Studies On The Biology Of Microplitis Pallidipes Szépligeti And Its Control Effects On The Population Of Spodoptera Exigua (Hübner)

In this thesis, the effects of five main components of an artificial diet (soybeanpowder, wheat bran, yeast, casein, cholesterin) on the pupation probability of beetarmyworm, Spodoptera exigua.(Hübner) was evaluated by the quadratic orthogonalrotation regression design. The biology and ecology of Microplitis pallidipesSzépligeti were investigated including oviposition, sex ratio, host selection between S.exigua and S. litura and functional response to different temperature regimes. Aminoacids from host haemolymph and the development of host larvaes parasitized by M.pallidipes were determined. The effects of SeNPV on M. pallidipes were initiallyinvestigated. Finally, The co-efficiency of this parasitism wasp and SeNPV to beetarmyworm was also investigated]. The main results were as follows:1) Wheat bran was the most important diet component that influenced pupation ofbeet armyworm,followed by yeast, casein, cholesterin, soybean powder. The optimumvalues for the component of artificial diet in factor analysis for soybean powder,wheat bran, yeast, casein, cholesterin were 10.99, 9.10, 3.99, 2.98 and 0.031,respectively.2) M. pallidipes emerged in the day-time, and most of them emerged in 8-16h. malewasps emerged earlier than that of females and 58.3ï¼…of them emerged in 0-8h.62.7ï¼…females emerged in 8-14h. The emergence time lasted for 6-7days, and morethan 90ï¼…wasps emerged during 1-3days. Both male and female wasps copulatedmore than once over their living time. Offspring from unmated females developed tomale wasps. The peak oviposition occurred in 1-3days after mating. Oviposition sitein host larva was in abdomen between the 5th and the last arthromere, and only oneegg was laid.3) M. pallidipes laid eggs in 1st to 4th instar larvae of Beet armyworm. The early 3rdinstar and the early 4th instar larvae were the preferable stage to be laid eggs. few eggslaid in the late 1st instar and the early 2nd instar larvae. 4)The highest parasitism for M. pallidipes occurred in the day time of 14-22h,followed by 8-14h and 22-8h during a day. The highest parasitism occurred in thesecond day after emerging, followed by the 1st day and the 3rd day during the periodof oviposition. The average number of host larvae parasitized by one female wasp was101.6. The proportions of host larva to be selected for parasitism from 1st to 4th instarwere 0.0863,0.2795,0.2609 and 0.3733, respectively. When female wasp mated onetime, the parasitism rates for 2nd-3rd instar larva between of S. exigua and S. lituraselected by the wasp were 0.5211 and 0.4789, respectively.5) M. pallidipes was found to lay the highest eggs when the density of host larva was20 per arena. The highest female ratio of M. pallidipes was found when one femalewasp copulated with 3 males. For mass rearing M. pallidipes, the ratio of wasp to hostlarva should be was 1:20 at 27℃and 14h light. Based on selection of this wasp todifferent host types, the 2nd instar -3rd instar larva of beet armyworm or S. litura wasthe suitable host to be provided..6) The instant attack ratio of M.pallidipes will rise as the temperature is rising,andthe treatment time was lower at 31℃than that at 23℃and 27℃. The functionalresponses of M.pallidipes were Hollingâ…¡,â… ,â… at 31℃,23℃and 27℃,respectively.7)The total amounts of amino acids for the parasitized and the non-parasitized larvaein 3 days were 3.634mg/mL and 4.534mg/mL, respectively, in 5 days were7.379mg/mL and 7.332mg/mL,respectively, and in 6 days were 5.977mg/mL and7.217mg/mL, respectively.In comparison of the control treatment,the kinds whichreducing in the amino acids content were few,the kinds increasing in the amino acidscontent were more in 3 days.The increasing in the content of Tyrosine was relativelyto the expression of store protein in advance.The content of Asparaginic acid in theparasitized larvae was higher than that in the control treament in 5 days and 6days;The content of Glucine, Serine,Glutamic acid in the parasitized larvae was lowerthan that in the control treatment,also the content in 6 days was lower than that in 5days for the parasitized larvae.The content of Proline in the parasitized larvae washigher than that the control treatment in 6 days obviously.There was difference in theaspects of amino acids content at different period of parasitising in the host,it indicated that the parasitiod absorbed amino acids differently, when mass rearing theparasitiod with artificial diet,the amino acids should be adjusted in the aspects ofkinds,content and proportion according to the different period of parasitising.8)The experiment of 3 factors among beet armyworm, SeNPV and Microplitis waspwas conducted,the results indicated that the virus in the virus-infected larvae of beetarmyworm had no obvious influence on the developmental duration of parasitewasp,the influence on the survival rate of parasite wasp was relate to the time ofexposure of host larvae to virus and the inoculation virus doses.The longer the time ofexposure of host larvae to virus was,the lower the inoculation virus doses was,themore the proportion of parasite wasp which finished development was,the time ofexposure of host larvae to virus was the main factor. The revised survival rate ofparasitism wasp in the 0d virus-infected larvae after inoculated with high dose ofvirus (1.71×10⁶ PIBs·mL^-1) was the lowest 31.63ï¼…, as though inoculated withhighest dose of virus (1.71×10⁷ PIBs·mL^-1), the revised survival rate of parasitismwasp in the 2d virus-infected larvae reached to 57.60ï¼…; The revised survival rate ofparasitism wasp in the 4d virus-infected larvae after inoculated with low dose of virus(1.71×10³ PIBs·mL^-1) was the highest (88.16ï¼…)。Mortality of virus-infect hostlarvae which parasitized by Microplitis pallidipes 0d post and inoculated with 1.71×10⁶ PIBs·mL^-1 virus was the highest 60.67ï¼…;But the mortality of virus-infect host larvaewhich parasitized by M.pallidipes 4d post and inoculated with 1.71×10³PIBs·mL^-1 virus was the lowest 11.12ï¼…. According to the rate of variance ofregression coefficient in the model 5.2, the contribution (Δ) of individual fact can beobtained,Δ₁=1.9462,Δ₂=0.9762.The effect of facts according to the contributionwas:X₁＞X₂, the time of inoculation was the main fact which influence the death ofhost larvae. The parasite wasp which developed in the virus-infected host larvae cantransmit virus, the rate of virus-transmission was 30.0ï¼…-100.0ï¼…, a female parasitetransmitted infective doses of the virus to an average of 0.5-7.2 healthy host larvaexposed to it.A female parasite which laid eggs in the larvae inoculated with virus 24-72h post transmitted infective doses of the virus to an average of 7.67 healthy hostlarva exposed to it. A female parasite from the cocoon contaminated with1.71×10³-1.71×10⁷ PIBs·mL^-1 SeNPV could transfer infective doses of the virus to an average of 0.14-5.50 healthy host larva; A female parasite exposed to the mixture ofdifferent doses virus and 10ï¼…honey-water solution could also transmit virus to anaverage of 0.0-5.0 larva.The field experiment of virus transmission of M.pallidipes was carried out,thenatural parasitism of M.pallidipes was 25ï¼…-28.8ï¼…,the revised mortality ofvirus-infected host larvae was 74.06ï¼….According to the results of experiments,when utilizing both Microplitis wasp andSeNPV to control the beet armyworm, such measures can be took: (1) Host larvae canbe virus-infected in the temporary same generation of released parasite wasp with thevirus solution of concentration of 1.71×10⁵-1.71×10⁷ PIBs·mL^-1 to inoculate the hostlarvae after releasing of parasite wasp in 3-4days and to let the adult wasps carry andtransmit virus; (2) At the peak of 1st-2nd instar larvae of beet armyworm releasingMicroplitis wasp and spraying virus solution when larvae reached 3rd instar stage tocontrol the contemporary generation,to induce the prevalence of SeNPV in the nextgeneration of beet armyworm and to add chance for the parasite wasp to increase.