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Introduction: Brown planthoppers (Nilaparvata lugens) are the most serious insect pests of rice, one of the world's most important staple crops. They reproduce year‐round in the tropical parts of their distribution, but cannot overwinter in the temperate areas where they occur, and invade seasonally from elsewhere. Decades of research have not revealed their source unambiguously. Methods and Results: We sequenced the genomes of brown planthopper populations from across temperate and tropical parts of their distribution and show that the Indochinese peninsula is the major source of migration into temperate China. The Philippines, once considered a key source, is not significant, with little evidence for their migration into China. We find support for immigration from the west of China contributing to these regional dynamics. Discussion: The lack of connectivity between the Philippine population and the mainland Chinese populations explains the different evolution of Imidacloprid resistance in these populations. This study highlights the promise of whole‐genome sequence data to understand migration when gene flow is high—a situation that has been difficult to resolve using traditional genetic markers. [ABSTRACT FROM AUTHOR]

BACKGROUND: Long‐term monitoring data is helpful to understand the fluctuation of susceptibility and pattern of cross resistance in insecticide resistance management. After the occurrence of imidacloprid resistance, the brown planthopper (BPH) has gradually developed resistance to thiamethoxam and clothianidin since 2010, but not to dinotefuran and nitenpyram. Here, we analyzed susceptibilities data of five neonicotinoids during 2005–2017 in East Asia and Vietnam to conduct cross‐resistance patterns among neonicotinoids. To determine the factors of development of cross resistance in laboratory bioassays, we used the imidacloprid resistant and control strains that were selected from filed populations in the Philippines and Vietnam. RESULTS: The Linear Mixed Models (LMM) analyses of insecticide susceptibility data showed that the slope values of imidacloprid resistance effects were 0.68 and 1.09 for resistance to thiamethoxam and clothianidin, respectively. Laboratory bioassay results showed that the LD50 values for thiamethoxam and clothianidin in resistant strains (1.4–5.5 μg g−1) were 3.2–16.4 times higher than those in the control strains (0.28–1.5 μg g−1). However, the increase in the LD50 values for imidacloprid was not related to that for dinotefuran and nitenpyram based on the results of the LMM analysis and laboratory bioassay. CONCLUSION: Our results demonstrate that the development of imidacloprid resistance result in strong‐cross resistance to some neonicotinoids, thiamethoxam and clothianidin, but not to others, dinotefuran and nitenpyram. We anticipate that our findings will be a starting point for understanding mechanism of the different trend of cross resistance by analyzing long‐term susceptibility data and laboratory bioassays in insect pests. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Rice hoppers can cause devastation to rice crops in SE Asia via disease spread and direct feeding. Current regulation is through pesticides; however, a more sustainable approach is to use the natural enemies of the hoppers. Here, we show how the combination of a process‐based model and field data can give insights into natural pest control, beyond those obtained through direct analysis of the field data.We use a stage‐structured host‐parasitoid model based on time‐delay ordinary differential equations (using the r package "stagePop"; Kettle & Nutter, 2015; Methods in Ecology and Evolution6:1484–1490) to investigate the interactions of four parasitoid genera and an egg predator on the eggs of two hopper hosts: the brown plant hopper (Nilaparvata lugens (Stål)) and the green leaf hopper (Nephottetix spp.).Model parameters are derived from 62 (×3) datasets from experiments in the Philippines. In these experiments, hopper eggs on rice plants were exposed in the field for 3 days and then taken back to the laboratory. The number of emerging hopper nymphs and parasitoid adults were then recorded. Single‐host and mixed host experiments were performed.The field data are not sufficient to fully constrain the model parameters so our results are given in terms of the value of an unknown parameter (γ; the number of hopper eggs killed per successful parasitism) which may be ascertained via future experiments.Synthesis and applications. Our model experiments suggest that although parasitoids are most likely the main control on hopper egg abundance, and despite the fact that the egg predator also consumes parasitoid eggs, the two‐enemy system (parasitoids and predators) is more effective at hopper egg control than if either enemy is present alone. Our results provide evidence in support of ecological engineering approaches that promote both parasitoids and egg predators. [ABSTRACT FROM AUTHOR]

BACKGROUND: Strong resistance to imidacloprid in Nilaparvata lugens (Stål) has developed in Southeast and East Asia. Although the mode of inheritance for resistance is very useful information for pest control, this information is unknown in N. lugens. Here, we established two resistant strains that were selected from field populations in Vietnam and the Philippines, and conducted crossing experiments to determine the inheritance pattern. RESULTS: The resistance ratio of 50% lethal dose (LD50) values for the two resistance‐selected strains, i.e., resistant strains originating from Vietnam (VT‐Res) and the Philippines (PH‐Res), to their control strains were ∼ 8‐ and 157‐fold, respectively. Reciprocal cross experiments between VT‐Res and the susceptible strain (S‐strain), and between PH‐Res and the S‐strain showed that the degree of dominance was 0.81 and 0.82, and 0.95 and 0.96, respectively. Analysis of the F2 populations and backcrosses to the parental strains indicated that resistance is a major‐gene trait following Mendelian inheritance. The strength of the resistance was suppressed by pre‐treatment with piperonyl butoxide, an inhibitor of cytochrome P450‐monooxygenases. CONCLUSION: Our results suggest that imidacloprid resistance in N. lugens is autosomal and an almost completely dominant major‐gene trait that is likely manifested by high expression levels of a detoxification enzyme. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

• The interannual and seasonal population dynamics of the two major rice planthoppers and their comigrating predator, the mirid, over the South China Sea using five consecutive years of searchlight trapping data. • Ovarian dissections revealed that most migrants were sexually immature. • Our trajectory simulations confirmed a new migratory route for these three species from the Indochina Peninsula into China through Hainan and into the Philippines. The mirid insect Cyrtorhinus lividipennis Reuter (Hemiptera: Miridae) is an economically and ecologically important enemy of insect pests of rice. Its comigration with its prey, two species of rice planthopper (RPH), is widely recognized, but has not been well characterized, especially in its year-round breeding region in Southeast Asia. In a 4-year trapping study of C. lividipennis and two types of RPH (Sogatella furcifera and Nilaparvata lugens) on an isolated island in the South China Sea, we obtained direct evidence that the mirid and its host RPHs were migrants and regularly comigrated across the sea from March to October every year; the peak period for the three species was from the late July to late August. Biomass of the mirid was significantly positively correlated with that of the two species of RPH in all migration periods. Moreover, the percentage of migrants was strongly female biased, and examination of ovaries indicated that almost all trapped females were virgins with little or no ovarian development, suggesting that most females that began the migration were sexually immature. Simulations of possible migration trajectories demonstrated that the three species mainly migrated between Indochina Peninsula and China (or the Philippines) in both directions. Collectively, these findings improve our understanding of the occurrence of the mirid and RPH across Southeast Asia and of the comigration of natural predators with their prey insects and will aid in developing more effective management strategies against RPH. [ABSTRACT FROM AUTHOR]

The article reports on the development of insecticide resistance to imidacloprid and fipronil. It mentions that in 2003, there were findings of brown planthopper (BPH) insecticide resistance to neonicotinoids in countries including Japan, China, and Vietnam. However, few studies have been done on insecticide resistance of BPH and whitebacked planthoppers (WBPH) to imidacloprid and fipronil. The article presents the results of studies on BPH and WBPH in countries including Japan, China, Vietnam, Taiwan, and the Philippines which showed species-specific insecticide resistance.

Migrations of the rice planthopper Nilaparvata lugens (Stål) (Delphacidae) from the Philippines to Taiwan, southern China, and southern Japan were analyzed using three-dimensional migration simulations. The results strongly suggested that the Southeast Asian population of N. lugens mixes with the East Asian population. This highlighted the possibility that planthoppers from the Southeast Asian population, which have properties different from those in the East Asian population such as feeding of resistant rice varieties and wing polymorphism, could migrate to Japan via southern China and Taiwan. This study, therefore, emphasizes the special care that should be taken to monitor the properties of immigrants to Japan. [ABSTRACT FROM AUTHOR]

Development of field resistance among Asian brown planthopper populations to insecticides contributes significantly towards the overall problem caused by the brown planthopper in rice production. We evaluated the susceptibility of brown planthoppers collected in the Philippines to the insecticides imidacloprid, fipronil and fenobucarb insecticides. Additionally we documented the changes in the populations' susceptibilities to the same insecticides when reared in insecticide-free environments. We found that brown planthopper populations collected in the Philippines between 2009 and 2010 were relatively susceptible to the tested insecticides when compared to historical data. Our findings provide baseline data for future studies. We also found that in populations characterized by high initial susceptibility to insecticides, the continued absence of insecticide selection pressure generally resulted in a slight decrease or no change in the populations' insecticide susceptibility. [ABSTRACT FROM AUTHOR]

Integrated biodiversity management aims to conserve the beneficial species components of production ecosystems and reduce the impacts of pests. In 2011 and 2013, experiments were conducted at Los Baños, Laguna, Philippines, to compare arthropod communities in rice plots and on levees with and without vegetation strips. Vegetation strips included spontaneous weeds, sesame and okra (2011), or mung bean (2013). The plots were treated with one of three nitrogen levels and in one experiment were planted with planthopper-resistant (IR62) and susceptible (IR64) rice varieties. Parasitoids and predators of lepidopteran pests and of the ricebug, Leptocorisa oratorius, were more abundant in high-nitrogen rice plots where their prey/hosts also had highest densities. Planthoppers and leafhoppers were more abundant in low-nitrogen plots. Weedy and sesame/okra bunds provided habitat for a range of natural enemies including spiders, parasitoids and predatory bugs, but did not have higher pest numbers than cleared bunds. Higher abundances of the predator Cythorhinuslividipennis and higher parasitism of planthopper (Nilaparvata lugens) eggs by Anagrus sp. were associated with sesame/okra bunds in late season rice plots. Mung bean also provided habitat for key predators and parasitoids that spilled over to adjacent rice; however, mung bean was also associated with higher numbers of lepidopteran and grain-sucking pests in the adjacent rice, albeit without increased damage to the rice. For ricebug in particular, damage was probably reduced by higher parasitoid:pest ratios adjacent to the vegetation strips. Varietal resistance and mung bean strips had an additive effect in reducing abundance of the planthopper Sogatella furcifera and the leafhopper Nephotettix virescens. Reduced numbers of these latter pests close to vegetation strips were often compensated for by other plant-sucking bugs, thereby increasing the intensity of potentially stabilizing interspecific interactions such as competition. We highlight the benefits of diversifying rice landscapes and the need to optimize vegetation strips, e.g., by including lepidopteran trap-plants, for intensive rice production systems. [ABSTRACT FROM AUTHOR]