Abstract
With the purpose of finding plant compounds with the potential use as herbicides and insecticides, a research was realized with the objective of evaluate the phytotoxic and dissuasive activity of four Chihuahua desert plants. The phytotoxic activity evaluation was tested on Lactuca sativa and Lolium perenne, while the dissuasive activity was realized on three species of phytophagous insects: Myzus persicae, Rhopalosiphum padi and Spodoptera littoralis. Raw extracts were used, the solvents hexane, methanol and ethanol of different plants’ organs (root, steam, leaf and flower) of four species: Fouquieria splendens (ocotillo), Larrea tridentate (governor), Astragalus mollissimus (wild grass) and Pachycereus pecten-aboriginum (echo), by the establishment of in vitro bioassays at a concentration of 10 mg/ml extract/solvent. In the toxicity bioassay, the percentage of germination, root and leaf length were measured. The results showed that the leaf extract of L. tridentata had phytotoxic activity for L. sativa, while for L. perenne the phytotoxicity was observed within the ocotillo, governor and echo extracts. In the dissuasive bioassay, each treatment had 20 repetitions with 10 adult insects per repetition. The methanolic extracts of F. splendens leaf and root, ethanolic extract of A. mollisimus sheet and the ethanolic extract of P. pecten-aboriginum stems showed moderate dissuasive response of feeding against M. persicae, presenting a settlement inhibition index of 53.53, 54.35, 60.00 and 48.84% respectively. Nevertheless, the results indicated that none of the 10 extracts tested on S. littoralis showed significant dissuasive properties for this Lepidoptera, while for R. padi all the tested extracts presented dissuasive properties. The treatments of the four vegetable species evaluated showed defensive or dissuasive properties of moderate to strong feeding against the insects M. persicae and R. padi, presenting interesting potential for being used as insecticides, while the tested extracts that presented phytotoxicity for both lettuce and ryegrass present possibilities for the realization of herbicides.
Highlights
The botanical compounds constitute an old alternative for the control of agricultural pests (Perez, 2012)
Phytotoxic effect on Lactuca sativa In regard with the inhibition of germination of L. sativa seeds, of the 12 treatments tested only the ethanolic extract of L. tridentata leaf showed germination delay compared to the control, observing 45% germination after 24 hours, reaching 92% after 120 hours and 95% after 144 hours (Figure 1)
Reported results from similar studies mention that researchers found inhibition of radicular and hypocotyl growth of L. sativa with extracts of NDGA (Nordihydroguaiaretic acid), the main component of L. tridentata leaf (Delgado et al, 2014)
Summary
The botanical compounds constitute an old alternative for the control of agricultural pests (Perez, 2012). In recent years, the use of such components as a source of biopesticide preparation has been returning (Celis et al, 2008), since these metabolites can be isolated and used in agriculture as an alternative for the integrated control of pests and diseases (Emilia et al, 2013). The aforementioned, together with the recognition of the biological properties of numerous plant species, has led to the search of new natural compounds extracted from plants with the potential use as insecticides and herbicides with less impact on the environment (Rodriguez and Barreto, 2015). There is a certain number of plant-based insecticides that are being marketed worldwide, such as azadirachtin, rotenone, nicotine and sabadilla (Mendoza et al, 2007, Perez, 2012). Botanical pesticides include nematicides that inhibit germination, fungicides and new herbicides (Nava-Perez et al, 2012)
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