| Nowadays green food have become increasingly important in people's lives.As a result,The 3R(residue,resistance and resurgence)problems which caused by overused of pesticides got increasingly concerns all of the world.Biological control was considered one of the best methods in pest management strategies.Previous studies showed that the parasitoid Cotesia vestalis(Hymenoptera:Braconidae)was an effective enemy in the control of the crucifer pest Plutella xylostella(Lepidoptera:Plutellidae).C.vestalis was proved could adapt to its host by many strategies,it also employ many abilities to adapt to the environment and reproductive success in the competition with other parasitoids.This paper studied the major biological and behavioural characteristics of parasitoid such as parasitism time,physiological characters and geographic strains on parasitical efficiency of C.vestalis,The main results are as follows:1.Effect of parasitism time on biological parameters of C.vestalis offspring:(1)When parasitism initiated at 2nd-instar P.xylostella larvae,the duration of egg and juvenile,the weight of parasitoid adult were no different when the host was parasitized one,three or six times.However,when the host only be parasitized one time,the cocoon duration was significantly longer(5.17 ± 0.47 d)than three times(4.89 ± 0.32 d)and six times(4.80 ± 0.41 d).When the host only be parasitized one time,the longevity of adult(8.41 ± 3.28 d)was significant longer than parasitized six times(6.00 ± 4.15 d).(2)When parasitism initiated at 3rd-instar P.xylostella larvae,cocoon weight and longevity of adult were no different when the host was parasitized one,three or six times.However,when the host be parasitized six times,the duration of egg and juvenile was significantly longer(8.50 ± 0.80 d)than one time(8.14 ±0.55 d)and three times(7.96 ± 0.65 d).when the host only be parasitized one time,the cocoon duration(4.88 ± 0.33 d)was significant shorter than parasitized three times(5.67 ± 0.82 d)and six times(5.71 ±0.77 d).(3)When parasitism initiated at 4th-instar P.xylostella larvae,C.vestalis produced less offspring than initiated at 2nd-or 3rd-instar P.xylostella larvae.While biological parameters such as egg and juvenile duration,cocoon weight,adult longevity were no different when the host be parasitized one,three or six times.2.Effect of physiological characters on attacking rate of C.vestalis female:When the female emerge 5 days before,its attacking time in 9 hours(122.83 ± 14.30 times)was significant higher when compare to the female which emerge 3 days before(87.17 ± 9.63 times)and emerge only one day(87.17 ± 6.07 times).Mating play roles in the competition of two parasitoid females.One mated female accompany with one virgin female got highest attacking rate(187.83 ± 24.89 times)in 9 hours,and significant higher than two mated female(107.00 ± 13.89 times)or two virgin female(112.00±8.97times).3.Vareity of parasitism ability in different geographic strains C.vestalis female in competition:When the interval of parasitism and superparasitism was short(<10 min),no matter the different emerge days,Zhejiang(ZJ)and Fuzhou(FZ)parasitoid produced similar numbers of offspring adult:ZJ parasitoids emerge one day and FZ parasitoids emerge three days(P = 0.369),ZJ parasitoids emerge three days and FZ parasitoids emerge one day(P = 0.160).However,mating play roles in competition of two strain parasitoids.When the interval of parasitism and superparasitism was short(<10 min),mating ZJ female did not showed produced more offspring in competition with virgin FZ female(P = 0.715),however,if the FZ female rather than the ZJ female had mated,Fuzhou strain C.vestalis produced more offspring adult than ZJ strain(P<0.05). |
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