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Diapause is an environmentally preprogrammed period of arrested development, and characterized by metabolic depression that can occur during any development stage of insect. The insect steroid hormone 20-hydroxyecdysone (20E), is converted from ecdysone by the cytochrome P450 enzyme shade (CYP314A1), and it exerts a potent effect on the induction and maintenance of diapause in obligatory diapause insects. However, the regulatory mechanism of 20E in obligatory diapause development remains unclear. In this study, the function of 20E in the pupal diapause of Bactrocera minax was investigated.We determined the expression pattern of Halloween P450 genes from larval to adult B. minax, and found differential expression of CYP314A1 from other P450 genes, with a high level in larvae and a low level in pupae. Dysfunction of CYP314A1 by dsCYP314A1 microinjection in third-instar larvae caused significant larval mortality or abnormal pupae. Compared with dsGFP and DEPC-water, dsCYP314A1-injected larvae had significantly reduced 20E titer and altered energy metabolism, and many individuals failed to pupate. Exogenous 20E microinjected into late third-instar larvae or 20E fed to early third-instar larvae both caused similar energy metabolism changes. The 20E-treated larvae of B. minax had reduced total lipids and increased amounts of trehalose and glycogen. Furthermore, 20E-treated diapause individuals showed rapid pupal development.The 20E biosynthesis was regulated by the expression of CYP314A1, and was involved in the induction and termination phase of obligate diapause by regulating energy metabolism in B. minax. © 2022 Society of Chemical Industry.

Mealybugs, such as Phenacoccus solenopsis, are highly sexually dimorphic. Winged adult males present such remarkable morphological differences from females that, to the untrained eye, conspecific adults of both sexes of P. solenopsis may be considered as two different insect species. A method to investigate sex-dimorphic mechanisms is by evaluating gene expression using RT-qPCR. However, the accuracy and consistency of this technique depend on the reference gene(s) selected. In this study, we analyzed the expression of 10 candidate reference genes in male and female P. solenopsis at different development stages, using common algorithms including the ΔCt method, NormFinder, geNorm, BestKeeper, and a web-based analysis tool, RefFinder. The results showed that EF1-β, RP-L32 and RP-18S were selected as the most stable genes by both the ΔCt method and NormFinder; TUB-α was the most stable gene identified by BestKeeper; and RP-L40 and RP-L32 were the most stable genes ranked by geNorm. RefFinder, a comprehensive analysis software, ranked the ten genes and determined EF1-β and RP-L32 as the most suitable reference genes for the various developmental stages in male and female P. solenopsis. Furthermore, the two most suitable reference genes were validated by examining expression of the juvenile hormone acid O-methytransferase (JHAMT) gene. Results of the validation portion of the study showed that JHAMT expression was sex-biased towards males and exhibited a dynamic and classic expression pattern among the P. solenopsis developmental stages. The results can help further our knowledge on the molecular mechanisms underlying sexual dimorphic development in P. solenopsis.

Phyllotreta striolata (Fabricius) is an important pest of Brassicaceae in Southeast Asia and North America. Using scanning electron microscopy, we observed the external structure, number, and distribution of the antennal sensilla in P. striolata females to discuss the putative function of these sensilla in host location and oviposition behaviors. The antenna of female P. striolata is filiform, composed of a scape, a pedicel, and a flagellum with 9 flagellomeres. Five types of sensilla were identified, including sensilla cheaetica, sensilla trichodea, Bohm bristles, sensilla auricillica, and sensilla basiconica (five subtypes, SB1-SB2). External structure and distribution of antennal sensilla are compared with data from other insect species. In addition, we discuss the possible functions of antennal sensilla based on their characteristics.

Organic materials in soils mainly consist of alkanes, esters, aromatic compounds and plant secondary metabolites, but they are different from one another in material type and quantity, depending on the types of slopes. This paper conducts a comparitive study on soils from slopes along the Suining-Chongqing Railway. Preparing soil samples from the rocky slope, the cultivated and uncultivated slopes by using ultrasonic methods, we measured the organic materials with a chromatograph mass spectrometer (QP2100). The results show that the number and types of organic materials decrease from the cultivated slopes to uncultivated slopes and then to rocky slopes. No contaminant appears in artificial soils on rocky slopes, but it is found in natural soils. Hence, it can be concluded that the reconstruction of soils on engineering slopes is beneficial not only for ecological restoration, but also for the prevention of pollution.

Understanding the relationship between fertilization and the incidence of insect pests is essential for the management of chemical fertilization and insect pests in modern agroecosystem. In this paper, effects of potassium supply alone and combination of nitrogen and potassium fertilizers on population dynamics and density of cotton aphid Aphis gossypii (Hemiptera: Aphididae) were investigated during seedling stage in Bacillus thuringiensis (Bt)-cotton production system. The results showed that high concentration of potassium fertilizer significantly reduced cotton aphid population density when nitrogen fertilizer was not used. Aphid population dynamics and density at peak time were obviously affected by the combination of nitrogen and potassium fertilizers in different rate, whereas different population dynamics of aphid were showed among different treatments. Compared with potassium fertilizer used alone, the same or significantly reduced aphid densities were observed in combination treatments of 120 kg/ha potassium with 108 kg/ha and 144 kg/ha nitrogen levels in both years. In addition, cotton aphid population density was significantly affected by interaction of nitrogen and potassium fertilizers in field experiments of two years, these results indicated that cotton aphid population density at seedling stage was suppressed by potassium fertilizer and the combination of potassium and nitrogen fertilizers in proper rate (K:N = 1:0.9 or 1:1.2 kg/ha). Suggesting that proper application of potassium and nitrogen fertilizers should be beneficial to controlling insect herbivores such as cotton aphid and plant growth at seedling stage of Bt-cotton field in Central China.

This paper studied the effects of planting different kinds of plant hedgerow (Amorpha fruticosa, Vetiveria zizanioides, Eulaliopsis binata, and Medicago sativa) on the population dynamics of wheat aphid and its natural enemies in the hillside wheat fields in Ziyang City of Sichuan Province, Southwest China. On the 20 degrees hillside, A. fruticosa hedgerow inhibited the occurrence of wheat aphid in the wheat field significantly, and the parasitoid densities were equal to or significantly lower than those in the wheat field with V. zizanioides hedgerow. On the 12 degrees hillside, M. sativa and E. binata hedgerows delayed the peak time of wheat aphid occurrence, and E. binata hedgerow suppressed the wheat aphid population density significantly. In the wheat field with M. sativa hedgerow, the parasitoid densities were significantly higher than those with no hedgerow. An equal or significantly higher ladybird density was observed in the field with M. sativa hedgerow. The olfactory responses showed that E. binata volatiles had repellent effect on both Sitobion avenae and Rhopalosiphum padi, but attracted a spider species of oxyopidae. M. sativa volatiles attracted S. avenae, whereas neither M. sativa nor E. binata volatiles caused obvious behavior response of ladybird adults. Therefore, planting A. fruticosa and E. binata as the hedgerows in hillside wheat fields could not only prevent the soil erosion from seasonal rainfall, but also benefit the control of pest insects.