life table parameters and digestive enzymes activity of helicoverpa armigera (lep.: noctuidae) on different tomato cultivars

the tomato fruit borer, helicoverpa armigera (hã¼bner), is a destructive insect pest of many host crops in iran and worldwide. the effect of different tomato cultivars (sun 6108 f1, rio grande ug, korral, ch falat, hed rio grande and cal jn3) was studied on life table parameters of h. armigera under laboratory (25 â± 1 â°c, 65 â± 5% rh and a photoperiod of 16: 8 (l: d) hours), and on the activity of some digestive enzymes of its sixth larval instars under field conditions. the larval period was longest on hed rio grande (35.500 â± 1.340 days) and shortest on korral (24.290 â± 0.688 days). the intrinsic rate of increase (rm) ranged from 0.094 â± 0.003 to 0.159 â± 0.002 (day-1), which was lowest on rio grande ug and highest on korral. the larvae reared on the leaves of sun 6108 f1 showed the highest amylolytic activity (0.062 â± 0.00004 mu mg-1), whereas the lowest activity was in the larvae fed on the leaves of cal jn3 (0.027 â± 0.00004 mu mg-1) and korral (0.027 â± 0.0001 mu mg-1). the amylolytic activity of larvae fed on the fruits of tomato cultivars was highest on cal jn3 (0.047 â± 0.0001 mu mg-1). also, the highest general proteolytic activity of h. armigera was in the larvae reared on the leaves of hed rio grande (3.235 â± 0.004 u mg-1) and fruits of rio grande ug (2.757 â± 0.135 u mg-1). it could be concluded that rio grande ug is unsuitable host for the growth and development of h. armigera.