Aqueous and Ethanolic Plant Extracts as Bio-Insecticides—Establishing a Bridge between Raw Scientific Data and Practical Reality

Abstract

Global demand for food production is causing pressure to produce faster and bigger crop yields, leading to a rampant use of synthetical pesticides. To combat the nefarious consequences of its uses, a search for effective alternatives began in the last decades and is currently ongoing. Nature is seen as the main source of answers to crop protection problems, supported by several examples of plants/extracts used for this purpose in traditional agriculture. The literature reviewed allowed the identification of 95 plants whose extracts exhibit insecticide activity and can be used as bio-pesticides contributing to sustainable agriculture. The option for ethanol and/or water extracts is more environmentally friendly and resorts to easily accessible solvents, which can be reproduced by farmers themselves. This enables a bridge to be established between raw scientific data and a more practical reality. Azadirachta indica, Capsicum annuum, Nicotiana tabacum and Tagetes erecta are the most researched plants and have the potential to be viable options in the pest management approach. Azadirachta indica showed the most promising results and Brevicoryne brassicae was the most targeted pest species, being tested against the aqueous and/or ethanolic extracts of 23 different plants. Maceration using dried material (usually leaves) is the extraction method preferred by the majority of authors.

Biological Activity of Phytochemicals from Agricultural Wastes and Weeds on Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

“…Ethanol and hexane are two solvents commonly used for extracting phytochemical metabolites of interest in biological control [37,42,43]. In the present work, the highest yields of phytochemicals were obtained from the dehydrated leaves of Meliaceae plants and using ethanol as a solvent.…”

“…Phytochemical extraction was conducted in batches of 5 g leaf powder soaked in 30 mL of solvent, either ethanol (Macron Fine Chemicals TM , Palo Alto, CA, USA, grade ACS reagent) or hexane (J.T. Baker, 98.5%) contained in a 200 mL beaker [37]. Extraction was carried out for 10 min at 25-30 • C using an ultrasonic homogenizer Hielscher UP200Ht (200 W, 26 kHz) implemented with a S26D7 sonotrode (Hielscher Ultrasonics GmbH, Teltow, Germany).…”

Chemical screening, insecticidal and reprotoxic activities of Tecoma stans ethanolic leaf extract against the vector mosquito Culex pipiens

“…Ethanol proved to be a better choice as an extraction solvent (Borges et al, 2020). It was used because it is, like water, versatile and relatively low‐cost solvent, and also to permit comparison with previous reports made with the same solvent (Draouet et al, 2020; Silva et al, 2018; Tavares et al, 2021). After 24 h, the solution was filtered (Whatman paper No.…”

Biorational Control of Callosobruchus maculatus (Coleoptera: Buchidae) in Stored Grains with Botanical Extracts

“…The practice of using plant extracts as biopesticides or medicines is well known [ 1 ]. As many as 2000 plant species are in use globally in the control of insect pests.…”