Vol.:(0123456789) 1 3 Waste and Biomass Valorization https://doi.org/10.1007/s12649-019-00682-1 ORIGINAL PAPER Insecticidal Effect of Olive Mill Wastewaters on Potosia opaca (Coleoptera: Scarabeidae) Larva Hanane Boutaj 1  · Abderrahim Boutasknit 1  · Mohamed Anli 1  · Meriame Ait Ahmed 2  · Abdelilah El Abbassi 3  · Abdelilah Meddich 1 Received: 31 August 2018 / Accepted: 15 April 2019 © Springer Nature B.V. 2019 Abstract Olive mill wastewaters (OMW) are an environmental problem in olive oil producing countries such as Morocco. OMW are characterized by an acidic pH, a high electrical conductivity, and a composition rich in water, organic matter, dry matter and phenolic compounds. These effluents are usually dumped directly into the ecosystems without any prior treatment. Therefore, to mitigate the effects of OMW on the environment and to get benefit from its high phenolic content, we opted to use them as bio-insecticides in their crude form. Thus, crude OMW were tested by spray toxicity bioassay against Potosia opaca var. cardui Gyllenhal larva. The results showed that crude OMW were effective against this pest causing a weight loss similar to Cordus insecticide (17% vs. 15%) and mortality almost similar to Kemaban insecticide. In spray toxicity bioassay, the median lethal times (LT 50 and LT 90 ) showed that OMW exhibited comparable insecticidal activity (LT 50 = 245.39 h, LT 90 = 323.86 h) to Kemaban insecticide (0.5 µL/mL, LT 50 = 208.01 h and LT 90 = 233.91 h). The biocide properties of OMW depend mainly on its phenolic content. Ten phenolic compounds were identified using HPLC analysis, two of them were found to be the major monomeric phenolic compounds in OMW, hydroxytyrosol (0.248 g/L) and tyrosol (0.201 g/L). The obtained results confirm the potential application of OMW to control plant pathogens. The development of sustainable strategies based on the reuse of OMW for pests control in view to reduce the use of chemical and synthetic pesticides, may have considerable economic benefits. Keywords Olive mill wastewaters · Potosia opaca · Date palm trees · Insecticidal activity · Biological control Statement of Novelty The contribution of this study is focused on the assess- ment of the potential application of olive mill wastewaters (OMW) to control a date palm pest, namely Potosia opaca. The insecticidal effect of OMW on P. opaca larva was compared to two commercial insecticides composed from chlorpyriphos-ethyl and/or cypermethrin. At the best of our knowledge, this is the first time to report the possibility of applying OMW to control P. opaca. Furthermore, this paper is presenting a sustainable strategy that has two purposes, on the one hand is the disposal of a highly polluting effluent from the agri-food industry and on the other, its valorization as a low-cost pesticide for date palm trees protection Introduction The date palm trees have many important socio-economic and ecological roles in oases ecosystems [1]. In Morocco, its culture is threatened by several constraints, including pests’ attacks [2, 3]. Phoenix dactylifera and Phoenix canariensis are strongly threatened by the red weevil caused by Rhyn- chophorus ferrugineus which causes huge economic losses * Abdelilah El Abbassi a.elabbassi@uca.ma * Abdelilah Meddich a.meddich@uca.ma 1 Laboratory of Biotechnology and Plant Physiology, Department of Biology, Faculty of Sciences – Semlalia, Cadi Ayyad University, 40 001 Marrakech, Morocco 2 Laboratory of Physico-Chemistry of Inorganic and Organic Materials, Ecole Normale Supérieure, Mohamed V University, Takaddoum, Rabat 10200, Morocco 3 Food Sciences Laboratory, Department of Biology, Faculty of Sciences – Semlalia, Cadi Ayyad University, 40 001 Marrakech, Morocco