Investigating the use of aquatic weeds as biopesticides towards promoting sustainable agriculture

Abstract

Aquatic weeds such as muskgrass (Chara spp.), water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), hydrilla (Hydrilla verticillate), filamentous algae (Lyngbya wollei), and duckweed (Lemna minor) thrive in farm canals within the Everglades Agricultural Area of South Florida. Their presence, particularly during the summer months is an environmental concern with regards to water quality, in addition to being a nuisance because of their ability to multiply and spread rapidly in open waters causing restricted drainage/irrigation flow and low dissolved oxygen levels. Chemical control is effective but can have undesirable off-target effects, so reduced herbicide use is desirable. Hence, need exists to discover ways in which these weeds could be best managed or utilized. The objective of this research was to evaluate the allelopathic effect of these weeds to determine their use as potential biopesticides. Six aqueous extracts were tested against 100 bacterial strains isolated from plants and soil to evaluate their antimicrobial activity. These extracts were also used to determine their insecticidal and antifeedant effects on fall armyworm (FAW, Spodoptera frugiperda). Both extracts and powder form of the aquatic weeds were tested for their herbicidal activity towards seed germination and growth of three common terrestrial weed species. At a dilution of 1:100 and 1:1,000, none of the aquatic weeds inhibited in-vitro growth of the bacterial strains, with one exception (filamentous algae extract at 1:100 reduced growth of one bacterial isolate by 54%). Water lettuce reduced the survival rate of FAW by 14% while hydrilla and duckweed caused 11% and 9% reduction of FAW growth, respectively. Powdered duckweed inhibited the growth of nutsedge by 41%, whereas filamentous algae powder and extract reduced germination of amaranth by 20% and 28%, respectively. Harvesting these weeds and converting them into useable compounds could not only eliminate the in situ farm

Fall armyworm (Spodoptera frugiperda): A threat in crop production in Africa and Asia

“…The use of ethanolic extracts of Argemone ochroleuca also reduced larval feeding activity (Martínez et al, 2017). Also, biopesticides from the extracts of weed like Water lettuce reduced the survival rate of FAW by 14% while hydrilla and duckweed caused 11% and 9% reduction of FAW growth, respectively (Fu et al, 2020). Zingiber officinale and Malva sylvestris were effective causing mortality for caterpillars of FAW (Rioba & Stevenson, 2020).…”

Mediterranean Plants as Potential Source of Biopesticides: An Overview of Current Research and Future Trends

“…Slight variations in the protocol involve inoculation of the agar containing the extract with a small volume from a liquid culture of the fungus [ 30 , 95 ] or with fungi-infected plant seeds [ 60 ] instead of an agar plug. Although the method is mostly used for fungal pathogens, Fu et al [ 144 ] employed the agar dilution method to test the antibacterial potential of water extracts from aquatic weeds against 100 bacterial strains that were inoculated on agar plates by streaking.…”

An Overview of Some Biopesticides and Their Importance in Plant Protection for Commercial Acceptance

“…It is observed that some plants produce allelopathic compounds which have the potential to prevent the growth, germination, survival, and reproduction of surrounding organisms. Neem (Azadirachta indica) extract kills many insects, while Eichhornia crassipes has the ability to inhibit the growth of Spodoptera litura, a lepidopteran pest [100][101][102][103]. Similarly, Chenopodium album is inhibited by the presence of duckweed and water lettuce [100].…”

“…Neem (Azadirachta indica) extract kills many insects, while Eichhornia crassipes has the ability to inhibit the growth of Spodoptera litura, a lepidopteran pest [100][101][102][103]. Similarly, Chenopodium album is inhibited by the presence of duckweed and water lettuce [100]. These examples illustrate that similar plants (or weeds) and their allelopathic chemicals have highly potent inhibitory properties against the pathogens and hence can be substituted for conventional chemical pesticides [103].…”