Antifeeding Activity of Several Plant Extracts Against Lymantria dispar L. (Lepidoptera: Lymantriidae) Larvae

Lymantria dispar L. is the most devastating polyphagous pest of deciduous forests, orchardsand urban greenery. To prevent damages that L. dispar larvae cause in forestry, agriculture andhorticulture, mechanical measures and the use of biological insecticides are the most frequentlyapplied practices. However, the use of conventional insecticides is inevitable in crop protectionand forest management on smaller areas, especially in gradation years. However, inadequateuse of these chemicals has led to disturbance of biocoenotic balance, outbreaks of somepreviously less harmful organisms and pesticide residues in soil and watercourses in someregions. To mitigate these consequences it is necessary to harmonize L. dispar control withintegrated management principles by applying selective and less toxic insecticides. Therefore,the potential of botanical insecticides and antifeeding substances is gaining in importance.The aim of this study was to assess the influence of ethanol extracts (1, 2 and 5%) of Ambrosiaartemisiifolia L., Erigeron canadensis L., Daucus carota L., Morus alba L. and Aesculus hippocastanumL. on the feeding intensity of L. dispar larvae, i.e. to evaluate their antifeeding activity underthe conditions of “no-choice” test. Ten larvae per repetition were placed in Petri dishes andoffered oak leaf slices (2 x 9 cm2/repetition) previously dipped in plant extract or ethanol (1, 2,and 5%) for the control. Feeding intensity, expressed as a percentage of consumed leaf area (%),was measured after 48 h. For assessing the antifeeding activity of plant extracts AFI was calculatedand the extracts were classified according to scale: no antifeeding activity, slight antifeedingactivity, moderate antifeeding activity and strong antifeeding activity. Data were analyzedusing a two-way ANOVA and Duncan`s multiple range test. The results indicate that plantspecies, i.e. the origin of extracts, had a significant influence on the feeding intensity of L. disparlarvae, while concentration and interaction (plant species x concentration) were not factorsof influence. Ae. hippocastanum and M. alba extracts significantly reduced the consumedleaf area (6.24, 18.93%, respectively), compared to the control (97.59%), while the extract of D.carota had a phagostimulative effect (98.88%). Based on AFI values, Ae. hippocastanum extract(87.10-89.05%) had a strong antifeeding activity, and M. alba medium-to-strong (64.33-71.37%).