Diet composition and lipids of in vitro-produced Heterorhabditis bacteriophora

Several entomopathogenic nematode species are currently under evaluation for mass production and field efficacy for biological control of insect pests. However, quality and quantity of in vitro-produced entomopathogenic nematodes vary considerably, depending on media, temperature, and production method. In addition, nematode production should be cost effective. We investigated nematode yield, production time, total lipid content, and fatty acid composition of Heterorhabditis bacteriophora produced in artificial media supplemented with different lipid sources. Lipid source significantly affected lipid quantity and quality in H. bacteriophora. Media supplemented with extractable insect lipids produced yields 1.9 times higher than did beef fat- or lard-supplemented media. Moreover, the developmental rate in media supplemented with host lipids was 1.7 times faster than that in media supplemented with beef fat or lard. Nematodes grown in media supplemented with insect lipids accumulated significantly higher lipid proportion per dry biomass than those grown in media supplemented with other lipid sources. H. bacteriophora produced in media supplemented with insect lipids, olive oil, or canola oil had similar fatty acid patterns, with oleic (18:1) acid as the major lipid fatty acid. Media supplemented with other lipid sources produced nematodes with fatty acid patterns different from those of media supplemented with insect lipids. We recommend addition of fatty acid mixtures that resemble natural host lipids for mass-producing entomopathogenic nematodes. This could provide nematode quality similar to in vivo-produced nematodes and could improve yield.