Studies On Effects Of Temperature And Phtotopemod On Diapause Regulation Of Two Pollinating Illicium Blossom Gall Midges

The yellow Illicium blossom gall midge Anabremia sp.and the red Illicium blossom gall midge Clinodisplosis sp.are obligative pollinating insects on Illicium verum.In this paper,the effects of environmental temperature,generation of two Illicium blossom gall midges,photoperiod and temperature on diapause induction and elimination of these two species of Illicium blossom gall midges were studied through field investigation and laboratory experiments.The main results are as follows:1.From September 2017 to September 2018,the air temperature and soil temperature of Illicium verum forest in Jiepai Branch of Guangxi State-owned Gaofeng Forest Farm changed in the same trend during the year,showed obvious seasonal changes.From June to August,the average air and soil temperatures were above 25?,and at night they were above 25?.In mid and late September,the average air temperature was still 25?,but the night temperature had dropped below 23?.Low temperatures below 19? began to appear.Mean soil temperature and night temperature were lower than 25 ?.After October,the average air and soil temperatures was below 25?.Night temperatures was below 20?.The average air and soil temperatures rose to above 25 ? until the middle and late May of the next year.2.The diapause state of the two Illicium blossom gall midges is cocoon larvae.Diapause cocoon larvae of two Illicium blossom gall midges are milky white.The sensitive stage of the two Illicium blossom gall midges were the young stage of larvae.At different temperatures,there were significant differences in the stages of development between the two Illicium blossom gall midges,and the developmental periods shortened with the increase of temperature.3.Anabremia sp.and Clinodisplosis sp.can occur five generations a year in Guangxi.Different generations had significant effects on diapause of the two Illicium blossom gall midges(P<0.05).The diapause rate of two Illicium blossom gall midges increased gradually with the increase of generations,and the diapause rate of the fifth generation was the highest.4.Anabremia sp.and Clinodi,splosis sp.were short-day diapause insects.Under 25?,short daylength could induce diapause of Anabremia sp.and Clinodisplosis sp.The diapause rates of Anabremia sp.and Clinodisplosi.s sp.under dif-ferent photoperiod conditions were significantly different(P<0.05).The critical photoperiod for inducing Anabremia sp.and Clinodisplosis sp.into diapause at 16? ranged from 12 hr/d to 14 hr/d.The critical photoperiod is between 10 hr/d and 12 hr/d at 19?.No photoperiod could induce diapause at 28?.Temperature and photoperiod co-regulate and induce the two Illicium blossom gall midges to enter diapause.Temperature plays a major role and photoperiod plays a supplementary role.5.Temperature had a significant effect on the diapause rate of Anabrenmia sp.and Clinodisplosis sp.(P<0.01).The diapause rate of Anabrenmia sp.and Clinodisplosis sp.decreased with the increase of temperature.Under total darkness,the diapause response curve showed that the critical temperatures of the Anabremia sp.and Clinodisplosis sp.were about 17.8? and 17.5?.Reaction curve of thermoperiod cycle(16?:28?)showed,The critical low temperature duration of Anabremia sp.is about 12.3h.The critical low temperature duration of the Clinodisplosis sp.is about 12.8h.Thermoperiod cycle affects diapause induction of two Illicium blossom gall midges by temperature of cryophase and duration of cryophase.The diapause rate decreases gradually with the increase of temperature in cryophase and the shortening of cryophase duration.Thermoperiod cycle(CT12:12)response under photoperiod 12L:12D showed that diapause induction was strongly influenced by dark-time temperature.6.Under natural conditions,the overwintering larvae of Anabremia sp.and Clinodisplosis sp.release diapause in the middle and late July of each year.The overwintering larvae of two species of gall midges collected in the field were placed in the laboratory at 25 C to release diapause.Date of emergence time of two species Illicium blossom gall midges was consistent with that of natural conditions.Indoor diapause release test showed that diapause population under indoor conditions of Anabremia sp.and Clinodisplosis sp.could terminate diapause in May.There was no significant difference in diapause termination rate and time between the two species under different photoperiods(P<0.05).Under different temperatures,the removal rates and diapause time of the two species were significantly affected.High temperature was beneficial to the diapause removal of the two species.