As a result of a laboratory experiment conducted in 2019-2021, a specific dependence of the anomalies frequency on the variety was revealed. All anomalies have a combined character, but there is no direct relationship between the totality of their manifestations. We recorded 17 violations of the normal structure: trematelitria, pupal imago, the right middle tibia partial atrophy, non-divergence of the pupal exuvium, pronotum deformity, dystrophy of the middle legs last segments, elytra hematomas, point injuries, brachelitria, complete reduction of the front right foot segments with the metatarsus preservation, gaping elytra suture, reduction of the right hind leg with the thigh base preservation, six-membered antennae, schistomelia, anomaly of the right and left wings cubital veins, wings deformities with external elytra asymmetry (Fig 1).
When feeding on the Belmonda variety, deformities were observed more often than on the others - in 97.3% of cases, in addition, anomalies in the development of larvae were observed on the Belmonda and Lilly varieties. The body became elongated, thin and stretched, parts of the old cuticle remained on the new integuments, the bristles were lost, as well as the structures located at the ends of the legs and mouth. The cuticle took on a uniform, dark gray color and several thoracic segments were dorsally inflated. The autopsy did not show the pathogenesis inherent in the parasite or mycosis development, which allowed us to conclude that the anomaly was non-invasive. Some pupae had areas with abnormally thin cuticles. At the same time, there was a change in pigmentation and the appearance of black spots as a result of hypermelanization. In 12% of cases on the Belmonda variety, there was a death during molting, in which the larvae remained entangled in old exuvia. The body of the pupa in 10% for the Lilly variety and in 4% on the Belmonda was wrinkled and deformed. At the same time, the frequency of individual anomalies - trematelitria, elytra pupoid deformity and elytra hematomas, correlate with those or higher for individuals raised on the Lilly, Dachny and Queen Anna varieties, respectively.
At the same time, a comparison of
H. vigintioctomaculata hemograms showed that nutrition on potato varieties showing the presence of immunological barriers led to sublethal changes in the hemolymph formula. Thus, the battening of an adult on the Belmonda variety led to pathological enocytoids vacuolization, a decrease in the size and clarity of the nucleus structure and spherulocytes protoplasm. In the Kazachok variety, there was a general cell degeneration, expressed in the displacement of the nuclei to the periphery, as well as in a decrease in the size of the shaped elements themselves. In general, the hemogram of
H. vigintioctomaculata on the varieties Belmonda, Kazachok, Queen Anna, Lilly, Red Lady, Labella had similar features to the picture described by a number of researchers for the effects of sublethal pesticides doses
(Giulianin et al., 2003; Gillund et al., 2011). Nutrition on potato also affected the terms of ontogenesis, survival and fat-feeding nutrition of the
H. vigintioctomaculata (Table 1, 2, Fig 2). According to the average long-term data, the Smak variety became the most optimal for feeding, growth and development of all potato ladybug age stages. It has the lowest mortality rate and the highest fecundity
(Matsishina et al., 2019). The least favorable varieties for the potato ladybug feeding are Queen Anne, Lilly, Dachny and Kazachok, which are characterized by the maximum mortality at acceptable shifts in ontogenetic terms. As a result of the study, the Belmonda variety which demonstrated a complex of immune barriers to the pest was distinguished. When feeding this variety, the highest mortality rate (100%) was recorded with the extension of the ontogenesis time frame.
The maximum values of pupal weight were observed for the varieties Smak (ā=54.38 mg) and Yubilyar (ā=41.5 mg). The minimum values were observed for the Belmonda variety (ā=12.28 mg). In the remaining varieties, uniform weight distribution was observed, which is consistent with the indicators of the ontogenesis and mortality terms. All of the above is a reliable criterion for high resistance of the Belmonda variety to
H. vigintioctomaculata (
Fasulati and Ivanova, 2015;
Shelley, 2000).
The results of laboratory experiments are also confirmed by studies in the entomophytopathological site conditions (ETHU) of potato ladybug natural settlement (Table 3). The largest number of ovipositors and eggs in them on the plant was observed in the Yubilyar variety (4/401), the smallest - in the Lilly variety (1.5/23.6).
The maximum number of older ages larvae and adults is recorded for the Smak variety, the minimum - for Red Lady in the case of adults and Labella - in the case of larvae. The highest damage score was observed on the Kazachok variety (5.0), the lowest - on the Labella variety (2.2). The Kazachok (5 damage points), Queen Anna (3.1 points) and Rad Lady (3.1 points) varieties showed signs of the presence of antibiosis and resistance to damage by phytophagous. Necrosis under the ovipositor and the appearance of additional stems were noted. For the Belmonda variety, manifestations of antixenosis were also recorded, which is expressed in the fact that the plants of this variety were not selected by the ladybug either for food or for laying eggs.
Among other things, we conducted experiments to study the distant orientation of larvae of the III-IV instars of the potato ladybug (Fig 3) to potato varieties. For food, they were offered leaves of the studied varieties, laid out in a gauze insulator at an equal distance from the larvae and each other. The study sample consisted of 25 individuals, the exposure time was 4 hours and the number of experiment iterations was 5. It was found that the variety Belmonda is unattractive for larvae. During the experiment, it was not selected for nutrition in any of the experiment iterations. At the same time, the Smack variety was absolutely attractive. The larvae that began to feed on other varieties soon left them, moving to the leaves of the Smack variety. To a lesser extent, they chose the Yubilyar, Dachny, Augustine and Kazachok varieties. The varieties Sante, Yantar, Lilly, Red Lady and Labella were selected on average by one individual from the sample.
All existing potato varieties are damaged to some extent by
H. vigintioctomaculata. The differences between them in the degree of damage are to some extent related to the biochemical composition, characteristics of leaves and regenerative capacity
(Nazarenko et al., 2002). Glycoalkaloids are also teratogens, causing various deformations and deviations in the development of insects
(Chen et al., 2018).
The cause of morphological deviations should be sought in the physiology of insects. All abnormalities are associated with impaired embryogenesis
(Telang et al., 2002; Miranda et al., 2016; Burand and Hunter, 2013;
Madhavi, 2019). According to the views of
Steinhaus (1952), disturbances in the morphology of the exoskeleton are non-infectious diseases of the insect organism. In our opinion, these may be features of the interaction of a phytophage and a plant, expressed in the form of antibiosis and antixenosis
(Shapiro et al., 1986). Phytophages choose plants of certain species and varieties as a food source, which is facilitated by compounds with repellent and attractant activity. This activity can be detected by the behavior of the larvae, insects spend much more time in search of food on resistant varieties of plants than on unstable ones
(Islam et al., 2011; Umamaheswari et al., 2021).
