Insecticidal activity of edible Crithmum maritimum L. essential oil against Coleopteran and Lepidopteran insects

Abstract

Crithmum maritimum L. (Apiaceae) is an edible plant that is used in salads or consumed as pickles in Cyprus. In our insecticidal screening study of the plant species of Cyprus, we have studied the insecticidal activity (contact and fumigant toxicity) of the essential oil of Crithmum maritimum against stored product pests Sitophilus granarius L., S. oryzae L., Tribolium castaneum Herbst., T. confusum Jacquelin du Val., Rhyzopertha dominica Fabricius., Oryzaephilus surinamensis L. (Coleoptera) and the field pest Spodoptera exigua (Hubner) (Lepidoptera). Dried leaves of C. maritimum afforded an essential oil with 0.22% (v/w) yield. The essential oil was analyzed with GC, GC-MS and the major components of the oil were identified as gamma-terpinene (39.3%), beta-phellandrene (22.6%), carvacrol methylether (10.5%) and (Z)-beta-ocimene (8.2%). Highest contact toxicity of the oil was observed against S. oryzae, R. dominica and O. surinamensis (1 mu L/insect application of 10% (v/v) oil solution in acetone, after 72 h, 93.30%, 83.26% and 70.33%, respectively). Highest fumigant toxicity was observed for S. granarius, S. oryzae and O. surinamensis (10 mu L/10 mL container application of 10% (v/v) oil solution in acetone, after 48 h, 100.00%, 100.00% and 90.75%, respectively). Essential oil was tested on S. exigua larvae at different development stages (3rd, 4th and 5th instar larvae). 100 mu L/mL essential oil was used with 1, 2 and 4 mu L/larvae concentrations for 3rd, 4th and 5th instar S. exigua larvae, respectively. The toxicity of the oil against the larvae was evaluated after 24 h. C. maritimum essential oil afforded 89% mortality against the 3rd instar larvae however the mortality was decreased to 50% in the 4th and none in the 5th instar S. exigua larvae. The oil also afforded considerable AChE and BChE enzyme inhibition (50.3% and 59.8%, respectively) using the Ellman spectrophotometric method. The essential oil did not produced considerable activity (10(4) fold lower than the positive controls) against the selected pathogens that could be found on wheat (Bacillus cereus, B. subtilis, Salmonella typhimurium, Staphylococcus aureus, Escherichia coli) using a microdilution method for antimicrobial evaluation