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The spruce bark beetle, Ips typographus, is an invasive forest pest that occurs across Eurasia. To further understand the mechanism of insect–host chemical communication and the feeding choices of adult I. typographus, we examined the sensilla on the antennae and mouthparts of I. typographus using scanning electron microscopy. No sexual dimorphism in sensilla type or distribution was observed. Ten subtypes of antennal sensilla were identified: sensilla trichodea Types I–III (TR1, TR2, and TR3); sensilla chaetica Types I and II (CH1 and CH2); sensilla basiconica Types I–III (BA1, BA2, and BA3); sensilla coeloconica (CO); and Böhm sensilla (BS). BA2 were the most abundant among the antennal sensilla in both sexes. Thirteen mouthpart sensilla subtypes were observed: sensilla trichodea Types I–IV (TR1, TR2, TR3, and TR4); sensilla chaetica Types I–III (CH1, CH2, and CH3); sensilla digitiformia (DI); sensilla basiconica Types I–II (BA1 and BA2); and sensilla styloconica Types I–III (ST1, ST2, and ST3). Among these, TR4 were the most abundant in both sexes. The apex of each maxillary and labial palp carried the same sensilla (BA2, ST1, ST2, and ST3), although the apex of the maxillary palp contained more total sensilla. The functional roles of each sensilla type are discussed based on their external structure and distribution. The results provide a theoretical basis for further studies on the olfactory and feeding behaviors and electrophysiology of adult I. typographus.

Background Trunk-boring pests (TBPs) are an important type of forest pest, TBPs not only feed on the branches and trunks of trees, but also spread quarantine diseases in forests. However, because the larvae of TBPs live inside the trunk and are well concealed, prevention and control are difficult. The lack of effective control methods leads to the death of many trees in forests. In this study, a novel nanopesticide featuring high bioactivity and slow-release properties was developed to control TBPs. Thiacloprid (THI), which is commonly used to control Coleoptera species, was used as a model pesticide. Results The oleophobic properties of bovine serum albumin (BSA) were exploited to encapsulate the hydrophobic pesticide THI by self-assembly, and the size of the obtained nanoparticles, THI@BSA·NPs, was approximately 23 nm. The loading efficiency reached 70.4%, and THI@BSA·NPs could be released continuously for over 15 days, with the cumulative release reaching 93.5%. The fluorescein isothiocyanate (FITC)-labeled nanoparticles were evenly distributed in the digestive tract and body surface of a typical TBPs, M. alternatus, and the stomach and contact toxicities increased by 33.7% and 25.9%, respectively, compared with those of free THI. Furthermore, the results showed that the transport efficiency of THI@BSA·NPs was highest at a concentration of 50 μg/mL, and the THI@BSA·NPs content in the trunk, from to lower to higher layers, was 8.8, 8.2, 7.6, and 5.8 μg/g. At the same time, THI@BSA·NPs also exhibited high transport efficiency in dead trees. Conclusion The transport efficiency and toxicity of the active ingredients are the key factors for the control of TBPs. This work provided idea for the application of biological delivery system encapsulated hydrophobic pesticides. The novel self-assembled THI@BSA·NPs have promising potential for sustainable control of TBPs.

Pine wilt disease is a devastating forest disaster caused by Bursaphelenchus xylophilus, which has brought inestimable economic losses to the world’s forestry due to lack of effective prevention and control measures. In this paper, a porous structure CuBTC was designed to deliver avermectin (AM) and a control vector insect Japanese pine sawyer (JPS) of B. xylophilus, which can improve the biocompatibility, anti-photolysis and delivery efficacy of AM. The results illustrated the cumulative release of pH-dependent AM@CuBTC was up to 12 days (91.9%), and also effectively avoided photodegradation (pH 9.0, 120 h, retention 69.4%). From the traceable monitoring experiment, the AM@CuBTC easily penetrated the body wall of the JPS larvae and was transmitted to tissue cells though contact and diffusion. Furthermore, AM@CuBTC can effectively enhance the cytotoxicity and utilization of AM, which provides valuable research value for the application of typical plant-derived nerve agents in the prevention and control of forestry pests. AM@CuBTC as an environmentally friendly nanopesticide can efficiently deliver AM to the larval intestines where it is absorbed by the larvae. AM@CuBTC can be transmitted to the epidemic wood and dead wood at a low concentration (10 mg/L).

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