Impact of chlorpyrifos used for desert locust control on non-target organisms in the vicinity of mangrove, an ecologically sensitive area

Abstract

Ecologically sensitive areas (ESAs) including the mangrove along the Red Sea Coast of Sudan may be subjected to adverse impacts of insecticides for controlling desert locust, Schistocerca gregaria (Acrididae). This study assessed potential impacts of an aerial application of chlorpyrifos (Ultra Low Volume [ULV], 279 g a.i. ha−1) during conditions resembling an operational treatment of desert locust. The surveyed non-target organisms were studied in one treated and one untreated area (88 ha each), during a 13-week pre-spray period and an 8-week post-spray period, from November 2001 to April 2002. Survival of caged prawns (Penaeidae) in the mangrove lagoon were tested in situ, and monitoring of relative abundances of non-target organisms included (i) terrestrial transect counts of hoopoe larks, Alaemon alaudipes (Alaudidae), and of antlion larval pits, Cueta spp. (Myrmeleontidae) and (ii) pitfall sampling of epigeal arthropods in the terrestrial zones from shore to cropland. The survival of Metapenaeus monoceros juvenile prawns fell dramatically between the third and fifth day after the application in the treated area compared to the untreated area, in which mortality was delayed. In the early mornings when control operations often occur, a northern and northwestern wind direction, i.e. from land towards the sea, dominates, thus adverse impact on the prawns is a risk. The abundance of antlion pits was reduced in the treated area following spraying, but not in the untreated. The same was true for observations of hoopoe larks, numbers of Mesostena angustata (Tenebrionidae), and Gryllus bimaculatus (Gryllidae), at species and family levels, and arachnids.