Biological impact of harmaline, ricinine and their combined effects with Bacillus thuringiensis on Spodoptera exigua (Lepidoptera: Noctuidae)

Abstract

The history of botanical pesticides reveals that their study did mainly focus on the determination of acute median lethal dose or concentration. In the current situation, it is the dire need to understand the sublethal eVects of the botanical extracts along with the traditional studies of lethal concentrations in order to comprehensively investigate the future role of the botanical extracts as pesticides. This study reveals the eVects of traditionally used medicinal plant extracts harmaline (H) and ricinine (R) either individually or in combination with Bacillus thuringiensis (Bt) on the acute toxicity and sublethal eVects on the nutrition and enzyme system of Spodoptera exigua. Harmaline and ricinine caused reduction in the growth of neonate larvae up to 93.12 and 84.31%. The EC 50 values of harmaline against fourth and Wfth instars were 0.24 and 0.27 mg/ml, but these values remained 0.49 and 0.54 mg/ml against fourth and Wfth instars after being treated with ricinine. The combination of harmaline and ricinine with Bt resulted in the increased eYciency of these chemicals as the mortality percentages signiWcantly increased up to 96 and 87.82% in signiWcantly less exposure time in case of H + Bt and R + Bt respectively, as compared to individual treatments. The nutritional analysis revealed the increased toxicity of harmaline and ricinine in combination with Bt, but H + Bt2 showed the higher eYciency with minimal relative consumption rate 2.50 mg/mg/day, relative growth rate 1.16 mg/mg/day and eYciency of conversion of ingested food 29.66% of control, respectively. Changes in antioxidant enzymes such as superoxide dismutase (SOD) and catalases (CAT) were noticed to some extent over diVerent exposure times at all the treatments. The highest SOD (+37.29%) and CAT (+29.27%) activity was observed at the 6th day of treatment with H + R + Bt2. The study clearly shows the signiWcantly increased eYciency of harmaline and ricinine in combination with Bt against S. exigua. This phenomenon can be helpful in order to develop better control strategies against diVerent notorious pests.

Genetic variation, phylogeographic structure of Spodoptera exigua in the welsh onion‐producing areas of North China

“…; Rizwan‐ul‐Haq et al. ; Guo et al. ), causing serious economic losses in some of the main crop‐producing areas.…”

Activities of digestive and detoxification enzymes in multiple generations of beet armyworm, Spodoptera exigua (Hübner), in response to transgenic Bt cotton

“…Furthermore, CarEs are glycoproteins and may play important roles in their catalytic activity (Gopalapillai et al 2005;Kroetz et al 1993). The occurrence of oxidative stress after exposure to pesticides and other xenobiotics has been widely documented in insects (Rizwan-ul-Haq et al 2009). Superoxide dismutase (SOD) plays an important role in balancing the herbivorous insects' oxidation and anti-oxidation effects and protecting the insects' cell from damage caused by harmful environment (Ahmad and Pardini 1990).…”

“…The beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), is a cosmopolitan pest that attacks many plant species, such as corn, cotton, beet, maize, soybeans, tomato, cabbage, and alfalfa (Dingha et al 2004;Rizwan-ul-Haq et al 2009). As a serious cotton pest, S. exigua is considered a secondary target pest of currently commercialized Bt cotton varieties in China (Xia et al 2000).…”

Field evolved resistance to carbamates, organophosphates, pyrethroids, and new chemistry insecticides in Spodoptera litura Fab. (Lepidoptera: Noctuidae)

“…Further work, however, is required to clarify the biochemical mechanisms influenced by different insecticides groups in S. litura. The retention of different compounds as effective and selective despite resistance is considered to be a desirable and achievable aim (Edge and James 1986;Rizwan-ul-Haq et al 2009). A resistancemanagement strategy of decreased selection pressure could be achieved by alternations with chemicals of different modes of action or by using insecticides when economic injury levels are achieved.…”