Life tables of the planthopper Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) on two wild rice species, Oryza officinalis Wall, ex Watt. and Oryza rufipogon Griff., and on 'Taichung Native 1' (O. sativa indica TN1) were studied at 27 degrees C in the laboratory. The raw data were analyzed based on the age-stage, two-sex life table to take both sexes and the variable developmental rate among individuals and between sexes into consideration. The intrinsic rate of increase (r), the finite rate (lamda), the net reproduction rate (R0) and the mean generation time (T) of N. lugens on O. officinalis were -0.0616 d(-1), 0.9402 d(-1), 0.10 offspring, and 36.7 d, respectively, showing that the species is resistant to N. lugens. The resistance of O. officinalis is expressed in the long developmental time from first to fifth instar of N. lugens, the reduced preadult survival rate, the short adult longevity, and low fecundity. However, the population parameters of the N. lugens on O. rufipogon and TN1 were 0.1096 d(-1), 1.1158 d(-1), 67.82 offspring, and 38.6 d and 0.1340 d(-1), 1.1434 d(-1), 144.77 offspring, and 37.2 d, respectively. These population parameters showed that N. lugens can successfully survive and reproduce on both O. rufipogon and TN1.
In this study, the first complete mitochondrial genome (mitogenome) sequence of Cacopsylla coccinae was determined by long PCR and primer walking methods. The complete mitochondrial genome is 14,832 bp in length and contains 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes as well as a control region. The overall base composition of the genome is A (38.16%), T (33.88%), C (17.95%) and G (10.01%). Stop codon was incomplete for coxII gene and ND1 gene. The gene overlaps were suggested between 13 pairs of the contiguous genes in C. coccinae. The mitogenome would contribute to resolving phylogenetic position and interrelationships of Cacopsylla.
Applications of fipronil (1.25ϫ10Ϫ2 mg) and fipronil (7.50ϫ10 Ϫ3 mg) significantly stimulated the fecundity of Nilaparvata lugens compared with the control. The stimulating effect of fipronil on fecundity was dose-dependent. Fifteen and 30 days after treatment, the quantity of honeydew significantly increased in 1.25ϫ10Ϫ2 mg fipronil treatment. Fifteen days after treatment, the effect of fipronil on the quantity of honeydew was dose-dependent. The results revealed that the fipronil treatment group had developmental advantages. Selection with 25 mg/l fipronil led to a continuous increase in the resistance ratio (from 1.0 to 30.05) in eight generations. The life table indicated that the resistant strain had obvious disadvantages, including decreasing the survival rate from 3rd to 5th instar in G8 generation and decreasing fecundity in G5 generation. Compared with the susceptible strain, resistant insects had a relative fitness of only 0.577 and 0.750. The lower fitness includes a lower larval survival rate from 3rd to 5th instar (in G8 generation), lower adult emergence rate (in G8 generation), lower copulation rate (in G8 generation), lower fecundity (in G5 generation) and fewer offspring. It was concluded that the brown planthopper had the potential to develop high resistance to fipronil but that the lower fitness of resistant hoppers could result in quick recovery of sensitivity when the population did not come into contact with fipronil. This means that a reasonable resistance management program with less fipronil use may efficiently delay or even stop resistance development.
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