Virulence of carboxymethyl cellulose formulation of Heterorhabditis bacteriophora and Steinernema carpocapsae against Phthorimaea operculella

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عنوان دوره: سومین کنگره بین المللی حشره شناسی ایران

Department of Plant Protection, Faculty of Agriculture, Azarbaijan Shahid Madani University, Tabriz, Iran,

Entomopathogenic nematodes (EPNs) from families Heterorhabditidae and Steinernematidae have proven to be effective biological control agents. Here the effect of storage period on virulence of carboxymethyl cellulose (CMC) formulated infective juveniles (IJs) of Heterrorhabditis bacteriophora and Steinernema carpocapsae was tested at monthly over 6 months storage period. Virulence of both EPNs was evaluated as LC50 values on Potato tuber moth (PTM) (Phthorimaea operculella) 2nd instar larva. PTM is one of the most important pests of the plant family Solanaceae such as potato crops. The virulence was evaluated in 24-well plates lined with two filter papers. IJs were applied in 1 ml distilled water to the filter paper surface before the PTM larvae were added to the wells. Untreated controls received only distilled water. Mortality was recorded daily for 7 days starting after 48 h. The experiment was conducted twice. The LC-values were calculated using probit analysis. Mortality data were corrected with that in controls and subjected to analysis of variance followed by Duncan's mean separation test. LC values for both EPNs had a good fit to the probit regression model. The analysis showed that LC50 of CMC formulated IJs of both studied EPNs weren’t affected by storage period. All recorded LC50 values had overlapped confidence intervals. In the case of H. bacteriophora recorded values of LC50 at one month interval for six months were117.09, 97.17, 112.91, 102.94, 114.10 and 123.14 IJs/L, respectively. For S. carpocapsae, the same values were 74.65, 66.80, 73.19, 71.70, 76.02 and 68.83 IJs/L, respectively. Although S. carpocapsae with ambusher foraging strategy appeared more virulent against PTM larvae but given the small size of the experimental arenas it is unlikely that recorded differences in virulence were related to the ambusher or sit-and-wait type foraging strategy of S. carpocapsae IJs that would have favored infection of the mobile larvae. Therefore, it is proposed that further research should be conducted in greenhouse and field studies with the combination use of these valuable biocontrol elements.



 

Virulence of carboxymethyl cellulose formulation of Heterorhabditis bacteriophora and Steinernema carpocapsae against Phthorimaea operculella Naser Eivazian Kary and Davoud Mohammadi Department of Plant Protection؛ Faculty of Agriculture؛ Azarbaijan Shahid Madani University؛ Tabriz؛ Iran؛ eivazian@azaruniv.ac.ir؛ dr.mohamadi@azaruniv.ac.ir Entomopathogenic nematodes (EPNs) from families Heterorhabditidae and Steinernematidae have proven to be effective biological control agents. Here the effect of storage period on virulence of carboxymethyl cellulose (CMC)؛ 97.17؛ 112.91؛ 102.94؛ 114.10 and 123.14 IJs/L؛ respectively. For S. carpocapsae؛ the same values were 74.65؛ 66.80؛ 73.19؛ 71.70؛ 76.02 and 68.83 IJs/L؛ respectively. Although S. carpocapsae with ambusher foraging strategy appeared more virulent against PTM larvae but given the small size of the experimental arenas it is unlikely that recorded differences in virulence were related to the ambusher or؛ it is proposed that further research should be conducted in greenhouse and field studies with the combination use of these valuable biocontrol elements. Keywords: Bioassay؛ Virulence.   Bioassay؛ Infective Juveniles؛ LC50؛ virulence