ارزیابی اثرات زیرکشندگی سم تیوسیکلام (اویسکت) روی پارامترهای دموگرافیک زنبور پارازیتوئید Habrobracon hebetor (Hym.: Braconidae)

Habrobracon hebetor Say (Hym.: Braconidae) as an ectoparasitoid of larval stage of lepidopterous pests is widely used in biological control programs. Thiocyclam-Hydrogen-Oxalate (Evisect 50% SP) is a contact-stomach insecticide with a 3-day pre-harvest interval (PHI). In the present study, the effect of sub-lethal concentrations (LC10, LC20 and LC30) of Evisect was evaluated on demographic parameters of H. hebetor. The estimated values of LC10, LC20 and LC30 were 234, 315 and 391 (ppm), respectively. Thus 70 of same-aged eggs were collected and placed into a Petri-dish and then were treated with sub-lethal concentrations and control. Eggs were individually collected and placed into a Petri-dishes (60 mm in diameter) and maintained at 25 ± 2 ºC, relative humidity of 65 ± 5% and a photoperiod 16: 8 (L: D) h. After adult emergence, number of offspring produced by each female was daily recorded until the death of last individual. Date analysis was performed according to Age-Stage Two Sex Life Table theory. The results obtained revealed that sub-lethal concentrations had significant effects on demographic parameters of this parasitoid wasp. The lowest values of population growth parameters, including net reproductive rate (R0) 3.24 ± 1.16 (offspring), intrinsic rate of increase (r) 0.040 ‌± 0.018 (day-1), finite rate of increase (λ) 1.054 ± 0.02 (day-1) and gross reproduction rates (GRR) 7.53 ± 2.67 (offspring) were recorded in LC30 treatment and significantly decreased in compare with control. But, the mean generation time (T) 22.195 ± 1.05 (day) increased in comparison with control .Sub-lethal concentrations of LC20 and LC30 had the most adverse effects on demographic parameters of H. hebetor. However, intrinsic rate of increase was not significantly affected by LC10 and was relatively safe for H. hebetor and could be an appropriate candidate for integration of chemical and biological controls, whereas sub-lethal concentrations (LC30) negatively affected the fecundity and sex ratio, and also the intrinsic rate of increase, finite rate of increase and mean generation time (T). Our findings revealed that increasing concentrations of Evisect had negative effects on the life table parameters of H. hebetor. As a result, this should be noted that low quantity of this insecticide should be used in combination with this parasitoid wasp in integrated pest management programs or parasitoid is released within a reasonable time after chemical control.