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Plant communication can influence the feeding habits of aphids
Published: 14 July 2023
It has been shown that the number of aphids can decrease when two cultivars of barley are mixed. The communication between different plants seems to play a role. In a study conducted by SLU, a barley plant of one cultivar was exposed to chemical signals from barley plants of other types. With a certain mixture of cultivars, aphids spent less time feeding and they did not grow as quickly. These are interesting results that could be beneficial in future plant protection.
Previous research at SLU has demonstrated that aphids can decrease in cultivar mixtures. However, both this and previous studies have shown that the specific combination of two cultivars is crucial to achieve this effect.
"The most important finding from this study is that the chemical interaction between plants can disrupt plant-feeding insects. If we learn to mix the right varieties, it could be applied in plant protection," says Sokha Kheam, a PhD student at the Department of Ecology, SLU.
Three different cultivars of barley were used in the study. Cultivar 1 was exposed to chemical signals from either cultivar 2 or cultivar 3. Researchers placed aphids on the plants from cultivar 1 and observed them throughout the experiment.
One of the combinations affected the aphids in an interesting way. The aphids spent less time feeding. They interrupted their sucking faster to insert their stylets at another spot and test there instead. They also grew slower, and it took them longer to develop into adult aphids capable of reproducing.
"Our hypothesis is that the barley plant activated its defense mechanism and, therefore, was less tasty for the aphids when exposed to signals from a specific type. This increases our understanding of what happens when different varieties are mixed," says Sokha Kheam.
The experiments were quite challenging.
"Weighing 24-hour-old aphids required a lot of patience and practice. I took the tiny nymphs from the plant with a small brush, weighed it, and put it back on the plant. After five days, I weighed them again," Sokha Kheam explains.
To track the aphids' feeding behavior, they used a method called electrical penetration graph (EPG). The middle-back of the aphid was attached with thin gold wire and the other end of the gold wire was inputted in the amplifier, functioning as an electrode. Another electrode was placed close to the plant in the soil. With that a computer can record the activity, generating a curves with different patterns depending on the feeding phases of the aphid. Examples of phases include inserting the stylets into the leaf cells and phloem sap/xylem sucking.
"Thanks to this method, we were able to analyze how much time the aphids spent in different phases. We observed that the aphids spent less time on feeding and more time moving to new spots with the specific combination," says Sokha Kheam.
Scientific article
Volatile interactions between specific undamaged barley cultivars affect aphid feeding behavior and performance, Kheam et al, Journal of Pest Science