Simoni Anese

Effect of Serjania lethalis ethanolic extract on weed control

The objective of this study was to evaluate the effect of the ethanolic extract of Serjania lethalis leaves and stems on the diaspore germination and seedling growth of wild poinsettia (Euphorbia heterophylla) and barnyardgrass (Echinochloa crus-galli). The crude ethanolic extract was prepared from 100 g of dry plant material dissolved in 500 ml of ethanol. The extracts were solubilized in a buffer solution containing dimethyl sulfoxide (DMSO) at concentrations of 10.0, 7.5, 5.0 and 2.5 mg mL-1. The effect of these extracts was compared with herbicide oxyfluorfen in bioassays. The ethanolic extracts of S. lethalis leaves and stems inhibited the germination and seedling growth of barnyardgrass and wild poinsettia in a concentration-dependent manner. The reduction in the root length of E. heterophylla seedlings might be attributed to the reduced elongation of metaxylem cells. The phytotoxicity of the extracts ranged according to the receptor species, and for some variables, the inhibitory effect was similar, and even superior, to that of the commercial herbicide. Thus, S. lethalis extracts might be a promising alternative for sustainable weed management.

Insecticidal action of Drimys brasiliensis Miers on black citrus aphid

The aim of this study was to evaluate the insecticidal effects of a hexane fraction and polygodial compound obtained from Drimys brasiliensis roots on the mortality of adults and nymphs of Toxoptera citricida (black citrus aphid). For the hexane fraction, solutions of 0.12, 0.25, 0.50, 1.0, and 2.0 mg mL-1 were prepared, and for the compound, solutions of 62.5, 125, 250, and 500 µg mL-1 were prepared. A control with water and dimethylsulfoxide (5 µg mL-1) was also included. Two hexane-fraction-solution application methods were evaluated: spraying directly onto the insect, and submerging a young Citrus limonia shoots in the solution, which served as a refuge for the aphids. Nymph and adult mortality were assessed at 24 and 48 h after solution application. The hexane fraction caused high mortality amongst the T. citricida nymphs and adults. The lowest LC50 value (0.301 mg mL) was recorded in the nymphs when the solutions were applied directly onto the insects. The polygodial compound that was isolated from the hexane fraction significantly increased the mortality of adults and nymphs, with LC50 values of 293.8 and 176.77 µg mL-1, respectively. The insecticidal activity observed may have been caused by this compound.