Castor bean (Ricinus Communis): A potential alternative to synthetic insecticides for the eco-friendly management of insect pests stored commodities
Habib-ur-Rehman1, Mansoor-ul-Hasan2, Saima Mirza1, Qurban Ali3, Najaf awais2 Storage is a vital part of farm produce Castor Bean in order to ensure the unceasing supply of food throughout the year. Since storage times, stored commodities have been vulnerable to attack by various insects and resulting in qualitative as well as quantitative losses in stored foodstuffs(Hasan et al., 2006).
Fumigants like methyl bromide and phosphine have been the key tools for the management of stored products insects but development of resistance in insects, residual effect in foods, environment pollutions issues are the chief stimuli triggering researchers to search out the potential and safe alternatives for efficient management of stored grain insect pests (Shaaya et al., 2003). Withdrawal of methyl bromide global scientific community has faced a significant challenge in stored commodities protection job: the adoption of safe and efficient alternatives to methyl bromide for storage facilities.
Now a day, it is generally recognized that there is no single substitute of methyl bromide and all tactics are focusing on different insect pest management methods that are applied in different conditions. Plant derived insecticides (plant extracts, oils etc.) can be useful in this demanding situation.
Extracts of plants such as Azadirachra indica, Allium sativum, Datura stomium, Allium cepa etc. have been used for the control of stored products insects. So far is the plant, Caster bean (Ricimus communis L.) belonging to family Euphorbiaceae, a small shrub that can attain 10 m or above height.
Being a drought tolerant plant it can grow in adverse/harse soil and climatics conditions. It is commonly distributed in countries like Asia, South Africa, Brazil and Russia (Rana et al., 2012). Castor’s seed comprises of nearly 50-55% oil contents that are rich in triglycerides, mainly ricin that marks it as non-edible.
Its oil is widely in derivatives like soap, varnishes, pharmaceuticals and as a lubricant for engines. The plant was selected for its easy availability and presence of reported novel bioactive components which interfere with the life cycle of the insect pests. Studies of aerial parts of the plant have reported the presence of active constituents like ricin, ricinine, N-demethylricinine, and flavonoids (Kang et al., 1985).
Ricin is the highly toxic bioactive component present in seeds but ricinine which is an effective insecticide is located in all parts of the plant. These compounds have shown remarkable insecticidal, antifeedent and repellent activities (Sharma et. el., 1986). Studies have reported toxic effects of R. communis extract against arthropod vectors like ticks, mites and mosquitoes. Brahim et al., 2006 studied the toxicity of aqueous extracts of the plant against mosquito larvae of Culex pipiens, Aedes caspius, Culiseta longiareolata and Anopheles maculipennis (Diptera: Culicidae).
The leaf extract of R. communis has been shown to possess insecticidal properties against insect pests like Spodoptera frugiperda (Rossi et al., 2012), Callosobruchus chinensis (Upsani et al., 2003) and Cosmopolites sordidus (Coleoptera: Curculionidae)(Tinzarra et. al.,2006).
Several studies have reported the toxic effects of various plant extracts in control of fly populations of M. domestica (Sukontason et. al., 200; Mishra et. al., 2011). So, further in depth study is urgent needed to synthesize the derivatives of these bio-active compounds for the commercialization and helping the farmers for the environment safe and efficient management of insect pests of stored food items to remove the hampering activity of stored grains insects for the consumers. This will overcome the all the issues relating to resistance in insects and hazards to surroundings.
Keywords: Castor bean, Ricin, Ricinine, Leaf extract, Callosobruchus chinensis , toxicity