Comparative effect of formulated kairomonal dusts on parasitization efficiency of Trichogramma spp.

Abstract

Aim: A number of chemicals released by phytophagous insects and plants serve as cues for their natural enemies. Egg parasitoid Trichogramma respond towards chemical cues present in the environment for locating their hosts. Formulations are the end user product for pest control because it contains the active ingredient present in it. The main objective of the present study was to understand the effect of different concentrations of kairomones and differentclayson various Trichogramma spp. Methodology: The nucleus culture of the host insect used in the present study was maintained on the eggs of rice meal moth Corcyra cephalonica on crushed sorghum grains. Culture of the parasitoid was maintained in glass vials of 10x2.5 cm size at 25±1 °C and 65±5% RH in a culture room on UV sterilized, 0-24 hr old C. cephlonica eggs. Twenty different combinations of three straight chain saturated hydrocarbons (Pentacosane, Docosane and Tricosane) used in three different combinations viz.,125 ng cm-2 (C2), 250 ng cm-2 (C2) and 375 ng cm-2 (C3), designated as 1, 2 and 3 were tested for their kairomonal response. Three different concentrations of each synthetic kairomone was prepared with HPLC grade hexane. Five kaiomonal dust formulations were prepared using three differentclays viz; kailonite, China clay and fuller's earth. Results: Trichogramma achaeae resulted in highest value of PAI (7.19) with kailonite clay, whereas China clay showed highest value of parasitism (9.79 %) and emergence (9.79%) with T. brasiliensis. Mean PAI ranged between 2.02 to 7.19 irrespective of Trichogramma spp. Maximum parasitization (9.96%) was observed in case of T. japonicum as against lowest in T. chilonis (6.48%) on kaolinite clay. Similarly, maximum adult emergence (7.42%) in T. japonicum was recorded as against lowest in T. chilonis (5.15%) on kailonite clay Interpretation: Natural enemies present in the environment to locate their hosts. Many a times these cues are associated with host and host by product itself. Therefore, it was found that the emission rate of synthetic kairomone was fastest from kailonite clay as compared to China clay and fuller's earth. T. achaeae resulted in the highest value of PAI (7.19) with kailonite clay, whereas China clay showed the highest value of parasitism (9.79%) and emergence (9.79 %) with T. brasiliensis. T. brasiliensis and T. japonicum with kairomonal formulation (Tricosane @0.0001 g 10 ml-1) and kailonite clay were found to be the best combination for any integrated pest management programm.