Can the air tell us when to apply crop protective product onto our crops?

Written by: Anastasia Sokolidi

The current way that we approach the treatment of our crop with regards to infection is that when we see visible symptoms we spray. Sometimes, in certain crops we apply crop protective product even before we see visible symptoms. Ideally, we want to spray as little as possible and only when necessary. Using less crop protective product will be better for the environment and for our growers pockets. However, too little and to late can cause severe damage to the crop with hundreds of pounds lost. To prevent that growers would rather spray than save money.

Since the industry and the people recognise the benefits of spraying less, a lot of research is being put into detecting infections even before any symptoms are visible on a plant. Some technologies that are being developed rely on robotics to scan our fields and rows of plants and tell us based on the images obtained that the plant is diseased or in distress (Singh, Sharma and Singh, 2020). However, this technology currently being developed and isn’t widely applied as it would rely on algorithms that are very hard to develop as well as symptoms from which it is hard to differentiate as to what the crop is infected with.

Another way is through molecular technologies. These technologies rely on the DNA/RNA of the pathogens in question and can be very sensitive and specific. The technology is similar if not the same as the current COVID-19 screening test that you do at home. However, that is only one of them. Other more sensitive tests that can be done in the lab and can tell you not only if it is a positive or negative result but also how much of the pathogen is present. These molecular technologies can be used in the field to test the leaves of the plants and can be bought from commercial industries (e.g. https://www.pocketdiagnostic.com). These are very good for being able to detect the pathogen in areas where you are uncertain what the pathogen that caused the problem is. They are also good at detecting the pathogen in the presence of a lot of other fungal spores. This is the technology that has allowed us to be able to detect the presence of fungi in the air.

People have been monitoring the air for a long time in order to detect what is present. This is used to do pollen counts and tell you when your hay fever will be at its worst. However, this technology can also be used to tell us exactly when and what type of fungal spores are in the air (Van der Heyden et al., 2021). In the older days it would require a lot of very specialized people to sit there and do it through a microscope however now it has been made easier and quicker by the molecular technologies previously mentioned. The molecular technologies have made the process faster and require less specialization allowing more people to analyse the samples collected. Through this innovation it allowed scientists to monitor real time not only what pollen is present but also what harmful fungal pathogens are present in the air that can infect and decimate the crops. This method has been successfully used to in the UK currently to inform farmers of the high-risk periods of Sclerotinia sclerotiorum infection in oilseed rape (https://ahdb.org.uk/sclerotinia-infection-risk-alerts-for-oilseed-rape ). A nasty fungal disease which will show symptoms on the plant only when it is to late to do anything about it.

Even though this technology is fantastic to use it still has several setbacks. First, it relies on what molecular technologies have been designed for a specific pathogen. Some pathogens are not that widely researched so no such molecular techniques have been created. This is a growing field so more and more such molecular tools are produced each year for fungal pathogens. The second setback is the fact that these technologies only work with fungal diseases, that at one point in their life, will be present in the air. Some fungal diseases don’t have a period where they are present in the air and instead like to lurk in the soils. These fungal diseases will not be detected by these techniques that samples the air. The last major set-back is that the equipment used to sample the air is reliant on people who need to analyse the samples. Currently all the samples produced with the air sampling equipment need to be taken to the lab and processed there. This gives a certain time gap between which the pathogen might be spreading through the crop and the growers won’t know about it. If doing real-time monitoring the maximum time set-back would be approximately 15 days. The next step would be to develop an air sampling equipment that would be able to collect the samples and do the analysis on-site without the need of a lab or people and send the results to the growers informing them of the presence and quantity of dangerous fungal diseases in the air.

Looking at the current day technology we can say that yes, the air can inform farmers when to apply crop protective product. However, the cost at which it is done is very great and even real-time monitoring takes time. This technology has all the potential to be used in wider applications but for it to be used widely used and integrated with the decisions that growers take to spray their crop the previously mentioned down-sides must be ironed out. This is in part what my PhD project is about. To work on improving the technology by developing new molecular techniques and working to improve the speed at which real time monitoring can be done.

References

Singh, V., Sharma, N. and Singh, S., 2020. A review of imaging techniques for plant disease detection. Artificial Intelligence in Agriculture, 4, pp.229-242.

Van der Heyden, H., Dutilleul, P., Charron, J., Bilodeau, G. and Carisse, O., 2021. Monitoring airborne inoculum for improved plant disease management. A review. Agronomy for Sustainable Development, 41(3).