Simple SummaryThe issues of relationships in the system “Henosepilachna vigintioctomaculata—potato plant” have not yet been studied. The highest level of stress was demonstrated by larvae feeding on the potato varieties Belmonda, Queen Anne, Lilly, and Dachny, while the lowest stress level was observed when larvae fed on variety Smak. The damage inflicted by potato ladybird beetles on potato leaves led to an increase in the content of glycoalkaloids in some varieties already within 24 h after the transfer of the phytophages. In most cases, the content of glycoalkoloids increased by 20% within five days. Variety Smak did not show a significant increase in the content of alkaloids in response to the damage. It was established that the higher the content of glycoalkaloids and the activity of proteinase inhibitors in the tissues of potato plants, the higher the level of stress in the potato ladybird beetles that feed on them.AbstractHenosepilachna vigintioctomaculatais an intrinsic element in the agroecosystem of potato fields. The issues of relationships in the system “potato ladybird beetle—potato plant” have not yet been studied. To study the effect of potato varieties on the potato ladybird beetle, only hatched and active larvae with a hatching rate close to 100% were selected from a laboratory colony. Larvae of the first summer generation collected in potato fields were used in our study to determine the level of adrenaline in the bodies of insects, fresh potato leaves were used to study the content of glycoalkaloids, the content and activity of proteinase inhibitors. The larvae that fed on plants of varieties Belmonda, Queen Anne, Lilly, Dachny, Kazachok, Yubilyar, and Avgustin demonstrated the highest level of stress while the stress level in those that fed on variety Smak was the lowest. The damage inflicted by potato ladybird beetles on leaves of some studied potato varieties led to a progressive increase in the content of glycoalkaloids already within 24 h after the phytophages had been transferred. In most cases, the content of glycoalkoloids increased by 20% within five days. Potato ladybird beetles feeding on plants of different potato varieties caused a progressive increase in proteinase inhibitors (% of the control). Plants of variety Smak did not show a significant increase in the content of alkaloids in the herbage in response to the damage. A correlation was established between the mortality rate, the activity of proteinase inhibitors, the dynamics of glycoalkaloids, and the level of adrenaline, which could be formulated as follows: the higher the content of glycoalkaloids and the activity of proteinase inhibitors in the tissues of potato plants, the higher the level of stress in the potato ladybird beetles that feed on them.