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Tuta absoluta (Meyrick) is a destructive pest of tomato crops. The cryptic nature of larvae often leads to low control efficacy. Sterile insect technique (SIT) has the potential to be an alternative management option for T. absoluta. In this study, the optimal dose for T. absoluta sterility was determined by estimating the effect of gamma radiation on parental generation (F0) and their descendants (first and second generation, F1 and F2). Adult emergence was not affected when T. absoluta pupae were exposed to gamma radiation at doses of 100~400 Gy. However, increasing doses of radiation increased deformed individuals and shortened their longevity. Furthermore, as the dose increased, F0 females showed decreased fecundity and fertility, and they were completely sterile when exposed to 300 Gy. The survival and sex ratio of females declined significantly in F1 of irradiated males with increasing doses. Moreover, we found that 300 Gy of gamma radiation did not affect the mating competitiveness of F0 males. Interestingly, this treatment caused a considerable reduction in the number of descendants and caused inherited sterility in F1 by lowering their fecundity and fertility. Therefore, the optimal radiation dose was 300 Gy, and the release of sterile adults may suppress T. absoluta population growth in the field. Our findings provide basis for controlling T. absoluta through SIT programs. [ABSTRACT FROM AUTHOR]

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 3rd instar T. absoluta with the LC50 of 0.04 mg L-1 after 72 h exposure. The LC10 and LC30 of spinosad significantly decreased the durations of various developmental stages and some reproductive parameters of parental (F0) T. absoluta compared to control. The developmental durations, survival rate, reproduction and life table parameters (intrinsic rate of increase, r; finite rate of increase, r; net reproductive rate, R0; and oviposition days, Od) were significantly decreased in the progeny generations (F1 and F2) following F0 exposure to the LC10 and LC30 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. [ABSTRACT FROM AUTHOR]

Climate change and global trade are two main drivers of shifts in the distribution of invasive insect pests. The Oriental fruit fly, Bactrocera dorsalis Hendel, is one of the most economically important invasive pests having detrimental effects on several vegetables and fruits. This highly invasive species originating from mainland Asia has now spread worldwide. The species has recently expanded its range northward into previously considered unsuitable areas such as Central China, which poses a significant new risk to agriculture in the temperate zone. In this study, we identified the limiting climatic conditions in the global distribution area. We combined MaxEnt and CLIMEX models to estimate the suitable areas of B. dorsalis under climate change scenarios. Moreover, the potential economic impact of B. dorsalis was predicted for citrus in China, with and without management practices, using the Monte Carlo simulation model. Results showed that current climatically suitable locations included parts of central and southern North America, north and east of South America, central Africa and Madagascar, east, south, and Southeast Asia, and northern Oceania. MaxEnt and CLIMEX predictions indicated that the suitable area of B. dorsalis would expand northward in North America and southward in South America under future climatic conditions. In China, the potential geographical distribution of B. dorsalis would expand northward into Henan, Shandong, and some parts of Hebei. Moreover, @RISK software analysis showed that B. dorsalis could cost the citrus industry in China 25.21 billion US dollars without management practices. These management measures would save 8.721 billion US dollars. These results provide in-depth information about the impact of climatic changes on the possible geographic range of B. dorsalis and its impact on the citrus industry in China. [ABSTRACT FROM AUTHOR]

Orius predators are important natural enemies of thrips, whiteflies and mites and are reared as commercial biological agents. Due to the importance of food sources in natural-enemy mass-rearing programs, researchers have been screening efficient food sources for the rearing of such enemies. In this study, we compared the demographic fitness of Orius strigicollis reared on 3 foods (i) frozen 48h-old eggs (FE) of Spodoptera frugiperda, (ii) frozen 24h-old 2nd instar larvae (FL) of S. frugiperda, and (iii) 2nd instar larvae of Frankliniella occidentalis (western flower thrips, WFT) using the age-stage, two-sex life table. According to the life table analysis results, O. strigicollis were successfully maintained on FL for consecutive generations, and the reproductive performance of individuals from the 1st (G1) and 6th (G6) generations was evaluated. Among the 3 tested foods, FE was the lowest suitable food, leading to slower development and lower O. strigicollis fecundity than with other foods. In overall, O. strigicollis showed similar fitness when reared on WFT and on FL (no difference in fecundity), although the intrinsic rate of increase (r) and finite rate of increase (λ) was lower on FL. The fecundity and longevity of G6 O. strigicollis reared on FL were not significantly different from those of G1. The results indicate that frozen S. frugiperda larvae could be a promising factitious food for the long-term rearing of O. strigicollis and more broadly that frozen larvae of Lepidoptera may be potential new factitious food sources for Orius spp. rearing. [ABSTRACT FROM AUTHOR]

Climate change generally influences all the living world, including insects, so all organisms cope with these stresses to survive. Temperature rise leads to increased insect pest severity, while cold acclimation helps insects to survive in temperate areas in several complex ways. The Oriental fruit fly, Bactrocera dorsalis, is one of the most economically important invasive pests of fruits and vegetables worldwide. In this study, we investigated the effect of low (LT: 3 °C) and high (HT: 38 °C) temperature stress on key biological and population parameters of B. dorsalis using an age-stage, two-sex life table approach. The results showed that the mean developmental duration of the larval stage was significantly prolonged in both HT (6.82 d) and LT (7.80 d) compared to the untreated group (6.33 d). The developmental duration of pre-adult stage was substantially increased when treated with LT (19.57 d) and HT (18.03 d) as compared to control insects (17.51 d). Compared to the control, the mean longevity of male and female flies was significantly prolonged in both LT and HT treatments. The adult pre-oviposition period (APOP), total pre-oviposition period (TPOP), and oviposition days of B. dorsalis were increased under both temperature stress conditions. The number of eggs per female was also significantly higher in LT (869.70 eggs) and HT treatments (846.90 eggs) compared to control (684.56 eggs). Furthermore, the total population size of B. dorsalis was highest in HT treatment followed by LT compared to control after 100 d. This study reveals that temperature stresses at larval stage increased the reproduction, development, and life span of B. dorsalis, these altered biological traits during the heatwave and cold conditions could have significant agricultural impacts. [ABSTRACT FROM AUTHOR]

Ecdysone receptor (EcR) plays important roles in molting, metamorphosis, and reproduction of insects. EcR ortholog and its function in melon aphid Aphis gossypii have not been documented yet. RNA interference (RNAi) is a reverse-genetic approach used to study functional genomics, but recently, it has also shown promise as a novel tool that could be used to control insect pests. In this study, reverse transcription-PCR (RT-PCR), quantitative real-time PCR (qPCR), RNAi, and bioassays were employed to isolate EcR gene and investigate its knock-down effects on aphids. The lethal and sublethal effects were also studied after silencing the EcR gene. The results showed that EcR gene is highly expressed (P < 0.006) in 2nd nymphal stage of A. gossypii while expression was statistically lower in all other developmental stages. Knock-down of EcR gene caused up to 43 and 68% mortality in 2nd instar nymphs after feeding dsEcR for 48 and 72 h, respectively, compared to the control. Moreover, RNAi-induced silencing of EcR gene caused sublethal effects on surviving aphids. Significantly lower longevity (about 42%) and fecundity (about 44.22%) were observed in insects fed with dsEcR solution at their nymphal stage. Analysis of gene expression showed that the mortality rates and the lowered longevity and fecundity were attributable to the down-regulation of EcR gene by RNA interference technology. Taken together, our results demonstrate that EcR is an essential gene for aphid growth and development and could be a potential target gene for the development of an RNAi-based bio-aphicide. [ABSTRACT FROM AUTHOR]

Cytochrome P450s (CYPs) genes are associated with insecticide resistance through overexpression and detoxifi- cation mechanisms in several insect-pest species. However, little is known about the role of P450s genes and their response to clothianidin resistance development in cotton-melon aphid, Aphis gossypii, a serious crop pest. In this study, we characterized CYP6CY14 and CYP6DC1 from CYP3 clad that are differentially expressed in aphids. Quantitative real-time PCR (qRT-PCR) analyses revealed that CYP6CY14 and CYP6DC1 expressions were significantly higher among thirty five cytochrome P450 genes in clothianidin-resistant strain (CT-R) of A. gossypii compared to the susceptible strain (CT-S). RNAi was conducted to knock-down the highly expressed CYPs genes (CYP6CY14 and CYP6DC1 from CYP3 clad) and study their detoxification effects on clothianidin. The apterous adult aphids became more sensitive to clothianidin, with a higher mortality rate than the control after silencing CYP6CY14 and CYP6DC1 genes. Bioinformatic analysis showed conserved motifs in amino acid sequences of CYP6CY14 and CYP6DC1 with other insect species. This study highlighted the functional importance of these P450 genes in insecticide resistance development and revealed that overexpression of CYP6CY14 and CYP6DC1 genes was responsible for the high levels of insecticide resistance in the A. gossypii population. [ABSTRACT FROM AUTHOR]