Efficacy of carboxymethyl cellulose for formulation of an entomopathogenic nematode, Heterorhabditis bacteriophora
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عنوان دوره: سومین کنگره بین المللی حشره شناسی ایران
نویسندگان
Department of Plant Protection, Faculty of Agriculture, Azarbaijan Shahid Madani University, Tabriz, Iran,
چکیده
For the first time the efficacy of carboxymethyl cellulose (CMC) was evaluated for formulation of dehydrated and non-dehydrated infective juveniles (IJs) of Heterorhabditis bacteriophora for one month interval during six months of storage period at 15 and 25 ºC. At both temperatures significant differences were recorded between treatments. The highest survival rate were observed at complete formulations which were included CMC trapped dehydrated IJs in the presence of formaldehyde. The results showed that in all formulations survival of IJs is superior at 15ºC. At the end of the storage period and complete formulation, IJs survival at 15 and 25ºC were 85.52 and 77%, respectively. Comparing the survival rates of IJs in formulations with dehydrated or non-dehydrated IJs revealed that efficacy of IJs anhydrobiosis in improving their survival is temperature dependent, as survival rate between formulations with dehydrated or non-dehydrated IJs was non-significance at 15ºC but significance at 25ºC. The response of IJs to the presence of formaldehyde as an antimicrobial agent was also temperature dependent as at 15ºC compared to formaldehyde-free treatment (68.92%) survival reduced at CMC trapped non-dehydrated IJs loaded with formaldehyde (45.14%) due to detrimental effect of formaldehyde. Both of these temperature dependent responses can be rationalize regarding H. bacteriophora cruiser foraging behavior and superior activity of contaminant microorganisms at higher temperature. Although IJs are cruiser and actively search for host but at 15ºC their activity and metabolic rate are too low then lower energy consumption supports IJs survival for longer period of time compared to 25ºC. On the other hand, in this thermal situation detrimental effects of contaminant microorganisms are low and not only antimicrobial presence doesn’t enhance but reduces IJs survival due to significant mortality effect on IJs. At room temperature formaldehyde enhance IJs survival by suppressing profound detrimental effects of contaminants. Analysis of combination effects of temperature × formulation showed that during six months of storage period mortality trend can be divided clearly to two separate phase, at phase I survival curve show steep slope and high mortality rate and phase II characterize by gentle slope and low mortality rate. These results can be exploited in mass production technology by screening inoculum from phase II of population with superior shelf life. Here, CMC emerged as suitable substrate for IJs formulation. Regarding its low cost and high water solubility it is proposed as a potential candidate for formulation of H. bacteriophora.
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