author(s)
B Dileep Kumar and G Sridevi

abstract
The effect of age of leaves on the larval weights of different instar larvae of Spodoptera litura showed that there was significant reduction in the larval weights when fed with dual toxin Bt cotton leaves compared non-Bt leaves. A perusal of the data at 60 days revealed that the larval weights of first instar after five days ranged from 1.17 mg to 1.40 mg across different BG-II hybrids which were on par and significantly different from non-Bt Orugallu Krishna (33.00 mg). Similarly after 10 days of feeding also, it ranged from 2.77 to 3.60 mg in BG-II hybrids which were on par. Significantly higher larval weight (266.00 mg) was registered in Orugallu Krishna. The larval weight of first instar Spodoptera fed on 90 days old cotton leaves ranged from 1.13 to 1.60 mg and 1.77 to 3.73 mg when fed for five and 10 days, respectively, in all the BG-II hybrids. Significantly higher larval weights (32 and 254 mg) were gained after five and 10 days, respectively in Orugallu Krishna. The perusal of data on larval weights of first instar Spodoptera when fed on 120 day old cotton leaves indicated that all Bt cotton hybrids were on par with larval weights ranging from 1.10 to 1.67 mg while significantly higher larval weight (28.00 mg) was registered in Orugallu Krishna after five days. Similarly after 10 days, it ranged from 3.23 to 4.03 mg among Bt cotton hybrids and 273.67 mg in Orugallu Krishna.