evaluation of life table parameters of coccinella septempunctata (l.) fed on macrosiphum rosae (l.)

introduction: macrosiphum rosae is one of the most important members of the aphididae (hemiptera) which feeds on plant juices, colonizes underside of leaves,stems and buds. this pest is a polyphagous insect vastly found in europe, asia and america. coccinella septempunctata (l.) (col: coccinellidae) is the successful biological control agent against aphids in under the greenhouse and field conditions. in the present study, the effects of constant temperature on the demography of c. septempunctata which feds on m. rosae was investigated. materials and methods: the predators were originally collected from the field (sorke hesar park in tehran) in march 2012 and reared on aphids in the germinator at 25 ± 1°c, 60 % ± 5 % relative humidity and photoperiod of 16l: 8d/h to lay their eggs and then females were removed after oviposition. these eggs were used for further examination. the life table parameters of c. septempunctata were measured under laboratory conditions at constant temperatures (14, 25 and 31) °c, relative humidity 60 ± 5 % and photoperiod of 16 hours light and 8 hours darkness with 100 repetitions. the different stages of the ladybeetles were fed with 20-100 aphids from different stages of m. rosae. the developmental time of immature stages of beetles were recorded every day. when adult females emerged, an adult male was introduced into the cells to fertilize of them and after that number of offspring produced was counted daily. sas software v 9.1 was used for data analysis. one-way anova was run to determine the significant differences between demographic parameter of c. septempunctata at two constant temperatures. if there were significant differences, the tukey's multiple tests were used for multiple comparisons (p < 0.05). results and discussion: there was no ovipostion at 14 °c. the intrinsic rate of increase (rm) of c. septempunctata at 25 and 31 ˚c were 0.170 and 0.186, the net reproductive rate (r0) were 187.55 and 76.74,the finit rate of increase were 1/18 and 1/20 and the mean generation time (t) of ladybird were 30.78 and 23.32 days, respectively. the lifetime oviposition and mean ovipositon rate were highest at 25 °c and lowest at 14 °c. the average total fecundities of c. septempunctata at 25 and 31 °c were 307.46 and 125.8 (eggs / femal). the average of adultʼs survival rate at three studied temperatures was analyzed by weibull model. the maximum of life expectancy rate is at 14 °c and the minimum rate is related to 31 °c. considering the high value of rm obtained from lifetime table of c. septempunctata in 25°c and 31°c, it can be concluded that the reproduction rate of this variety is at a high level. among the three studied temperatures, in 31°c, the beetle had the highest intrinsic rate of natural increase and the maximum rate of fertility calculated in 25°c. conclusion: considering that the rose bush is on the main vegetation in the urban area and m. rasae is rose̕ s main pest, high amount of pesticides are used for fighting this pest in the parks and in planted areas each year. in addition to removing natural enemies, these poisons cause environmental pollution and pose hazardes for the citizens who are directly exposed to this pollution. the higher values of rm in comparison to values calculated in studies of the other researchers with similar temperatures, shows the appropriate feeding value of this predator for c. septempunctata. thus, application of biological control, supporting natural enemies of pests and breeding and releasing of fruit full insects like c. septempunctata, are the alternative ways to using poisons and pesticides.