International audience

The South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is considered one of the most economically important invasive pests that causes severe damage to tomato crops. The biopesticide spinosad is widely used for controlling T. absoluta. This study aimed to investigate the spinosad-induced intergenerational sublethal effects on T. absoluta. Results showed that spinosad exhibited high toxicity against 3 rd instar T. absoluta with the LC 50 of 0.04 mg L -1 after 72 h exposure. The LC 10 and LC 30 of spinosad significantly decreased the durations of various developmental stages and some reproductive parameters of parental (F 0 ) T. absoluta compared to control. The developmental durations, survival rate, reproduction and life table parameters (intrinsic rate of increase, r; finite rate of increase, ; net reproductive rate, R 0 ; and oviposition days, O d ) were significantly decreased in the progeny generations (F 1 and F 2 ) following F 0 exposure to the LC 10 and LC 30 of spinosad as compared to the control group. Additionally, the mRNA expression levels of development and reproduction related genes such as Vg, VgR, and JHBP were down-regulated in parental and progeny generations at both spinosad treatments as compared to control treatment. The resistance related cytochrome P450 genes CYP321C40 and CYP6AW1, followed by CYP4M116, CYP9A307v2, CYP15C1, CYP339A1, and CYP6AB327 were up-regulated at spinosad-treated groups in the parental and progeny generations of T. absoluta as compared to control. Overall, these results showed that although spinosad exhibited high toxicity and induces intergenerational sublethal effects on the parental and progeny generations, the indiscriminate and long-term application might causes resistance development in of T. absoluta.

The European spruce bark beetle Ips typographus (L.) is a pest causing severe damage to Norway spruce-dominated forests in Europe. Microorganisms play an essential role in the species life history, including nutrition, fitness as well as in overcoming host defenses. Here, we performed high-throughput 16S rRNA metabarcoding of I. typographus across different populations in Europe. We investigated four postglacial refugial areas in Europe and focused specifically on a current bark beetle hot spot in the Dolomites where we compared populations with different epidemiological phases (outbreaking vs. non-outbreaking) and across different seasons (pre-overwintering vs. overwintering). Our results show that the bacterial community structure varied among populations from the refugial areas and geographic regions within the Dolomites. We found a significant difference in the bacterial community between preoverwintering and overwintering individuals, highlighting a potential role of the microbiome in I. typographus overwintering but we did not find differences between epidemic and endemic populations. The genera Erwinia and Pseudoxanthomonas -previously reported for their role in nutrition and protection from conifer defense compounds -were present in every individual across all populations, suggesting that these taxa form the bacterial core community of I. typographus. Furthermore, several additional bacterial taxa occurred in all populations, but with variable frequencies within and between individuals. This study highlights a complex interaction of various bacterial taxa across different regions and ecological phases of I. typographus populations and provides new insights into the role of microorganisms in the biology of this important pest species.

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