Two insect growth regulators (IGRs), diflubenzuron and lufenuron were
tested against cotton leafworm Spodoptera littoralis at Sakha Lab-field by feeding the
2^nd, and 4th instar larvae on treated cotton leaves for 48 hrs and untreated leaves till
pupation for four indicated intervals (zero, 7, 14, 21 days treatment). Also, the
effecting of these compounds on the daily rate of consumed food by the, 4th, s", and
6^th instar larvae was recorded. The results showed the following: The tested compounds were highly effective at O-time interval (initial kill after 5 days
post-treatment) recording 95 and 99 % mortality with ciflubenzuron and lufenuron
respectively on the 2^nd instar larvae, while the percent mortality were 91 and 97 on
the 4th instar larvae. The tested compounds could be arranged according their residual effect (7 - 21
days post treatment~ in descending order as follows, diflubenzuron (78 %) and (79.3
%) on the 2^nd and 4t instar larvae respectively and lufenuron (97.6 %) and (87.6 %)
on the 2^nd and the 4th instar larvae. Diflubenzuron induced zero % pupation on the 2^nd instar larvae and 11.1 % on the
4th instar larvae, while lufenuron induced zero % pupation with the two instar larvae
comparing with control, where the percent pupation were 91.7 % and 89.5 % with
the 2^nd and the 4th instar larvae. Lufenuron was the highest effective toxicant, where it prevented the larvae to reach
pupal stage for 7 and 14 days post treatment. Significant differences were recorded between control and other treatments in the
daily rate of consumed food treated with diflubenzuron and lufenuron by the 4^th, 5^th,
and 6^th instar larvae.