Susceptibility of field populations of Blattella germanica (Blattaria: Blattellidae) to spinosad.

The German cockroach is an important household insect pest worldwide and acts as a mechanical vector and reservoir for pathogenic agents. The aim of this study was to examine the basic laboratory toxicity of Blattella germanica to spinosad. The M, T, A22, AZAR4, BOOSTAN7 and ABAN21 strains were collected from field populations of six infested kitchen student dormitories and the SAMAN strain was collected from a residential area after insecticide spraying control failure in Tehran, Iran. Technical grade spinosad was delivered in 0.5 microL acetone to the first abdominal sternum of briefly CO2-anesthetize adult male cockroaches by topical application bioassay. Treated males monitored for mortality. Mortality data from the replicates was assessed by probit analysis. The average LD50 of susceptible strain was 494.3, 148.8 and 55.1 ng per insect after 24, 48 and 72 h, respectively. The LD50 of spinosad decreased with time in the field population strains. All German cockroach strains showed a similar susceptibility or lower tolerance (1.6-folds) for spinosad compared with the susceptible laboratory strain and the steep slopes of dose-response curves indicated that the field population of these German cockroach strains was homogenous in response to spinosad. These results indicated that the spinosad was relatively slow-acting in topical application bioassay, with LD50 values decreasing until 72 h and becoming stable thereafter. The effectiveness of spinosad against susceptible and the field population German cockroach strains in laboratory condition showed that spinosad probably could be useful for the control of the German cockroach.

Cholinesterase activity among spray workers in Iran.

In this study whole blood cholinesterase activities of the agriculture and hygiene spray workers exposed to organophosphorus and carbamate compounds from different parts of Tehran Province in Iran were determined. Lovi Bond method was used in three stages including prepare the questionnaires about spray worker body health conditions, taking their blood samples before and after working and their insight to insecticides and prepare the required solutions. Results showed that no any changes were observed in the 50% of the spray worker blood cholinesterase activity after working. In the 32.4% of them, cholinesterase activity has decreased up to extensive poisoning and in the 17.6% of them cholinesterase activity was much decreased at the end of an acute or severe poisoning, whereas in testifier workers less than 5.9% of them cholinesterase activity was decreased and in the 94.1% of testifier workers cholinesterase activity was normal. Analysis of the data demonstrated that no significant relationship between spray worker blood cholinesterase activity, age groups, history of working, knowledge, cigarette smoking, history of toxicity and their responsibilities were observed. The measurement of pre-exposure cholinesterase values is essential for comparison of the values after pesticide application.