Golden Apple Snail: Double "Killer" of Rice Fields and Health

Recently, many netizens posted on social media that they found pink mulberry-like egg masses on plants in rivers and ponds. These are actually the eggs of the golden apple snail.

You can encounter this small brown snail in rice fields, ponds, and even in the famous West Lake and Erhai Lake in southern my country. It looks unremarkable, even a bit like a field snail, and lays eggs not far from the water surface. Although it has an auspicious name, it is actually a very destructive invasive alien species.

Introduced into my country as an edible snail

Pomacea canaliculata is the trade name of the bottle snail, which is native to the Plata River Basin in South America. This snail grows and reproduces quickly, has a varied diet, is highly resistant to adversity, is easy to breed and has low cost.

In the 1980s, it was introduced into my country as an edible snail and promoted for breeding. Around 1990, it was abandoned in the wild by breeders due to poor returns, causing serious spread. In recent years, some people's release of the golden apple snail has also exacerbated the spread of the golden apple snail. According to media reports, the golden apple snails in West Lake may have come from tourists' release.

Harm to ecology and human health

It is hard to say whether you will live long or die if you come into contact with golden apple snails, but there is a risk of infection. Like the giant African snail, the golden apple snail is also the intermediate host of the Guangzhou roundworm.

Surveys show that in some areas of southern my country, the probability of golden apple snails being infected with Angiostrongylus cantonensis can be as high as 13.91%, second only to giant African snails and significantly higher than round pond snails. Therefore, whether golden apple snails are cooked or not, it is not recommended for consumption.

The golden apple snail can produce 2-3 generations a year and is described as having a "wide-ranging diet and eating anything green". It has become a major pest in rice fields in East and Southeast Asia. The main period of damage is from transplanting rice seedlings to drying the fields. The golden apple snail will bite and cut the main tillers and effective tillers of rice, resulting in a reduction in effective ears and a decrease in yield, with the degree of reduction in yield reaching 10%-90%.

At the same time, the golden apple snail also has a significant negative impact on local ecological functions and biodiversity. For example, it causes a decrease in native snails such as the ring-shaped snails, and also eats aquatic plants, significantly reducing their biomass. Its activities change the physical and chemical properties of water bodies and are one of the causes of eutrophication.

There is still a long way to go in prevention and treatment

The eggs of the golden apple snail are brightly colored and are 10-30 cm from the water surface, making them easy to identify. If they occur sporadically or it is inconvenient to use drugs for prevention and control, they can be removed manually. For adult snails, they can be directly salvaged and removed. In addition, nets can be used in waterways for filtration and isolation.

In farmland control, water-dry crop rotation or appropriate dry-wet alternation can be used. Before planting, high-power rotary tillers can be used to plow and prepare the land to break up larger golden apple snails to reduce their population size. Rice-duck co-cultivation and rice-field fish farming can also be used for biological control.

The eggs of the golden apple snail are poisonous, but there are reports that Chinese soft-shell turtles and some ants can eat snail eggs. Chemical control can also be carried out in rice fields when necessary, such as using copper sulfate before transplanting rice, or using drugs such as snail killer amine in rice fields, but because the latter is highly toxic, it is necessary to prevent pollution and secondary damage.

The invasion of the golden apple snail reminds us that before introducing alien species, on the one hand, we must conduct an ecological assessment and on the other hand, we must formulate management measures to deal with possible escape and spread.

(The author Ran Hao is a member of the China Science Writers Association)

Quick Questions and Answers

How to distinguish between golden apple snails and field snails

In terms of appearance, the golden apple snail is usually flatter, with a thinner shell and lighter color. The field snail, on the other hand, is taller, with a sharp top, a hard, thick and darker shell. In terms of reproduction, the golden apple snail lays eggs, forming red or pink egg masses, while the field snail is ovoviviparous, giving birth to baby snails directly.

How to distinguish snail meat without shell?

When observing the golden apple snail, you can see that it has two pairs of tentacles distributed in a "//\\" pattern, while the field snail has only one pair of distinct tentacles. The meat of the golden apple snail is slightly yellowish brown, while the meat of the field snail is bluish gray.