Pesticides: better harvest or danger on the ground? : News 2019: University of Hamburg

July 11, 2019, by Dr. med. Livia Rasche, CEN University of Hamburg

Photo: unsplash.com/J.Brands

What do women farmers in Africa, women farmers in Africa, do when temperatures rise or extreme rainfall becomes more frequent? For farmers around the world, climate change is a challenge. Should they change and grow other fruits in the future? Or invest better in new techniques such as irrigation?

In order to identify the appropriate plants and intelligent techniques, we develop special calculation models at the University of Hamburg. With their help, we simulate future yields for large arable land. It is thus possible to estimate the evolution of the potato crop at a given location, at higher temperatures and at higher rainfall. The models help determine the best mix of irrigation and fertilization currently. I can also test new techniques without having to spend a lot of time in the field.

But the results are incomplete because a central tool was lacking until now: pest control with pesticides. While in Europe we are more likely to think of toxic residues of fruits and vegetables, pesticides in other countries are almost luxury goods. Smallholder farmers in Africa, for example, suffer significant losses from insects and fungal attacks. A cure can prevent this, but is often too expensive. Globally, losses caused by pests and fungi are about 20% for wheat, corn, potatoes and soybeans, and 30% for rice. Bridging this gap can help fight hunger.

At the same time, pesticides cause big damage. This shows a whole series of deaths and poisonings in cotton growing in India over the past 20 years. The extinction report of the recently published IPBES species also seems critical.

So what quantities bring a much higher yield – and what price do we pay in terms of health and nature conservation? To find out, pesticides must be included in the agricultural model. But the complicated life cycle of the pests has prevented it so far. It is extremely difficult to integrate the effect of an insect species on a plant in a computer model. This is partly because it does not cause permanent damage. While their eggs are still harmless, caterpillars and larvae usually eat vigorously. Adult animals then have even less appetite.

In addition, different insects attack different parts of the plant. Nibbling on the leaves can be sweet. But if the stem is eaten away, the plant is dead and, with the help of an entomologist, I have deepened the biology of the corn borer and the potato cicada for finally understand their influence on mathematical formulas.

But is my new model correct? In addition, I evaluated field trials with corn, soy and potatoes in the United States. Between 1985 and 2014, crops were grown in different climatic zones. All data are well documented: sowing, development, fertilization, pesticide use, density and pest yield. That was my real world control data. For 14 fields, I simulated the returns. I fed my model with the weather data of each year and the documented actions of the farmers. A complete success: the calculated yields are in very good agreement with the real crops! The new tool can therefore make reliable predictions about pesticides and yields.

Now, I'm interested in the actual costs of pesticides. The consequences for nature and health should also be included in the balance sheet. Until now, the benefits accrue only to the producers, but the follow-up costs must be borne by the company. My farming model can help find and quantify these costs.