Elif Fatma Topkara

Herbivorous insect infestations are a serious problem that threatens the plants. To cope with this issue, plants utilize various defense mechanisms. Malacosoma neustria L. (the lackey moth) (Lepidoptera: Lasiocampidae), which causes significant damage by feeding on many shrub-like and woody plants during its larval stage, is a worldwide pest. Sea buckthorn, Elaeagnus rhamnoides L. (Rosales: Elaeagnaceae), which has economic, ecological, and medicinal importance, is one of the plants most preferred by this insect. The changes in the amounts of secondary compounds, fresh and dry weights, the levels of chlorophyll a, chlorophyll b, and total chlorophyll, the contents of total protein, the contents of malondialdehyde (MDA), the activities of ascorbate peroxidase (APX), superoxide dismutase (SOD), and catalase (CAT) in leaves of the M. neustria-infested and non-infested E. rhamnoides were compared in this study. The leaves of E. rhamnoides were collected from the Kızılırmak Delta in Samsun Province, Turkey. The moth-infested and non-infested leaves constituted experimental groups. As a result, it was determined that the fresh weight and the content of protein in the lackey moth-infested leaves decreased. In contrast, the levels of total chlorophyll, chlorophyll a, and chlorophyll b, the content of MDA, the activities of SOD, CAT, and APX increased. Additionally, it was found that both the amount and composition of secondary compounds differ between the moth-infested and non-infested leaves. In conclusion, our findings indicate that E. rhamnoides defends itself against M. neustria infestation, which is a biotic stress factor, through both ROS-scavenging enzymes and its secondary compounds..

With the rapid expansion of nanotechnology, studies focusing on the toxicity of nanomaterials to living organisms are increasing. Nanoparticles (NPs) are widely used in pest control because of their various toxicological effects on insects. The changes in the amounts of malondialdehyde (MDA), the activities of NADPH oxidases (NOX), superoxide dismutase (SOD) and catalase (CAT), and the amount of glutathione (GSH) of Malacosoma neustria L. (Lepidoptera: Lasiocampidae) larvae, a polyphagous species, exposed to different concentrations of copper oxide (CuO) and zinc oxide (ZnO) NPs were compared in this study. M. neustria eggs were collected from the Kızılırmak Delta in Samsun Province, Türkiye, in May 2022. The 2nd instar larvae of M. neustria were divided into seven different groups: one control, three with varying concentrations of CuO NPs (40, 200, and 1000 mg/L), and the other three with different concentrations of ZnO NPs (40, 200, and 1000 mg/L). As a result of the study, it was determined that the amounts of MDA and GSH and the activities of NOX, SOD, and CAT of the larvae exposed to both nanoparticles were higher compared to the control. As a result of the study, it is indicated that oxidative stress occurs in the insect exposed to toxic nanoparticles, and the insect defends itself against these nanoparticles with both enzymatic and non-enzymatic defenses. It is suggested that these nanoparticles can be utilized to control insects.

Pine processionary moths Thaumetopoea pityocampa and Thaumetopoea wilkinsoni are among the most harmful insects that cause severe damage to pine forests in many countries, including Türkiye. The aim of this study was to evaluate the efficacy of entomopathogenic fungi (EPF) isolates of Beauveria bassiana (PA-4 and KTU-24), Metarhizium anisopliae (KTU-51), and M. floviridae (AS-2) against the 2nd instar larvae of T. pityocampa and T. wilkinsoni under laboratory conditions. T. wilkinsoni eggs were collected from pine trees at Ondokuz Mayıs University Kurupelit Campus in Samsun, Türkiye, in 2021, while T. pityocampa eggs were collected from Kahramanmaraş province, Türkiye, in 2021, and the 2nd instar larvae were used for the experiment. Four fungal isolates were sprayed on the larvae at 2 mL for each concentration (1 × 105 - 1 × 108 conidia mL-1). At a concentration of 1 × 108 conidia mL-1, mortality rates for T. pityocampa larvae were 55.6-100%, while mortality rates for T. wilkinsoni larvae were 56.8-100%. It was found that two isolates of B. bassiana were virulent for both T. pityocampa and T. wilkinsoni, and the KTU-24 isolate was the most virulent isolate, causing the lowest LC50 values ​​​​(2.2 × 105 for T. pityocampa and 4.3 × 105 for T. wilkinsoni) and the shortest mean survival time for both larval species. It is suggested that the KTU-24 isolate can be used in the biological control of pine processionary moth species.

The pine processionary moth Thaumetopoea wilkinsoni (Tams, 1926) (Lepidoptera: Notodontidae) is one of the most harmful species that causes destruction in pine ecosystems and also causes critical skin reactions in humans and animals due to its urticating hairs. This study aimed to evaluate the efficacy of different strains [Bti ATCC 35646 (wild-type strain), Bti pHT315, and Bti pHTppk (mutant strain)] of Diptera-targeted Bacillus thuringiensis subsp. israelensis (Bti) and toxins (spore/crystal mixtures) obtained from these strains against the 4th larval stage of T. wilkinsoni under laboratory conditions. T. wilkinsoni eggs were collected from pine trees at Ondokuz Mayıs University in Samsun, Turkey, in 2022. Pine needles were contaminated with bacterial strains of different concentrations (1 × 10⁷, 1 × 10⁸, 1 × 10⁹ cfu/mL) in 5 mL and toxins in different concentrations (0.15, 0.3, 0.6, 1.25, 2.5, 5 mg/mL) in 2 mL. Larvae were placed in containers with 30 larvae in each group and were observed for 25 days. As a result of the study, Bti ATCC 35646 with 63.4% mortality and the lowest LC₅₀ value of 1.2 × 10⁹ cfu/mL among the three strains of Bti and Bti pHTppk with 76.7% mortality and the lowest LC₅₀ value of 1.2 mL among the toxins from the Bti strains had found to be virulent for T. wilkinsoni. The results obtained from our study suggest that Diptera-targeted Bti is virulent to T. wilkinsoni and that this strain and spore/crystal mixture can be used in the biological control of this species.

Pinus species, used in traditional medicine and are an important industrial plant, suffer severe ecological and economic losses with the invasion of Thaumetopoea wilkinsoni (the pine processionary moth). Due to the damage caused by T. wilkinsoni, a biotic stress factor, the changes occur in the ecological and physiological parameters of Pinus species, which also try to cope with abiotic stress. The changes in fresh/dry weight, percent water content, chlorophyll a and b content, the total protein content, malondialdehyde (MDA) amounts, and superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities in leaf samples of the pine processionary moth-infested and non-infested Pinus sylvestris L. and P. nigra Arn. species were compared in the study. The leaf samples of P. nigra and P. sylvestris were collected from the Ondokuz Mayıs University Kurupelit Campus in Samsun, Turkey, in 2020. Individuals of the moth-infested and non-infested P. sylvestris and P. nigra formed two distinct experimental groups. It was found that the fresh/dry weight, percent water content, chl a and b content of the moth-infested individuals of both species were significantly decreased compared with non-infested individuals; the total protein contents, lipid peroxidation and SOD, CAT, APX activities were found to be significantly increased. It was also determined that the moth-infested individuals of both species had the most sesquiterpenes and the least monoterpenes. Our results clearly show that P. nigra and P. sylvestris defend themselves when attacked by the pine processionary moth, both by changing the amount of secondary metabolites and by reacting as antioxidative defense responses.

Background: The pine processionary moth Thaumetopoea wilkinsoni Tams, 1926 (Lepidoptera: Notodontidae), causes severe skin reactions to animals and humans. The insect also destroys pine ecosystems by feeding on pine leaves at its larval stage. Instead of chemical control, eco-friendly biological control methods should be preferred to combat this species. Results: The purpose of this study was to evaluate the efficacy of Beauveria bassiana isolate (GOPT-331) and Metarhizium brunneum isolates (ORP-13 and ORP-18) against the second and fourth larval instars of T. wilkinsoni under laboratory conditions. T. wilkinsoni eggs were collected from pine trees at Ondokuz Mayıs University in Samsun, Turkey, in 2021, and the second and fourth larval instars were used for the experiment. Two milliliters of a spray of the three fungal isolates was applied to the larvae for each concentration (1 × 10⁵–1 × 10⁸ conidia ml⁻¹). The mortality rates of GOPT-331, ORP-13, and ORP-18 were changed between 91.1 and 100% for the second-instar larvae and between 86.6 and 97.7% for the fourth-instar larvae at 1 × 10⁸ conidia ml⁻¹. The ORP-13 isolate showed the lowest LC₅₀ values. Conclusion: In conclusion, it is suggested that all the three isolates were virulent to T. wilkinsoni and can be used for biological control of this species. The promising results from the study were obtained from trials conducted under controlled laboratory conditions, and it will be critical to explore the potential of these promising entomopathogenic fungi in field conditions.

Background: The European tent caterpillar Malacosoma neustria Linnaeus, 1758 (Lepidoptera: Lasiocampidae), a worldwide pest, feeds on a wide variety of woody and shrub-like plants in its larval stage and causes extensive economic losses. In the fight against this species, environmentally friendly biological control methods should be preferred instead of chemical control. The aim of this study was to evaluate the efficacy of entomopathogenic fungi (EPF) Metarhizium brunneum (ORP-13) and Beauveria bassiana (GOPT-301-2) isolates against the fourth instar larvae of M. neustria under laboratory conditions. Results: M. neustria eggs were collected from the Kızılırmak Delta of Samsun Province, Turkey, and the fourth instar larvae were used in the experiment. Larvae in the control group were fed on sterilized leaves of Eleagnus rhamnoides. Both fungal isolates were applied onto the larvae at 2 ml for each concentration (1 × 10⁶, 1 × 10⁷, and 1 × 10⁸ conidia ml⁻¹). Ten larvae were placed in each group, and sterilized E. rhamnoides leaves were offered to the larvae. The study was carried out in 9 replicates for each group, and the larvae were observed for 14 days. As a result of the study, it was found that the survival rates of the larvae decreased as concentration increased. It was determined that both isolates caused 100% mortality at 1 × 10⁸ conidia ml⁻¹ concentration. The lowest LC₅₀ value was found in larvae exposed to the ORP-13 isolate. Conclusion: It has been suggested that M. brunneum and B. bassiana isolates were virulent for M. neustria larvae and can be used for biological control of this species.

In this study, the effects of various secondary metabolites in the economically important plants on the pupal weight, the pupal total protein and the pupal total lipid contents of Hyphantria cunea larvae infected by Bacillus thuringiensis subsp. kurstaki were investigated. In order to find out their effects on the larvae, the phenolic compounds present in Morus alba (mulberry), Malus pumila (apple), Prunus dometica (plum), and Juglans regia (walnut) leaves samples, which are the most preferred by H. cunea and have economic importance, were determined by phytochemical methods. The changes observed in the pupae’s weights, total protein and lipid contents were related to the plant leaves’ chemical contents. Among the non-infected groups, the mulberry-fed group had the highest both pupal weight and the pupal protein content. The minimum amount of gallotannin, as well as the catechin and rutin contents, was present in the mulberry leaves. The minimum pupal weight and the pupal protein contents were obtained in the larvae fed by the apple leaves with the highest rosmarinic acid and protocatechuic acid. The pupal weights and the pupal total protein contents were decreased by the bacterial infection, while the pupal total lipid contents increased by the bacterial infection. As a result of this study, the effects of both plant secondary metabolites experimentally used and B. thuringiensis infection on the pupal parameters of H. cunea were shown to be statistically significant.

The effects of copper, nickel, and zinc and the potent antioxidant gallic acid on the antioxidant enzyme activities of Hyphantria cunea larvae infected with Bacillus thuringiensis subsp. kurstaki have been identified in this study. With metal exposure, all the enzyme activities have increased. Antagonistic effects were observed in the combination of gallic acid with all three metals on the activities of superoxide dismutase and catalase. In glutathione peroxidase activity, an antagonistic effect was observed in gallic acid plus nickel group, while there was a synergistic effect for gallic acid plus zinc and gallic acid plus copper. Activities of these enzymes in larvae exposed only to the metals increased in the infected groups; while exposure to gallic acid alone elicited a decrease. As a consequence, it was found that enzyme activities were affected by both metals and gallic acid and infection.