| Dolycoris baccarum is widely distributed in China and other countries in the palaearctic region.It is a pest of a variety of crops.It enters diapause as an adult to overwinter,and the overwinter adult is the source of the next year.Therefore,the study of developmental duration and diapause influencing factors is of great significance to the analysis of population dynamics,prediction and comprehensive control.In this paper,the effects of development duration,photoperiod and temperature on diapause in the population of Hohhot in Inner Mongolia were studied.The main results were as follows:1.The developmental duration under different temperature and photoperiod conditions were observed:The developmental duration from egg to adult under different temperature and photoperiod conditions was observed.With the prolongation of photoperiod at 20 ?,the development duration was significantly prolonged(One-Way ANOVA,P<0.01).When the photoperiod was prolonged at 25 ?,the development duration was significantly prolonged(One-Way ANOVA,P<0.01),but when the photoperiod was extended to 16L: 8D and 18L: 6D,the development duration was significantly shortened(P<0.01).When the photoperiod was 12L: 12 D and 16L: 8D,the development duration was significantly shortened with the increase of temperature(One-Way ANOVA,P<0.01).The linear regression method of temperature and development rate was used to calculate the development threshold temperature and the sum of effective temperatures of each development stage of the population of Dolycoris baccarum in Hohhot.The development threshold temperature of eggs,nymphs and whole generations were 13.38,14.61 and 12.63?,respectively,and the sum of effective temperatures were 51.81,384.62 and 625 diurnal degrees,respectively(d??).2.Effect of photoperiod on diapausesAt 20?,all the individuals entered diapause under the photoperiod conditions of 10L: 14 D and 12L: 12 D,but the diapause rate significantly decreased at 14L: 10 D and 16L: 8D(One-Way ANOVA,P<0.01).At 25?,diapause rate decreased significantly with the prolonging of photoperiod(One-Way ANOVA,P<0.01).The theoretical curve was obtained by using linear regression analysis to calculate the critical photoperiod of diapause in the Hohhot population of the Dolycoris baccarum at 25?.The results showed that female and male were 14.61 h and 14.10 h,respectively.3.Effect of temperature on diapausesThe diapause rates at 20?,25?,27.5? and 30? at 12L: 12 D were observed.The results showed that the diapause rate was above 95%,When the photoperiod was 12L: 12 D,the effect of temperature on diapause was not obvious,but that of photoperiod was significant.When the photoperiod was 16L: 8D,the effect of temperature on diapause rate was obvious,and the diapause rate decreased significantly with the increase of temperature(One-Way ANOVA,P<0.01).4.Observation of preoviposition and spawning individual ratio of diapause adults under 12L: 12 D photoperiod at 25? and 30?Diapause adults were reared in pairs and observed for 120 days.The adults at 25? and 30? began to lay eggs after 55±2.45 days and 43±1.63 days respectively.The proportions of spawning individuals were 46.67± 1.41% and 61.29± 1.67%,respectively,with significant differences(One-Way ANOVA,P<0.01).The results show that the development duration of Dolycoris baccarum is affected by the photoperiod as well as the temperature.At the short photoperiod of 10L: 14 D and 12L: 12 D,the diapause rate of Dolycoris baccarum was the highest,and the diapause rate was highest at 20?.With the prolongation of photoperiod and the increase of temperature,the diapause rate decreased.Moreover,when the diapause adults remained at 25? and 30?,the diapause was removed and the eggs were laid after 55±2.45 days and 43±1.63 days,respectively.And the proportion of female spawning individuals at 30? was significantly higher than that at 25?. |
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