PH24 Environmental Assessment, Environmental Toxicology
Exhibit Hall
8:00 AM - Thursday
(PH261) Comparative avian risk assessment of acridid control in the Sahel based on probability of a kill and hazard ratios.
Mullié, W.C.1, 2, Mineau, P.3, 1 FAO, Locustox Project, BP 3300, Dakar, Senegal, Senegal2 Centre for Ecotoxicological Research in the Sahel, BP 3300, Dakar, Senegal, Senegal3 National Wildlife Research Centre, Canadian Wildlife Service, Carleton University Campus, Ottawa, Canada K1A OH3, Canada K1A OH3
ABSTRACT- Cyclic upsurges of Desert Locusts and almost annual proliferation of grasshopper populations in the Sahel urge Plant Protection Services to treat up to millions of hectares of cultivated, savannah and desert areas with insecticides. Few studies have addressed avian risks of acridid control in the Sahel, but concern has been expressed that many cases of poisoning remain undetected or unreported. Data were collected from plant protection services in Senegal and Niger, and from FAO for NE Africa, on insecticides used for locust and grasshopper control on 3.67 x 106 ha, between 1986 and 2001. Data included date, locality, formulation, dose rate and pest species. The probability of bird mortality for the active ingredients in each individual formulation was calculated by using logistic regression, based on models recently developed by Mineau (2002). These models were constructed from empirical findings of mortality associated with either conventional spraying equipment of Ultra Low Volume (ULV) spraying. Minimum and maximum product-specific application rates were used to bracket the probability of mortality for each application. By factoring in use data, these probabilities were converted to estimated minimal, maximal and mean surface areas on which bird mortality was deemed to have occurred. The mean surface areas with predicted bird mortality were cumulated and expressed as a proportion of the total area treated. These proportions are called Hazard Ratios (HRs). HRs were used to rank the potential impact of each active ingredient. Average Hazard Ratios decreased over time from 0.47 to 0.25 for grasshopper control, and from 0.60 to 0.41 for locust control. Important differences between regions were found, with HRs for grasshopper control in Senegal being twice as large as those for Niger. This could be attributed to differences in the choice of insecticides and dose rates applied. It was calculated that bird mortality has occurred on 0.97 to 1.53 x 106 ha. HRs resulting from grasshopper control were only 20% lower than those from locust control, although recommended dose rates for the latter are twice those for grasshopper control. Fenitrothion (75.4%), chlorpyrifos (12.5%) and diazinon (10.1%) contributed most to the overall HR.
Key words: sahel, avian risk assessment, insecticides, acridid control