Anti-termite efficacy of Capparis decidua and its combinatorial mixtures for the control of Indian white termite Odontotermes obesus (Isoptera: Odontotermitidae) in Indian soil

Abstract

Capparis deciduas and its combinatorial mixtures were evaluated to observe the anti-termite efficacy against Indian white termite Odontotermes obesus. These have shown very high termiticidal activity and wood protection in the soil. It is proved by very low LD 50 values i.e. 0.0218mg/g and 0.021mg/g obtained in stem fractions CDS3 and CDS7 respectively. When other ingredients, were used to prepare combined mixtures with C. decidua these have shown synergistic action and caused very high termite mortality in termites. Besides this, both tag binding and wood seasoning experiments significantly cut down (p<0.05 and 0.01 level) in termite infestation in garden saplings and in seasoned dry wood planted in the garden soil. Above treatments have successfully obstructed the ascending and descending movements of termites and prohibited mud plastering and tunnel formation in workers. It was found statistically significant at the level 0.05. @JASEM Termites are highly destructive polyphagous insect pests, which largely damage house hold materials, finished goods, plants and agricultural crops such as sugarcane, millet, barley and paddy. Termite colonies also heavily attack fodder crops and make tunnels in subtropical and tropical soil. For termite control in the field various synthetic chemicals such as cyclodiene (Sim et al., 1998), cypermethrin (Valles and Woodson, 2002), hydroquinone and indoxocarb (Hu, 2006) have been used. But these pesticides were found cost effective, detrimental to environment and kill non-target organisms. Due to their longer residual persistence and very high toxicity, many synthetic pesticides are banned. Hence, their new alternatives have been discovered in form of natural or plant origin pesticides. These plant-origin pesticides are found much safer and easily biodegradable in the soil in comparison to synthetic pesticides. In the past for termite control few plant species such as Pseudotusuga menziesii, Lysitoma seemnii, Tabebina guaycan, Diospyros sylvatica (Ganapaty et al., 2004), Curcuma aromatica and Euphorbia kansuii (Shi et al., 2008), have been explored for their anti-feedant and insecticidal activities. These extracts heavily deter termite feeding and reduce their survival (Boue and Raina, 2003). Besides crude extracts, few active anti-termite compounds have also been isolated from plants (Kinyanjui et al., 2000) and their diverse biological activities such as anti-feedent, repellent and toxic activities have been established in field termites (Motohashi et al., 2000; Blaske and Hertel, 2001; Blaske et al., 2003). However, to enhance the lethality and target specificity of natural pesticides few synergists are also used. These synergists in form of poison baits more efficiently exploit feeding and tunneling behavior in termites. In the present study, anti-termite efficacy of various solvent fractions of C decidua was determined. For this purpose various toxicity, repellency, wood seasoning and tag binding bioassays were conducted in the laboratory and field. MATERIALS AND METHODS Termite O. obesus were collected from infested logs found at the University of Gorakhpur U.P. India and near by forest area of Eastern Uttar Pradesh, India. Termites removed from plant biomass and logs were maintained in glass jars (height-24", diameter 10") in complete dark conditions at 28±2 0 C, 75±5 RH. Termites were fed on green leaves. Stem, leaves, flowers and fruits of Capparis were chopped in small pieces, milled to make powder, and extracted sequentially with acetone, methanol, chloroform and water. Solvent was evaporated to prepare residues. The extracts were filtered with Whatman paper No. 1 and were concentrated under vacuum (30 0 C) to make about one third of original volume or until most of the solvent is removed. The remaining aqueous solution was partitioned with chloroform to remove non-polar compounds. The aqueous extracts were combined and concentrated under vacuum and freeze-dried. Preliminary trials were made in the laboratory to test the anti-termite efficacy of C. decidua. For toxicity bioassay, various serial concentrations of different extracts were loaded on Whatmann paper strips (1x1 cm 2) and air dried to remove the solvent. These pre-coated solvent free strips were placed in the center separate Petri dishes (42mm diameter) as tests and uncoated as control. Twenty-five worker termites were released in the Petri dish to observe the mortality and feeding behavior. Besides this, in field experiments solid wood sticks (3 ft length X 3.2' diameter) seasoned in various mixtures for 48 hrs were planted in garden soil in separate pits of 2.75 feet depth. Separate pits