Residues and dissipation kinetics of two imidacloprid nanoformulations on bean (Phaseolus vulgaris L.) under field conditions

The current study investigates the dissipation kinetics of two imidacloprid (IMI) nanoformulations (entitled: Nano-IMI and Nano-IMI/TiO2) on common bean (Phaseolus vulgaris) seeds under field conditions and compares them with 35% Suspension Concentrate (SC) commercial formulation. To do so, it sprays P. vulgaris plants at 30 and 60 g/ha within green bean stage, sampling them during the 14-day period after the treatment. Following extraction and quantification of IMI residues, dissipation data have been fitted to simple-first order kinetic model (SFOK) and to first-order double-exponential decay (FODED) models, with 50% and 90% dissipation times (DT50 and DT90, respectively) assessed along the pre-harvest interval (PHI). With the exception of Nano-IMI at 60 g/ha, other decline curves are best fitted to the FODED model. In general, dissipation is faster for Nano-IMI (at 30 g/ha: DT50 = 1.09 days, DT90 = 4.30 days, PHI = 1.23 days; at 60 g/ha: DT50 = 1.29 days, DT90 = 4.29 days, PHI = 2.95 days) and Nano-IMI/TiO2 (at 30 g/ha: DT50 = 1.15 days, DT90 = 4.40 days, PHI = 1.08 days; at 60 g/ha: DT50 = 0.86 days, DT90 = 4.92 days, PHI = 3.02 days), compared to 35% SC (at 30 g/ha: DT50 = 1.58, DT90 = 6.45, PHI = 1.93; at 60 g/ha: DT50 = 1.58 days, DT90 = 14.50 days, PHI = 5.37 days). These results suggest the suitability of Nano-IMI and Nano-IMI/TiO2 application at both rates in terms of their residues on P. vulgaris seeds

Comparative life table of Aphis craccivora (Hem.: Aphididae) on host plant, Robinia pseudoacacia under natural and laboratory conditions

-The cowpea aphid, Aphis craccivora Koch, is an important pest of Robinia pseudoacacia Frisia. Life table parameters of A. craccivora were determined under natural (16- 33ºC and 32-89% RH, respectively) and laboratory (25 ± 1ºC, RH of 70 ± 5% and a photoperiod of 16:8 h (L: D) conditions. The data were analyzed using the age-stage, two-sex life table theory. Each experiment was replicated 45 times for each condition. There was significant differences between the survivorship, fecundity and longevity of the A. craccivora in laboratory and natural conditions. Under natural conditions, A. craccivora had a significant shorter nymphal developmental time, adult longevity and life span than those reared under laboratory conditions. However, the intrinsic rate of increase (r), net reproductive rate (R0), the finite rate of increase (λ) and gross reproductive rate (GRR) under laboratory conditions, were higher than those obtained in field, the higher mean generation time (T) was found in the field. All in all, the results of this study showed that two different conditions (field and laboratory) had significant influence on developmental times and life table parameters of A. craccivora and it is hard to escape the obvious conclusion that we must prevent the unsuitable extrapolation of laboratory results to field applications. The results obtained here, could also help us to understand the population dynamics of A. craccivora under field condition and to develop effective integrated pest management (IPM) programs