Efficacy of some biopesticides and plant secondary metabolites against fall webworm hyphantria cunea drury (F. Arctiidae-lepidoptera) in the lab conditions

Abstract

The paper presents the efficacy of the some biopesticides used in the experiments to control fall webworm (Hyphantria cunea), comparatively to some plant secondary metabolites from autochthonous flora. From the first category there were used: spinosad, a secondary metabolite produces by the fermentation from Saccharopolyspora spinosa mushroom and is the active principle of the commercial products of the Naturalyte class; azadyrachtines – a group of limonoids, obtained from the seeds of the Neem tree (Azadirachta indica), and milbecmectin, a product obtained from a metabolite of the Streptomyces hygroscopicus subsp. aureolacrimans bacteria. The results revealed the efficacy of all bio insecticides against fall webworm in 2-7 days period after treatment. Spinosad presented a quick action, comparatively to the other bio pesticides. The secondary metabolites, used into fall webworm control, were extracted from autochthonous plants: the common ladyfern (Drioperis filix mas), the perennial sage (Salvia nemorosa), the wormwood (Artemisia dracunculus, A. vulgaris, A. absinthium) the European birthwort (Aristolochia clematidis), Cow parsnip (Heracleum spondylium), the hedge nettle (Stachis sylvatica), the speedwell (Tanacetum vulgare), the nettle (Urtica dioica), the danewort (Sambucus ebulus) and the yew tree (Taxus baccata) to fall webworm. Plants extracts were obtained from dried ground plants, using 25 g/ 1 litter of cold water, stirred for 24 hours. The extracts in ethylic alcohol were made using the same method, 25 g dried plants in 200 ml alcohol and completed up to 1 litter with water. The experiments were carried out under laboratory conditions, treatments being applied on shoots with leaves affected by fall webworm, placed in growth boxes. Each variant had three replications and each replication contained three infested shoots. The treatments were applied with manual small pumps. Efficacy (E%) was calculated after Săvescu-Iacob formula. The majority of alcoholic plant extracts influenced the decrease of leafs consumption as extracts with water. Extracts of metabolites influenced the eating with repellent effects against larvae, no palatable etc. The future experiments must use more chemical analyses to discriminate the main metabolites, which influence the worm activities.