Effects of plant essential oils on the changes of digestive enzymes in the ectoparasitoid, Habrobracon hebetor Say, with description of its digestive tube

Habrobracon hebetor Say is an ectoparasitoid wasp with wide range of hosts and nutrition is an important factor for the success of this natural enemy. In this research, sublethal effects of the essential oils isolated from five medicinal plants including Allium sativum L., Rosmarinus officinalis L., Piper nigrum L., Salvia officinalis L., and Glycyrrhiza glabra L. were investigated on the amylolytic and proteolytic activity of this important biocontrol agent, under the laboratory conditions. GC–MS analyses of the essential oils showed that tetracosamethyl cyclododeca siloxan, α-pinene, caryophyllene, β-thujone, and aristolene were dominants compounds of them, respectively. The enzymatic activity in this parasitoid wasp was also investigated by LC 30 treatment of the female wasps by the essential oils that were 2.22, 2.48, 5.41, 6.30, and 8.72 µl/l air, respectively. The results showed that this parasitoid wasp have narrow oesophagus, big crop, long midgut, and ten malpighian tubes in its digestive tube. In addition, there were significant differences among the treatments about the enzymatic activity ( F 5, 144 = 13.861 and 177.172) except protein content ( F 5, 144 = 2.458). About the amylase, the highest activity was seen in the control (0.0435 ± 0.0023 mU/mg) and the lowest being in A. sativum essential oil (0.0295 ± 0.0010 mU/mg). Moreover, the highest and lowest proteolytic activities were observed in the control (4.9817 ± 0.0268 U/mg) and S. officinalis essential oil (4.3340 ± 0.0881 U/mg). Thus, S. officinalis and G. glabra due to the lowest negative effects on the enzymes can be applied in integration with this biocontrol agent in IPM programs.