Study On Reproductive Behavior And Behavioral Response To Host Plant Of Diaphania Angustalis(Snellen)

Diaphania angustalis(Snellen)is a major defoliator of Alastonia schalaris(L.)which is an important landscaping and medical tree.The larvae of D.angustalis can curl the leaves of A.schalaris.With characteristics of strong concealment,large appetite and high rate of reproduction,the damage it caused is devastating and can last for a long period of time.While the situation in south China is getting even worse in recent years,we still lack effective methods to protect A.schalaris from D.angustalis.The planting and management of A.schalaris is closely linked to human daily life so that chemical pesticide control methods should be avoided.In this term,pheromone trapping is considered to be an appropriate management strategy for D.angustalis.Therefore,the reproductive behavior rhythm and the relationship between reproduction fitness and host plant interaction were studied,then the combined effect of sex pheromone and host plant volatiles were explored via SEM and TEM,GC-MS and GC,EAG and indoor wind tunnel test.The aim of this study was to clarify the effect of mating interference mechanism and host plant on the behavioral response of D.angustalis,and to provide basic informations for the exploration of a new environmental-friendly prevention and control technology of D.angustalis.The main results are as follows:(1)D.angustalis can occur for 6?7 generations a year in Nanning,Guangxi.Both male and female adults need supplementary nutrition before mating and oviposition.The longevity of adults was significantly prolonged after they were provided with supplementary nutrition(Female:19.63±0.54 d,P<0.000;Male:20.63±0.43 d;P<0.000).Adult eclosion,calling,mating and oviposition occurred in the scotophase.The eclosion peak of male and female adults occurred in the first half of the scotophase,and the eclosion peak of female was1 day earlier than that of male.Female virgins began to show courtship behavior from 2 days old,and the courtship rate reached the peak at 4 days old and can last to 6 days old,then decreased;after 5 days old,the daily calling peak advanced to 2nd to 3rd hours at the scotophase,and the calling ability decreased.The premating period of male and female was 3.99 days and4.61 days respectively.The mating peak occurred in the 4th to 6th hour of the scotophase,and the mating duration ranged from 60 to 120 minutes.The average oviposition period of mating females was 5.2±1.41 days.There were 66.4%of their eggs which were laid in the 2 days after mating.The average single female fecundity was 592.5±25.3 eggs.(2)The male of D.angustalis could mate at most twice in their lifetime,but multiple mating could reduce their reproductive fitness.The female could only mate once in their lifetime.The mating experience of the male could affect the hatching rate of eggs,but had no significant effect on their fecundity and longevity.Within 18?32?,temperature had no significant effect on the sex ratio of the adults,and the ratio of female to male ranged from 1:1.05 to 1:0.78.At 25?,mating rate,fecundity,hatchability of offspring and reproductive expectation of the female were at the highest level.At 18?,mating rate and hatching rate of the female decreased significantly,and the relative reproductive expectation decreased by 66%.The results indicated a sexual-related different effect,for the reproductive fitness of D.angustalis was affected by the age of male and female adults.Delayed mating of male had a significant negative impact on the mating rate,which was stronger than that of female;the delayed mating of male and female both resulted in a significant reduction in mating rate,while the former treatment was more affected than the female;delayed mating of male and female could significantly shorten the oviposition period of female,and there is interaction between male and female;delayed mating of female had a strong negative effect on the fecundity;with the delayed mating of female,the hatching rate of eggs decreased significantly..(3)In the case of without-host,the mating rate was lower than the case of with-host by20%,the fecundity was decreased by 174.5 eggs,the oviposition period shortened by 1.21 days,and the pre-mating period was prolonged by 1.14 days.Besides,the host could not affect the hatching rate of eggs.The study of sex pheromone indicated the host plants had a regulatory effect on sex pheromone release.In the absence of host plant stimulation,the content of sex pheromone in the gonads of 6 to 8 days old virgin female were significantly higher than that of the virgin females with host plants,virgin females could slowly release sex pheromones,and this led to delayed mating.(4)Morphological characterization of antennal sensilla of D.angustalis.Through scanning electron microscope technology,we observed the morphology and distribution of the antennal sensillum on D.angustalis.There are eight types of antennal sensilla,namely,sensilla trichodea,sensilla chaetica,sensilla coeloconica,sensilla auricillica,sensilla styloconica,sensilla squamiformia,capitate peg and B(?)hm bristles.These sensilla showed difference in number and distribution between female and male.Sensilla were distributed on the ventral of antennae.The shape and number of sensilla were different between male and female.The size of sensilla coeloconica of male was significantly larger than that of female.The number of sensilla trichodea of male was significantly more than that of female,while the number of sensilla chaetica I and sensilla auricillica of female was significantly greater than that of male.Holes were found in sensilla trichodea,sensilla chaetica and sensilla auricillica via TEM.Compared similarities of sensilla types between D.angustalis and 6 Crambidae moths by hierarchical cluster analysis,D.angustalis was grouped generally similar to Cnaphalocrocis medinalis but was grouped separately from Maruca testulalis.(5)There is only one active component of D.angustalis sex pheromone in Guangxi local population,E10E12-16CHO,an unsaturated aldehyde with two double bonds.This indicated that the differentiation in sex pheromone composition occurred among geographical regions.The production of sex pheromone of D.angustalis has an obvious dynamic rhythm.The accumulation of sex pheromone reached the highest at 3 days old of female,and then began to decline.Although the peak of female courtship and mating was at 4 days of age,it suggested a certain kind of synergy mechanism do exist between the release of sex pheromone and its reproductive behavior.(6)In the wind tunnel experiment,both male and female adults of D.angustalis could be attracted by the extract of the volatile matter of A.schalaris,and the number of females attracted by the extract is more than that of male.The results of GC-MS and GC-EAD showed that there were eight components in the volatiles of the leaves of A.schalaris,which were p-Xylene,Cyclohexanone,Benzaldehyde,Acetophenone,Nonanal,4-Ethylbenzaldehyde,Decanal and4'-Ethylacetophenone.The EAG concentration gradient experiment indicated that the EAG reaction of adults to Nonanal,4-Ethylbenzaldehyde,Decanal and 4'-Ethylacetophenone was stronger than other substances.In the indoor wind tunnel experiment,the number of females attracted by A₁(eight components in the volatiles of the leaves of A.schalaris),A₂(Benzaldehyde,Acetophenone,4-Ethylbenzaldehyde and 4'-Ethylacetophenone),A₃(Cyclohexanone,Nonanal,Decanal and 4-Ethylbenzaldehyde)and A₅(Decanal,4-Ethylbenzaldehyde and 4'-Ethylacetophenone)formula to less than 15 cm near the lure core were significantly more than that of other formulas,while the males showed no significant difference at this stage.The results indicated that,compared with the simple formula of plant volatiles,the formula of plant volatiles additive pheromone had greater attraction effect on the adults,especially the males.Among eight kinds of plant volatiles additive pheromone,M₂ had the most attraction to the males within 15 cm,which was significantly more than the single pheromone formula and other formulas.The results of field test showed that M₅ formula containing only sex pheromone could induce a large number of males,while M₂ and M₄ formula containing three components(Decanal,4-Ethylbenzaldehyde,4'-Ethylacetophenone)plus sex pheromone could respectively induce virgin females in Binyang and Shangsi,though the effect was not good.In this study,the reproductive behavior of D.angustalis,the effects of mating frequency,delayed mating and host plant on reproductive fitness of moths were determined.And the feasibility of using sex pheromone methods to control the population density of the D.angustalis was confirmed.The active components of sex pheromone of D.angustali in Guangxi population were differentiated.It is necessary to consider the difference of population from different regions,when using sex pheromone to control D.angustali.The results of this study can provide a decision-making reference for the development of safe and efficient control techniques for D.angustalis,and also have great significance to theoretical and practical value.