Ovicidal and larvicidal activity ofspinosad against egyptian cotton leafworm

Abstract EN

One of our objectives this investigation is to detemhne the ovicidal action of spinosad (Tracer®) compared to chlorpyrifos (Darsban®) and tri ; h«nuron (Alsystin®) against 0-1 day old eggs of cotton leafworm, Spodoptera littoralis.

The residual toxicity of these insecticides to the neonates is also evaluated.

Toxicity ofspinosad against 2nd, 3rd and 4lh instar larvae of s.

littoralis by dipping technique and against the 4ÜI instar larvae by topical application was carried out.

The joint toxic action of spinosad with cypermethrin, chlo ^ yrifos and methomyl against 4th instar larvae of 5.

littoralis was also studied.

Spinosad has an ovicidal activity lower than chlorpyrifos and triflumuron.

Although spinosad has low ovicidal activity, it has the highest residual activity against the neonates after 24h of hatching.

Spinosad has the highest total mortality (% killed eggs + % neonate mortality after 24h of hatching) compared to chlorpyrifos and triflumuron.

According to the LC50 values, susceptibility of s.

littoralis larvae to spinosad is decreased considerably as the larvae advance in age and ^eight.

Second instar larvae were ore susceptible to spinosad than the 3rd instar larvae which were more susceptible than the 4lh instar larvae.

The LCso values by dipping technique were 41.

7, 138.1 and 196.7 ppm for 2nd, 3rd and 4th instar larvae, respectively.

Toxicity ofspinosad by topical application is enhanced by increasing the exposure time where 10 values were 0.

51, 0.

12 and 0.09 Jig/mg body weight after 24, 48 and 72h of treatment, respectively.

Data revealed that dipping treatment exerts toxicity more than the topical application.

In respect with the joint toxic action, the combination of spinosad and cypermethrin results in a synergistic effect or an additive efleet as calculated by the co-toxicity factors.

The combination of spinosad with chlorpyrifos or methomyl results in additive effect or antagonistic effect ; this will shed some lights on the possible joint toxic action and the sequence of alternative spraying programs