| The fruit flies on Cucurbits were major pests on cucurbitaceous vegetables. The kinds of fruit flies on Cucurbits and their occurrence and population dynamics were investigated in Nanning, and the biological and ecological characteristics of the dominant species, melon fly, Bactrocera cucurbitae (Coquillett), were studied in this paper. The research results provided a foundation data for scientific prediction and pest control for melon fly. The main results were as follow:1. Two fruit flies, B. cucurbitae and B. tan were found infested the Cucurbits in Nanning, Guangxi, and the dominant species was melon fly. They could damage the fruits and stems of Cucurbitaceae vegetables. The extent of losses was significantly difference between hosts. The squash was infested most seriously, and the bitter gourd was follow. The musk melon, watermelon and cucumber were seriously infested by these kinds of fruit flies, also. The rates infested of crops by fruit flies were affected by the phenological period.2. The melon fly and B.tau occurred year-round in Nanning. The amount of population of melon fly was more than B.tau in the flied. The increasing peak of melon fly appeared from mid of June to mid of August. There were two increasing peak for the amount of population of the B. tan, with the 1st peak period from January to March, and the 2nd peak period from June to July.3. There were 6 to 7 generations of melon fly in one year under various natural temperatures condition and 9 to 10 generations under constant temperatures condition in Nanning. The generations overlap obviously and the adult and pupa were able to over-winter successfully under natural temperatures. There was no over-winter phenomenon for the fly under constant temperatures.4. The attraction of the difference colors to the adult of melon fly was significantly different. The yellow colors with the wavelength of 573.58 nm and 571.65nm had significant attractive ability to the female and male adult, respectively. There was no significantly different response to the same color between female and male.5. The melon fly could develop normally from 15℃to 30℃, and the most suitable temperature range was 25℃to 30℃for it. The development zero temperature (C) were 10.56,7.33,10.77,9.72 and 10.77℃for egg, larval, pupa, pre-oviposition and generation, respectively. The effective accumulated temperature (K) to egg, larval, pupa, pre-oviposition and generation were 12.68,117.91,107.15,364.43 and 602.17 day-degrees, respectively. The fly had maximum number of eggs laid under the condition of 25℃, with 1428.3 eggs per female.There were close relationship between the populations of melon fly with temperatures. The population trend indexes gone beyond 1 under the temperature condition from 15℃to 30℃. The most suitable temperature range for the increasing of population was from 25℃to 30℃, and the fly had maximum population trend indexes with 447.37 and 301.19 at 25℃and 30℃, respectively.The feeding preference of melon fly on 24 species of fruits was determine. The results indicated that squash, bitter gourd, cucumber, watermelon, netted melon, musk melon and pumpkin were the suitable host plants to melon fly, and mango, carambola, plum, guava were unsuitable for the development and reproduction of it.The population trend indexes of melon fly gone beyond 1 on suitable hosts. The fly had maximum population trend index with 564.09 times on cucumber. The fly fed on squash had the maximum intrinsic increase rate with 0.0884 times, and the population double time was 7.8414 days, suggesting that squash be the most suitable host for the development, survival and reproduction of melon fly. |
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