Pomacea canaliculata: harmless and useless in its natural realm (Argentina)

Apple snails in genus Pomacea are widely known as agricultural pests across Southeast Asia; however, they are mostly considered harmless and useless organisms in Argentina, where they are autochthonous. Rice is not a main crop in Argentina, only nontillage rice fields appearing to be vulnerable to apple snail attacks. There are no definite reports of health hazards derived from apple snails in this country, they are used neither as human food nor for other purposes, and consequently there is no official policy referring to apple snails in Argentina. This paper presents an intensive review of the basic knowledge on apple snails published by Argentine researchers concerning taxonomy, distribution, habitat, morphological variation, plasticity of life cycle and reproduction, symbionts, and natural enemies. Both morphological and biological features of Pomacea canaliculata prove to be very variable and adaptable to wide variations in envi ronmental conditions. Natural control by predators and competitors does not seem to be the cause for not being a pest in Argentina, since snails are still very abundant in their natural environments around and within the rice fields, even beyond the risk densities reported in Asia. Individual rice fields are very large in Argentina (up to 4,000 ha). Soil has to be plowed dry, using heavy machinery that probably kills most buried apple snails. Dry direct seeding on plowed soil and relatively late flooding appear to be important factors that minimize the economic loss due to apple snails. A comment is added on a project on integrated management of aquatic weeds, including the use of Pomacea canaliculata as a weed control agent, which was conducted on Southern Buenos Aires Province in the 1970s. There are strong arguments against introducing species into new habitats due to the unpredictability and irreversibility of these actions. So indiscriminate spreading of apple snails a s weed controllers must be strongly discouraged, except in cases where the risks are reasonably ruled out.