A new model for analyzing color vision in aphids

Aphids land on their favorite color, bright yellow. Credit: Jean-Louis Wolff and Sasha M. Kirchner

Aphids are one of the least welcome visitors to the garden. These tiny insects can cause major damage in agriculture, but how do you choose host plants? What are the basic mechanisms behind it? Researchers from the Universities of Bonn and Kassel now present two new models that can be used to analyze aphids’ color vision, and thus how animals respond to plants. This opens up new possibilities for future research on this topic – but it may also be suitable for agricultural applications. The study was published in the journal Philosophical Transactions of the Royal Society B: Biological Sciences.

It was known for years that aphids particularly fond of the color Yellow, which is why yellow traps are sometimes used in agriculture to spot aphids in crops. In their current study, the researchers spread a total of more than 200 color traps with about 70 different colors in the field in two successive springs.

Using a spectrophotometer, they measured the so-called reflectance spectra of the individual colors of each wavelength. Study leader Professor Thomas F. of Crop Science and Resource Conservation (INRES) at the University of Bonn.

Then the reflection data and the behavioral data, that is, the number of aphids caught in each trap, formed the basis for two mathematical models. The goal was to correlate the reflexive and behavioral data, and in this way learn the wavelengths critical to the aphid response.

Two models with similar results

In the first model, the scientists combined already known data about the photoreceptors that are stimulated when aphids forage for food. The second model does not contain physiological data and only considers the behavior of the animals and the measured reflectance data for each color. For this model, the researchers applied a special statistical method called partial least squares regression (PLSR).

Both models came to similar conclusions. First, they confirmed aphids’ preference for yellow. Second, both models suggested a specific neural mechanism that controls the visual behavior of aphids. Dr. Sasha M. says: Kirchner of the University of Kassel: “We were surprised by the fact that the results of both evaluations were very similar.” “But the result is so powerful that it can’t be a mathematical tool.”

One conclusion for the researchers: even for aphid species that do not Physiological data To date, a new assessment method, combined with selected color stimuli, can help provide more accurate information on visual behaviour. “In this way, we may be able to avoid costly electrophysiological studies in animals in the future,” notes Döring, who is a member of the Interdisciplinary Research Area “Sustainable Future” and the PhenoRob Group of Excellence at the University of Bonn.

A bridge between biology and agriculture

With their study, researchers combine biological and agricultural research in a special way. In neuroscience, aphids do not usually serve as model organisms to study the underlying mechanisms. However, in agriculture, such behavioral analyzes are often not applied due to the level of detail. “We tried to build a bridge between applied science and basic research in our study,” says field ecologist Thomas Doering.

Specifically, new models can help improve current agricultural practices, such as so-called mulching methods that can change the visual background of crops and thus “disguise” host plants from pests. The results could also be relevant to attempts to change the color of the leaves, for example through special breeding or fertilization. The current study already provides evidence that wheat leaves are more attractive to aphids when fertilized with low levels of nitrogen than when treated intensively with nitrogen.

Why the color yellow?

The question remains as to why aphids prefer yellow – their food is the leaves of green plants. “We can now explain it physiologically, but the primary benefit of aphids is still unclear,” says Thomas Doering.

In future studies, he and colleagues would like to investigate the effect of UV light in more detail, which is interesting both for applications in crop protection and from a biological perspective.

In addition, the study provides preliminary evidence that some types of aphids respond somewhat differently than the majority. Whether this behavior is fundamentally different should also be clarified in further investigations.


Aphids manipulate their food


more information:
Thomas F. Döring et al, A Model of the Color Preference Behavior of Migratory Aphids in Spring, Philosophical Transactions of the Royal Society B: Biological Sciences (2022). DOI: 10.1098 / rstb.2021.0283

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