Research On Mechanism Of Disrupting Mate And Selection Of Attractive Sources Based On Mating Behaviors In Grapholita Molesta (Busck)

The oriental fruit moth (OFM), Grapholita molesta (Busck), is a cosmopolitan pest that occurs in major fruits areas. Feeding by larvae causes damage to the growth of sprouting shoots and fruits attacks, and it almost all orchard fruits and is a major pest of stone fruit, pears, peaches, and apples. Recently, control methods based on insect sex pheromones have great potential for pest management. Semiochemical-mediated mating disruption controls insect species mainly by using chemicals involved in its own communication system, so analysis of probable modes of actions is useful to determine the reasons behind success and failure of various formulations. Thus, we carefully studied mating behaviors of insects and behavioural role of attractive sources in Grapholita molesta in order to improve mating disruption and attractive technology. The major results are summarized as following:Behavioral mechanism of mating disruption in Grapholita molesta Emergence, mating and reproductive behaviors of Grapholita molesta. We determined 1) the sequence of activities during emergency and mating; 2) the ratio of females and males after emergency; 3) the daily periodicity in emergence and mating; 4) the age and duration during mating; 5) fecundity and egg fertility; 6) remating. In this study, laboratory and field observations indicated the ratio of females and males was approximately 1.01:1 and 1.04:1, respectively. The activity time in one day mainly included between 4:30 a.m to 7:30 a.m for emergency and between 18:30 p.m and 20:30 p.m for mate, and the peak of the laboratory-reared culture occurred one hour earlier than the field-sampled populations. The first mating occurred on the first night after adult emergence and the majority of pairs mated on the second and forth night after emergence. Most pairing took 24.9 minutes, and fertilized 26.5 eggs per pair, and there was also a positive linear correlation between female fecundity and egg fertility per pair during their lifetime. Females averagely mated once and lasted for 32.9 minutes, and males usually mated twice and lasted for 23.2 minutes, indicating a male-biased operational sex ratio. For multiple mating of female moths, female fertility averaged 33.3 and its percent egg fertility was 50.7%; for multiple mating of male moths, female fertility averaged 32.8 and its percent egg fertility was 49.4%. The longevity of female and male moths averaged 8.4 days and 8.8 days, respectively. Sequential mating by males had no effect on fecundity or egg fertility. There was no correlation between egg fertility and the number of times males had previously mated, indicating that male ejaculates were not limited.Mating and reproductive potential to different scenes of mating disruption in Grapholita molesta. In the subsequent disruption experiments, we changed different operational sex ratio based on the adult sex ratio after emergency, different delayed mating based on mating age and different multiple mating based on sexual experience in both sexes to test their effects on mating and reproductive behavior experimentally. Firstly, our results indicated that according to ratio of females and males after emergency was approximately 1:1, when the number at copulation of females was positively disrupted (corresponding to increasing number), either copulation number and fecundity of all mating partners increased or egg fertility decreased significantly with the more female biased adult sex ratio, and when the number at copulation of females was negatively disrupted (corresponding to decreasing number), copulation number and fecundity of all mating partners decreased significantly with the more male biased adult sex ratio and there was only significantly different for egg fertility in the more male biased adult sex ratio, and when the number at copulation of males was positively disrupted (corresponding to increasing number), egg fertility decreased significantly with the more male biased adult sex ratio, and when the number at copulation of males was negatively disrupted (corresponding to decreasing number), there was only significantly different for egg fertility in the more male biased adult sex ratio. Also, our results indicated that according to the first and peak mating respectively occurring on the 1st day and the 2nd～3th day after emergence during 8 days of mating period, when the age at copulation of males was disrupted (corresponding to older males mated with young females), and when the age at copulation of females was disrupted (corresponding to older females mated with young males), when age at copulation of both the male and female were disrupted (corresponding to mating of same-age males and females), fecundity and egg fertility decreased with growing old for males, female, as well as both males and females, respectively. Lastly, our results indicated that according to 10% of the pairs recopulating and 78% mating only once, when sexual experience of male was disrupted (corresponding to virgin or mated males mated with virgin or mated females, respectively), males were capable of mating multiple times, and when sexual experience of female was disrupted (corresponding to virgin or mated females mated with virgin or mated males, respectively), female appeared to be essentially monandrous, thus revealing a potential polygyny. Therefore, females play a main role and males playe a secondary role in the behavioral mechanism of mating disruption for a dual system of mate recruitment in certain Lepidopterous species.Selection of Different Attractive Sources in Grapholita molesta in the Field Effects of trap plcements on pheromone-baited trap catch efficacy for Grapholita molesta moths in a peach orchard. We examined the effects of trap height, trap location, and inter-trap spacing on trap catches in a conventional peach orchard. Traps were placed at heights of up to 3.0 m above the ground and sets of nine traps were positioned in grids with inter-trap distances of 10 to 50 m to determine optimum trap location and spacing. Traps were checked daily over 10 days for males during four periods corresponding to peak moth flight. Moth catches were higher when traps were placed toward the tops (2.5 m) and outside the canopy (3.0 m). Although differences were not significant, moth catches in traps located upwind and outside were higher than in the central trap for all inter-trap distances. When inter-trap distances were shorter than 30 m, interference between traps occurred.Optimum ratio and dose of Different Attractive Sources in Grapholita molesta in the field. The best ratio and doses of four attractive sources including sex pheromone (PH), host-plant volatiles (PP), food bait (FL) as well as sweet and sour liquid (SS), were selected in peach orchards. We found that the best ratio and dose of sex pheromone, host-plant volatiles, food bait, and sweet and sour liquid were ratio 7 & dose 4, ratio 2 & dose 0.1, dose 12D and ratio 4, respectively.Behavioural Role of Attractive Sources in Grapholita molesta Scanning electron microscopy studies of antennal sensilla of Grapholita molesta. In order to provide requisite background information on further chemical ecology studies, we examined the external morphology of the antennal sensilla of Grapholita molesta using scanning electron microscopy. Antennae of male and female Grapholita molesta are filiform in shape, seven morphological sensilla types were recorded in both sexes, including two types of the highly abundant and widely distributed sensilla trichodea (ST I and ST II) and sensilla auricillica (SGE I and SGE II), sensilla chaetica, sensilla basiconca, sensilla coelocomica, sensilla styloconica, sensilla auricillica and sensilla gemmiformium. The ST I are presumably chemoreceptors, while the ST Ⅱ may function as mechanoreceptors. The sensilla styloconica are thermo-hygroreceptors. The sensilla styloconica is abundant in males, whereas females have great number of the sensilla gemmiformium. The shape, structure, distribution, and size of antennae of males and female were not similar, thus revealing the differences between the sexes in the division of labour.Behavioural role of individual components of a multichemical attractant system in Grapholita molest. According to the aheived the ratio and dose of four kinds of Grapholita molest sex pheromone components, the precise communicative roles of individual pheromonal components was determined by the electroantennogram (EAG) response, behaviour observation in wind tunnel and catching moths in the field. We found that that cis-8-dodecenyl acetate (Z8-12:Ac) is a primary attractant pheromone component, and could attract male moths to arrive at the nearby source and vertical rotate around the source. The trans-8-dodecenyl acetate (E8-12:Ac) is a primary synergist, could have strong effect on antenne of male moths and attract male moths to leave a releasing cage and upwind orient. The cis-8-dodecen-l-ol (Z8-12:OH) and dodecanol (12:OH) are two secondary synergists, and could attract male moths to reentry fly and arrive at the source or contact on the lures, respectively, and could have the joint synergism attracting effect, when individually mixed with E8-12:Ac.Behavioural response of four attractive sources in Grapholita molesta. According to the aheived the ratio and dose of four attractive sources including sex pheromone (PH), host-plant volatiles (PP), food bait (FL) as well as sweet and sour liquid (SS), they were mixed and then tested by the electroantennogram (EAG) response, behaviour observation in wind tunnel and catching moths in the field, respectively. Female and male moths had significantly higher EAG responses to PP+SS, PP+SS+FL and PH+PP+SS compared with others, and female had significantly higher EAG responses compared with male. Attractive sources in combination were examined in a wind tunnel. There was not significantly different in percentage of responding moths among the attractive sources in combination, and more female moths were attracted than male moths. The lures, PH+FL, FL and PH+PP+SS+FL stimulated more females to land around the odor source, landing proportion of which was 41.7±7.9%,40.0±10.6% and 35.0±5.6%, respectively. The lures, PH, PH+PP and PP+SS stimulated more males to land around the odor source, landing proportion of which was 23.3+7.6%,20.0+10.0% and 20.0±8.66%, respectively. In the field, there was significantly different in trap catches among the attractive sources in combination during the peak period of the 1st,2nd and 3rd generations, except for overwintering generation, and attractive sources in combination including FL+SS, PH, PH+FL, PH+FL+SS, PH+PP+SS+FL, PH+SS, PP+FL+SS and PP+SS captured more moths than others, and more male moths were captured than female moths. Hence, the optimate attractivity of PH to male moths, the close-range attractivity of FL to male and female moths, the strong response of SS to antennae of female moths, and the coattractant role of SS only when mixed with other attractive sources revealed that the attractive sources in combination containing PH and FL appeared high-performance.Optimation of Attractive Sources in combination in Grapholita molesta in the field To determine the optimal attractive source in combination, the best media and antioxidant were successively added to attractive source in combination including PH and FL. We found that of all the media, C1 of b μl were superior to others in terms of our selected attractive source in combination. When adding the antioxidant in concentrations of between 1 and 5, AO, our seclected sex pheromone captured more male moths than others, and then when adding the antioxidant in concentrations of SAO2, AO, the duration and mean catches of attractive sources in combination were longer and more than others and controls, respectively.In conclusion, according to the systematic researches on behaviors of mating disruption and selection of attractive sources in Grapholita molesta, we not only obtained the important informations on chemical communication of sexual behaviors in reproduction in Grapholita molesta, but also determined the precise informations on behavioural role of attractive sources in Grapholita molesta, which will provide guidances for successful implementation of Semiochemical-mediated controlling technologies and theoretically reveal coattraction of females and males is meaningful.