Potential of Oscheius tipulae nematodes as biological control agents against Ceratitis capitata.

A survey to collect soil nematodes with potential to control Ceratitis capitata flies was carried out in different locations in Tunisia. Several nematode isolates were recovered, laboratory colonies were established, and their taxonomic identities were determined based on molecular methods. Among all the recovered nematode isolates, two of them, Oscheius tipulae TC2 and OC2, were evaluated for their capacity to control C. capitata flies and for their ability to kill and reproduce on Galleria mellonella larvae. Our results show a great potential of these two isolates as biocontrol agents as they kill C. capitata eggs and pupae and interfere with the metamorphosis of C. capitata larvae. More specifically, TC2 and OC2 nematodes killed 39 and 31% of C. capitata eggs, respectively, impaired the metamorphosis of up to 77% and up to 67% of C. capitata larvae, respectively, and killed up to 66% and up to 58% of C. capitata pupae, respectively. The efficacy of TC2 and OC2 nematodes was particularly high on C. capitata pupae, and significant insect mortalities were observed even at concentrations of 1 and 5 nematodes/pupae, respectively. We also found that TC2 and OC2 nematodes efficiently kill and reproduce in G. mellonella larvae, suggesting that these insects could be used for mass-multiplication of these nematodes. These results reveal the potential of O. tipulae to complement integrated pest management programs against C. capitata flies.

Improvement of egg hatch of Ceratitis capitata (Diptera: Tephritidae) for enhanced output.

Embryonated eggs of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) genetic sexing strain (GSS), VIENNA 8 were treated with low concentrations of five disinfectants-formaldehyde, iodine, sodium hypochlorite, peracetic acid, and quaternary ammonium--for decontamination and egg hatch improvement. The newly laid eggs were successfully treated with formaldehyde at 100 ppm for 1 min with 74.2% hatching and with quaternary ammonium at 150 ppm for 1 and 2 min with 70.4 and 69% hatching, respectively. Increased formaldehyde concentration may have affected the embryos, because it resulted in a decrease in the hatching percentage. However, egg viability was not impaired and hatch was not affected by quaternary ammonium treatment compared with controls and eggs treated with other disinfectants. Quaternary ammonium shows promise for decontaminating eggs and improving egg hatch.