The larvae of Lucilia sericata induce myiasis and transmit mycobacterial infections to humans and animals. Consequently, the blowfly should be controlled for human welfare and economic reasons. Methods The insecticidal effect of fenugreek (Trigonella foenum-graecum), celery (Apium graveolens), radish (Raphanus sativus), and mustard (Brassica compestris) against the third larval instars of L. sericata was evaluated, for the first time, through ingestion assays. The effect of sublethal concentrations on certain biological aspects, such as the pupation rates and adult emergence, was revealed. Results The LC 50 values were 2.81, 4.60, 6.93, and 7.92% for fenugreek, celery, radish, and mustard, respectively. The adverse effects on larval treatment also included the survival of pupae and adults. The pupation rate was strongly decreased after treatment with 16% fenugreek and celery. Moreover, adult emergence was suppressed after treatment of larvae with 8% mustard, 12% radish, and 16% fenugreek and celery oils. The number of emerged males exceeded the number of females, which could lead to population decline. Morphologic abnormalities of larvae, pupae, and adults were recorded after treatment with all tested oils. Conclusion The results suggest that oils may represent new and safe potential insecticides for the control of blowflies.