Screening of Chemical Control for Potato Blight

To screen chemicals for controlling potato blight effectively, randomized block experiment was adopted, the control efficiency of five chemicals for Carbendazim, Metalaxyl, Dithane mancozeb, Curzate, Cymoxanil mancozeb was explored. The results showed that the efficiency of Metalaxyl was much better than that of other conventional chemicals in controlling potato blight, up to 70.59% ; the mean control efficiency of Curzate and Cymoxanil mancozeb was 68.76% and 67.05% ; the control efficiency of Carbendazim was lower, 55.76%. Big and middle tuber rate, tuber weight per hole, plot yield, unit area yield of potatoes in Metalaxyl treatment were the highest, 78.05%, 437.24 g/hole, 34.0 kg/21.6 m2 and 15 748.61 kg/hm2, 49.12% higher than the control yield. The indexes of potatoes in Cymoxanil mancozeb treatment were the second highest, 73.33%, 385.31 g/hole, 32.8 kg/21.6 m2 and 15 192.78 kg/hm2, 43.86% higher than the control yield.

Screening of Dominant Species of Triehogramma sp. and Evaluation of Field Control Effect

[Objective]The paper was to screen out the dominant species of Trichogramma sp.parasitized on Osirinia nub ilalis eggs and to evaluate the field control effect of Trichogramma sp..[Method]Six kinds of fresh egg masses of Trichogramma sp.parasitized on O.nubilalis were used to screen out three dominant species of Trichogramma sp.,and the single factor experimental design was used to evaluate field control effect.The dominant species were determined by combining yield,recovery yield loss rate and yield increase rate.[Result]T.osiriniae had the highest parasitic rate on O.nub ilalis;the parasitic rate of egg masses was 74.0%,and the parasitic rate of egg granules was 65.4%.The second was T.dendrolimi;the parasitic rate of egg masses was 62.0%,and the parasitic rate of egg granules was 59.5%.The parasitic rates of egg masses and egg granules of T.chilonis were 58.0%and 47.1%,respectively.The three Trichogramma sp.were the dominant bee species parasitized on O.nubilalis eggs.The average control effect of T.osirinae parasitized on O.nubilalis in the field was 73.86%;the average control effect of T.dendrolimi was 68.47%;and the average control effect of T.chilonis was 47.97%.The recovery yield loss rates was 9.58%,7.02%and 4.02%,and the yield increase rates were 9.65%,7.47%and 4.52%,respectively.[Conclusion]Considering the control effect and cost control comprehensively,T.dendrolimi should be used to control O.nubilalis in actual production.

Application of a catch-based method for stock assessment of three important fisheries in the East China Sea

Most fisheries in China do not have maximum sustainable yield（MSY） estimates due to limited and poor data.Therefore, finding a common method to estimate MSY or total allowable catch（TAC） for fishery management is necessary. MSYs of three important fisheries in the East China Sea were evaluated through a catch-based model.Estimates for intrinsic rate of increase（r） and five levels of process error were considered. Results showed hairtail Trichiurus japonicas（Temminck and Schlegel） and small yellow croaker Larimichthys polyactis（Bleeker） fisheries experienced overfishing from the mid-1990 s to the early 2000 s, and the suggested TACs were 55.8×10^4 t and9.06×10^4 t, respectively. Decades of overfishing in wintering and spawning grounds of large yellow croaker Larimichthys crocea（Richardson） caused the fishery＇s collapse in the 1980 s, and it has not recovered until today.The Catch–MSY model generated similar estimated MSYs with other methods and may be a useful choice for the assessment of regional stocks in China.