Bactrocera minax, one of the most devastating citrus pests in Asia, has two developmental stages (mature larva and pupa) that complete their life cycle in the soil. Currently, southern China has a climate with abundant autumn rains, and soil moisture can be a major factor affecting the survival of larvae and pupae of B. minax. In the present study, we evaluated the effects of water immersion and high soil moisture content on the development of mature larvae and pupae of B. minax. When immersed in water for 1 d, 100% of mature larvae of B. minax were knocked out. When larvae were immersed for less than 6 d, however, more than 92% of knocked-out larvae recovered within 24 h. The days of water immersion with 50% and 90% recovery ratios (indicated as RD₅₀ and RD₉₀) were 10.3 d and 6.4 d, respectively. When larvae were immersed less than 6 d, the mortality ratios of larvae were not significantly different from those that were not immersed at all. The days of immersion causing 50% and 90% mortality of larvae (MD₅₀ and MD₉₀, respectively) were 7.6 d and 11.1 d, respectively. The pupation ratios of larvae were also observed to be not significantly different compared to non-immersion, and the days of immersion causing 50% and 90% pupation (PD₅₀ and PD₉₀, respectively) were 6.6 d and 0.8 d, respectively. Larval respiration rates were reduced after water immersion as a strategy for larval survival. High water content was not detrimental to pupae of B. minax. Adult emergence did not significantly decrease in soil with high water content, even though pupae were under those conditions for 161–175 d. The respiration rates of pupae were lower in soil with different moisture levels and were not significantly different, which ensured the survival of pupae in high water content. Reduced respiration rate is a strategy for survival of larvae and pupae, and remarkable tolerance to high moisture conditions could explain the high rate of spread and geographical distribution of B. minax. The results of this study provide a reference for the occurrence and control of B. minax.

The Jack Beardsley mealybug, Pseudococcus jackbeardsleyi Gimpel & Miller (Hemiptera: Pseudococcidae), a globally devastating, invasive polyphagous insect, causes great damage to many fruits, ornamentals, vegetables, and food crops worldwide. It is of Neotropical origin and has invaded throughout America and in parts of Asia, Africa and Oceania, and is still expanding its invasion ranges. Therefore, a method for quick and correct identification of this invasive species is crucial for quarantine and spreading interruption of it. In present study, we report the first record of P. jackbeardsleyi on the Chinese mainland, which would cause great damage to many crops. The identification of P. jackbeardsleyi was verified via morphological characters and DNA barcoding. One pair of species-specific polymerase chain reaction (SS-PCR) primers was designed based on variations in the sequences of the mitochondrial cytochromecoxidasesubunitI gene among P. jackbeardsleyi and 28 other mealybug species. No cross-reaction was detected among 21 closely related species using this SS-PCR assay, demonstrating the specificity of this marker. Furthermore, this method was successfully applied to detect individuals from different developmental stages and adult debris across four geographic populations of P. jackbeardsleyi, showing the high stability of the assay. Additionally, the detection limit of the marker was 55.94 ± 5.05 pg/µl of P. jackbeardsleyi DNA, illustrating the high sensitivity of the assay. The SS-PCR assay developed in this study provides a rapid, simple and reliable method for the identification of P. jackbeardsleyi, which should be crucial in the plant quarantine, early detection and sustainable management of this globally invasive pest.

The globally invasive cassava mealybug Phenacoccus manihoti Matile-Ferrero is a pernicious pest of cassava, and its recent introduction into Asia has raised considerable alarm. To slow or prevent further invasion, an accurate, simple, and developmental-stage-independent detection method for P. manihoti is required. In the present study, a PCR method based on a species-specific mitochondrial DNA cytochrome oxidase I (SS-COI) marker was developed for rapid identification of P. manihoti. One pair of SS-COI primers (PMSSZW-1F and PMSSZW-1R) was designed based on sequence variations in the COI gene among P. manihoti and related mealybug species. Specificity of the primer pair was validated on 21 closely related species. Sensitivity tests were performed on four immature developmental stages and female adults. Efficacy tests demonstrated that at the relatively low concentration of (135.2±14.7) pg μL⁻¹ resuspended DNA, the specific fragment was detected in all replicates. Furthermore, the SS-COI primer pair was assayed on three populations of P. manihoti from major exporting countries of cassava. The PCR assay was proved to be a rapid, simple, and reliable molecular measure for the identification of P. manihoti. This tool will be useful for quarantine, monitoring, and management of this invasive pest.