How in-field diagnostics can reduce waste on farms and promote sustainable agriculture

Did you know that on a global scale up to 40% of crops are lost to pests and diseases? This article provides an overview on the waste associated with farming, contributing to global food insecurity, and how on-site diagnostics can be part of the solution.  

The Problem of Food Waste on Farms

Globally every year, crop pathogens lie in wait to strike plants, causing farmers constant worry as to when and where disease will break out. A spray and pray policy is no longer feasible under a zero carbon farming format.

Farmers will have to utilise all the tools in their diagnostic kit box to find precision solutions. Knowing you have a problem isn’t easy and it’s no good being Captain Hindsight. On a global scale up to 40% of crops are lost to pests and diseases. A shocking waste of resources when more than 820 million people on the planet do not have enough to eat.

Qualitative losses can pertain to cosmetic appearances such as bruised apples, the wonky carrot or disease symptoms such as spotting on vegetable leaves or sprout buttons, a reduction of essential substance, a change in taste or mycotoxin contamination. The latter, if ingested may give rise to lethal consequences.

Not only for animals but humans too. As we extend our gaze to plant based diets a potential collision with climate change could await. Here, precision farming and targeted use of fungicides provide a useful tool to prevent our fruit and cereals being at risk to mycotoxin creep.

Major Fruit and Vegetable Waste on Farms

In the UK, our fruit and vegetables are produced to an exceptionally high standard and graded into Extra (superior quality), Class 1 (good quality) and Class 2 (reasonably good quality). Nevertheless, a significant volume is wasted.

For cabbages alone, £4.5 million losses occur in storage to disease. This is not just a UK problem, a study in the US estimated some 23% of fruit and vegetables do not make it to the retail stage; instead, they’re lost during the production, handling or storage phase.

This increases to a staggering 64% in total loss, if you include the post retail phase. Across Europe upwards of 50 million tonnes of fruit and vegetables are discarded. Therefore, around 20% to 50% of fresh produce is perfectly edible, but just not attractive enough to sell according to sellers. More concerning is that this is despite the use of pesticides and cultivars with improved genetic resistance.

We cannot escape from the fact we are over producing food to ensure High Income Countries (HIC) have cosmetically perfect produce on the supermarket shelves. By effectively preventing disease from the outset, the requirement for food overproduction and food wastage could be reduced. Targeting treatments only when they are required and with precision presents an opportunity to farm sustainably with reduced outputs.

An opportunity to improve soil quality, reduce power usage, plastics and water consumption. Not only helping to protect our environment but reduce the potential of crop resistance or new pathogen variants able to overcome disease control measures. Here there are parallels with the overreliance and misuse of antibiotics which has led to a serious threat not only to public health but animal welfare.

How to Reduce Food Waste On Farms and Improve Food Security

Disease diagnosis and pathogen detection are central to protecting and reducing food waste. Early diagnosis can provide the grower with useful information on optimal crop rotation patterns, varietal selections, control measures, harvest date and post-harvest handling strategies.

Pathogen detection prior to infection or symptom development can stop or reduce disease transmission and epidemics. Whether a plant, animal or human, early diagnosis is the key to breaking transmission and a successful control programme.

However, the isolation and identification of crop pathogens are commonly made only after disease symptoms are observed. Time consuming and expensive, these measures can delay the application of a treatment at an important stage in a crops life cycle. As a result, prophylactic spray and pray treatment programmes have been devised and often liberally applied. Over time this can give rise to pesticide resistance.

The timely detection and identification of economically important disease potential provides the initial key to drive a successful and informed control strategy. It is however only part of the solution, the success of which will depend on how the information is evaluated and then incorporated within an integrated crop disease management system (ICDMS).

Early detection allied to key environmental parameters to control disease at the onset can lead to an increase in production, an improvement of resource efficiency and make a substantial contribution to food security.

Farm food waste reduction case study: Let’s talk strawberries!

In the UK alone and, on an annual basis, it is estimated 10-20% reduction of soft fruit strawberry marketable yield, is as a result of fungal rotting. All 5,000 hectares of strawberries grown on UK farms (and 2,000 hectares of raspberries) are considered at risk from soft fruit rot disease.

Soft fruit rot losses are not restricted to the UK but a world-wide problem and on multiple crops. Globally, in strawberries alone, soft fruit rot pathogens could cost producers upwards of 2 billion in lost revenue.

Rot pathogens can limit marketable product by affecting the growth, quality and storability of the fruit. Grey mould, caused by Botrytis cinerea is considered the most important post-harvest strawberry fruit rot pathogen. Botrytis cinerea infects over 200 plant species and worldwide, it causes annual losses of $10 billion to $100 billion. Botrytis is able to counteract a broad range of plant defence chemicals.

Which Rots are Causing Strawberries a Problem and Why ?

Botrytis cinerea is highly adaptive and versatile crop pathogen developing resistance to almost every mode of action chemistry, including pyraclostrabin/boscalid, fenhexamid, and iprodione. Globally, on-farm strawberry production generally relies on pre and post-harvest fungicide applications. These are not only costly in terms of prophylactic fungicide usage, man hours to apply but increases risk of treatment resistance and impacts on the environment.

A DEFRA report identified strawberries on average received 13 fungicides with only 0.2% of strawberries not treated. Two other rot pathogens which growers face are Mucor and Rhizopus. Like Botrytis, they are not limited to soft fruit and have a wide host range to include melon, peach, sweet potato and head-rot of sunflower. Unlike Botrytis both Mucor and Rhizopus can cause human infection.

Mucormycosis is an increasingly common fungal infection (caused by Rhizopus and Mucor species) with a high mortality rate in immunocompromised patients reported. For example, the mortality rate was 46% among people with sinus infections, 76% for pulmonary infections, and 96% for disseminated mucormycosis.

In soft fruit production, Botrytis, Mucor and Rhizopus are the silent rots hiding behind the mask of latent infection, risking consignment rejection by retailers at point of sale. If they can evade this, which they often do, will lurk and later appear on fruit in your fridge or fruit bowl.

How Do We Stop These Rots And Leave Them At The Farm Gate?

You will no doubt have heard recently of the UK government harnessing nucleic acid based technologies to identify COVID infection at the point of need. Most recently, lab-free tests such as the COVID Nudge which is a sample to answer RT-PCR test (reverse transcription polymerase chain reaction test – turning RNA into DNA for PCR) in just under an hour turn around. In diagnosis and controlling human infectious diseases, these technologies are becoming an invaluable tool in the medical diagnostic kit bag.

Where PCR is the most familiar nucleic acid amplification technique, RPA (recombinase polymerase assay) and LAMP (loop-mediated isothermal amplification) provide compelling nucleic amplicon-based technologies for crop-side plant pathogen diagnosis. Particularly, when combined with lateral flow devices.

Although, for fungal crop pathogens the speed, cost-effectiveness, robustness and simplicity is not so clear cut. Fungal spores are notoriously difficult to crack open for extraction of their DNA and extraction from soil / growing mediums can prove challenging.

The crop-field setting is an interesting environment to operate in and cost has to be a consideration. The UK government is reported to have provided a £168 million order for 5.8 million high speed DNANudge COVID test kits. Both in agriculture and horticulture, producers are often operating within very slim profit margins and throughout the production process, the risk of total crop loss.

For uptake, the diagnostic test must be accurate, provide sample coverage or crop representation, be cost effective, easy to use, simple to interpret and inform decision making.

How The Lateral Flow Test Can Reduce Waste On Farms

So, lets step back and think about low cost, simple to use diagnostic tests which work at the point of need. As our Chief Scientific Officer Prof Paul Davis says:

“We kept coming back to it, there is nothing simpler or better than the lateral flow”

Over the counter antibody based tests have been used for years (since the early 1980s) to provide simple, low cost (under £10 pounds / test) robust diagnostic tools for use at home. Just think of the home pregnancy test kit. A technology that provides a lab on a stick which, by the scientific community, is more commonly known as a lateral flow assay device (LFA).

Prof Paul Davis, founder of Mologic and Chief Scientific Officer has deep knowledge of LFAs and the only remaining practicing scientist from the original technology development team (Davis, May and Prior in the 1980s), that led to the creation of UniPath Clearblue brand for home pregnancy testing. Since the development of this technology in the 1980’s, the LFA has been applied to other market sectors to include veterinary, agriculture, the food industry, environmental health and forensic science. 

In plant health, this technology has been used extensively and successfully for bacterial and viral crop pathogens. However, for fungi where many share a complex array of carbohydrate based common immunodominant sites, attaining test specificity is difficult. Fungal diversity in the environment is estimated at between 1 and 5 million species (to include multiple races, pathotypes and complex life cycle stages). Finding and selecting the perfect diagnostic probe for lateral flow assay can be more than challenging although not impossible!

So, lets step back and think about low cost, simple to use diagnostic tests which work at the point of need. As our Chief Scientific Officer Prof Paul Davis at GADx (formerly Mologic) says:

“We kept coming back to it, there is nothing simpler or better than the lateral flow”

How GADx Supports Farmers And Growers In Reducing Food Waste With LFA tests

There are strong links between health outcomes and food insecurity. With roughly 83 million people being added to the world’s population every year, and with the upward trend in population size expected to continue. Mologic seeks to apply its expertise and technology to support global food security.

Partnering with Berry Garden GrowersWCG PershoreNIAB EMR and with funding support from Innovate UK we have been able to develop LFAs which can be used to measure airborne load for Botrytis.

Being able to measure the concentration of this spore type in the crop air allows us to identify times at when the strawberry crop could be exposed to rot infection. This can be further improved by allying spore availability with the environmental conditions (temperature, humidity, surface wetness).

AgriAlert: GADx’s Solution For The Agriculture Sector

To find out more about GADx Agri-Alert and how our strong expertise in research and diagnostics can support you, please click here. That’s a lot of hard graft in industry and academia, and that’s the foundation of our successes. Our product development isn’t limited to human healthcare. We have a dedicated team who apply our experience and knowledge of lateral flow to the non-human sector.

Frequent testing is invaluable and so it is vital to find ways to drive down the cost of kits and increase production levels. As a social enterprise, GADx can transform this process because it ‘breaks the link’ of ‘having to make profit for shareholders’.

Paul Davis
Co-founder of Mologic and pioneer of lateral flow diagnostics.