Impact of oxymatrine on the predatory efficiency of larval Chrysoperla carnea (Neuroptera: Chrysopidae) on the okra leaf hopper Amrasca biguttula biguttula (Ishida).

Abstract

The effect of the insecticide oxymatrine on the predatory efficiency of the green lacewing, Chrysoperla carnea Stephens (Neuroptera: Chrysopidae) on the okra leaf hopper Amrasca biguttula biguttula (Ishida)  was measured with functional response equation. The second and third instar larvae of the predator Ch. carnea that treated with oxymatrine are demonstrated type 2 functional responses , the consumption rate increases at a decelerating rate, gradually levelling off at maximum rate. The attack coefficient (a) of the second larval instar was 2.27 and 0.97 with significant differences and the handling time were 0.0048 and 0.0052 day  for control and the treated larvae  respectively, theoretical maximum predation rates (T/th) were 208.3 for control treatment and 192.31 for treated larvae. The attack coefficient values (à) of third larval instar was 3.17  and 1.64 ,  the handling time was 0.0036 ,and 0.005day respectively. Theoretical maximum predation rates (T/th) were 277.8 and 200 for control treatment and treated larvae respectively .