Effects Of Photoperiod And Light Intensity On Oviposition Rhythm Of Grapholita Molesta Busck

Grapholita molesta Busck is a serious worldwide fruit pest and its host range is very wide,including peach,pear,apple,etc.which belonging to rosaceae.The G.molesta mainly damanged young shoots or fruits as larvae,which seriously affected the yield and quality of the fruits.It has become one of the important factors influence fruit quality and high-yield cultivation in China.At present,G.molesta was mainly controled by chemical control methods,supplemented by sex pheromone trap and mating disruption technology.But due to its boring,hidden characters,the larvae once bore into tender shoots or fruits,the chemical pesticides couldn’t control it anymore,so there need a highly efficient and pollution-free control method for G.molesta.Oviposition period is one of the key periods for prediction and comprehensive control,so it is very important to understand the oviposition rhythm and its regulatory factors of G.molesta.However,the induction and regulation mechanism of oviposition rhythm of G.molesta is still unclear.In our research,tests were conducted outdoor and indoor,by changing the oviposition environmental factors of G.molesta(photoperiod and light intensity),comparative analysis of different illumination conditions G.molesta adult oviposition rhythm,make clear the relationship between photoperiod,light intensity and oviposition rhythms,to provide the reference to regulate the oviposition rhythm as well as the application in the actual production.The main research results are as follows:1.The oviposition activity of G.molesta in natural showed obvious rhythm,and present a single peak curve.When the local sunset time was19:30,the oviposition peak appeared between 19:00 and 20:00,and the maximum spawning quantity was 195,and the spawning quantity in peak period accounted for 50.12% of the total daily spawning quantity.The oviposition peak occurs at 0.5 hours around sunset.2.Under the conditions of continuous light and continuous darkness,it was found that the peak period of spawning was from 19:00 to 21:00 in both conditions,and the amount of spawning in the peak period under continuous light accounted for 42.81%,50.71%,53.65%,34.94% and37.39% of the total daily spawning in both conditions.Under continuous darkness,the spawning amount in peak period accounted for 53.20%,55.11%,40.42%,36.16% and 46.98% of the total daily spawning amount,respectively.The spawning rhythm was obvious and showed free operation rhythm.3.The results showed that G.molesta adult when the photoperiod was15L:9D,the spawning quantity in the peak period of 5 d accounted for56.36%,36.33%,53.64%,36.18% and 38.23% of the total daily spawning quantity,respectively,and the spawning peak occurred between 19:00 and21:00,which was consistent with the free movement rhythm.When the photoperiod was 9L:15D,the spawning quantity in the 5 d peak period accounted for 48.20%,43.19%,46.94%,47.23% and 49.39% of the total daily spawning quantity,respectively,and the spawning peak occurred between 19:00 and 21:00,which was consistent with the free operation rhythm.When the photoperiod was 12L:12D,the spawning quantity in the5 d peak period accounted for 34.94%,60.10%,57.10%,49.43% and52.82% of the total daily spawning quantity,respectively,and the spawning peak occurred at 21:00-23:00,which was 2 h later than that in 15L:9D and9L:15D.4.Under the photoperiod of 24L:0D and the illumination intensity of5000 lux,G.molesta adult were treated with intermittent illumination intensity of 2000 lux,1000 lux,500 lux and 100 lux,respectively,from17:00 to 19:00 every day.Under different intermittent light intensity,there were significant differences in the amount of oviposition during peak period(P < 0.05).When the intermittent light intensity was 2000 lux,the spawning peak appeared between 19:00 and 21:00,which was consistent with the free operation rhythm.The spawning quantity in the peak period accounted for 63.14% of the total daily spawning quantity.When the intermittent light intensity was 1000 lux,the spawning peak appeared between 19:00 and 21:00,which was consistent with the free operation rhythm.The spawning quantity in the peak period accounted for 37.40% of the total daily spawning quantity.When the intermittent light intensity was500 lux,the spawning peak appeared between 19:00 and 21:00,which was consistent with the free operation rhythm.The spawning quantity in the peak period accounted for 57.23% of the total daily oviposition quantity.When the intermittent light intensity was 100 lux,the oviposition peak appeared between 17:00 and 19:00,and the oviposition amount in the peak period accounted for 47.83% of the total daily oviposition amount compared with the free operation 2 h earlier.5.Effects of light intensity on growth,survival and reproduction of G.molesta.Under the photoperiod of 15L: 9D and different light intensity,all the developmental stages were affected,but the influence degree varied with the developmental stages.The results showed that under 1000 lux,2000 lux and 10000 lux light intensity,there was no significant difference in the development duration of eggs,which were all 3 days.There was no significant difference in hatching rate,which were all > 87%.There was no significant difference in the larval development duration under different light intensity,which were all 13-14 days.There was no significant difference in larval survival rate under different light intensity.The pre-pupal stage of G.molesta was significantly different under the different light intensities.Under the 200 lux light intensity,the pre-pupal stage of G.molesta was only 2 days,while under the 1000 lux and 10000 lux light intensity,the average pre-pupal stage of G.molesta were 3 days.