Trichogramma dendrolimi is one of the most successfully industrialized Trichogramma species used to control agricultural and forestry pests in China. However, the molecular mechanisms underlying its host recognition and parasitism remain largely unknown, partially due to the limited genome information of this parasitoid wasp. Here, we present a high-quality de novo assembly of T. dendrolimi through a combination of Illumina and PacBio sequencing technologies. The final assembly had a length of 215.2 Mb and contains 316 scaffolds with a scaffold N50 size of 1.41 Mb. Repetitive sequences with a length of 63.4 Mb and 12,785 protein-coding genes were identified. Significantly expanded gene families were identified to be involved in the development and regulatory processes, while remarkably contracted gene families were involved in the transport processes in T. dendrolimi. The olfactory and venom-associated genes were identified in T. dendrolimi and 24 other hymenopteran species, using uniform methods combining BLAST and HMM profiling. The identified venom genes of T. dendrolimi were enriched in antioxidant activity, tricarboxylic acid cycle, response to oxidative stress and cell redox homeostasis. Our study provides an important resource for comparative genomics and functional studies to interpret the molecular mechanisms underlying host recognition and parasitism of Trichogramma species.

Trichogramma dendrolimi Matsumura is widely used as a biological control agent of many lepidopteran pests. Diapause has been used as an effective method to preserve the Trichogramma products during mass rearing production. However, it currently takes at least 70 days to break diapause, and we tested whether gradually increasing the temperature instead of using constant temperature could reduce the time of diapause termination and offer a higher flexibility to Trichogramma producers. The diapause termination rates of individuals kept at different conditions were measured, and five groups for which diapause termination rate reached the 95% were selected to test five biological parameters, including the number of eggs parasitized, the parasitism and emergence rates, the female sex ratio, the wing deformation rate, and the parasitoid longevity. Compared to the currently used procedure (70 days at 3 °C), treatments with at least two different temperatures resulted in higher parasitism and emergence rates while keeping the other parameters constant. The treatment that consisted of at least two different temperatures preceded by only 55 days of induction period had the highest population trend index, meaning that the population under these conditions grows more rapidly. Our results demonstrate that gradually increasing temperature allows T. dendrolimi to complete diapause earlier than at present while increasing its potential pest control capacity and providing additional flexibility in mass production of T. dendrolimi.

Trichogramma wasps, egg parasitoids widely used to control lepidopteran pests, have long eluded in-depth molecular mechanistic studies due to their minute size and genetic tool scarcity. While previous RNAi efforts were restricted to T. dendrolimi, we developed the first cross-species RNAi system for both T. dendrolimi and the previously intractable T. ostriniae. Temporal expression profiling identified white and laccase 2 as stage-specific RNAi targets, peaking during prepupal/pupal stages, which were tested across species and developmental stages using microinjection and soaking dsRNA delivery methods. Survival analysis prioritized soaking for T. dendrolimi prepupae/pupae, while microinjection was essential for T. ostriniae to bypass prepupal mortality during soaking. Concentration-dependent RNAi targeting the white gene achieved 85.61% transcript reduction in T. dendrolimi via soaking and 89.36% in T. ostriniae via microinjection at 2000 ng/μL, correlating with 64.06% and 32.09% white-eyed pupae, causing a significant reduction in eye pigments. For the laccase 2 gene, soaking at 2000 ng/μL induced 88.35% transcript reduction in T. dendrolimi and 73.31% in T. ostriniae, leading to incomplete cuticle tanning and sclerotization. This study resolves the long-standing challenge of genetic manipulation in Trichogramma wasps, providing a universally applicable framework to decipher parasitoid–host interactions at the molecular scale, which is useful for sustainable pest management strategies.

The application of insect pheromones for pest control aligns with the principles of plant protection and is crucial for sustainable production. In this study, a composite electrostatically spun fibre membrane with a core–shell structure was prepared using a coaxial electrostatic spinning technique, employing polystyrene (PS), polylactic acid (PLA), and the sex pheromone of Chilo suppressalis (SPCS) as raw materials. The results demonstrated that the surface morphology of the composite fibers mitigated the rapid release of the sex pheromone during the slow-release process, significantly enhancing its controlled release. Under optimal test conditions, the fiber diameter averaged 1.66 μm, the encapsulation rate of the Chilo suppressalis sex pheromone was 82.3% ± 1.2%, and the delayed release lasted approximately 14 weeks in laboratory conditions and 8 weeks in natural field conditions. FTIR analysis confirmed the binding of PS/PLA with the Chilo suppressalis sex pheromone, while TGA tests demonstrated excellent thermal stability. In field trapping tests for rice stem borers, the core–shell structured film exhibited a longer slow-release duration than commercial cores. This structure offers a more stable and effective design concept for insect pheromone carriers.

Phyllotreta striolata is a global pest of cruciferous vegetables, and controlling its soil-dwelling larvae is challenging. The lack of standardized larval bioassay methods hinders the screening of effective biocontrol agents. In this study, we established a stable and standardized laboratory-efficacy trial system for P. striolata larvae. Indoor rearing techniques were optimized for Brassica juncea var. foliosa and Brassica juncea var. megarrhiza were identified as the optimal host plants, with ideal oviposition conditions at 26–28 °C using black flannel substrate, and soil-cultured Brassica rapa var. pekinensis as the host plant. Based on these findings, a larval bioactivity assay was established using B. juncea var. megarrhiza slices on water-agar. This system maintained a natural larval mortality rate below 5% within 48 h, meeting the bioassay requirements. The reliability of the system was validated by evaluating the activity of the engineered Bacillus thuringiensis (Bt) strain G033A against larvae, where the LC₅₀ value decreased from 23.013 mg/mL to 7.295 mg/mL with an extended treatment time (12–48 h). Using this standardized method, novel Cry proteins with high activity against P. striolata larvae were screened. Cry8Ca and Cry8Ga proteins exhibited LC₅₀ values of 2.243 mg/mL and 1.649 mg/mL, respectively.