Synthetic insecticides are effective in controlling insect pests but can also harm nontarget organisms and the environment. During the last 40 years, there has been an increasing interest in alternative insecticides, particularly those derived from plants, commonly known as botanical insecticides. However, commercially available botanical insecticides remain limited. Rotenone is one of the earliest identified compounds and was used as fish poison and pest management. Due to its link with Parkinson disease, the use of rotenone was banned in many developed countries. Rotenone used to be isolated from Derris spp. and Lonchocarpus spp., and it can also be isolated from Tephrosia species. In this article, we present basic botanical information on selected Tephrosia species and their major compounds related to insecticidal activities and highlight the current use of extracts derived from some species, Tephrosia vogelii in particular, for control of insect pests in stored grains and crop production. The crude extracts contain multiple bioactive compounds, mainly rotenone, deguelin, rotenolone, and tephrosin, which act in either additive or synergistic fashion, resulting in effective control of insect pests. There are about 400 species in the genus Tephrosia, and species and even strains or variants vary greatly in these active compounds. We argue that a systematic evaluation of bioactive compounds in different species are needed, and species or strains with high insecticidal activities should be selected for use in the sustainable control of insect pests.

Botanical pesticides have received increasing attention for sustainable control of insect pests. Plants from the genus Tephrosia are known to produce rotenone and deguelin. Rotenone is known to possess insecticidal activities against a wide range of pests, but deguelin’s activities remain largely inconclusive. On the other hand, the biosynthesis of rotenone and deguelin may vary in Tephrosia species. This study analyzed the rotenone and deguelin contents in 13 strains across 4 Tephrosia species over 4 growing seasons using HPLC. Our study shows that the species and even the strains within a species vary substantially in the biosynthesis of rotenone and deguelin, and their contents can be affected by the growing season. After identification of the LC₅₀ values of chemical rotenone and deguelin against Aphis gossypii (Glover) and Bemisia tabaci (Gennadius), leaf extracts derived from the 13 strains were used to test their insecticidal activities against the 2 pests. The results showed that the extracts derived from 2 strains of T. vogelii had the highest insecticidal activity, resulting in 100% mortality of A. gossypii and greater than 90% mortality of B. tabaci. The higher mortalities were closely associated with the higher contents of rotenone and deguelin in the two strains, indicating that deguelin also possesses insecticidal activities. This is the first documentation of leaf extracts derived from 13 Tephrosia strains against 2 important pests of A. gossypii and B. tabaci. The strain variation and seasonal influence on the rotenone and deguelin contents call for careful attention in selecting appropriate strains and seasons to produce leaf extracts for the control of insect pests.