Repellency of Urtica dioica (Urticaceae) and Erigeron anuus (Asteraceae) to Plodia interpunctella (Lepidoptera: Pyralidae) larvae

Plodia interpunctella Hübner 1813 (Lepidoptera: Pyralidae) is a cosmopolitan insect pest that attacks a wide range of stored food commodities. In the last decade, the search for effective plant-based insecticides as alternatives to synthetic agents has become a very important issue. The objective of this study was to test the repellent activity of 1%, 2% and 5% methanolic extracts of two weed plant species, Urtica dioica L. (Urticaceae) and Erigeron annuus (L) Perss. (Asteraceae) against two maturity groups of P. interpunctella larvae - younger (II-III larval stage) and older (IV-V larval stage). Total phenolics, tannins, flavonoids and antioxidative activity were determined for both tested extracts by spectrophotometric analyses. The 2% extract of U. dioica had an extremely repellent effect (class V) on the younger group of larvae, while the 5% extract had a strongly repellent effect (class IV) on the older group. Oppositely, the 5% extract of E. annuus was strongly repellent (class IV) against the younger, while it was extremely repellent (class V) against the older group of larvae. Both tested weeds’ extracts have a high potential to be used as botanical repellents against larvae of P. interpunctella .