The cotton aphid (Aphis gossyp'i Glover) is one of the most important pests infesting cotton in the cotton areas of North China. Since 1953 organophosphorus insecticides such as parathion and systox have been used to control the aphids for keeping up good yield of cotton. After several years. the concentration and the amount of spray were increasing in the field. In the early 1980's highly effective pyrethroid insecticides such as decis and sumicidin were largely imported into China. When first used 2. 5% decis emulsion was diluted in the ratio from 1110000 to 1812000. However in 1985 the resistance of cotton aphid to pyrethroids increased by 171 times in general, 3230 times in some cotton fields. Thus it has prompted us to investigate the mechanism of resistance to insecticides and to search for the strategy to control the resistant aphids.Experiments showed that the use of synergists including SV, (0, 0-diethyl, 0-phenyl p h w phorothionate) and PB has given evidence indicating mixed function oxidases (MFO) . a-NA esterases and a-NA carboxylesterase are involved in the formation of resistance. The results also showed that the sensitivity of AChE to paraoxon in resistant aphids was lower than that in susceptible aphids.Experiments showed that SV1 was particularly synergistic to organophosphorus or pyrethroid insecticides and had played an excellent role in overcoming the resistance of cotton aphids to insecticides.
various areas of effort and add details of the authors' recent original researches. It is these reports of previously unpublished work that make this compilation of special value. The volume should be of interest and use to medical entomolo-gists, sanitarians, and sanitary engineers concerned with the operational aspects of insect control; to public health administrators responsible for the prevention of arthropod-borne diseases; and to the scientists involved in the laboratory study of insecticides. JUSTIN M. ANDREWS Perinatal Medicine, is in the direct line of tradition of the academy's publication on maternal mortality in 1933 which did so much to destroy the professional and public complacency toward maternal deaths existing at that time. The present report should be of the utmost interest to health workers, in both clinical and public health practice, who wish to bring about a further reduction in perinatal deaths and provide the best care for other infants in the light of present-day knowledge. The detailed description of the method, forms, and questionnaires used, along with the critical comments about the study itself and suggestions emanating from the experience gained, should be of value to individuals planning similar studies. A detailed analysis was made in each case of the clinical and pathological records , supplemented in many instances by interviews with physicians, nurses, and other persons. In those instances in which the results of the analysis were not clear-cut, the cases were referred for review by panels, each of which consisted of an obstetrician, a pediatrician, and a pathologist. All cases were classified according to preventability, taking into consideration such factors as adequacy of prenatal care, medical judgment , medical technics, fault of family, qualifications of medical attendant, and pediatric care. The study concluded that 35 per cent of all the deaths were preventable. Errors in medical judgment were considered to be present in 31 per cent, unsatisfactory pediatric care in 27 per cent, and errors in medical technic 24 per cent, although these were not necessarily considered as directly related to pre-ventability of death in a given case. Preceding the actual statistical analysis is a series of dramatic cases illustrating the various responsibility factors, which makes the subsequent statistical material more alive and meaningful.
SV1 was observed to have obvious synergism and could delay housefly (Musca domestica vicina) resistance development to Dipterex. The penetration rates of Dipterex through housefly cuticle were determined in a susceptible and two resistant strains. The results indicated that the penetration in the resistant housefly strains was obviously slower than in the susceptible one. The penetrating rate of SV1+ Dipterex (in mixture) was higher than that of Dipterex. The penetration reduction in resistant houseflies may be an important factor in bringing forth resistance. The increase of the penetrating rate of Dipterex and the decrease of its metabolic rate are regarded as the important mechanisms of SV1 synergism to Dipterex.
The individual esterase activity which is measured by filter paper test (FPT) method may determine the resistance of cotton aphids Aphis gossypii (Glover) against organophosphorus (OP) insecticides. For testing accurately resistant level caused by different insecticides, we applied FPT method for measuring inhibitory action of methyl‐parathion, monocrotophos and omethoate to α‐NA esterase of individual cotton aphids, and compared the inhibitory frequencies of these three insecticides to susceptible population (BCA) and resistant population (GCA). Results showed that their inhibitory frequencies of the susceptible population were evidently higher than that of the resistant population. The inhibitory rate of α‐NA esterase in F1 generation individual cotton aphids by monocrotophos was low when the cotton aphid population had been treated in advance with monocrotophos, but it got to 75%‐90% when the cotton aphid population had been untreated in advance with monocrotophos. Besides, the differences in esterase activity were not obvious between them. In same region when cotton aphids were treated with insecticides the inhibitory frequency of esterases in individual by the insecticides was lower than counterparts in individual cotton aphids which were not treated with insecticides. All these demonstrated that inhibitory frequency of α‐NA esterase in individual cotton aphids by OP insecticides could be used as a technique of forecasting pest resistance.
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