Predating Potential And Fitness Of Harmonia Axyridis On Spodoptera Litura And Acyrthosiphon Pisum

Insect pests are the real concern and cause significant damage to agricultural products.Among them Spodoptera litura（Fabricius）（Lepidoptera:Noctuidae）and Acyrthosiphon pisum（Harris）（Hemiptera:Aphididae）are the serious insect pests with extensive host range of economically important crops.They cause significant losses to important agronomic,ornamental and horticultural crops,respectively.They are worldwide in distribution and primarily managed through pesticides,which resulted in health and the environmental challenges.The multicolored Asian ladybird beetle Harmonia axyridis（Pallas）（Coleoptera:Coccinellidae）is a voracious predator that preys upon soft bodied hemipteran and lepidopteran pests including eggs and early-instar caterpillars.Temperature variations and type of prey/food significantly affect the predating potential,biological parameters of a predator.To the most of current research,the studies regarding the predating potential and fitness of H.axyridis using two-sex life table tool on S.litura and A.pisum at different temperatures are lacking.The current study aimed to evaluate the functional response of various stages of H.axyridis fed on different densities of both preys at various temperatures.Moreover,the age-stage,two-sex life table tool was used to assess the efficiency of H.axyridis as a biocontrol agent against these pests.The main results are as follows:1)Temperature-dependent functional response of H.axyridis on S.litura and A.pisum at five different temperatures in laboratorya)Consumption and functional response of H.axyridis on S.litura eggsFunctional response of H.axyridis at larval and adult stages was evaluated in this study,using different densities of S.litura eggs as the prey at various temperatures varying between 15 and 35°C.Based on logistic model findings,linear parameters of various predatory stages of H.axyridis at various temperatures were significantly negative,which indicate a type II functional response.The theoretical maximum number（T/T_h）of eggs consumed increased with increasing temperature across all predatory stages.According to the random predator equation,the coefficients of attack rate（a）increased and that of handling time（T_h）decreased as the temperature increased.The fourth instar and adult stages were superior candidates for biocontrol of the target prey,typically at higher temperatures.The maximum attack rate(0.546±0.058 h^-1)and lowest handling time（0.189±0.004 h）were exhibited by the females at 30 and 35°C,respectively,whereas these parameters were inferior for early instars.Our findings clearly depict that the fourth instar and adult predators are efficient egg consumers and can serve as potential suppressors of S.litura population.b)Consumption and functional response of H.axyridis on lower stage（first and second instar）of S.litura larvaeThe consumption rate of H.axyridis（when offered S.litura first and second instar larvae as prey）and functional response（over different prey densities）were investigated at five different temperatures varying between 15 and 35°C.The consumption rate was inversely related to size of S.litura larvae.All stages of H.axyridis exhibited a type II functional response at all tested temperatures against both immature stages of S.litura.The highest estimated value of attack rate（a）(1.213±0.197 h^-1)and the shortest value of handling time（T_h）（0.122±0.004 h）were obtained for the female at 35°C feeding on first instar larvae of S.litura.The attack rate of female decreased from 1.213±0.197 h^-1to 0.158±0.011 h^-1as the prey size increased from first to second instar.Adults and fourth instar showed the maximum daily prey consumption against the first instar of prey at higher temperature and it started decreasing as the prey size increased.Thus,our results suggest that H.axyridis could be a highly efficient biological control agent of S.litura larvae.c)Consumption and functional response of H.axyridis on A.pisumIn this study,functional response of H.axyridis at larval and adult stages was studied,using A.pisum nymphs as the prey at various temperatures varying between 15and 35°C.H.axyridis larvae and adults also exhibited type II functional response to different densities of A.pisum.For fourth instar larvae and female H.axyridis adult,the successful attack rate（a）were 0.234±0.014 h^-1and 0.247±0.015 h^-1,respectively;the handling time（T_h）were 0.132±0.005 h and 0.156±0.004 h,respectively.Fourth instar larvae and female H.axyridis consumed more A.pisum nymphs at higher temperatures.The results of our study revealed high performance of fourth instar larvae and female H.axyridis and the importance of temperature in their efficiency.2)Using an age-stage,two-sex life tables to determine fitness traits of H.axyridis at two different temperaturesThis study explains the age-stage,two-sex life table traits of H.axyridis on A.pisum and S.litura（eggs and first instar larvae）at two temperatures（i.e.,25 and 30°C）in laboratory.The egg development period was minimum at 30°C（with A.pisum=2.52±0.07 d,with S.litura eggs=2.47±0.07 d and S.litura first instar larvae=2.40±0.07 d）than other tested temperature.The adult female longevity was significantly higher at 25°C（with A.pisum=83.25±9.21 d,with S.litura eggs=91.21±2.79 d and S.litura first instar larvae=104.42±1.55 d）.Similarly,the fecundity of H.axyridis was recorded highest at 25°C（with A.pisum=708.8±50.59 eggs/female,with S.litura eggs=484.74±19.32 eggs/female and S.litura first instar larvae=765.33±13.43 eggs/female）than other tested temperature.There were significant differences in the population parameters of H.axyridis at both temperatures.The life table traits of H.axyridis showed significant survival and fecundity at both temperatures and preys.Studies on fitness of H.axyridis could be used for optimizing mass rearing when feeding on A.pisum and S.litura eggs and larvae at different temperatures.In conclusion,H.axyridis can be used as a potential biological control candidate against A.pisum and S.litura in integrated pest management.