh and a much lighter weight ‘purpose designed’ field mesh had consistent results, though there were more blight lesions under the field mesh.  A small amount of black-coloured mesh anecdotally trialled in the first year also had very good blight suppression.  Temperature and humidity measurements during the second years trial, indicate that climate is not the driver of the differences, and that other factors, potentially a physical aspect of the mesh are hypothesised as being the main cause.

As far as the researchers are aware, no one has researched mesh crop covers on potatoes before, and the effect of the mesh on blight is entirely novel.  If this is a real and consistent effect, especially if it can be improved by manipulating the physical characteristics of the mesh, it could possibly lead to a physical control for potato blight.  Considering the ongoing concerns about blight developing increased resistance to agrichemicals, and the desire to phase out copper based fungicides in organics, the ability to physically, rather than chemically (or biologically) control blight could be a significant boon for organic and conventional farmers and growers. 

The researchers from New Zealand are therefore keen to find overseas collaborators interested in studying the blight effect.

* TIPI is the Technology Innovation Platform of the International Federation of Organic Agriculture Movements

Text: Charles Merfield, Biological Husbandry Unit, Lincoln University, New Zealand

More information


Charles Merfield, Biological Husbandry Unit, Lincoln University, New Zealand, e-mail charles.merfield(at)

Research info

For full information on the research please visit 

Facebook Discuss the effects of mesh crop covers on the TIPI Facebook page