Agasicles hygrophila is a classical biological agent used to control alligator weed (Alternanthera philoxeroides). Previous research has indicated that the heat shock factor (HSF) is involved in regulating the transcriptional expression of Hsp70 in response to heat resistance in A. hygrophila. However, the regulatory mechanism by which AhHsf regulates the expression of AhHsp70 remains largely unknown. Here, we identified and cloned a 944 bp AhHsp70 promoter (AhHsp70p) region from A. hygrophila. Subsequent bioinformatics analysis revealed that the AhHsp70p sequence contains multiple functional elements and has a common TATA box approximately 30 bp upstream of the transcription start site, with transcription commencing at a purine base approximately 137 bp upstream of ATG. Promoter deletion analyses revealed that the sequence from −944 to −744 bp was the core regulatory region. A dual-luciferase reporter assay indicated that overexpressed AhHsf significantly enhanced the activity of AhHsp70p. Furthermore, qPCR showed that AhHsp70 expression increased with time in Spodoptera frugiperda (Sf9) cells, and AhHsf overexpression significantly upregulated AhHsp70 expression in vitro. Characterization of the upstream regulatory mechanisms demonstrated that AhHsf binds to upstream cis-acting elements in the promoter region of AhHsp70 from −944 to −744 bp to activate the AhHSF–AhHSP pathway at the transcriptional level to protect A. hygrophila from high temperature damage. Furthermore, we proposed a molecular model of AhHsf modulation of AhHsp70 transcription following heat shock in A. hygrophila. The findings of this study suggest that enhancing the heat tolerance of A. hygrophila by modulating the upstream pathways of the Hsp family can improve the biocontrol of A. philoxeroides.

Agasicles hygrophila Selman and Vogt is used in the biological control of the invasive weed Alternanthera philoxeroides (Mart.) Griseb. However, with the northward establishment of A. philoxeroides in China, the weak adaptivity of A. hygrophila to cold weather has resulted in the ineffective control of A. philoxeroides in northern China. Cold acclimation can significantly enhance insect cold tolerance, enabling them to cope with more frequent climate fluctuations. To improve the biological control efficacy of A. hygrophila in cold climates, we compared the effects of rapid cold hardening and acclimation on A. hygrophila under laboratory conditions. On initially transferring adults from 26 to −10 °C for 2 h, mortality reached 80%. However, when pre-exposed to 0 °C for 2 h and then transferred to −10 °C for 2 h, adult mortality was reduced to 36.67%. These findings indicate that cold acclimation can enhance the cold tolerance of A. hygrophila under laboratory conditions. However, the beneficial cold acclimation effects waned after more than 15 min of recovery at 26 °C. Exposure to 15 °C for 24 h or gradual cooling from 0 to −10 °C at 1 °C·min⁻¹ also induced cold acclimation, indicating that long-term cold and fluctuating cold acclimation are also potentially effective strategies for enhancing low-temperature tolerance.

Understanding the host-selection behavior of herbivorous insects is important to clarify their efficacy and safety as biocontrol agents. To explore the host-plant selection of the beetle Ophraella communa, a natural enemy of the alien invasive common ragweed (Ambrosia artemisiifolia), we conducted a series of outdoor choice experiments in cages in 2010 and in open fields in 2010 and 2011 to determine the preference of O. communa for A. artemisiifolia and three non-target plant species: sunflower (Helianthus annuus), cocklebur (Xanthium sibiricum), and giant ragweed (Ambrosia trifida). In the outdoor cage experiment, no eggs were found on sunflowers, and O. communa adults rapidly moved from sunflowers to the other three plant species. Instead, adults preferred to lay eggs on A. artemisiifolia, followed by X. sibiricum and A. trifida, although very few eggs were observed on A. trifida. Observing the host-plant selection of O. communa in an open sunflower field, we found that O. communa adults always chose A. artemisiifolia for feeding and egg laying. Although several adults (<0.02 adults/plant) stayed on H. annuus, no feeding or oviposition were observed, and adults quickly transferred to A. artemisiifolia. In 2010 and 2011, 3 egg masses (96 eggs) were observed on sunflowers, but they failed to hatch or develop into adults. In addition, some O. communa adults crossed the barrier formed by H. annuus to feed and oviposit on A. artemisiifolia planted in the periphery, and persisted in patches of different densities. Additionally, only 10% of O. communa adults chose to feed and oviposit on the X. sibiricum barrier. These findings suggest that O. communa poses no threat to the biosafety of H. anunuus and A. trifida and exhibits a robust dispersal capacity to find and feed on A. artemisiifolia. However, X. sibiricum has the potential to be an alternative host plant for O. communa.

Alternanthera philoxeroides (Amaranthaceae), commonly known as alligator weed, is a globally invasive and detrimental perennial weed. Agasicles hygrophila serves as an important biocontrol agent for alligator weeds. However, during mid-summer, when temperatures increase, A. hygrophila populations experience a significant decline, leading to ineffective weed control. This study has examined the impact of periodic heat events on the reproduction and survival of A. hygrophila females and males using various mating combinations and durations of temperature treatments. The results demonstrated significant effects on all of the studied parameters across mating combinations when compared with the control. Under the same temperature combination, the fecundity and survival rates of females, as well as the egg-hatching rate, decreased significantly with increasing repeated heat exposure. Furthermore, the egg-hatching rate varied significantly among different temperatures and time-interval combinations. In addition, the females displayed greater sensitivity to heat stress than males in terms of fecundity. These findings enhance our understanding of A. hygrophila population dynamics during summer and provide insights into the release of biocontrol agents in diverse regions with varying climates.

Venom-mediated systemic toxicity is not fully understood. This study explored the dose-dependent effects of Vespa mandarinia venom (VMV) on mice via integrated transcriptomic and metabolomic analyses. Subcutaneous VMV injection induced dose-dependent hypothermia: 80 μg caused severe transient hypothermia and partial mortality, while 40/60 μg led to reversible hypothermia within 24 h. Whole-blood sequencing identified 2400–3281 differentially expressed genes (DEGs) per group, including 1764 shared DEGs. Immune-related pathways were significantly activated, with hub genes validated by qRT-PCR. Serum metabolomics revealed alterations in organic acids, alkaloids, and other metabolites. Integrative transcriptome–metabolome analysis predicted the potential involvement of various pathways in VMV-induced toxicity, including ferroptosis (shared in low-dose VMV groups) and apoptosis. Cumulatively, this study confirms that VMV induces immunometabolic reprogramming, providing a molecular framework for understanding venom-induced systemic toxicity.

Agasicles hygrophila (Chrysomelidae) is a specialized biological control agent for the invasive alligatorweed, Alternanthera philoxeroides. In mid-summer in Changsha City, Hunan Province, rising temperatures caused a substantial decline in the local A. hygrophila population, resulting in ineffective weed control. However, the beetle continued to feed on A. philoxeroides during the same period in Wanning City, Hainan Province. We hypothesized that heat events are the key factors driving the differing fluctuations between the two geographic populations. In this study, we investigated the development, survival, and fecundity of these two geographic populations across multiple consecutive generations under periodic heat exposure. There were no significant differences in fecundity, developmental duration, or survival across three consecutive generations for both populations under periodic heatwave 33 °C (4 h) compared with the control 30 °C (4 h). Population development has remained robust in both cases. However, periodic heat stress at 36 °C (4 h) significantly impacted the development and fecundity of the Changsha population, including reduced female fecundity, prolonged developmental periods across all stages, and decreased survival rates, all adversely affecting population development. The Wanning population experienced a slight decline in female fecundity during the treatment. At 39 °C (4 h), all the F2 generation eggs of the Changsha population failed to hatch. The sex ratio was significantly skewed toward females. While the Wanning population produced F2 generation larvae, none of them developed to the pupal stage. Neither population completed F2 generation development. These findings elucidate the effect of heat stress on cumulative generational effects in both populations of A. hygrophila. They also suggested that the Wanning population might possess greater heat tolerance than the Changsha population, providing valuable insights into the adaptive strategies for insects and other organisms facing climate change.