Insecticide-mediated changes in the population and toxicity of the thrips species, Frankliniella occidentalis (Pergande) and Thrips flavus (Schrank) (Thysanoptera: Thripidae).

Frankliniella occidentalis (Pergande) and Thrips flavus (Schrank) (Thysanoptera: Thripidae) cause considerable damage to agricultural crops. In this study, we investigated the variations in the population density of these 2 thrips species in 2 sites (Dabai and Heilongtan) with different insecticide application levels. Bioassays were performed to determine the susceptibility of both thrips species to imidacloprid, abamectin, and high-bromine cyhalothrin in summer. The results showed that the F. occidentalis species were more abundant in Dabai than in Heilongtan during both winter and summer. The proportions of F. occidentalis in winter and summer were 28.32-43.35% and 61.79-76.02%, respectively. Moreover, F. occidentalis resistance against the 3 insecticides was significantly higher than that of T. flavus in both 2017 and 2019. Compared with 2017, the LC50 values of F. occidentalis populations in Dabai to imidacloprid, abamectin, and lambda-cyhalothrin increased to 100.076, 16.52, and 130.44 mg/liter, respectively. The number of F. occidentalis, reaching the proportion of 91.63% in 90 days, was significantly higher than that of the control after imidacloprid treatment. In conclusion, thrips interspecies competition is affected by the irrational use of insecticides, which may cause the replacement of native species by invasive species, thereby leading to an outbreak.

Effects of different host plants on the growth, development, and fecundity of Phthorimaea absoluta (Lepidoptera: Gelechiidae): an evaluation based on the age-stage two-sex life table.

This study aimed to investigate the growth and development parameters of Phthorimaea absoluta (Meyrick) population at each stage when feeding on 4 host plants: Lycopersicon esculentum, Solanum tuberosum, Solanum melongena, and Nicotiana tabacum. The objective was to predict population dynamics and develop appropriate control strategies. The age-stage sex-life table was used to evaluate survival rate, fecundity, life expectancy, reproductive value, population parameters, and population growth prediction of P. absoluta after feeding on the 4 Solanaceae plants. The results showed significant variations in the fecundity parameters of P. absoluta among the different host plants. The L. esculentum population exhibited the highest average egg-laying period (13.17 ±â€…0.61 days) and average egg production (219.31 ±â€…21.02 eggs), while N. tabacum had the lowest values (4.56 ±â€…0.26 days and 26.08 ±â€…2.53 eggs, respectively). The gross reproduction rate of P. absoluta feeding on L. esculentum was 146.43 ±â€…21.00, which was 1.80, 3.77, and 6.39 times higher compared to S. tuberosum, S. melongena, and N. tabacum, respectively. The average age period and population doubling time of P. absoluta feeding on L. esculentum were lower than those of the other 3 host plants. These results indicated that while P. absoluta can complete a generation on L. esculentum, S. tuberosum, S. melongena, and N. tabacum, L. esculentum is the most suitable host for its growth and development. Therefore, in the occurrence and adjacent areas of P. absoluta, relevant authorities should promptly monitor and control its population in the planting areas of Solanaceae plants to prevent further spread.

Population Numbers and Physiological Response of an Invasive and Native Thrip Species Following Repeated Exposure to Imidacloprid.

Frankliniella occidentalis and F. intonsa are devastating pest insects that target Rosa rugosa, Chrysanthemum morifolium, and Phaseolus vulgaris, which are important economical horticultural plants in China. Meanwhile, R. rugosa and C. morifolium are important cash plants in Kunming, South China. We focus on the population performance of these two thrips species on these three host plants with or without repeated exposure to imidacloprid in Kunming. In the field, the population numbers of F. occidentalis developed faster and were larger on these three sampled host plants, especially under imidacloprid exposure, compared with F. intonsa. The activity of the detoxifying enzymes (CarE, AchE, and MFO) and the antioxidant enzymes (CAT and POD) in both thrips species were significantly enhanced under imidacloprid exposure, whereas the activities of SOD in both thrips were significantly decreased on these three host plants, compared with the control. Overall, enzyme activity of F. occidentalis showed a greater increase than that observed in F. intonsa in most cases, which could be exploited in further studies on thrips resistance management.