Botanical insecticides based on oils and plant extracts have proven to be an efficient alternative method for pest control, as required by agroecological systems. Tephrosia vogelii has been used in agriculture as a source of green manure and in the control of pests and diseases. There are few studies regarding the use of compounds derived from the secondary metabolism of this plant.

Scientists at Universidade Federal do Espírito Santo (Alegre, Brazil) have identified the chemical compounds present in the essential oil of Tephrosia vogelii flowers to test its use to control the aphid Cerosipha forbesi in the strawberry crop.

Bioassays were carried out under laboratory and semi-field conditions, with different concentrations of the essential oil to estimate the lethal concentrations LC50 and LC90. Only two groups of terpenic compounds were identified in the essential oil of T. vogelii: monoterpenic hydrocarbons (alpha-pinene, limonene and ocimene) and oxygenated sesquiterpenes (nerolidol, spathulenol and farnesol).

"The essential oil of T. vogelii presented toxic effect against C. forbesi, with the LC50 and LC90 of the insect population estimated at 0.106 and 0.380 mL/L, respectively. Under semi-field conditions, mortality increased at higher concentrations, and the LC50 and LC90 were estimated at 0.114 mL/L and 0.465 mL/L, respectively. Mortality over 90% was observed within 24 h after the application of the essential oil, an high mortality occurred with a possible neurotoxic action to the aphid, for all of the tested concentrations," the scientists explain.

The LC50 and LC90 results of the tests carried out under greenhouse conditions show that the essential oil of T. vogelli flowers can be used in the management of strawberry pests, since it can be applied at low doses without phytotoxic effect.

Source: Ana Terra Bravim dos Santos, José Salazar Zanuncio Junior, Luciana Alves Parreira, Karla Maria Pedra de Abreu, Carolina de Oliveira Bernardes, José Romário de Carvalho, Luciano Menini, 'Chemical identification and insecticidal effect of Tephrosia vogelii essential oil against Cerosipha forbesi in strawberry crop', 2021,
Crop Protection, Volume 139.