To define the cost function of irrigation pipes of certain region,engineering cost data of irrigation pipes per unit length in the region are needed. However,the cost data are difficult to collect,and the cost of some irrigation projects cannot reflect the current price level owing to their old construction time.With regard to the above-mentioned,cost information of market materials and budget norm of engineering,etc.are introduced to calculate the engineering unit price of pipes with various diameters,and then through statistical analysis,the cost function of irrigation pipes is yielded.
[Objective]The present study was conducted to investigate the infectiousness of insect microsporidia to silkworm and its propagation in silkworm in order to study the control of silkworm pebrine. [Method]Five kinds of microsporidia were collected from field insect species, viz., Pieris rapae, Hemerophila atrilineata and Podenia litura from sericultural areas of Guangxi. By using microsporidia of Bombyx mori Nosema bombycis (N.b) as the control, the infectivity of different microsporidia to B.mori and their propagation in silkworm body were investigated. [Result]The IC50 (50% infectious concentration) of the microsporidia isolated from P. rapae (PrL M), H.atrilineata (PaB M I), H.atrilineata (PaB MⅡ),Slitura (SI M I), Slitura (SI MⅡ), and N.b were 4.67×104, 8.12×105, 1.13×107, 8.14×107, 3.51×107 and 1.16×104 individual/mL, respectively. The reproductive capacity of 5 kinds of insect microsporidia was low, and there were only 1-10 spores in each field of microscope for PrL M and PaB MI, and only 1 spore in several fields of microscope for PaB MⅡ, Sl MⅠand Sl MⅡ. There were more schizonts in silkworm intestinal wall after infected with PrL M and PaB MⅠ, but they hardly grew into mature spores. [Conclusion]Insect microsporidia in field had stronger cross-infection damage on Bombyx mori, especially on production of silkworm eggs, but they had low reproductive capacity in silkworm body.
【Objective】 The Crop System Simulation Framework (CSSF) is the basis of the reconfigurable simulation software about the crop model resource mapping and design. 【Method】 This research bring the technology of ontology into the field of crop system simulation. Based on the physiological and ecological processes of crop growth, the common characteristics and relationships of crop system (wheat, rice, cotton, rapeseed) modeling processes, model algorithm and model parameters were analyzed and extracted with the ontologies of simulation and crop simulation, the CSSF were constructed. 【Result】 CSSF includes outer (CMOKF) and inner (CMIKF) knowledge frameworks of crop modeling. CMOKF describes the outer common characteristics driven by time, space and environment, while CMIKF describes the inner common characteristics of models components and models algorithm about phasic and phenological development, biomass accumulation, dry matter distribution and yield formation, organ built, plant-soil water dynamics and nutrient balance simulation. 【Conclusion】 CSFF realized the knowledge level sharing the crop modeling concepts, processes, structures and methods, and could play a guiding role on designing the reusable crop model software architecture.
[Objective]Effects of host’s environmental humidity on pathogenicity of Beauveria bassiana during white muscardine epidemic were studied to provide references for adopting proper treating and controlling measures to eliminate the influence of white muscardine on silkworm production . [ Method ] White muscardine silkworm bodies collected from Xiangzhou County of Guangxi were used to investigate their changes in different humid environment and pathogenicity every 15 days. [Result ]White muscardine silkworm bodies were observed at temperature of 25 ℃ in 60%, 75% and 90% RH environment, respectively. The results showed that there was a close relationship between humidity and survival ability of Beauveria bassiana. In storage environment of 60% RH, silkworm bodies remained intact and hard with yellowish white conidium clearly seen on 60 d. The pathogen activity went down progressively at increasing humidity. Those three treatments all had strong pathogenicity of Beauveria bassiana to 2nd -instar of silkworm during the first 30 days. Their LT50 was 2.915, 3.071 and 5.222 d, respectively. At 60%-75% RH, Beauveria bassiana still had strong toxicity to silkworm on 45-60 days, while at 90% RH, conidium number dramatically fell on the 45th d, hence its pathogenicity could not be detected. [Conclusion]Within 60 days, pathogenicity rate of Beauveria bassiana to silkworm was high, therefore it was useful to reduce reinfection of Beauveria bassiana by removing the diseased silkworm body timely and inactivating body pathogenicity.
Research into insecticide resistance in the natural enemies of pest insects has both theoretical and practical significance for the combined use of chemical and biological control in integrated pest management(IPM). Insect natural enemies have huge potential value in pest control if they can be used simultaneously with insecticides in IPM. Current understanding of pesticide resistance in the natural enemies of pest insects is reviewed, including the effects of insecticides, present knowledge of insecticide-resistance, resistance mechanisms and factors limiting the development of insecticide resistance. The prospects for the future development of populations of natural enemies with high insecticide resistance is also discussed.
Susceptibility levels of whitebacked plathopper (WBPH, Sogatella furcifera Horvath) and brown planthopper (BPH, Nilaparvata lugens Stal) to 13 insecticides were monitored in laborato- ry by using standard topical application method. The monitoring results during 1987～1991 indicated: (1) Strains of WBPH and BPH were most susceptible to carbofuran, the lowest to malathion. The LD_(50)values fluctuated among years as the two kinds of hoppers were migrant pests. (2) The develop- ment of resistance in WBPH population was faster than that of in BPH population. Compared with LD_(50)values of some insecticides of Nagata (1967), WBPH (Zhejiang, 1990) had a 110.56-fold re- sistance to malathion, 48.90-fold to fenitrothion, and BPH had a 11.61-fold resistance to malathion, 6.11-fold to fenitrothion at the same monitoring method. (3) There was a negative rela- tion between resistance level of BPH population and the local chemical used. (4) There existed a wide variation of toxicity of the different insecticide varieties of the organophosphorous. The toxicity of monocrotophos was more than 10 times as high as that of malathion.
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