Study On Storage And Releasing Techniques Of Coccophagus Japonicus Compere

Coccophagus japonicus Compere is an important parasitic natural enemy with good control effect on the rubber pest Parasaissetia nigra Nietner.Due to the lack of effective storage and releasing techniques,the popularization and application of C.japonicus in production are limited.In this paper,the effects of low temperature storage on the emergence rate,adult longevities and fecundities were studied in order to evaluate and determine the best storage conditions.The high temperature adaptability,outdoor emergence rate,longevities,dispersal distance and the ratio of wasp to scale were studied before release,and the releasing technique was clarified.The results are as follows:1.Storage conditions of C.japonicusStorage time,temperature and age are important factors affecting the storage of C.japonicus.After low temperature storage,the emergence rate,adult longevities,oviposition,parasitism rate of C.japonicus and the emergence rate of their offspring all decreased to some extent.The pupae of C.japonicus all emerged into adults within 3-4 days after low temperature storage,and the begining time of emergence moved up with the extension of storage time.Storage time and temperature had significant effects on the pupae survival of C.japonicus,and the emergence rate increased with the storage temperature.The emergence rates of 3-day-old pupae stored at the same temperature for the same time duration were higher than those of 1-day-old pupae.The emergence rate of 3-day-old pupae averaged96.00% after 7 days storage at 10℃ and averaged only 44.67% after 27 days storage at10℃.The emergence rate of 3-day-old pupae averaged 96.67% after 7 days storage at 12℃and averaged 85.33% after 33 days at 12℃.There were few emerged wasps in incubator after 25 days storage at 14℃.The longevities of emerged adults after cold storage decreased significantly with the decrease of temperature and the extension of storage duration,respectively.After storage for 23 days at 10℃ and 14℃,The longevities of emerged adults were 11.11 and 12.80 days in average,respectivley.After storage at 12℃ for 19 days to 33 days,the egg production and parasitism rate of adult wasps emerged from 3-day-old pupae decreased with storage time and the lowest peak occured at 33 days,which were 21.67 and34.44%,respectively.In summary,short-term storage(less than 27-33 days)at 12℃ had little effects on the survival of 3-day-old pupae of C.japonicus.12℃ and 3-day-old pupae could be used as storage conditions for the wasp.2.High temperature training of parasitoids before releasingHigh temperature training at 30℃ and 32℃ could improve the high temperature tolerance of C.japonicus.Both fluctuating and direct warming could improve the survival rates of wasps exposed to short-term high temperature.The emergence rates of stored and unstored pupae increased significantly at 39℃ when they were directly exposed to 30℃ for5 hours.The emergence rates of stored and unstored pupae also increased significantly at39℃ by training under fluctuating temperatures from 27℃ to 30℃.Therefore,a certain degree of high temperature training of C.japonicus can be carried out before releasing at high temperatures.3.Factors influencing field releasing of C.japonicusThe emergence rates and longevities of C.japonicus outdoors were lower than those indoors.The season and time of releasing are the important factors affecting outdoor emergence rates of the wasp.In summer(temperature range: 28-35℃),the highest emergence rate was 87.33% at 18:00,and the lowest was 68.67% at 12:00.In winter(temperature range: 19-26℃),the time of releasing had no significant effect on emergence rates.The optimal ratio of wasp to scale insect at releasing was 1:60.When the wasps were released after 10 days at the ratio of wasp to scale insect 1:60,the parasitism rate was48.97%,which was significantly higher than that at the ratio of 1:80,but had no significant differences with those at the ratio of 1:20 and 1:40.After outdoor releasing,the wasps had good control effect on the scale insects within the distances of 6m,but mainly concentrated in the range of 0-3m.When P.nigra broke out in a large scale in net room,the parasitic rate of C.japonicus could reach 58.63% in half month and 96.74% after one month.