Information – Crop Management – Production
Mesh crop covers for potato blight and pest control
The BHU is selling 3.7 meter wide, 0.6 mm hole mesh as a service for home gardeners, lifestyle blockers and market gardeners. Larger widths (up to 13 m) and lengths (200 m) and smaller hole sizes (0.3 mm) for commercial producers are available from www.seedandfield.co.nz .
Commercial growers / farmers – if your considering trialling mesh please contact me [email protected] 021 0231 8901 as I can probably save you a lot of time and money and happy to have a short chat at no charge.
The Future Farming Center has now been researching the use of mesh on potatoes for tomato potato psyllid (TPP) and blight control since 2011. Below are a number of reports on individual experiments, and, an overview of the commercial use of mesh, which is also informative for home gardeners, plus a large amount of media coverage, including on tomatoes and other crops.
The overall conclusions so far are:
- Mesh gives as close to 100% control of TPP as it is possible to get – much better control than insecticides / agri-chemicals (see 2016-17 trial). This means mesh also effectively achieves 100% control of Candidatus Liberibacter solanacearum (CLso). It also controls nearly every other potato pest, both insects and vertebrates.
- Mesh has often achieved a considerable reduction in potato blight, BUT, it is unknown if it is early (Alternaria solani) and/or main / late blight (Phytophthora infestans) and in either case the cause is unproven.
- Experiments modifying the light spectrum (see 2015-16 trial) , particularly UV light (both a and b bands) indicate that UV light may have a role in both blight reduction and also indicate why when TPP get under the mesh, they don’t thrive. But, the case is NOT proven, yet. If funding can be found, this is the priority for future research. Please contact me at [email protected] if you can help with funding.
- Mesh is a form of protected cropping – the ‘lowest’ form, shared with frost cloths, then the next step up is cloches, then polytunnels and the pinnacle of protected cropping – glasshouses. Like other forms of protected cropping mesh improves the crop’s microclimate, including slight increase in temperature, which adds up to a considerable increase in growing degree days, reduced relative humidity at higher temperatures (above 15°C, see the 2016-17 trial, for details) and reduced wind damage. Based on the 2016-17 trial, where mesh outperformed agrichemicals, and out-yielded the theoretical maximum yield for Canterbury, shows that mesh is directly increasing yield due to the protected cropping effect, excluding any gains from pest & disease reduction.
- For commercial potato producers, mesh costs considerably less than agrichemicals, and with higher yields, the increase in profit can be massive – see the 2016-17 trial for details.
- The ‘fly in the ointment’ at present is that aphids, particularly the green peach aphid, (Myzus persicae) is penetrating the mesh as newly born nymphs, which, can result in aphid outbreaks under the mesh, particularly when it is dug in which prevents the aphid’s natural enemies getting under the mesh to control the aphids. Therefore, mesh should not be completely dug in, rather, the ends should be left open, even with a bit of potato haulm poking out, to allow the beneficial insect to get in and control the aphids. As per the 2015-16 trial, mesh has a considerable inhibiting effect on TPP so any that do get underneath do not prosper. The best long-term option for aphid control in commercial potato production is to adapt aphid biocontrol techniques and agents from the glasshouse sector. This however, is a substantial piece of research and requires significant, multi-year funding. Again, please contact me at [email protected] if you can help with funding for the aphid or any other research.
- TPP are also highly attracted to UV-A light.
2011-12 First year laboratory and field trials – extension publication and journal publication. Includes the first result of mesh reducing potato blight and TPP and general information about mesh and how to make the metal anchor stakes.
2012-13 Second year field trial – extension publication and journal publication. The second years trials compared two mesh types with a null control and demonstrated significant increase in yields and dramatic reduction in TPP populations.
2015-16 Third year of trials – Effect of UV light on foliar potato blight and psyllid yellows. The third year of trials compared six different covers, both mesh and polythene with different UV spectral properties and found a large and significant impact on potato blight and psyllid yellows.
2016-17 Fourth year of trials – Final results from the 2016-17 Field Trial of Mesh vs. Agrichemicals. This is the first time that mesh has directly been compared against the best agrichemical regime under full commercial production conditions and has unambiguously show that mesh generates higher yields and dramatically increased profit, compared with chemicals.
2017 Mesh crop covers for pest control in commercial crop production. A short report that explains the history of mesh crop covers, their benefits and their current use in commercial production.
2017-18 The use of UV-A light insect traps for TPP control and monitoring in glasshouses. While not on potatoes, it is on TPP, which was the original impetus for the mesh research, and it has relevance to the UV-potato research.
2018-06 Testing the compatibility of mesh crop covers with desiccant sprays in seed potato production (PDF file) Report on the experiments conducted with the Foundation for Arable Research (FAR) and Potatoes NZ on the use of mesh on seed potato crops and if desiccants can be successfully sprayed through mesh.