The most thorough description available is by Hayes et al. (2012), in which P. canaliculata and P. maculata are compared. The following brief description is modified from that publication.
The most recognizable sign of the presence of P. canaliculata (and other related apple snail species) is their bright-pink egg masses, which are laid on emergent vegetation (including wetland crops) and other hard surfaces above the water line, such as rocks, logs and bridge supports (Hayes et al., 2009b). These egg masses are very noticeable and can even be seen from a moving vehicle.
Related invasive species
- Pomacea canaliculata
Related Farm Practice
- Damage
- Feeding
- Corms
P. canaliculata is a freshwater snail native to parts of Argentina and Uruguay. The distribution of P. canaliculata has been steadily increasing since its introduction to Asia, primarily as a human food resource but perhaps also by the aquarium trade, beginning around 1979 or 1980 (Mochida, 1991;Halwart, 1994a;Cowie, 2002;Joshi and Sebastian, 2006). Once introduced to an area, it spreads rapidly through bodies of water such as canals and rivers and during floods. It feeds on aquatic plants and can devastate rice (in South-east Asia), taro (in Hawaii) and other aquatic or semi-aquatic crops. It may out-compete native apple snails (Halwart, 1994a;Warren, 1997), prey on native fauna (Wood et al., 2005, 2006) and alter natural ecosystem function (Carlsson et al. 2004a). It is also an important vector of various parasites including the nematode Angiostrongyulus cantonensis, which causes human eosinophillic meningitis (Lv et al., 2011;Yang et al., 2013).
In wetland rice the first symptom of damage by P. canaliculata is a reduced plant stand where the snails have severed the plant stalks below the water level. The tillers are cut first and then the leaves and stems are consumed under water. The crop is highly vulnerable at the early seedling stage. In taro, damage to the corms is readily visible, and active snails are easily seen feeding on both corms and leaves that have drooped so that their tips break the water surface.
The list of crops and other plants affected is not an exclusive list of all wild plant species potentially affected. P. canaliculata is primarily a generalist macrophyte herbivore and determining what plants it does not eat may be more important than generating a long list of plants it will eat (Cowie, 2002).
Regarding the most important crop affected, rice, it is the young seedling stage that is most vulnerable (Halwart, 1994a;Okuma et al., 1994b;Schnorbach, 1995;Naylor, 1996;Cowie, 2002;Wada, 2004). All parts of wetland taro plants are eaten because the snails can access the leaves when they droop down to the water surface.
Because of its generalist feeding habits, P. canaliculata has been suggested as a biological control agent for aquatic and wetland weeds in rivers (Cazzaniga and Estebenet, 1985;Fernández et al., 1987) and rice fields (Okuma et al., 1994b;Wada, 1997;Joshi et al., 2006). It can be used to control weeds without eating the rice plants only if rice seedlings are transplanted and at the 3-leaf stage (21 days), so that they are too tough for the snails to eat, and the ground is allowed to dry until water is introduced to a 2 cm depth after 6-8 days after transplanting (Joshi et al., 2006).