Study On Ecological Adaptability Of Invasive Alien Pest Tuta Absoluta

Tuta absoluta is a serious invasive alien pest originated from South America,which is destructive to global tomato industry.This pest spreads extremely fast,and has already occurred in the neighboring countries and some regions of China.If spread successfully,it would cause unpredictable economic loss to tomato production in China.As an invasive pest,stress tolerance is one of the key factors that affect its invasion success.The developmental temperature and the extreme temperature tolerance have important influence on the spread and population expansion after invasion.Meanwhile,the host adaptability and reproductive characteristics of the T.absoluta are also of great significance for the adaptation and spread mechanism of this pest in the newly invaded areas.Therefore,in this study,we studied the invasion adaptability of T.absoluta from three aspects:temperature,host plants and reproductive mode.The results are as follows:1.Development of T.absoluta at 15℃,20℃,25℃ and 30℃ and 35℃ were investigated respectively.The results showed that T.absoluta could complete development from 15℃ to 30℃,the developmental duration became shorter with the rise of temperature.The developmental duration of immature stage was 59.5 days at 15℃ and 19.6 days at 30℃.T.absoluta could not complete development at 35℃.The survival rates of egg duration were between 90%and 93%at 15℃,20℃,25℃ and 30℃,but decreased significantly to 11%at 35 ℃.The survival rate of immature stage at 25℃(70%)was the greatest,followed by 63%at 20℃,51%at 15℃;the survival rate at 30℃ was the lowest,which is 45%.The intrinsic rates of natural increase of T.absoluta at 15 0C,20 ℃,25℃ and 30℃ were 0.0322,0.0984,0.1434 and 0.0612,respectively.Consequently,the optimal developmental temperature of T.absoluta was 25℃.2.The cold tolerance of T.absoluta was evaluated in the laboratory.The results showed that the average supercooling point of female adults was the lowest,which was-20.01℃,followed by male adults-19.08℃,male pupae-18.42℃,larvae-18.52℃,female pupae-17.68℃.The supercooling point of eggs was the highest,which was-14.05℃.There was no significant effect for the survival rates of eggs,larvae,female and male pupae and male adults when exposed at 5℃,0℃ and-5℃ for up to 10 h.There was no significant effect for the survival rates of female adults when exposed at 5℃ and 0℃ for up to 10 h.At-5℃,the survival of female adults changed as the exposure time,yet,the survival rates were all above 50%.The low temperature exposure that had a significant impact on survival of eggs was-10℃ for at least 10 h,or-15℃ for at least 6 h.For larvae,the low temperature exposure that caused significant death was-15℃ for at least 4 h,-10℃ at least 6 h.For female pupa and male pupa,the low temperature exposure that caused significant death was-15℃ for at least 1 h.For female and male adult,exposed at-10℃ for at least 4 h could resulted 100%death.These results indicate that T.absoluta can tolerance extreme low temperature,suggesting that it has high ability to survive in cold winter.3.We studied the effect of 4 cultivated solanaceous plants,tomato(Lycopersicon esculentum Mill.),potato(Solanum tuberosum L),eggplant(S.melongena L.)and pepper(Capsicum annuum L.),on the oviposition selection,development and population growth parameters of T.absoluta.The results showed that the oviposition preference of T.absoluta on 4 host pants were as follows:tomato,potato,eggplant and pepper.The egg duration on pepper was the longest and the newly hatched larvae could not survive on pepper leaves.The survival rate of entire immature stage on tomato was greater than that on potato and eggplant,but the mean developmental duration on tomato was the longest.The female fecundity and longevity on tomato were greater than that on potato and eggplant.The intrinsic rates of natural increase of T.absoluta fed on tomato,potato and eggplant leaves were 0.1434,0.1406,and 0.1133,respectively.Consequently,tomato was the most suitable host plant of T.absoluta,yet,the pest could not finish development on pepper.T.absoluta had great population growth potential on potato and eggplant and could become a serous pest on these two hosts under favorable conditions.4.It has been reported the presence of deuterotokous parthenogenetic population in T.absoluta.In this study,we investigated the reproductive mode of T.absoluta experimental population.The results showed that virgin females could lay eggs,yet,the egg number was significantly lower than sexual females.Moreover,the eggs produced by virgin females could not hatch.Consequently,the experimental population we used was sexual population.