Lugens Adults Research Articles

Resistance Monitoring of Nilaparvata lugens to Pymetrozine Based on Reproductive Behavior

On the basis of the inhibition effects of pymetrozine on the reproductive behavior of N. lugens, we established a bioassay method to accurately evaluate the toxicity of pymetrozine in N. lugens and clarified the level of pymetrozine resistance of N. lugens in the field. In this study, pymetrozine's effects on the fecundity of N. lugens were evaluated using the topical application method and rice-seedling-dipping method. Moreover, the resistance of N. lugens to pymetrozine in a pymetrozine-resistant strain (Pym-R) and two field populations (YZ21 and QS21) was determined using the rice-seedling-dipping method and fecundity assay methods. The results showed that treatment of N. lugens third-instar nymphs with LC15, LC50, and LC85 doses of pymetrozine resulted in a significantly reduced fecundity of N. lugens. In addition, N. lugens adults treated with pymetrozine, using the rice-seedling-dipping and topical application method, also exhibited a significantly inhibited fecundity. Using the rice-stem-dipping method, pymetrozine resistance levels were shown to be high in Pym-R (194.6-fold), YZ21 (205.9-fold), and QS21 (212.8-fold), with LC50 values of 522.520 mg/L (Pym-R), 552.962 mg/L (YZ21), and 571.315 (QS21) mg/L. However, when using the rice-seedling-dipping or topical application fecundity assay method, Pym-R (EC50: 14.370 mg/L, RR = 12.4-fold; ED50: 0.560 ng/adult, RR = 10.8-fold), YZ21 (EC50: 12.890 mg/L, RR = 11.2-fold; ED50: 0.280 ng/adult; RR = 5.4-fold), and QS21 (EC50: 13.700 mg/L, RR = 11.9-fold) exhibited moderate or low levels of resistance to pymetrozine. Our studies show that pymetrozine can significantly inhibit the fecundity of N. lugens. The fecundity assay results showed that N. lugens only developed low to moderate levels of resistance to pymetrozine, indicating that pymetrozine can still achieve effective control on the next generation of N. lugens populations.

Toxicity of water pepper, Persicaria hydropiper (L.) extracts against Nilaparvata lugens (Stål) and non-targeted effect on earthworm

Nilaparvata lugens is a monophagous pest of rice crop. Various strategies have been employed to manage this pest. We evaluated the toxicity of Persicaria hydropiper (L.) leaf extracts against N. lugens along with chemical insecticide, imidacloprid. P. hydropiper leaf extracts produced significant mortality against N. lugens nymphal and adult stages in a dose dependent manner. Different concentration of P. hydropiper extracts with two controls (acetone and water) in toxicity assay revealed LC50 values of 620 ppm against N. lugens adults, whereas 230 and 130 ppm for larger and smaller nymphs, respectively. Imidaloprid yielded an LC50 of 510–560 ppm against nymphs and adults. Nine vital compounds were identified from the P. hydropiper extracts based on gas chromatography-mass spectrometry analysis (GC-MS). Additionally, P. hydropiper extracts was found harmless to non-target organism, as they did not produce any toxicity on earthworm, Eisenia foetida. Hence, present results indicated that P. hydropiper extracts can be used as efficient alternate to synthetic insecticides against N. lugens in rice.

The endophytic bacterial entomopathogen Serratia marcescens promotes plant growth and improves resistance against Nilaparvata lugens in rice

Entomopathogenic bacteria are commonly used as biological agents to control different insect pests. However, little is known about the role of bacterial entomopathogens as endophytes in regulating both plant growth and resistance against insect pests. Here, we applied the entomopathogenic bacterium Serratia marcescens S-JS1 via rice seed inoculation and evaluated its effects on host plant growth and resistance against the rice pest Nilaparvata lugens. Furthermore, the induction of defense-related secondary metabolites by the bacterium was assessed by GC–MS/MS. We showed that S-JS1 was able to endophytically colonize the roots and shoots of rice seedlings following seed inoculation. Colonized plants showed increased seed germination (9.4–13.3 %), root (8.2–36.4 %) and shoot lengths (4.1–22.3 %), and root (26.7–69.3 %) and shoot fresh weights (19.0–49.0 %) compared to plants without inoculation. We also identified the production of indole-3-acetic acid by S-JS1, which is likely involved in enhancing rice plant growth. In a two-choice test, N. lugens adults preferred to feed on untreated control plants than on plants treated with S-JS1. In the no-choice feeding tests, the survival of N. lugens nymphs that fed on S-JS1-treated plants was significantly lower than that of nymphs that fed on untreated plants. Additionally, seeds treated with 109 cfu/mL S-JS1 resulted in elevated levels of secondary metabolites, which may be associated with N. lugens resistance in rice plants. Therefore, we suggest that the entomopathogenic bacterium S. marcescens be considered a potentially promising endophyte for use in an innovative strategy for the integrated management of insect pests.

Greenhouse and field evaluation of essential oil formulations on Nilaparvata lugens Stal and their natural enemies

Citronella and clove (CiC) and lemongrass and clove (LeC) mixtures, each at the ratio of 1:1, citronella, lemongrass, and clove oils and solution without EOs (blank) were tested. To determine the effect of the EOs on oviposition deterrent and mortality of N. lugens adults, the rice plants were sprayed with each solution, allowed to dry, then the seedling was kept by a plastic cage that had the top part covered with perforated cloth. Three pairs of N. lugens adults were introduced into the cage. The observation was conducted on the number of eggs laid and the mortality of adults. An experiment on the mortality of nymphs was carried out by spraying the rice seedlings containing 10 nymphs and caged as above. The field experiment was conducted by spraying the rice plants with those solutions. The formulas of CiC and LeC at the concentration of 10 ml/L deterred oviposition of N. lugens by 64.6 and 57.4% respectively. Both EOs caused mortalities in adults at 43.3% and nymphs of N. lugens as much as 60-64%. Those formulas applied twice a week were effective to control N. lugens with the value of efficacy 70.2 and 50.4% respectively and safe to natural enemies in the field.

N-glycosylation Site Analysis Reveals Sex-related Differences in Protein N-glycosylation in the Rice Brown Planthopper (Nilaparvata lugens)

Glycosylation is a common modification of proteins and critical for a wide range of biological processes. Differences in protein glycosylation between sexes have already been observed in humans, nematodes and trematodes, and have recently also been reported in the rice pest insect Nilaparvata lugens Although protein N-glycosylation in insects is nowadays of high interest because of its potential for exploitation in pest control strategies, the functionality of differential N-glycosylation between sexes is yet unknown. In this study, therefore, the occurrence and role of sex-related protein N-glycosylation in insects were examined. A comprehensive investigation of the N-glycosylation sites from the adult stages of N. lugens was conducted, allowing a qualitative and quantitative comparison between sexes at the glycopeptide level. N-glycopeptide enrichment via lectin capturing using the high mannose/paucimannose-binding lectin Concanavalin A, or the Rhizoctonia solani agglutinin which interacts with complex N-glycans, resulted in the identification of over 1300 N-glycosylation sites derived from over 600 glycoproteins. Comparison of these N-glycopeptides revealed striking differences in protein N-glycosylation between sexes. Male- and female-specific N-glycosylation sites were identified, and some of these sex-specific N-glycosylation sites were shown to be derived from proteins with a putative role in insect reproduction. In addition, differential glycan composition between males and females was observed for proteins shared across sexes. Both lectin blotting experiments as well as transcript expression analyses with complete insects and insect tissues confirmed the observed differences in N-glycosylation of proteins between sexes. In conclusion, this study provides further evidence for protein N-glycosylation to be sex-related in insects. Furthermore, original data on N-glycosylation sites of N. lugens adults are presented, providing novel insights into planthopper's biology and information for future biological pest control strategies.

Efficacy of Entomopathogenic Fungi Against Brown Planthopper Nilaparvata Lugens (Stål) (Homoptera: Delphacidae) Under Controlled Conditions

The current study was conducted to evaluate the efficacy of entomopathogenic fungi (EPF) as an alternative strategy for the sustainable control of Nilaparvata lugens. Three species of EPF, Beauveria bassiana, Metarhizium anisopliae and Lecanicillium lecanii, were tested against N. lugens with two suspensions of each tested EPF applied in different treatments. The observed mortality of N. lugens adults during the overall exposure period for the lowest and highest concentrations of each EPF ranged from 0–100%. At both highest and lowest concentrations of EPF, when sprayed on adult, the mortality of N. lugens was higher as compared to when sprayed on the stem pieces as food. A higher mortality rate was observed when the stem pieces were absent than when stem pieces were present. Maximum percent mortality of N. lugens was recorded due to the spray of highest concentration of M. anisopliae on only stem pieces (82.67%) and on adult N. lugens provided with stem pieces as food (93.33%) after 14 days of exposure interval. On the other hand, B. bassiana and L. lecanii were also responsible to cause more than 50% mortality of N. lugens in both treatments after 14 days of exposure interval. Results also indicated that maximum and minimum percent mycosis and sporulation from dead cadavers of N. lugens were recorded in both conidial suspensions of L. lecanii and M. anisopliae, respectively, in all treatments. The high efficacy levels recorded in the current study indicates that M. anisopliae can be effective biological control agents against N. lugens.

The role of chemosensory protein 10 in the detection of behaviorally active compounds in brown planthopper, Nilaparvata lugens.

Chemosensory proteins (CSPs) play important roles in insects' chemoreception, although their specific functional roles have not been fully elucidated. In this study, we conducted the developmental expression patterns and competitive binding assay as well as knock-down assay by RNA interference both in vitro and in vivo to reveal the function of NlugCSP10 from the brown planthopper (BPH), Nilaparvata lugens (Stål), a major pest in rice plants. The results showed that NlugCSP10 messenger RNA was significantly higher in males than in females and correlated to gender, development and wing forms. The fluorescence binding assays revealed that NlugCSP10 exhibited the highest binding affinity with cis-3-hexenyl acetate, eicosane, and (+)-β-pinene. Behavioral assay revealed that eicosane displayed attractant activity, while cis-3-hexenyl acetate, similar to (+)-β-pinene significantly repelled N. lugens adults. Silencing of NlugCSP10, which is responsible for cis-3-hexenyl acetate binding, significantly disrupted cis-3-hexenyl acetate communication. Overall, findings of the present study showed that NlugCSP10 could selectively interrelate with numerous volatiles emitted from host plants and these ligands could be designated to develop slow-release mediators that attract/repel N. lugens and subsequently improve the exploration of plans to control this insect pest.

Characterization of heat shock protein 70 transcript from Nilaparvata lugens (Stål): Its response to temperature and insecticide stresses

The brown planthopper, Nilaparvata lugens, possesses a strong adaptability to extreme temperature and insecticide stresses. Heat shock proteins (Hsps) are highly conserved molecular chaperones and play a pivotal role in response to various environmental stresses in insects. However, little is known about the response of Hsps to stresses in N. lugens. In the present study, an inducible Hsp70 (NlHsp70) was isolated from this insect and transcriptional expression patterns of NlHsp70 under temperature and insecticide stresses were analyzed. The full-length of NlHsp70 was 2805bp with an open reading frame (ORF) of 1896bp, showing high homology to its counterparts in other species. Expression of NlHsp70 was not altered by heat shock for 1h, nor following recovery from thermal stress. Conversely, decreased expression of NlHsp70 was observed in response to cold shock. In addition, the expression of NlHsp70 increased after imidacloprid exposure. RNA interference experiment combined with insecticide injury assay also demonstrated that NlHsp70 was essential for resistance against insecticide exposure. These observations indicated that NlHsp70 was an important gene involved in the resistance or tolerance to environmental stresses in N. lugens. Interestingly, weak changes in mRNA expression levels of two thermal-inducible Hsp genes, NlHsp90 and NlHsc70 were observed in imidacloprid-exposed N. lugens adults, suggesting that different Hsps may respond differential to the extreme temperature and insecticide stresses.

Effects of exogenous plant growth regulator abscisic acid-induced resistance in rice on the expression of vitellogenin mRNA in Nilaparvata lugens (Hemiptera: Delphacidae) adult females.

Recent study showed that exogenous abscisic acid (ABA) acts as a regulator of plant resistance. This study investigated average injury scale and callose contents of rice, and vitellogenin ( Nlvg ) mRNA expression in Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) adult females after third instar nymphs fed on exogenous ABA-treated susceptible [Taichung Native one (TN1)] and moderately resistant (IR42) rice cultivars. The results showed that exogenous ABA significantly decreased average injury scale of rice and Nlvg mRNA expression in N. lugens adults compared with the control (without ABA spraying). Nlvg mRNA expression in N. lugens adults decreased significantly after third instar nymphs fed on ABA-treated (5, 20, and 40 mg/liter) TN1 for 1 and 2 d, and for IR42, after fed on ABA-treated (20 and 40 mg/liter) rice plants for 1 d and after fed on ABA-treated (5, 20, and 40 mg/liter) rice for 2 d decreased significantly. The callose contents showed no significant change for TN1, while for IR42, significantly increased in roots and sheathes after N. lugens infestation under ABA treatments (20 and 40 mg/liter) compared with the control. The decrease of Nlvg mRNA expression may be partially attributed to the increase of callose content of plants. The results provide a profile for concerning the effects of ABA-induced rice plants’ defenses on phloem-feeding insects.

The role of ants, especially the fire ant, Solenopsis geminata (Hymenoptera: Formicidae), in the biological control of tropical upland rice pests.

Predatory ants are omnipresent year-round in upland (dryland) rice fields in the Philippines. At least 14 species were identified of which the very aggressive Solenopsis geminata (Fabricius) and also Tapinoma sp. nr indicum Forel usually predominated. Some highly aggressive species, notably Pheidolegetonspp. and Bothriomyrmex dalyi Forel were localized. Solenopsis geminata flourished within many fields, not only during the crop season but also throughout dry season fallows where they remained aggressively predatory. Rice plants infested with brown planthopper Nilaparvata lugens (Stål) were usually found within a few hours and S. geminata workers were quickly recruited to N. lugens aggregates. Predation was usually incomplete and workers began to solicit the few remaining late instar or adult N. lugens survivors. These oviposited but no second generation nymphs appeared. There was a surge of recruited ants at the time of N. lugens egg hatch when surviving adults were also killed. Initially, S. geminataalone killed N. lugens aggregates less quickly than with the whole predator complex but ultimately its sole effect was as great as that of the complex. Scattered N. lugens adults, corresponding to numbers that initially colonize rice plants, were eliminated as quickly by S. geminata alone as by the predator complex. Tapinoma indicum occurring separately or with S. geminataon the same plant contributed to predation of N. lugens especially on young nymphs. Solenopsis geminataattacked other insects on rice notably leaffolders of which 97% mortality was recorded when they were exposed throughout egg and larval stages. The role of S. geminataas a predator of upland rice pests is discussed in the context of known biological control of pests of non-rice dryland crops in the tropics and sub-tropics by S. geminata and other Solenopsis spp.

Seasonal abundance of macropterous Nilaparvata lugens and Sogatella furcifera based on presumptive macroptery in fifth‐instar nymphs

Abstract. 1. The seasonal changes in abundance of macropterous N. lugens (Stal) and S. furcifera (Horvath) (Homoptera: Delphacidae) are described based on observed numbers of adults and presumptive macroptery in fifth‐instar nymphs occurring in rice crops in the Philippines.2. Percentage presumptive macroptery in fifth‐instar nymphs was correlated with nymphal density over the range of 0–20 nymphs per hill for females of both species and 5–20 nymphs per hill for male N. lugens.3. Lunar phase had no effect on wingmorph expression in either species.4. Comparison of the percentage macroptery in fifth‐instar nymphs with subsequent percentage macroptery in N. lugens adults for one season showed net emigration occurred from 60 DAT (days after transplanting) to harvest except for a period of net immigration lasting 7–10 days at approximately 95 DAT for both sexes.