Evaluation of tansy essential oil as a potential "green" alternative for gypsy moth control

Gut bacterial microbiota of Lymantria dispar asiatica and its involvement in Beauveria bassiana infection

The gut bacterial microbiota of insects has been shown to play essential roles in processes related to physiology, metabolism, and innate immunity. In this study, we firstly performed a broad analysis of the gut bacteria in Lymantria dispar asiatica, one of the most devastating forestry defoliators. We analyzed the bacterial composition among different individuals from lab-reared or wild-collected using 16 s rRNA-sequencing, revealing that the gut bacteria of wild-collected larvae were highly diverse, while lab-reared larvae were only associated with a few genera. We found Lactobacillus sp. present in all the gut samples, which indicates that it is part of the core microbiome in the caterpillar. Further Beauveria bassiana infection-based assays showed that the mortality of non-axenic L. dispar asiatica larvae was significantly higher than that of axenic larvae at 72 h. Moreover, we isolated several bacteria from the hemolymph of the non-axenic larvae infected by B. bassiana, which may be caused by the translocation of gut bacteria from the gut to the hemocoel. Reintroduction of Enterococcus sp., Pseudomonas sp., Enterobacter sp., and Microbacterium sp. into axenic larvae recurred the larval mortality in their non-axenic counterpart. Taken together, our study demonstrates that the gut bacteria of L. dispar asiatica are highly volatile, and different bacteria taxa can promote host infection by entomopathogenic fungus, providing a new strategy for the pest management.

Lymantria dispar (L.) (Lepidoptera: Erebidae): Current Status of Biology, Ecology, and Management in Europe with Notes from North America

The European Spongy moth, Lymantria dispar (L.) (Lepidoptera: Erebidae), is an abundant species found in oak woods in Central and Southern Europe, the Near East, and North Africa and is an important economic pest. It is a voracious eater and can completely defoliate entire trees; repeated severe defoliation can add to other stresses, such as weather extremes or human activities. Lymantria dispar is most destructive in its larval stage (caterpillars), stripping away foliage from a broad variety of trees (>500 species). Caterpillar infestation is an underestimated problem; medical literature reports that established populations of caterpillars may cause health problems to people and animals. Inflammatory reactions may occur in most individuals after exposure to setae, independent of previous exposure. Currently, chemical and mechanical methods, natural predators, and silvicultural practices are included for the control of this species. Various insecticides have been used for its control, often through aerial sprayings, which negatively affect biodiversity, frequently fail, and are inappropriate for urban/recreational areas. However, bioinsecticides based on various microorganisms (e.g., entomopathogenic viruses, bacteria, and fungi) as well as technologies such as mating disruption using sex pheromone traps have replaced insecticides for the management of L. dispar.

Potential of Essential Oils from Anise, Dill and Fennel Seeds for the Gypsy Moth Control

The gypsy moth (Lymantria dispar L. (Lepidoptera: Erebidae)) is a serious pest of hardwood forests. In the search for an environmentally safe means of its control, we assessed the impact of different concentrations of essential oils (EOs) from the seeds of three Apiaceae plants (anise Pimpinella anisum, dill Anethum graveolens, and fennel Foeniculum vulgare) on behavior, mortality, molting and nutritional physiology of gypsy moth larvae (GML). EOs efficacy was compared with commercial insecticide NeemAzal®-T/S (neem). The main compounds in the Eos were trans-anethole in anise; carvone, limonene, and α-phellandrene in dill; and trans-anethole and fenchone in fennel seed. At 1% EOs concentration, anise and fennel were better antifeedants and all three EOs were more toxic than neem. Neem was superior in delaying 2nd to 3rd larval molting. In the 4th instar, 0.5%, anise and fennel EOs decreased relative consumption rate more than neem, whereas all three EOs were more effective in reducing growth rate, approximate digestibility and efficiency of conversion of food into body mass leading to higher metabolic costs to GML. Decrease in consumption and metabolic parameters compared to control GML confirmed that adverse effects of the EOs stem from both pre- and post-ingestive mechanisms. The results indicate the potential of three EOs to be used for gypsy moth control.

Repellent activity of Tanacetum parthenium (L.) and Tanacetum vulgare (L.) essential oils against Leptinotarsa decemlineata (Say)

The Colorado potato beetle, Leptinotarsa decemlineata (Say), is one of the most destructive pest species to have developed resistance to most chemical insecticides. We determined the composition and evaluated the potential of Tanacetum parthenium L. and Tanacetum vulgare L. (Asteraceae family) essential oil (EO) application as an alternative eco-friendly control strategy against L. decemlineata. We assessed the antifeedant activity for L. decemlineata larvae and adults by estimating the damage to potato leaves treated with three concentrations of EOs dissolved in ethanol (0.125, 0.25 and 0.5%). Results showed that T. parthenium EO was more effective against larvae, and T. vulgare was more effective against adults. In an olfactometer assay, the time required to choose an untreated leaf disc did not depend on the Tanacetum species, or life stage examined. However, the concentration of EO exhibited a significant effect on the behaviour of both developmental stages. At higher EO concentrations, both third instar larvae and adults require less time to choose an untreated leaf disc. Additionally, T. parthenium EO provoked more rapid movement away from the treated leaf disc than T. vulgare, especially at the highest concentration. Successful modification of L. decemlineata behaviour by the two Tanacetum oils suggests that they possess the potential for use in potato protection.