Life history parameters of Thrips tabaci (Thys.: Thripidae) on cucumber, sweet pepper and eggplant under laboratory conditions

Onion thrips, Thrips tabaci Lindeman, is one of the most important pests of vegetables and ornamentals all over the world. Its role has been proved in the transmission of different viruses to several plants. In this study, life history parameters of T. tabaci were calculated on three host plants, cucumber, sweet pepper and eggplant. Experiments were conducted at 25 ± 1οC, 60 ± 10% R.H. and photoperiod of 16: 8 (L: D) hours. The results showed that host plants affect life history of onion thrips significantly. Intrinsic rate of population increase (rm) was 0.296, 0.158 and 0.234 female on female per day on cucumber, sweet pepper and eggplant respectively. Other parameters like λ (finite rate of increase) were 1.334, 1.171 and 1.264; T (mean generation time) were 14.879, 19.092 and 16.779; DT (doubling time) were 2.343, 4.384 and 2.956 days. Finally, R0 (net reproductive rate) was 81.581, 20.461 and 51.141 female/female in one generation. With regard to highly significant effect of host plants on life history parameters of onion thrips, it is probable that this problem could be used for control of onion thrips on sweet pepper more effectively than on cucumber and eggplant

Influence of female body weight on reproduction in laboratory-reared Podisus nigrispinus and Podisus maculiventris (Heteroptera: Pentatomidae)

Fresh body weight like body size is considered as a relevant index for evaluating insect reproduction and development. Previously, a correlation between female body sire and reproduction has been proved for field-collected specimens of the predatory stink bug Podisus maculiventris. The current investigation was carried out using P. maculiventris and Podisus nigrispinus reared for several years under laboratory conditions. For each species, three weight groups were selected from seven-day-old adults with mean body weights (+/-SD) of 62.6+/-1.6, 72.5+/-1.3, and 83.9+/-3.2 mg and 93.6+/-4.5, 104.8+/-2.7, and 115.7+/-4.6 mg for P. nigrispinus and P. maculiventris, respectively. Evaluated characteristics were: preoviposition period, total number of eggs, eggs per batch, eggs per female per day, egg load at the time of death, percentage egg hatch and female longevity. Generally, no significant differences were found among the weight groups in both species indicating that there is no clear relationship between weight and fecundity of laboratory-reared Podisus bugs. The relevance of these findings for the mass rearing of predatory soldier bugs is discussed

Resistance of canola cultivars affect life table parameters of Nysius cymoides (Spinola) (Hemiptera: Lygaeidae)

A life table can be used as an important and appropriate tool to evaluate the susceptibility or resistance level of different host plant cultivars to insect pests. In the current study, we determined the suitability or inferiority of five different canola cultivars (Hayula420, Hayula401, Hayula50, Hayula60, RGS) to Nysius cymoides, under laboratory conditions. Data were analysed based on the age-stage, two-sex life table theory. Nysius cymoides which fed on Hayula420 had the longest nymphal period, while those which fed on Hayula50 had the shortest nymphal period. Developmental times (sum of incubation and nymphal periods) was longest for those which fe d on Hayula420 and the shortest for those which fed on Hayula50. The adult pre-oviposition period (APOP), total pre-oviposition period (TPOP), mean fecundity, and adult longevity of adults reared on different canola cultivars showed significant differences. The highest and lowest net reproductive rates (R0) were obtained for those which fed on Hayula420 (11.40 offspring per individual) and Hayula401 (5.47 offspring per individual), respectively. The highest value (0.0395 d–1) for the intrinsic rate of increase (r) was obtained for those which fed on Hayula 60 cultivar and the lowest value (0.0261 d–1) for those which fed on Hayula401 cultivar. The shortest and longest mean generation times (T) were obtained for those which fed on RGS and H401 cultivars, respectively. The lowest and highest values of life expectancy (exj) were obtained for those which fed on RGS and Hayula420 cultivars, respectively. The results showed that Hayula401 and RGS were not susceptible cultivars to N. cymoides. These cultivars showed higher resistance to N. cymoides, while Hayula60, Hayula420, and Hayula50 were found to be suitable cultivars but with lower resistance to N. cymoides, respectively