The BHU Future Farming Centre

Information - The FFC Bulletin - 2018 V1 January

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2015-16 Third year of trials - Effect of UV light on foliar potato blight and psyllid yellows.

The third year of mesh crop cover trials for potato blight and tomato potato psyllid (TPP) control from the Future Farming Centre (published out of order, after the 4th year's trial!).  This research provides a key piece of information regarding the ‘spectral filter’ effect of mesh crop covers and the impact of reduced UV light levels on potato blight and also psyllid yellows.  Lower levels of UV strongly correlated with reduced foliar blight symptoms, and as a surprise bonus, the same was found for psyllid yellows  more... 

Crop Rotations - A Planning Manual from SARE

SARE (Sustainable Agriculture Research & Education) in the USA have published a crop rotations planning manual.  While ostensibly for organic farms, it is just as applicable to any production system organic, conventional, sustainable, biological, etc.  And coming from SARE it is a classic example of great extension literature, with both the underpinning theory, and a big focus on practical examples including real-world farmers.  So do look beyond the word ‘organic’ in the title and don't look beyond the ‘free’ attribute, at least for the PDF. Go to the SARE download and info page...

The BHU Future Farming Centre

Information - Crop Management - Production

Mesh crop covers for potato blight and pest control - 2015-16 Third year of mesh trials - Effect of UV light on foliar potato blight and psyllid yellows

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Effect of UV light on foliar potato blight and psyllid yellows. January 2018. Report number 01-2018. Download the full report.


Previous FFC field trials have found that mesh crop covers can significantly reduce the amount of main and/or early potato blight (Phytophthora infestans and Alternaria solani) but that under-mesh microclimate, both temperature and relative humidity (RH) did not appear to be the cause.

It was hypothesised that the cause of the blight reduction could be a spectral filter effect, where the mesh is changing the light spectrum reaching the crop, particularly reducing ultraviolet (UV) light levels, which is inhibiting blight.

A field trial was conducted in the 2015-2016 season to compare six different crop coverings with different spectral and UV transmission properties for their effect on blight. This included two meshes that had been used in previous years field trails, two meshes from Israel designed for use in protected cropping with contrasting UV transmission levels, and two polythene polytunnel sheets with high and near zero UV transmission but nearly identical visible light transmission, plus a null control.

Due to the likelihood of polythene sheets killing the potato plants due to overheating if laid directly on the crop, as is done with mesh crop covers, large cloches were used and the sheets were laid onto the cloche hoops.

The control plots had the lowest minimum, average and maximum temperatures and highest maximum RH, with minimum and average RH not being statistically significant. The temperatures of mesh treatments were higher than the control and lower than the polythene treatments, the latter also had the lowest maximum RH.

Foliar blight was assessed using a visual key. There was a strong correlation (R2 = 0.72) between the amount of UV light under the treatments and the amount of blight, with lower UV levels corresponding to lower blight.

Due differences in foliar tomato potato psyllid (TPP) symptoms (psyllid yellows) appearing among the treatments as the trial progressed, psyllid yellows were also measured and a similarly strong correlation (R2 = 0.68) was found between reduced UV levels and psyllid yellows.

There appears to be a clear link between the amount of UV light and foliar symptoms of both blight and TPP. However, correlation is not causation, and the number of causal mechanisms for both are numerous, so, more controlled forms of research to demonstrate causality, especially for both blight species is essential.

The relationship between yield and UV levels was unclear. There were still large and statistically significant increases in yield over the control from two best mesh treatments of 135% and 149%, which is consistent with previous and subsequent field trials and indicates the clear benefits of mesh crop covers for potato production.

The polythene sheets, did not perform as well as mesh, and it is speculated that aspects of the microclimate under the cloches, beyond the temperature and humidity measured in this trial, may have had an effect.

However, there was a clear relationship between UV light levels and tuber sizes with higher UV treatments having higher numbers of small tubers and lower UV treatments having a larger proportion of large tubers, which is consistent with previous and subsequent field trials.

In conclusion, the original aim of finding a relationship between UV light levels and potato blight has been successful, with the added bonus of finding a relationship between UV light and psyllid yellows. However, the linkage between UV light levels and yield is unclear, and may be influenced by other factors such as cloche microclimate.

Considering the importance of potatoes as a food crop, not only in the developed world, but particularly the developing world, this and other FFC research, shows the unparalleled potential of mesh crop covers to revolutionise potato production both for pest and disease control while achieving a large reduction in the use of, and reliance on, agrichemicals pest control.

The BHU Future Farming Centre

Information - Weed Management

Electrothermal weeding in the 1980s

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The follow photos show some of the electrothermal weeding equipment from the 1980s  All photos copyright Dr Mike Diprose.




The BHU Future Farming Centre

Information - Weed Management

Electrothermal Weeding Demonstration Project

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The BHU Future Farming Centre is running a project to develop an electrothermal demonstration weeder for pasture and cropping weeds. 

March 2018 update

Enough farmers and growers have committed to the project, that an application to AGMARDT is being written with the deadline for Monday 5 March. 

Feb 2018 project update

As of 13 Feb, I have emailed all the people who have expressed an interest in the project to date.  I am gathering information on those that want to join and contribute, particularly, those interested in having a demonstration in their geographical area, e.g., possible locations include Southland, Canterbury plains,  Marlborough, South Wairarapa, Hawkes Bay, Waikato and Northland. 

The aim will be to have a field day at each location to demonstrate the machine.  This will include detailed use and safety training for those farmers/growers wishing to test the machine themselves.  Then the aim is to leave the machine for one to two weeks with the trained farmers to test it on a wider range of weeds and farms than is be possible at a fielday.  They can then briefly write up their findings, along with before and after photos, that will be collected into a case study report.  


Electrothermal weeders are a ‘back to the future’ technology that has been widely researched in the past, especially in the 1980s, but failed to gain traction due to the dominance of herbicides.  Electrothermal is now back, with one of the key researchers from the 1980s, Dr Mike Diprose, coming out of retirement to bring it back to the market, though the start-up company Ubiqutek ( The resurgence of electrothermal is hugely important because electrothermal is the only non-chemical weed control technology that has a systemic weed kill effect, i.e., its as close to a non-chemical glyphosate (Roundup) as is ever likely to exist.  With glyphosate resistance growing exponentially, along with other herbicides, and a growing demand for non-chemical weed control technologies, that electrothermal is back is big news.  For more information on electrothermal please see the FFC Bulletin article

While Ubiqutek are putting electrothermal weeders back on the market the first machines are ‘only’ hand held weeders aimed at the urban weed control market, e.g., councils, and their contractors.  With their current limited personnel and financial resources it will be some years before machines aimed at agriculture and horticulture are produced.  The FFC project therefore aims to accelerate the design and demonstration of electrothermal machines for commercial producers.  This webpage aims to explain what the project is about and garner support.  

In any normal situation, Ubiqutek and their NZ distributor Hotgrass ( as the owners / suppliers of the weeders would be developing field weeders themselves, however, not only are both very small business start-ups with limited resources, they also lack expertise in what is required of farmers and growers from field machines especially for the different sectors, e.g., pasture, cropping, viticulture and other permanant crops, and therefore how to design them.  The aim of the project is therefore to not only accelerate the development of a field weeder but also ensure that NZ farmers & growers can get weeders designed to meet their needs.  

Clearly Ubiqutek and Hotgrass also stand to benefit from this project, and, they have therefore agreed to contribute to it as well.  Ubiqutek have agreed to contribute:

  • Design and specification of 50Hz transformer with variable voltages
  • UK build of transformer and shipping to New Zealand
  • Build costs for 50Hz transformer
  • Remote support during integration of 50Hz transformer with mechanical platform
  • Supply of samples of next generation modules
  • Redesign of next generation modules for higher voltages (if required)
  • Remote support during integration of next generation modules with mechanical platforms

Hotgrass will contribute

  • Construction of electrical components in NZ
  • Contribution financially of up to $20,000 towards the project
  • Development and delivery of a training package for operators
  • Eventual manufacturing of field machines (via third party)
  • Sales and marketing of the product

The project timeline and outline is:  

(1) To get a list of producers interested in the project together by the middle of February. 

(2) Once the level of interest has been determined, then, a project plan with costings will be drawn up, and, the amount of funding required from farmers & growers will be determined.  I’m hoping that this will be around $500 to $1,000 depending on how many people are interested.  Only then will producers be asked to commit to the project.  Two amounts will be proposed, one, based on securing AGMARDT funding (see below) and the higher one other should funding not be secured.  

(3) A funding application will be made to AGMARDT (deadline 6 March) to leverage the cash contributions from producers.  The current AGMARDT board are really keen on cutting edge / slightly risky projects, and this project should be right in the sweet spot.  The Future Farming Centre has also had two other projects recently funded by AGMARDT, including soil thermal weeding, so, it has a good track record.  

(4) The demo machine will be built over winter, ready for demonstrations during the following spring and summer.  Demonstrations will be held around the country so that all the producers who have contributed to the project can see the machine in action and what it can do.  

(5) After the machine has been demonstrated and designs finalised, Ubiqutek and Hotgrass will then be in a position to manufacture and supply machines.  

The reason the weeder is called a demonstrator, is because there was a very substantial amount of research done and commercial machines built and used in the 1980s.  This included in field crops, and even a machine that killed 20 foot high scrub - see for photos.  Electrothermal has therefore already been shown to achieve a systemic weed kill on a wide range of plants and production scenarios, so, no actual research is required.  The project is therefore focused on designing the application machinery for the different sectors, and then demonstrating that farmers and growers like yourself, on real weeds on real farms, to give you confidence that electrothermal will work for your farming system and what its value could be. 

So, please let me know if you are interested in continuing to be involved with the project - no financial commitment is required at this time.  If so please email me at This email address is being protected from spambots. You need JavaScript enabled to view it. and I’ll put you on the email list.  

And, I need help to spread the word about this project, so please let anyone else you think would be interested know about the project - e.g., send them a link to this page. 

And finally, Hotgrass, is doing a series of demonstrations around the country which you may be interested in attending - see this webpage for dates, locations etc., and while the demos will be of the handheld machine, they can still clearly demonstrate the potential of electrothermal.  

Many thanks

Charles ‘Merf’ Merfield

Head of the BHU Future Farming Centre

The BHU Future Farming Centre

Information - Crop Management - Production

Mesh crop covers for potato blight and pest control - 2016-17 Fourth year of trials - Field Trial of Mesh vs. Agrichemicals

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Handout from the field day on the 14 March 2017

Final results from the 2016-17 Field Trial of Mesh vs. Agrichemicals. August 2017. Report number 8-2017. Download the full report

(The interim report has been withdrawn as the final report contains a range of new and updated information as well as being reordered to make it more user-friendly.  If, however, you need a copy of the interim report please contact Merf at This email address is being protected from spambots. You need JavaScript enabled to view it. with the reason you need a copy.)


A large-scale field trial, under commercial conditions, was conducted to compare three meshes with different hole sizes (0.3, 0.4 & 0.7 mm) with a ‘full monty’ fungicide & insecticide regime and a null control, on their effects on tomato potato psyllid (TPP, Bactericera cockerelli) aphids, and potato blight (Phytophthora infestans and Alternaria solani). 

Mesh practically eliminated TPP (total of 12 individuals across all three mesh treatments) compared with chemicals (total of 1,614) and the control (total of 1,250).  From this result, added to previous years results, it is concluded that mesh is effectively a 100% means of controlling TPP on potatoes. There is also a very low chance of TPP developing ‘resistance’ to mesh, and so it can be considered a permanant and complete solution to the TPP problem, i.e., the TPP problem on potatoes has been solved if growers use mesh crop covers. 

As mesh prevents TPP even landing on the potato crop it is believed that it will also achieve close to 100% prevention of Candidatus Liberibacter solanacearum (CLSo) infection of potatoes.  Due to insufficient funds, only 20 tubers from the control and 20 from the mesh 0.3 mm were tested with all control tubers infected and zero infection from mesh tubers. 

Yield was significantly increased by mesh, with a bulk yield of 94.53 t/ha for the best mesh compared with 84.47 t/ha for agrichemicals and 74.97 t/ha for the control, a 12% increase over chemicals and 26% increase over the control.  Mesh marketable yield for tubers >60g was 86.5 t/ha, and 68.2 t /ha for >125g tubers, a 24% and  60% increase over agrichemicals.  Average tuber weight and maximum tuber weight from mesh both increased 67% over agrichemicals.  This yield increase considerably exceeds the industry target of 12% yield increase over ten years, providing more than double the target in a single year not a decade. 

The best two mesh yields also exceeded the modelled / theoretical maximum yield of 90 t/ha. 

Mesh is cheaper than agrichemicals which coupled with higher yields means that mesh increased the field gate returns by between $4,531 to $21,110 (27% to 75%) from a lower input - lower return to a higher input - higher return scenario.  This considerably exceeds the industry target of a increase in returns of $1,500 over ten years, but achieving that increase in one year. 

Mesh also impacted microclimate with an increase in temperature, giving a 19% increase in growing degree days, as well as reducing relative humidity, at temperatures above 15°C and also considerably reducing wind damage to the haulm. 

As in previous trials, aphids got under the mesh and large populations started to build so were controlled by Chess.  All other means by which the aphids could be getting under the mesh are now considered exhausted and it is hypothesised that winged adults are alighting on the mesh, producing nymphs which can then penetrate the mesh.  Due to the very small holes that aphid nymphs can get through, coupled with mesh inevitably getting damaged / holed in real-world use, it is considered impossible to have an aphid proof mesh.

Therefore, a biocontrol program, based on existing glasshouse practices, needs to be developed to control any aphids that get under the mesh, along with the residual TPP.  This should then achieve as close to zero insect pests in potatoes as it is possible to attain. 

Due to low blight levels this year, this trial has produced little information on blight, apart from an indication that mesh and agrichemicals achieved similar control of blight which in turn had statistically lower levels than the control. 

A range of future research is considered vital to create a fully farm-ready mesh system for potatoes:

  • Solving the aphid problem with biocontrol, particularly for the seed industry;
  • Control of blight both early and late needs to be causally proven;
  • Direct growth / yield benefits of mesh need elucidating;
  • The ability of mesh to control all other potato pests needs to be established.



The Biological Husbandry Unit Organics Trust Board


The BHU Farm


The BHU farm, also known as 'the unit' is a ten hectare site, situated at the Horticultural Research Area (HRA) at Lincoln University.

Its role is support the Organic Training College, and the Future Farming Centre, by providing research and demonstration facilities.