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[Objectives] To determine the sensitivity of Spodoptera frugiperda in Fujian province to six insecticides recommended by the Ministry of Agriculture and Rural Affairs. [Methods] The leaf dip method was used to determine the lethal concentration 50 (LC50) of six insecticides (emamectin benzoate, spinetoram, indoxacarb, chlorantraniliprole, clorfenapyr and lufenuron) to S. frugiperda, collected in Jian'ou county of Nanping city, Yong'an county of Sangming city, Fuqing county of Fuzhou city and Changtai county of Zhangzhou city. The LC50 values of these six insecticides were also compared between specimens collected in Jian'ou and Changtai populations in spring and autumn. [Results] The susceptibility of S. frugiperda to the insecticides tested varied significantly among populations. The LC50 of emamectin benzoate in the Changtai and Fuqing populations was about twice than that in the Jian'ou and Yong'an populations, and the LC50 of indoxacarb in the Changtai and Fuqing populations was about 3 times than that in the Yong'an population. The susceptibility of S. frugiperda to insecticides also varied between seasons. The LC50 of chlorantraniliprole and clorfenapyr to the Changtai population was 0.20 times and 2.26 times, respectively, in autumn than that in spring, and the LC50 of emamectin benzoate and indoxacarb to the Jian'ou population was 4.75 times and 2.20 times, respectively, in autumn than that in spring. Rearing ten successive generations without insecticide exposure caused the LC50 values of lufenuron, indoxacarb and chlorantraniliprole to decrease 8.15, 22.87 and 10.58 fold, respectively, compared to the F1 generation. [Conclusion] Field populations of S. frugiperda in Fujian province are generally still sensitive to the six tested insecticides in 2020. In Changtai and Jian'ou, the sensitivity of S. frugiperda to chlorantraniliprole, clorfenapyr, indoxacarb, lufenuron differed significantly between spring and autumn. [ABSTRACT FROM AUTHOR]

BACKGROUND The leaf surface microstructure can greatly influence predator feeding behavior. However, its effects on predator oviposition preference, which is crucial for arthropod fitness at the population level, are largely unknown. This study aimed to test leaf discs and plants of five common host plant species of Bemisia tabaci, including Chinese kale, cotton, cucumber, eggplant, and sweetpotato, to determine the oviposition preference and offspring and adult performance of the whitefly predator Serangium japonicum. Cannibalism risk, attachment force, microstructure of the abaxial leaf surface (ALS), and ladybeetle tarsal morphology were examined. RESULTS: Ladybeetle's oviposition preference had no correlation with offspring performance but positively correlated with fecundity. Further, oviposition preference to leaf discs and fecundity positively correlated with attachment force. The cannibalism risk was not significantly different between plant species. The ALS of Chinese kale and eggplant supported the smallest and the largest attachment forces, respectively. The first one had epicuticular wax crystals, whereas the latter had stellate trichomes. The ALS of cotton and sweetpotato did not bear wax crystals or long trichomes. Cucumber leaves were covered with tapered trichomes. Tenant setae on the distal second tarsomere and a pair of curved, tapered claws on the distal fourth tarsomere were the attachment structures of S. japonicum, which interacted with the plant surface structures and generated the attachment force. CONCLUSION: Plant morphological traits, associated with ladybeetle attachment force and adult performance might be key factors in ladybeetle oviposition preference, and are expected to occur in other host plant herbivore–predator systems. [ABSTRACT FROM AUTHOR]

Biological activity of capsaicin and its effects on development and fecundity in Bemisia tabaci were tested in the laboratory. The results showed that capsaicin induced direct mortality in different developmental stages of B. tabaci, and the mortality of whiteflies were significantly dosage-dependent. The toxicity of capsaicin to different developmental stages of B. tabaci by either leaf-dip or egg/larval-dip bioassays (the LC50 for adult, egg and nymph were 3525.79, 1603.29 and 1526.27 mg • L-1, respectively) was higher than that by systemic bioassay (the LC50 for adult, egg and nymph were 5360.04, 2359.19 and 5897.43 mg • L-1, respectively), and toxicity of capsaicin to eggs was higher than to adults in both bioassay methods. 2000 and 4000 mg • L-1 concentrations of capsaicin had strong antifeedant effect on B. tabaci, as exemplified by reduced honeydew excretion of adults feeding on leaves treated with capsaicin compared with untreated leaf discs. Capsaicin also had strong oviposition deterrence against B. tabaci, with 94. 2% of selective oviposition deterrence rate and 83. 0% of nonselective oviposition deterrence rate when exposed to 4000 mg • L-1 concentration for 24 h. We did not find effect on development time of B. tabaci eggs and nymphs, and on molting rate of adults when exposed to capsaicin at 500, 1000 and 2000 mg • L-1 concentrations, however, exposure to 4000 mg • L-1 concentration of capsaicin significantly affected development time of B. tabaci nymphs and molting rate of adults. Exposure to capsaicin also significantly reduced fecundity of B. tabaci adults, and this reduction was significantly dosage-dependent. [ABSTRACT FROM AUTHOR]

The development of insecticide resistance in field populations of Bemisia tabaci from different regions of Fujian Province, China were monitored with adult leaf-dipping bioassay. Compared with bioassay data of 2005, all field populations tested in 2009 still had high levels of resistance to the lambda-cyhalothrin, fenpropathrin and chlorpyrifos, low levels of resistance to methomyl, and no resistance to abamectin. However, resistance to the neonicotinoids imidacloprid and thiamethoxam had increased from moderate levels (23 folds and 25 folds, respectively) in 2005 to high levels (103 folds and 228 folds, respectively) in 2009 in Zhangzhou population, and low levels (1. 53-3 folds and 1-7-5-5 folds, respectively) in 2005 to moderate levels (23-33 folds and 29-49 folds, respectively) in 2009 for other populations. The biotype of eight B. tabaci populations collected from different regions and hosts were determined according to the mitochondria cytochrome oxidase I (mtCO I ) sequence, and two different biotypes (B-biotype and indigenous whitefly) were detected. The samples collected from geographical regions and hosts showed a prevalence of the B-biotype, and indigenous whitefly (unknown biotype) existed only in croton of Zhangzhou. Host plants and temperature had limited effects on insecticide development in B. tabaci, while extensive and high frequent use of neonicotinoids could be the most important factors responsible for rapid development of insecticide resistance in field populations of B-biotype B. tabaci. [ABSTRACT FROM AUTHOR]

Based on the observation of free diffusion in petri dish and biology, the selection behavior and biological parameters of Bemisia tabaci Gennadius biotype B on host plants cucumber, eggplant, pepper, cotton, and sweet potato were investigated. No difference was observed in the individual number of B. tabaci on the five host plant leaves during the early period of free diffusion (within 2 h), but changes were found within the following periods (4-48 h), i.e., the B. tabaci individuals increased on cucumber, decreased on pepper, and were relatively stable on eggplant, cotton, and sweet potato, which indicated that there were significant differences in the selectivity of B. tabaci on the five host plants, with the highest selectivity to cucumber and the lowest selectivity to pepper. Pretreatment by starvation and imidacloprid did not affect the selectivity of B. tabaci. There were significant differences on the honeydew excretion of female B. tabaci adults on the host plants, which was in the order of cucumber > sweet potato > cotton > eggplant > pepper. The average longevity of B. tabaci adults on cucumber, eggplant, sweet potato, and cotton was significantly longer than that on pepper, and the total number of eggs laid per female on cucumber, eggplant, sweet potato, and cotton (224.33, 182.33, 191.73, and 172.60 respectively) was significantly larger than that on pepper (only 47.83). No significant differences were observed in the hatching rate and development period of the eggs on the five host plants. The development period of nymphs on cucumber, eggplant, sweet potato, and cotton was 10.60 d, 11.96 d, 11.11 d, and 13.20 d, and the mortality was 5.21%, 27.78%, 17.24%, and 37.11%, respectively. The nymphs failed to develop normally on pepper. [ABSTRACT FROM AUTHOR]

Simple sequence repeats (SSR) and random amplification of polymorphic DNA (RAPD) molecular markers were used to assess the genetic diversity of 80 isolates of Phytophthora infestans in potato (Solanum tuberosum) from Fujian, Heilongjiang, Hebei and Inner Mongolia Provinces in China. Polymorphism was identified by 13 SSR primers and 14 RAPD primers in the isolates of P. infestans in potato. A total of 76 bands were amplified by SSRs, with the percentage of polymorphic bands (PPB) being 78.9% and the similarity coefficient ranging between 0.00 and 0.42. A total of 189 bands were amplified by RAPDs, with the percentage of polymorphic bands being 95.2% and the similarity coefficient ranging between 0.04 and 0.66. Analysis of genetic diversity showed that there exists higher genetic variation in the Fujian population in comparison to the populations of Heilongjiang, Hebei and Inner Mongolia. Nei's genetic identity analysis indicates that the genetic similarity between populations of Heilongjiang and Inner Mongolia is the highest and that between Fujian and Hebei is the lowest. A cluster analysis revealed that isolates from Fujian, in the south of China, are distantly related to those from Heilongjiang, Hebei and Inner Mongolia in the north, and the Fujian population is distributed among more groups than the other three, exhibiting a higher genetic diversity. [ABSTRACT FROM AUTHOR]

Biological activity of capsaicin and its effects on development and fecundity in Bemisia tabaci were tested in the laboratory. The results showed that capsaicin induced direct mortality in different developmental stages of B. tabaci, and the mortality of whiteflies were significantly dosage-dependent. The toxicity of capsaicin to different developmental stages of B. tabaci by either leaf-dip or egg/larval-dip bioassays (the LC50 for adult, egg and nymph were 3525.79, 1603.29 and 1526.27 mg x L(-1), respectively) was higher than that by systemic bioassay (the LC50 for adult, egg and nymph were 5360.04, 2359.19 and 5897.43 mg x L(-1), respectively), and toxicity of capsaicin to eggs was higher than to adults in both bioassay methods. 2000 and 4000 mg x L(-1) concentrations of capsaicin had strong antifeedant effect on B. tabaci, as exemplified by reduced honeydew excretion of adults feeding on leaves treated with capsaicin compared with untreated leaf discs. Capsaicin also had strong oviposition deterrence against B. tabaci, with 94. 2% of selective oviposition deterrence rate and 83. 0% of nonselective oviposition deterrence rate when exposed to 4000 mg x L(-1) concentration for 24 h. We did not find effect on development time of B. tabaci eggs and nymphs, and on molting rate of adults when exposed to capsaicin at 500, 1000 and 2000 mg x L(-1) concentrations, however, exposure to 4000 mg x L(-1) concentration of capsaicin significantly affected development time of B. tabaci nymphs and molting rate of adults. Exposure to capsaicin also significantly reduced fecundity of B. tabaci adults, and this reduction was significantly dosage-dependent.

Abstract: The development of insecticide resistance in field populations of Bemisia tabaci from different regions of Fujian Province, China were monitored with adult leaf-dipping bioassay. Compared with bioassay data of 2005, all field populations tested in 2009 still had high levels of resistance to the lambda-cyhalothrin, fenpropathrin and chlorpyrifos, low levels of resistance to methomyl, and no resistance to abamectin. However, resistance to the neonicotinoids imidacloprid and thiamethoxam had increased from moderate levels (23 folds and 25 folds, respectively) in 2005 to high levels (103 folds and 228 folds, respectively) in 2009 in Zhangzhou population, and low levels (1.5-3.3 folds and 1.7-5.5 folds, respectively) in 2005 to moderate levels (23-33 folds and 29-49 folds, respectively) in 2009 for other populations. The biotype of eight B. tabaci populations collected from different regions and hosts were determined according to the mitochondria cytochrome oxidase I (mtCO I ) sequence, and two different biotypes (B-biotype and indigenous whitefly) were detected. The samples collected from geographical regions and hosts showed a prevalence of the B-biotype, and indigenous whitefly (unknown biotype) existed only in croton of Zhangzhou. Host plants and temperature had limited effects on insecticide development in B. tabaci, while extensive and high frequent use of neonicotinoids could be the most important factors responsible for rapid development of insecticide resistance in field populations of B-biotype B. tabaci.

Based on the observation of free diffusion in petri dish and biology, the selection behavior and biological parameters of Bemisia tabaci Gennadius biotype B on host plants cucumber, eggplant, pepper, cotton, and sweet potato were investigated. No difference was observed in the individual number of B. tabaci on the five host plant leaves during the early period of free diffusion (within 2 h), but changes were found within the following periods (4-48 h), i.e., the B. tabaci individuals increased on cucumber, decreased on pepper, and were relatively stable on eggplant, cotton, and sweet potato, which indicated that there were significant differences in the selectivity of B. tabaci on the five host plants, with the highest selectivity to cucumber and the lowest selectivity to pepper. Pretreatment by starvation and imidacloprid did not affect the selectivity of B. tabaci. There were significant differences on the honeydew excretion of female B. tabaci adults on the host plants, which was in the order of cucumber > sweet potato > cotton > eggplant > pepper. The average longevity of B. tabaci adults on cucumber, eggplant, sweet potato, and cotton was significantly longer than that on pepper, and the total number of eggs laid per female on cucumber, eggplant, sweet potato, and cotton (224.33, 182.33, 191.73, and 172.60 respectively) was significantly larger than that on pepper (only 47.83). No significant differences were observed in the hatching rate and development period of the eggs on the five host plants. The development period of nymphs on cucumber, eggplant, sweet potato, and cotton was 10.60 d, 11.96 d, 11.11 d, and 13.20 d, and the mortality was 5.21%, 27.78%, 17.24%, and 37.11%, respectively. The nymphs failed to develop normally on pepper.

Resistance to 13 insecticides in field populations of Bemisia tabaci from six regions (Fuzhou, Zhangzhou, Longyan, Sanming, Nanping, Ningde) of Fujian Province, China was monitored by adult leaf-dipping bioassay. Compared with the susceptible SUD-S strain, all the six field populations exhibited high levels of resistance to lambda-cyhalothrin (838.38-2460.52 fold), fenpropathrin (244.64-834.29 fold), cypermethrin (116.02-266.35 fold), deltamethrin (81.75-124.18 fold), acephate (425.18-875.56 fold) and chlorpyrifos (54.53-78.43 fold), moderate levels of resistance to dimethoate (14.16-17.66 fold), low to moderate levels of resistance to dichlorvos (6.23-11.25 fold) and low levels of resistance to methomyl (4.07-5.66 fold), respectively. Among these six field-collected populations, only Zhangzhou population had moderate resistance to imidacloprid, acetamiprid and thiamethoxam (23.08 fold, 10.32 fold and 24.60 fold, respectively). All field strains tested displayed no resistance to abamectin.