| Grapholitha molesta (Busck) is one of the bore-fruit pests which can feed tender shoots and fruits of members of the family Rosaceae in the world. In the history, most large scale outbreaks in G. molesta have occurred on peach, pear and apple. G. molesta have the obvious characteristic that is migration among different host plants. Peach trees are the primary host plants of G. molesta in the early season, and then shifts to pear and apple trees in the late season. It is the primary parasitic relationship that G. molesta depend on host plants for growth and reproduction. Contrarily, G. molesta can be affected by changeable physical and chemical properties of host plants, and the influence centrally reflect on oviposition selection of females and feeding behaviors of larvae. The systematic research of the two aspects can help to understand the response behavior of G. molesta for host plants.Therefore, this study systematically research the oviposition selection of females and feeding behaviors of larvae on different host plant material in different generation occurrence time. The main results as follows:1. Oviposition preference of adults:On the variety level, numbers of eggs were laid on PT (32.2%), SL (24.7%), XL (16.3%), YT (13.9%) and MT (10.8%) which were higher than others in adult occurrence time of over winter generation. More eggs were laid on YT (28.4%), XHL (26.7%), MT (25.2%) and PT (11.0%) in first generation occurrence time. The females of second generation time were more prefer to lay eggs on YT (39.4%), XL (22.2%) and PT (13.5%). In the third generation time, more eggs were found on XL (33.1%), MT (18.1%), XHL (18.1%), YT (13.8%) and DX (10.7%). On the species level, more eggs were laid on peach (41.0%,64.6% and 61.8%) from over winter generation to second generation occurrence time, and the females of third generation time were more prefer to lay eggs on pear (46.0%).2. Feeding performance of larvae:Total length of tunnel had no significant correlation with larval position, but had positive significant correlation with larval development time. On the variety level, larvae developed better on YT and DX (the total length of tunnel is 1.56cm and 1.59cm respectively, the development time is 8.63 d and 9.00 d respectively) than others in larvae occurrence time of first generation. The larvae of second generation time growth better when feeding PT, YT and MT (the total length of tunnel is 3.99cm,5.46cm and 6.64cm respectively, the development time is 11.33 d,12.38 d and 13.50 d respectively). In the third generation time, YT, XHL and PT were more favorable for larvae growth (the total length of tunnel is 3.02cm,3.41cm and 3.69cm respectively, the development time is 10.50 d,13.20 d and 11.45 d respectively). Larvae of over winter generation time had better performance on PT, YT and MT (the total length of tunnel is 2.70cm,3.31cm and 4.38cm respectively, the development time is 10.33d,10.74 d and 11.77 d respectively). On the species level, better performance of larvae appeared on peach in first, second and over winter generation time (the total length of tunnel is 1.83cm,5.05cm and 3.47cm respectively, the development time is 8.75 d,12.14 d and 10.92 d respectively), and appeared on pear and peach in third generation time (the total length of tunnel is 3.56cm and 3.68cm respectively, the development time is 13.80 d and 11.48 d respectively).Therefore, G. molesta dispersedly laid eggs on peach and pear in different occurrence time except third generation which centrally laid eggs on pear. Peach was more suitable for G. molesta larvae developing except that suitability of pear was higher than peach in third generation time. We hypothesized the migration routes of G. molesta among the main hosts (peach, pear and apple). Migration time occurred from adult emergence period of second generation to third generation. Fitness of peach was descended, but fitness of pear was increased along with change of phenophase. Migration route was a circle that a part of peach generation which beyond the scope of hold move from peach orchard to pear orchard, complete one generation development and then move back to peach orchard for over wintering. Overall, adults and larvae were drove by host plant at the same time. |
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