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[Objectives] To determine the role of nitrogen in the population explosion of the Asian corn borer, Ostrinia furnacalis (Guenee), we compared the effects of artificial diets with different nitrogen contents on food utilization by, and nutritional content of, this species. [Methods] Five artificial diets (N1, N2, N3, N4 and N5) with nitrogen contents of 3.94%, 7.33%, 10.69%, 18.84% and 30.31% were fed to 3rd, 4th and 5th-instar larvae, and differences in food utilization and larval nutritional indices between treatment groups were compared and analyzed. [Results] The highest food utilization rate (16.28% ± 0.89%) and food conversion rate (41.05% ± 4.07%) was recorded in 3rd instar larvae in the N3 treatment group, significantly higher than the corresponding values in the N4 and N5 treatment groups. The lowest food utilization and food conversion rate, 3.32% ± 0.57% and 2.36% ± 0.69%, respectively, were recorded in the N2 treatment group. The highest food utilization rate in 4th instar larvae, 22.13% ± 1.51%, was recorded in the N5 treatment group. 5th instar larvae in the N5 and N4 treatment groups had the highest food utilization and approximate digestibility; 24.29% ± 7.01% and 40.93% ± 2.94%, respectively, but dietary nitrogen had no significant effect on food conversion and relative growth rates (P > 0.05). The nitrogen use efficiency of 3rd, 4th and 5th-instar larvae all increased with dietary nitrogen content; the highest nitrogen use efficiencies for each instar (72.33%, 86.09% and 90.91%, respectively) were all recorded in the N5 treatment group. [Conclusion] Dietary nitrogen has a direct impact on food utilization by, and the nutritional indices of, Asian corn borer larvae, and dietary nitrogen significantly increased food use efficiency, relative feeding rate and nitrogen use efficiency of 4th-instar and 5th-instar larvae. [ABSTRACT FROM AUTHOR]

The occurrence of Bemisia tabaci poses an increasingly serious threat to cotton and vegetable crops in Xinjiang, China. Currently, neonicotinoid insecticides are commonly used to control the insect, to which resistance is inevitable due to intensive use. However, the resistance status and mechanism of B. tabaci to neonicotinoid insecticides in Xinjiang are poorly understood. Cytochrome P450 monooxygenases represent a key detoxification mechanism in the neonicotinoid resistance of B. tabaci. In this study, the resistance level to imidacloprid and thiamethoxam was investigated using the leaf dipping method in five field populations of B. tabaci from Turpan (TP, two sampling sites), Shache (SC), Hotan (HT) and Yining (YN) in northern and southern Xinjiang. The expression changes of eighteen cytochrome P450 genes from the select B. tabaci populations were determined by real‐time fluorescence quantitative PCR (qPCR). The bioassay revealed that the five populations tested had developed moderate to high levels of resistance to imidacloprid (12.26–46.07‐fold), while the populations remained sensitive to thiamethoxam except for HT, which had a low level of resistance. The qPCR results showed that the expression levels of five P450 genes, CYP4G68, CYP6CM1, CYP303A1‐like, CYP6DZ7 and CYP6DZ4, were significantly higher in some resistant field populations than in the susceptible strain. Resistance to imidacloprid in field populations of B. tabaci might be associated with the increased expression of these five cytochrome P450 genes. The results are useful for further understanding the mechanism of neonicotinoid resistance and will contribute to the management of insecticide‐resistant B. tabaci in Xinjiang. [ABSTRACT FROM AUTHOR]

Leptinotarsa decemlineata adults exhibit a season-dependent activity. In spring, post-diapause beetles often fly a long distance from overwintering sites to potato fields. In summer and autumn, the flight ability is sharply reduced. Proline is the main energy substrate of L. decemlineata during flight and proline dehydrogenase (ProDH) catalyzes the first step in proline catabolism. Here we identified a putative LdProDH gene; it had three cDNA isoforms which shared the same 5′UTR and coding region, but differed in the lengths of 3′UTRs (515, 1 092 and 1 242 bp for isoforms-1, -2 and -3, respectively). LdProDH encoded a 616 amino acid protein that showed high sequence similarity to ProDH-like proteins from other insect species. LdProDH was expressed in the third and fourth instars larvae and adults, but not in pupae. Dietary ingestion of bacterially expressed LdProDH-dsRNA by adults significantly decreased its messenger RNA (mRNA) level, and caused an elevation of free proline content in the hemolymph. Further observation revealed that three canonical polyadenylation signals (AATAAA) were tandemly located in the 3′UTR of isoform-3. The first, second and third polyadenylation sites gave rise to isoforms-1, -2 and -3, respectively. Analysis of the genomic DNA uncovered that the three isoforms resulted from alternative polyadenylation. The mRNA level of isoform-1, which expressed at low levels in pre-diapause adults, became abundant in post-diapause beetles. It is indicated that the LdProDH expression is fine-tuned through 3′UTR to control proline catabolism for the season-dependent activity of L. decemlineata adults. [ABSTRACT FROM AUTHOR]