Climate Change Increases Pressure On Crops

A decline in the availabe active substances, pathogens developing resistances to active substances, and climate change are presenting new challenges for plant protection. Ralph Hückelhoven, professor of plant pathology at the Technical University of Munich (TUM), explains how resistant varieties, strengthened plant defenses, and digital methods can help protect crops more effectively in the future.

Professor Hückelhoven, what exactly are we referring to when we talk about plant protection?

Plant protection is much broader in scope than just chemical plant protection. The goal is to keep plants healthy for as long as possible. Integrated plant protection therefore begins with the selection of crops and varieties suited to the location. It also includes the use of beneficial organisms, properly dosed fertilization, and physical measures such as plowing or pruning diseased plant parts. Only when these measures are no longer effective and economic damage is imminent are chemical pesticides used.

Many experts say that plant protection is undergoing a transition. How would you characterize that?

I see three key challenges. Agriculture is expected to ensure high yields and high-quality food, yet fewer effective plant protection products are available: pathogens are developing resistance, and few new products are being approved. Additionally, chemical active substances are often publicly not very highly accepted. Farmers must therefore meet increasing demands with fewer options available to them. In the medium term, this will require a transformation or innovation in plant protection.

What innovations do you have in mind here?

I see great potential in what's known as "gentle genetic engineering." This approach uses only genes from within a single plant species to breed more robust plants. Take barley, for example: Different varieties are resistant to various fungi. If we identify the genes responsible for this and combine them using this technique, we can create a barley variety that is more resistant to several of these pathogens and requires less chemical plant protection.

Do you know of any examples where this is already being used?

Yes, several-for example, bananas. Globally, primarliy one single variety is grown in agricultural production; the plants are genetically nearly identical. This makes them particularly susceptible to new pathogens such as the fungus that causes Panama disease. The fungi spread worldwide via trade routes, for example. The fungus causes the plants to wilt and produce fewer fruits. No commonly available pesticide can provide lasting protection for the plants in this case. And because most bananas grown worldwide are sterile clones, breeders are unable-or only very limitedly able-to genetically adapt them to this pathogen. In Australia, trials are now underway using resistance genes from a wild banana. These could be introduced into the cultivated banana using gentle genetic engineering, resulting in a significantly more robust banana plant. Currently, this is the best way to combat Panama disease using biological plant protection methods.

How is climate change altering the interactions between plants and pathogens?

Whether and to what extent a plant catches a disease depends on the interaction of three factors: the plant, the pathogen, and the environment. When the environment changes, this has a direct effect on the plant-for example, if it becomes too dry or too hot. On the other hand, a changing climate and extreme weather events also affect the pathogens. While some pathogens suffer as well, others benefit directly from the changes or can more easily infect a plant weakened by the weather. Some frost-sensitive pathogens are now able to spread more easily globally and are moving further north. Another fact that is often underestimated is that existing pathogens can adapt quickly to the new conditions-in some cases, faster than plant breeding can adapt the plants.

So are pathogens one step ahead of plants when it comes to adaptation?

Pathogens such as bacteria or fungi go through many generations in a short period of time and have very large populations. This allows beneficial mutations to accumulate and spread rapidly. Plants adapt much more slowly, as they go through significantly fewer generations in the same amount of time. In agriculture, we must therefore support crop plants to partially offset this evolutionary imbalance-for example, by specifically developing more resistant varieties.

When you think about the future of plant protection-what does it look like?

Precision agriculture holds great potential. Using remote sensing data or drones, we can pinpoint exactly where intervention is needed in a field. This allows us to apply crop protection products only where the pathogen is present in the field, thereby reducing the amount used.

Another point is the aforementioned progress in resistance breeding and gentle genetic engineering. Resistant plants require less support from the farmer and less chemical crop protection. Here, too, we can hope for significant savings.

Alternatives to chemical crop protection are also of interest. Many common crop protection products directly inhibit pathogens-fungicides, for example, target fungi. However, we can also approach the problem from the opposite angle and instead help the plant defend itself by specifically stimulating its immune system. The application of beneficial microorganisms-for example, those from the plant's natural microbiome-can also support plant health. There are promising scientific findings in this area.

My vision is an integrated plant protection approach that combines these strategies: resilient varieties, the targeted strengthening of the plant's immune system, and digital methods that allow for more precise application of plant protection products. To achieve this, we need technical innovations, appropriate policy frameworks, and societal acceptance. However, it will also be crucial whether the new methods are not only effective and environmentally sound but also economically viable for agricultural operations.

About the person:

Professor Ralph Hückelhoven is a professor of plant pathology at TUM. From 2019 to 2024, he served as a board member and chairman of the German Society for Phytomedicine.