Improvement in mass production and storage of entomopathogenic nematodes, Steinernema abbasi and S. carpocapsae

Abstract

Mass production and storage of entomopathogenic nematode are regarded as key factors for commercializing this parasitic pathogen. The results of these study studies have confirmed using the solid culture in PE pack for successfully mass producing infective juveniles (IJs) of two entomopathogenic nematodes, Steinernema abbasi and S. carpocapsae, for the first time in the previous literatures. While inoculating 30,000 and 300,000 IJs, the yields are not significantly different between the two treatments and the yields are higher than 106 IJs/g in both nematode species. The yields of both nematodes using this method were similar with an average of ca. 1.38107 IJs/g. The cultured nematodes could be stored in PE pack containing sponge blocks. The survival rates of the stored IJs were from 70% to 90% after storing for 1 to 122 days. The results indicated that sponge in PE pack could prolong the storage period. As bioassayed with larvae of Spodoptera litura, the IJs stored for different numbers of days might cause 80 to 90 % larval mortality. The PE pack-produced S. abbasi and S. carpocapsae IJs were dead within 24h when stored at 25% or 50% RH, while the survival rate of IJs decreased with the storing time after storing for one day under 75% RH. Meanwhile, the survival rate of IJs also decreased gradually starting at 1 day and was lowered to 20% and 50% at 32 days after storing at 97% and 100% RH, respectively.

蟲生線蟲商品化製劑過程中量產及增長儲存期是重要的課題，因此本研究首度利用太空包固體培養方式量產Steinernema abbasi及S. carpocapsae兩種線蟲，在接種不同IJs比較上，接種30,000及300,000在IJs產量上無明顯差異，皆可達106 IJs/g。另外固定接種34 × 103 IJs/g於太空包中比較兩種線蟲之IJs產量，兩種線蟲間產量無顯著差異，平均產量1.38×107 IJs/g以上，證實的確可達到大量生產之目的。針對兩種線蟲在人工培養過程中，回收及保存之改進，利用海綿保存兩種線蟲，經儲存在不同天數下觀察1至122天，其存活率可達到70-90％，證實海綿可長期保存線蟲。將不同儲存天數之線蟲對斜紋夜蛾幼蟲(Spodoptera litura)五齡幼蟲進行生物檢定，其致病力可達80-90％，具高效之殺蟲力。另外，在儲存時溼度的調控對線蟲存活力具影響性，而利用太空包生產之線蟲在不同保存溼度測試中，在相對溼度25、50、75、90、97及100％下對S. abbasi及S. carpocapsae之影響效果，在25和50％ RH環境下，線蟲在24h內即失去活力；而75％ RH則是隨儲存時間增長而存活率漸減，且一天後則無存活率；另外100與97％ RH則在一天後開始有存活率漸減之趨勢，觀察至第32天為止降至20- 50%。