Golden apple snail: The dangerous pest on rice

The Family of apple snails (Ampullariidae J. E. Gray, 1824) has 105-170 freshwater species with 9 genera and more than 150 nominal species. The Synonyms of this family is Pilidae. This family consists of two subfamilies (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005), that used classification by Berthold (1991): -Tribe Ampullariini Gray, 1824 – synonyms: Pilidae Preston, 1915 (inv.); Lanistimae Starobogatov, 1983; Pomaceinae Starobogatov, 1983. -Tribe Sauleini Berthold, 1991. There are 9 extant genera in the family Ampullariidae: +Tribe Ampullariini Gray Ampullaria , Pila, Lanistes, Pomacea. +Tribe Sauleini: Saulea , Asolene, Felipponea, Marisa , Pomella . The Golden apple snail Pomacea canaliculata is classified under the canaliculata complex. 

This is a groups of very closely related species which are very variable in size and appearance. The relative species: -Pomacea diffusa. -Pomacea paludosa. -Pomacea patula catemacensis Baker -Pomacea maculata, raremy makes its way Origin and distribution of the golden apple snails (GAS) The GAS Pomacea canaliculata is widely distributed in the lentic habitats throughout the Amazon Inferior Basin and the Plata Basin: Southeast Brazil, Argentina,Bolivia, Paraguay and Uruguay. GAS Pomacea canaliculata is one of the most Southern America occuring. Pomacea canaliculata is a species of large freshwater snail with gills and an operculum, an aquatic gastropod mollusk in the family Ampullariidae, the apple snails.

Native range: temperate Argentina northwards to the Amazon basin. The native distribution of P.canaliculata is basically tropical and subtropical, including Argentina, Bolivia, Paraguay, Uruguay, and Brazil. The southernmost record for the species is Paso de las Piedras reservoir, south of the Buenos Aires province,Argentina. Non-indigennous distribution This species also occurs in the United States, where the initial introductions were probably from aquarium release, aka “aquarium dumping”. 

The non-indigenous distribution includes: Langan Park and Three Mile Creek in Mobile, Alabama; a pond bordering the Mobile-Tensaw River Delta in Baldwin County, Alabama ; Little Wekiva River, Orlando, Florida; a lake near Jacksonville, Florida; Lake Mirimar in San Diego County, California; a pond near Yuma, Arizona; and numerous locations in Hawaii. Established populations exist in California and Hawaii. Introduced range: Last decades GAS Pomacea canaliculata has spread to South-East Asia and can now be found in Indonesia, Thailand, Vietnam, Cambodia, Hong Kong, southern China, Japan and the Philippines. The snail also invaded in the Southern parts of theUSA (Texas and Florida, upto central Ohio) and is expected to spread futher in the comming years. Possibly the species is making its way to Australia too. 

Most of southern, eastern and south-east Asia, including the Philippines, Japan, Taiwan, Vietnam, Cambodia, Thailand, Laos, Korea, Sri Lanka, parts of Indonesia and Malaysia, southern China, Singapore; also Hawai‘i, Guam, and Papua New Guinea; the Dominican Republic; the USA (Florida, Texas, California). The species has been found in China since 1981. Its initial point of distribution in China was Zhongshan city. Pomacea canaliculata is also a very common in the aquarium trade, but its voracious appetite gives the GAS family in general a bad reputation in the aquarium hobby. Genera Pomacea are New World genera (native to South America, Central America, the West Indies and the Southern U.S.A.).

The genera Afropomus, Lanistes, and Saulea are found in Africa.The genus Pila is native to both Africa and Asia. Description -Organism type: mollusc Pomacea canaliculata is a freshwater snail with a voracious appetite for water plants including lotus, water chestnut, taro and rice. 

Introduced widely from its native South America by the aquarium trade and as a source of human food, it is a major crop pest in south east Asia (primarily in rice) and Hawaii (taro) and poses a serious threat to many wetlands around the world through potential habitat modification and competition with native species. -

Body: 

The colour of the body varies from yellow (cultivated), brown to nearly black, with yellow spots on the siphon, but not as much on the mouth as in. When at rest, the tentacles are curled under the shell. 

Shell description 

The shells of these apple snails are globular in shape. Normal coloration typically includes bands of brown, black, and yellowish-tan; color patterns are extremely variable. Albino and gold color variations exist. The size of the shell can be up to 75 mm in length. The shell of this apple snail species is globose and relatively heavy (especially in older snails). The 5 to 6 whorls are separated by a deep, indented suture (hence the name ‘canaliculata’ or ‘channeled’). The shell opening (aperture) is large and oval to round. Males are known to have a rounder aperture than females. The umbilicus is large and deep. The overal shell shape is similar to that of Pomacea lineata, except the deeper sutures and more globose shape in canaliculata. The size of these snails varies from 40 to 60 mm wide and 45 to 75 mm high depending on the conditions. The colour varies completely yellow and green (cultivated forms) to brown with or without dark spiral bands (wild form). The shell growth of this species occurs mainly in spring and summer, while it stagnates in fall and winter. Large (up to 7 cm), more or less globular freshwater snails. Aquarium trade snails are often smaller. Shell colour generally brownish or greenish, often with spiral banding patterns around the whorls. Some aquarium bred animals are bright golden yellow. Body colour can vary from dark, almost black to pale cream. Their presence is often first noted by observation of their bright pink egg masses laid on solid surfaces up to about 50cm above the water surface.

Operculum

The operculum is moderately thick and corneous. The structure is concentric with the nucleus near the centre of the shell. The colour varies light (in young snails) to dark brown. The operculum can be retracted in the aperture (shell opening).

Eggs

The reddish (due to the high carotenoid content) eggs are loosely attached to each other. They are attached on object above the waterline and their size varies from 2.20 to 3.5 mm (0.09 to 0.14 inch) diameter. An average clutch contains 200 to 600 eggs. 

Pomacea canaliculata depositing the eggs on a trunk. Eggs of the non-native Pomacea canaliculata on a rock at the border of the Kranji Reservoir, Singapore (12/9/2000). Note that the bright orange colour is hidden by the dry surface. Pomacea canaliculata is more likely to eat your plants, which makes it less suitable for most aquaria. These snails also come in different shell and body colours. Life cycle of the golden apple snails (GAS) +Adult This species, unlike most snails known to common people, is not androgynous but gonochoristic. It means it has males and females! GAS P. canaliculata is sexual mature at the size of 2.5 cm/1 inch. Sexes are separate. -Females lay clusters of bright pink eggs attached to solid surfaces (rocks, walls, logs, emergent vegetation, trash) up to usually about 50cm above the water surface. 

Females are mostly larger while males have a wider aperture (shell opening). Many apple GAS deposit the eggs above the waterline in a calcareous clutch. This remarkably strategy of these aquatic snails protect their eggs against predation by fish and other water inhabitants. The apple snail genera Pomacea and Pila, is the tubular siphon at their left side, used to breathe air while they stay submerged, thus making them less vulnerable to snail eating birds. 

The reproductive rate of this snail varies with the temperature and partly by the availability of food. During fall and winter, the reproduction rate is at its lowest point, while with the raising temperatures in spring their reproduction rate increases. There are more ways to determine the snail’s sex, not all of them are 100% sure. At a temperature of 25oC (77oF/298oK), breeding is at maximum rate. Reproductive output can be enormous. Clutch size is up to 1000, but averages probably 200-300. 

Clutches are laid every few weeks. -Eggs:The female lays its eggs above the water surface at a clutch containing about 200-600 eggs.These eggs will hatch within about 2-3 weeks, depending on temperature an humidity of the air (the air above the water surface should have high humidity)- thus, a glass cover on the tank is essential (water level should be about 5-7.5cm/2-3inch below the glass cover). Eggs generally hatch within 10-20 days, but may take longer, probably depending on ambient temperature regime. In temperate climates the egg-laying period of this species extends from early spring to early fall while in tropical areas reproduction is continuous. 

The duration of the reproductive period of P. canaliculatadecreases with latitude, to a minimum of six months in the southern limit of its natural distribution. -The young snails are about 2.5mm (0.09inch) after hatching and immediately start eating; they will also need a constant supply of calcium (both in water and by food). Keeping the young snails with the adults might become a problem after a while, due to competition over food and calcium,so it is advisable to grow them separately. The young snails get to sexual maturity at the size of about 2.5cm (1inch). Longevity is up to 4 years. Reproductive maturity is reached in 3 months to 2 years, depending on ambient temperature regime. 

Habitat Breathing 

The Golden Apple Snail is amphibious. While there is a sufficient level of dissolved oxygen in the water, they will hardly leave the water and will breathe by their gills. If the level of dissolved oxygen gets to low, the snails will go up to the surface and breathe with their lung (mostly by using its siphon, a tube that it extracts to the water surface). While filling their lung with air, the snails extract and contract their body, so that the pressure differences cause their lung to deplete and refill. 

Feeding habits of the golden snails (GAS)

GAS Pomacea canaliculata is extremely polyphagous, feeding on vegetal (primarily macrophytophagous, feeding on floating or submersed higher plants), detrital, and animal matter. Diet may vary with age, with younger smaller individuals feeding on algae and detritus, and older, bigger (15mm and above) individuals later shifting to higher plants. In captivity, as well as eating vegetables and fish food pellets, GAS will also eat other foods if they are available. 

They will sometimes eat brine shrimps and other frozen foods, or dead fish and insects. Generally, they will also eat any of the microscopic vegetation that grow on the tank rocks or walls. Snails will climb out of the water to reach food that is above the waterline. Because of their ability to do this they have become a nuisance in Asia, where they feed on crops. 

This species negatively impacts rice and taro agriculture worldwide where it has been introduced. This species lives in freshwater habitat. A highly generalist and voracious macrophytophagous herbivore. Most plants are eaten, though it does show some preferences, for instance in Hawai‘i it will not eat water hyacinth. Eats almost all types of plants. As this snail is fast growing, it needs calcium rich water, so it can grow with a healthy shell – the calcium is used as calcium – carbonate to create the shell, lack of calcium will cause the shell to be thinner and more susceptible to breaking and eventually, the snail will die. Ecology for the golden apple snails (GAS) 

-The GAS are amphibious animals; They are widely distributed in lakes, ponds and swamps throughout its native range of the Amazon Inferior Basin and the Plata Basin. These amphibious animal remains submerged during the day, hidden in vegetation near the surface. They are more active during the night, and leave the water in search for fresh vegetation. When it is night time, the GAS becomes active and engages in behaviors relating to feeding, as well as mating and laying eggs. 

The GAS are exceptionally well adapted to tropical regions characterized by periods of drought alternating with periods of high rainfall. This adaptation is reflected in their life style; they are moderately amphibious. They have an operculum which enables the snail to seal the shell entrance to prevent drying out while they are buried in the mud during dry periods. In captivity, GAS are most active at night. During the day they usually retreat to somewhere shaded. In an aquarium that is well lit, the exterior of the shell of apple snails may grow filamentous green algae. This is one possible source of food for juvenile snails. 

The activity rate of this snail varies highly with the water temperature. At 18°C they hardly move around, this in contrast with higher temperatures e.g. 25°C. PH should be in range of 6.5-7.5, best at 7. Water hardness (GH and KH) isn’t significant. Water contain HEAVY METALS are lethal to the snails! Pomacea canaliculata is more resistant to lower temperatures than most other snails from the genus Pomacea .

The golden apple snail (GAS) is a dangerous rice pest in Asia The GAS Pomacea canaliculata (Lamarck) is a recently introduced rice pest inAsia. The planting method greatly influences the period of susceptibility to snail damage: wetbed-transplanted 20-day-old seedlings were less damaged than dapog-transplanted 13-day-old seedlings or direct-seeded rice. Seedlings 30 days old were more tolerant of snail damage than younger seedlings. 

The GAS Pomacea canalicualata was originally introduced from South America to south-east Asia around 1980s, as a local food resource and as a potential gourmet export item. The markets never developed; the snails escaped or were released, and P. canaliculata became a serious pest of rice throughout many countries of south-east Asia. The GAS now is a major rice exotic invasive pest in Asia. The yield loss caused by P. canaliculata in rice was estimated varying from 5 % to 100 % depending on locality and the level of infestation in most Asian countries. 

In China, GAS was first introduced into Guangdong province of China in 1981 and became a serious pest of rice since 1984. In the Philippines, it is considered the number one rice pest and has caused huge economic losses.

During the 1980′s the introduced snails rapidly spread to Indonesia, Thailand, Cambodia, Hong Kong, southern China, Japan and the Philippines and there are indications that they are currently invading Australia. Nevertheless, apple snails are considered a delicacy in several regions and they are often sold in Oriental markets for consumption. In the 1980′s, GAS Pomacea canaliculata was introduced in Taiwan to start an escargot industry. 

Such food culture can provided protein for the local population, especially useful for the farmers, who primary live on a rice diet, low in proteins. However, the snails didn’t become a culinary success. It also became quickly clear that the imported species were able to transfer the Angiostrongylus cantonensis (rat lungworm) parasite just like the native apple snail population (Pila).However, the snails did not become a culinary success. 

It was introduced to Hawai‘i in 1989, probably from the Philippines, and for the same reasons as for its initial introduction to south-east Asia. Already, introduced P. canaliculata has been implicated in the decline of native species of Pila apple snails in south-east Asia. Also, native species of Pila in thePhilippines are reported to have declined as a result of extensive pesticide applications against introduced P. canaliculata. This parasite spends a part of its life cycle in apple snails and can infect humans when the snail isn’t cooked long enough before consumption. Instead of becoming a food source they escaped, and became a serious pest, posing a real threat to the rice production and the environment. 

Instead of becoming a valuable food source, the introduced snails escaped and became a serious threat to rice production and the native ecosystems. During the 1980s the introduced snails rapidly spread to Indonesia, Thailand, Cambodia, Hong Kong, southern China, Japan and the Philippines. In 1989 GAS Pomacea canaliculata was introduced in Hawaii to serve as a food source and aquarium pet. Some snails escaped to the wild and turned into a serious pest in the taro and rice fields. Although a few restaurants serve them, the apple snail didn’t become a great gastronomic success here either. 

Recent research reveals the catastrophic nature of the Pomacea invasion in new habitats: the snail herbivory drastically alters the state and function of invaded natural wetlands. When the plants are consumed, nutrients in the system are shunted to phytoplankton instead of the plants which creates dense algal blooms (Carlsson et al in press. 2004). 

 In China, GAS was first introduced into Guangdong province in 1981 and became a serious pest of rice since 1984 (Halwart, 1994). The first record for GAS infestation on rice and Zizania latifolia in Yuyao City of Zhejiang province was found in 2002, and became a serious pest in rice and Z. latifolia fields in 2004 (Pan et al., 2008). Z. latifolia, is one of the most important aquatic and economic vegetable crops cultivated in the Southeast China since ancient time (Guo, 2007). 

Nowadays, around 100 thousands hectares of Z. latifolia were planted in more than ten provinces in China(Chen, 1991; Zhai et al., 2001). The yield loss caused by GAS in rice was estimated varying from 5 % to 100 % depending on locality and the level of infestation in most Asian countries (Halwart, 1994; Naylor, 1996). Numerous measures have been taken to control GAS, in Z. latifolia fields. The molluscicide was usually used to kill GAS with a serious environmental and human health consequence, and the hand-picking was proved to be a time-consuming work (Yu et al., 2001; Chen et al., 2003). 

Thus, local farmers did not adopt these methods extensively for GAS control. Recently, the biological control was applied to suppress the occurrence of GAS by releasing biological agents such as fishes and ducks in crop fields. However, due to the low efficiency of fishes and ducks, especially for controlling the adult GAS (Yoshie and Yusa, 2008), the Chinese soft-shelled turtle (Pelodiscus sinensis), was tentatively selected as a new biological agent to control GAS in Z. latifolia field (Zheng et al., 2005). P. sinensis is widely distributed in Eastern Asia and usually take up 4 ~ 6 years to reach sexual maturity adulthood. P. sinensis consumes insect larvae, small fish, small aquatic animals and seeds of marsh plants (Nuangsaeng and Boonyaratapalin, 2001). 

Furthermore, P. sinensis is of high commercial value and is commonly cultured in Malaysia, Indonesia and China for food consumption (Jia et al., 2005). The objective of this study is to quantify the role of P. sinensis in biologically controlling GAS in Z. latifolia field. Human uses from Golden apple snails (GAS) Use as a human food item In Veracruz, Mexico, there is a subspecies of apple snail known as P.patula catemacensis Baker, 1922. This subspecies is endemic to Lake Catemaco. This large snail is locally known as “tegogolo” and is prized as a food item. In Northeast Thailand these snails are collected and consumed. They are picked by hand or with a handnet from canals, swamps, ponds and flooded rice paddy fields during the rainy season. During the dry season when these snails are concealed under dried mud, collectors use a spade to scrape the mud in order to find them. The snails are usually collected by women and children. 

After collection, the snails are cleaned and parboiled. They are then taken out of their shells, cut, and cleaned in salted water. After rinsing with water, they are mixed with roasted rice, dried chili, lime juice, and fish sauce, and then eaten. Note! Parasites in Golden apple snails In China and Southeast Asia, consumption of raw or undercooked snails of Pomacea canaliculata and other snails is the primary route of infection with Angiostrongylus cantonensis causing angiostrongyliasis. 

This parasite can infect humans if snails are eaten that have not been thoroughly cooked first. Approximately 1.0 % of the Pomacea canaliculata on sale on local markets in Dali City, Yunnan, China were found to be infected with Angiostrongylus cantonensis in 2009. Use as a common aquarium animal In the 1980s, GAS Pomacea canaliculata was introduced in Taiwan to start an escargot industry. 

It was thought that such food culture could provide valuable proteins for farmers, who primarily live on a rice diet. However, the snails did not become a culinary success. Hawaii experienced the same introduction of Pomacea for culinary purposes, and its taro industry is now suffering because of it. The common GAS is Pomacea canaliculata; this snail is more likely to eat aquatic plants, which makes it less suitable for most aquaria. This species can also have different shell and body colours. 

This species is considered to be in the top 100 of the “World’s Worst Invasive Alien Species”. Use as a bio-control agent Pomacea and Marisa species have been introduced to Africa and Asia in an attempt to control other medically problematic snails in the family Planorbidae: Bulinus species and Biophalaria species, which serve as intermediate hosts for trematoda parasites. These parasites can cause swimmers itch and schistosomiasis, a disease that affects over 200 million people in tropical regions. 

One of the species introduced as bio-agent is Marisa cornuarietis; this snail competes with other snails and also directly preys on other species. Management of golden apple snails (GAS) in wetland rice Preventative measures The primary management approach must be prevention. Strict quarantine must be enforced to prevent introduction and spread. Incipient invasions must be eradicated rapidly while it is still possible to do this. 

For rice and taro fields, it is preferable to use plants from areas that are known to be apple snail free. If that’s not possible, examine the plants and make sure that there are no apple snails or other unwanted snails and also check for egg clutches. The use of a screen on water inlets helps to retard the spread of apple snails. Screens should be cleaned regularly to obstruction. Around rice and taro fields, a barrier of copper could be used to slow the snail spreading to some extent. Copper is toxic to snails and they do not cross this material. The copper wire or strip should be placed above the water level, on the border of the field. Control Eradication of established populations is probably not possible. 

Numerous measures have been tried in attempts to control GAS in agricultural settings. These include: widespread use of pesticides, with serious environmental and human health consequences; biological control, notably the use of fish and ducks; a range of cultural and mechanical control measures. None has proven entirely effective, safe, and economically viable. None is likely to be appropriate in natural ecosystems. In rice and taro fields, hand picking is a successful method to control GAS populations without harming the environment. The disadvantage is that it only works when done on regular base. 

The best results are obtained if the hand picking is done as a community effort. All visible snails should be collected with a scoop net or by hand. After collection the snails can be used for human consumption (beware of parasites!), crushed to serve as a food source for fish or destroyed otherwise. Eggs should not be forgotten during collection! Baited traps filled with lettuce, cassava and taro leaves can be used to attract the snails and to facilitate the collection. All vegetation and obstacles around fields should be removed as much as possible as the snails need this to deposit their eggs. 

When there are no suitable eggs-laying sites available, the snails are forced to deposit the eggs on the bare ground where the eggs are very vulnerable and easily fall into the water, which drowns the eggs. Before draining a field, make shallow trenches so that the snails will congregate in the trenches and can be captured easily. 

This species has been nominated as among 100 of the “World’s Worst” invaders. Biological control of golden apple snails (GAS) Biological control of GAS Pomacea canaliculata by Chinese soft-shelled turtle, Pelodiscus sinensis in the wild rice, Zizania latifolia field Source: Shengzhang Dong; Guowan Zheng; Xiaoping Yu; Changhuan Fu The wild rice, Zizania latifolia Turcz, used to be one of the important aquatic vegetables cultivated in China. Recently, the GAS Pomacea canaliculata (Lamarck) was found to be a major invasive pest attacking Z. latifolia. To control efficiently GAS, predation by the Chinese soft-shelled turtles (Pelodiscus sinensis) on GAS was evaluated in laboratory and field trials. P. sinensis had a strong predatory capacity and selectivity for GAS both in laboratory and field conditions. All the sizes of P. sinensis prefer to capture smaller snails. 

The optimum number of P. sinensis released in Z. latifolia field was dependent on the density of over-wintered GAS, and varied between 30 and 50 turtles per 666.7 m2. The number of GAS declined in the fields with turtles as compared to turtle-free field. A pattern of releasing P. sinensis in Z. latifolia fields was developed and widely adopted by farmers because of much more benefit besides biologically controlling GAS. This feeding behavior was also found in common carp Cyprinuscarpio (Teo, 2006). It is concluded that P. sinensis is one of the most hopeful biological agents for GAS because they not only prey the young snails, but also attack the adult ones efficiently. To control GAS, several effective predators have been introduced into agricultural ecosystem, including various ducks and fishes (Teo, 2001; 2006).

 Domestic ducks were proven effective for biological control of young GAS in paddy field and could prey equally well under low and high pest population densities (Cowie, 2002). In conclusion, both laboratory trials and field survey results showed that using P. sinensis biologically to control GAS was recommended as an optimal method in wild rice fields infected by GAS. Control of Golden Apple Snails (GAS) by Tillage and Crop Rotation Techniques Tillage Tillage and soil puddling crush snails. The effect varies depending on the snail size and soil hardness. Tillage has greater effects on larger snails. Ten to 40% of GAS smaller than 20 mm are killed by tillage, while 40-90% mortalities are attained with GAS bigger than 20 mm. GAS mortalities are 14-20% higher when soil is compacted (hard) after rice harvest than when soil is friable (soft) after the harvest of wheat (winter crop with no irrigation). Deep cultivation is not necessary because 80% of GAS are found within 6 cm depth of soil. Higher mortalities are attained by intensive tillage, where a field with compacted soil is tilled shallow with a faster cultivator rotation, resulting in smaller cultivation pitch. Puddling using a paddy harrow is also effective. A field experiment revealed that when the average GAS size was 21 mm, GAS density was reduced by 40% after puddling. Thus, tillage and puddling are good methods for decreasing GAS density before growing of paddy crops. Crop Rotation Crop rotation is a practical way to significantly reduce GAS density in a paddy field in Japan.

Rice-soybean rotation as a summer crop is common in south Japan. After growing soybean in the previous summer, GAS densities in paddy fields are always very low before rice planting, although GAS are usually not eradicated. No paddy fields after soybean have been found above the tentative control threshold in direct-sown rice (0.5 GAS/m2). Thus, without extra control measures, farmers carry out direct seeding of rice as well as transplanting where seedlings are more tolerable than sprouts. Besides soybean, rotation with other upland crops or vegetables is also effective. Extremely low GAS density before growing paddy crops is attained by tillage and desiccation during upland crop cultivation and low temperature during winter in temperate countries. In the tropics, climatic conditions and crop cycles are different, thus, the effects of crop rotation should be evaluated in such areas.

Drainage immobilizes snails. More preventative measures should be undertaken in high-risk (>/2 snails m than in low-risk 2 snails m -z) fields. Snails can be controlled in low-risk fields by employing one or two cultural methods. Dapog or direct-seeded methods would benefit from drainage and mechanical control (hand-picking). Using molluscicide at low dosage If cultural methods cannot be carried out, snails can be controlled with molluscicide at low dosage. High-risk fields, on the other hand, should be protected with a combination of cultural and mechanical methods. These methods can be substituted with low or high dosages of molluscicide. Molluscicide alone, however, requires a dosage of (1.5 kg a.i. ha which most farmers cannot afford. 

References 

http://rotem.hubpages.com/hub/Golden-Apple-Snail
http://en.wikipedia.org/wiki/Ampullariidae
http://www.mendeley.com/research/management-golden-apple-snail-pomacea-canaliculata-lamarck-rice-13/ http://www.agnet.org/library.php?func=view&id=20110714110545&type_id=7 http://www.issg.org/database/species/ecology.asp?si=135 http://www.cdfa.ca.gov/phpps/ppd/Entomology/Snails/Applesnail.htm 6-http://www.applesnail.net/
TV news on the topic: http://www.tv3.cat/videos/1478229/El-caragol-poma-envaeix-lEbre.

Weaver Ants: The Living Pesticide

Scientific classification 

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Hymenoptera

Family: Formicidae

Sub family: Formicinae

Tribe: Oecophyllini

Genus: Oecophylla Smith, 1860 (15-20 species).

Species:2

Diversity species Oecophylla longinoda in blue, Oecophylla smaragdina Fabricius, 1775 in red.

Introduction

Oecophylla is a genus of large arboreal ants of the African, Asian, and Australian tropics. The weaver ants belong to the ant genus Oecophylla (subfamily Formicinae) which contains two closely related living species: O. longinoda found in Sub-Saharan Africa and O. smaragdina found in southern India, southeast Asia, andAustralia. They are provisionally placed in a tribe of their own, Oecophyllini.

The weaver ant genus Oecophylla is known about 18-20 species from Africa to Asia in the tropics. Weaver ants are best known for their remarkable nest construction. Using precise coordination, the weaver ants create very strong ant chains by linking legs to pull and bend leaves into desired tent like positions.

The ants then use their own larvae to secrete a silk that is used to stitch leaves together to create a nest. They may have several nests dominating a few trees at once. These conspicuous insects are weaver ants, creating nests by pulling living tree leaves together and securing them with silk produced by the ants’ larvae. Colonies are territorial, covering several trees and containing dozens of nests. They are very aggressive territorial ants and for over 1000 years they have often been used by farmers to control agricultural pests. Oecophylla smaragdina workers have a vice like grip and tremendous strength.

A worker has been recorded to support 100 times its own weight whilst standing upside down on glass! Weaver ants are reddish ants that live in the tropical forests of Africa and India and many countries in southeast Asia. They are also found in Australia and theSolomon Islands. Their nests are found in forest trees. A Queen of Oecophylla smaragdina that has shed its wings Weaver ant nest on a Mango tree nest in Kinnerasani Wildlife Sanctuary, Andhra Pradesh, India.

The life cycle Weaver ants or Green ants (genus Oecophylla) are eusocial insects of the family Formicidae (order Hymenoptera).Weaver ants get their name from their habit of binding fresh leaves with silk to form their nests. Oecophylla weaver ants vary in color from reddish to yellowish brown dependent on the species. Oecophylla smaragdinafound in Australia often have bright green gasters. In Vietnam they are called “kiến vàng” (yellow ants). The life cycle of the ant has four stages: egg, larva, pupa, and adult. Eggs of weaver ants The queen ant starts the ants’ nests/colonies. She flies and searches for mate/s. She can mate with one or a few males (one at a time) in the air, or on low vegetation, or on the ground.

Once mated, she looks for a nest site, either on trees or open fields. Once situated, she gets rid of her wings, seals herself into a small chamber and lays a small batch of eggs. The eggs then hatch into larvae. The queen is located in one nest and her eggs are distributed to all the other nests where workers and soldier ants are found. She spends her life laying eggs.

The workers are females and do the work in the nest. The larger ones are the soldiers who defend their colony. Fertilized eggs develop into females (workers and the queen) and unfertilized eggs into males. Female ants have 2 copies of each chromosome while males have one. Larvae and Pupa of weaver ants The larvae feed on the unfertilized eggs as food which the queen lays especially for them. The first brood of workers are normally smaller since she can only provide a limited amount of food. Once the ants mature, they leave the nest and begin to look for preys.

They bring food to the queen and their siblings so that later offspring are bigger. As the colony reaches maturity, it begins to produce the queens and males for the next generation. Males can remain in the nests for some months and most of them will die within a few days after leaving their nests. The larvae have special glands to produce lots of strong silks (adults do not produce silk).

One colony is found over several nests that may be placed in various locations in a tree, or several trees, or in fields. The worker ants form a chain along the edge of the leaf and pull the edges together by shortening the chain by one ant at a time. Once the leaf edges are in place, each ant holds one larva in its mandibles and gently squeezes the larva to produce silk. The silk is used to glue the leaf edges together.

Pupae are laid in nest with a short time before become adults. Adult weaver ants Adult weaver ants are reddish to brown in color and have 10-segmented antennae with 2-segmented clubs. Their eyes are relatively larger than those of other species of ants. They do not have stingers, but can give painful bites caused by the chemicals secreted from their abdomen.

They make nests in trees or on leaves of legumes, or in bunds or levees of the fields. They have the most complex nests among ants’ nests. They use fresh leaves to build nests . Queen 20-25mm, a strong ant, normally green and brown, monogyn (one queen per colony). Workers 5-6mm. Mostly orange. Sometimes this species has green gasters.Minor workers tend to look after the brood and farm scale bugs for honey dew. Major workers 8-10mm. Mostly orange, this ant has long strong legs, long flexible antennae and large mandibles. These ants forage, maintain and expand the nest. A dealate queen of O. smaragdina having shed her wings after a mating flight. O. smaragdina major workers inspecting and cleaning (allogrooming) another worker on its return to the nest.

Their lifecycle spans a period of 8 to 10 weeks. The main characters Diet They farm scale bugs for their honeydew, and eat small insects. Weaver Ants eat any small creatures that they can find, but they are particularly attracted to nectar. The weaver ants do not have a stinger, but inflict a painful bite which is aggravated by irritating chemicals secreted from their abdomen. Like many other ant species, weaver ants prey on small insects and supplement their diet with carbohydrate-rich honeydew excreted by small insects (Hemiptera). Colony productivity Weaver ant colonies are founded by one or more mated females (queens). A queen lays her first clutch of eggs on a leaf and protects and feeds the larvae until they develop into mature workers. The workers then construct leaf nests and help rear new brood laid by the queen.

As the number of workers increases, more nests are constructed and colony productivity and growth increase significantly. Workers perform tasks that are essential to colony survival, including foraging, nest construction, and colony defense. A colony may be dispersed over several nests which may be placed in various locations in a tree, or even span several trees. The queen is located in one nest and her eggs are distributed to the other nests.

Social organization 

Weaver ants are Social insects. The exchange of information and modulation of worker behaviour that occur during worker-worker interactions are facilitated by the use of chemical and tactile communication signals. These signals are used primarily in the contexts of foraging and colony defense. Successful foragers lay down pheromone trails that help recruit other workers to new food sources.

Pheromone trails are also used by patrollers to recruit workers against territorial intruders. Along with chemical signals, workers also use tactile communication signals such as attenation and body shaking to stimulate activity in signal recipients. Multimodal communication in Oecophylla weaver ants importantly contribute to colony self-organization.

Like many other ant species, Oecophylla workers exhibit social carrying behavior as part of the recruitment process, in which one worker will carry another worker in its mandibles and transport it to a location requiring attention. Nest-building Weaver ants’ nests are among the most complex ants’ nests. The ants choose living leaves to build nests.

These provide well camouflaged protection from predators and the elements. To create their neat nest, chains of worker ants form along the edge and pull the edges together by shortening the chain by one ant at a time. Once the edges are in place, an ant holds one of their larvae in its mandibles and gently squeezes it so the larvae produces silk. The silk is used to glue the leaf edges together. The larvae have special glands to produce lots of strong silk.

The adults do not produce silk. The nest starts very simply. A group of worker ants finds a leaf that is soft and easy to bend. Several ants line up. Each holds an edge of a leaf in its mandibles and feet. Slowly, the ants pull the two leaf edges together. More and more workers join in. They link their feet and pull until the two leaf edges are nearly touching. Weaver ant nests begin small but can sometimes become so large they connect branches of neighboring trees.

A giant weaver ant nest may look like it is damaging the leaves and branches of a tree. But weaver ants actually protect the tree they are living in. The ants act like miniature bodyguards for the tree. They keep other animals like birds, reptiles, and other insects from living in the tree or eating it. Sharing the same resource or living space is called symbiosis. Oecophylla weaver ants are known for their remarkable cooperative behaviour used in nest construction.

The time required to construct a nest varies depending on leaf type and eventual size, but often a large nest can be built in significantly less than 24 hours. Although weaver ant’s nests are strong and impermeable to water, new nests are continually being built by workers in large colonies to replace old dying nests and those damaged by storms.

Next, other worker ants carry larvae from the old nest and gently squeeze them between their mandibles. This causes the larvae to ooze a thin thread of silk. Then the workers get busy. Just like tiny tailors, they stitch the leaves together. In fact, another name for weaver ants is “tailor ants.” Treetop nests can become extremely large. Sometimes they even connect branches from two nearby trees. Other features Role in the habitat: Weaver ants are exploited by plants and animals.

Some plants such as the Sea Hibiscus (Hibiscus tiliceaus) secrete nectar in their leaves to attract these ants, which in turn protect the plant from insect leaf eaters. The nasty bite of the ants also discourages larger herbivores. Some other creatures also exploit the Weaver Ant’s sweet tooth. Some caterpillars of the Lycaenidae and Noctuidae butterfly families secrete a honey dew that attracts these ants to protect them. Some of these caterpillars are more sinister and use their bribe to gain entry into the ant’s nest and devour their larvae! Some jumping spiders look and more importantly, smell like ants, and in their disguise, enter the ant’s nest to devour them and their larvae.

Miniature bodyguards for trees: A giant weaver ant nest may look like it is damaging the leaves and branches of a tree. But weaver ants actually protect the tree they are living in. The ants act like miniature bodyguards for the tree. They keep other animals like birds, reptiles, and other insects from living in the tree or eating it. Sharing the same resource or living space is called symbiosis. A sweet deal: Weaver ants have a “sweet tooth” that some creatures use to their advantage.

Certain butterfly caterpillars produce drops of a sweet liquid called honeydew. The honeydew attracts weaver ants to the caterpillars. The ants then protect the caterpillars. Weaver ant workers take great care of the colony’s larvae. They feed them and are very careful when they move them. The larvae produce the special silk that holds the colony’s nest together. The uses of weaver ants Ant eaters Weaver ant pupae are harvested and sold as food in markets in Thailand and the Philippines.The taste of the pupae has been described as creamy flavor. People also eat adult weaver ants. Their taste is described as lemony or creamy and sour.

The Dayaks in Borneo mix adult ants with rice for extra texture and flavor. Weaver ants are fierce biters, so people who harvest them have to be extra careful! Use as tradictional medicines People who live near weaver ants sometimes use them as a type of medicine. The ants have a strong chemical in their bodies called formic acid. The ants use the formic acid to protect their nests. People have discovered that they can collect a few of the worker ants and crush them to make a special mixture. The mixture is then used to fight infections.

This kind of medicine is called traditional medicine. Studying traditional medicines like this may help scientists find new methods to cure diseases. The larvae and pupae are collected and processed into bird food, fish bait and in the production of traditional medicines in Thailand , Vietnam and Indonesia. Use as a living insecticide The ancient Chinese as early as in 300 AD, exploited the voracious appetite of these ants by using them to control insect pests in their citrus orchards.

They use them to control insect pests in their citrus orchards. To do this, they first put a weaver ant nest in an orchard. Then, they place bamboo strips among the trees to serve as “ant bridges.” These ant bridges encourage the ants to colonize all the trees. More fruit growers are now bringing back this traditional practice of using weaver ants for pest control. It is a cheaper way of dealing with insects that have developed resistance to chemical insecticides.

Large colonies of Oecophylla weaver ants consume significant amounts of food, and workers continuously kill a variety of arthropods (primarily insects) close to their nests. Insects are not only consumed by workers, but this protein source is necessary for brood development. Because weaver ant workers hunt and kill insects that are potentially harmful plant pests, trees harboring weaver ants benefit from having decreased levels of herbivory.

They have traditionally been used in biological control in Chinese and Southeast Asian citrus orchards from at least 400 AD. Many studies have shown the efficacy of using weaver ants as natural biocontrol agents against agricultural pests. The use of weaver ants as biocontrol agents has especially been effective for fruit agriculture, particularly in Australia and southeast Asia.

Fruit trees harboring weaver ants produce higher quality fruits, show less leaf damage by herbivores, and require fewer applications of synthetic pesticides. Farmers in southeast Asia often build rope bridges between trees and orchards to actively recruit ants to unoccupied trees. Established colonies are often supplemented with food to promote faster growth and to deter emigration.

Today in plant production, Weaver ants are usud in biocontrol to kill many kinds of insects on plant fruit trees. Their type: generalist predator and their hosts: citrus stinkbug, leaf-feeding caterpillars, aphids, citrus leafminer, leafhoppers, plant hoppers, bugs, moths, adult black bugs, and small animals. In Mekong delta of Vietnam, weaver ants are used as living pesticides to kill many insect species on fruit plant trees from hundreds of years to now a day.

Conservation and management

Weaver ants thrive well in undisturbed places and plenty of green leaves. Plant fruit trees or shrubs in or around your new citrus orchard however, banana, sapodilla, and papaya are less suitable. Introduce only native weaver ants to the orchard when no black ants’ species are present to ensure the establishment of a weaver ant colony. Provide them with food during the dry season such as dried fish and shrimp, cut into pieces that are small enough for the individual ant to carry.

Put bamboo or wooden strips between trees to guide the ants to transfer from one tree to another for them to build new colonies in other trees. To expand weaver ants’ colonies to other field crops, tie a rope to a tree where they live, to guide them to the areas you want them to colonize. Monitor regularly the ant colonies.

Like other insects, ants are easily being killed by pesticide.

References 

http://www.myrmecos.net/formicinae/oecophylla.html

http://en.wikipedia.org/wiki/Oecophylla_smaragdina

http://en.wikipedia.org/wiki/Weaver_ant From Wikipedia.

http://www.antark.net/ant-species/weaver-ant-oecophylla-smaragdina.html

http://www.springerlink.com/content/l5n03712j4825517/

http://www.globio.org/glossopedia/article.aspx?art_id=11&art_nm=Weaver+Ants

http://www.new-ag.info/03-2/develop/dev02.html http://www.naturia.per.sg/buloh/inverts/weaver_ants.htm

More on:

http://plantloveandgrow.wordpress.com/2013/06/23/weaver-ants-the-living-pesticide/

How to Farm Organically

According to the United States Department of Agriculture, organic agriculture is an ecological production management system that promotes and enhances biodiversity, biological cycles and soil biological activity. It is based on minimal use of off-farm inputs and on management practices that restore, maintain and enhance ecological harmony. The USDA also says that organic farming entails the use of cover crops, green manures, animal manures and crop rotations to fertilize the soil, maximize biological activity and maintain long-term soil health. Also, biological control, crop rotations, and other such natural techniques should be used to manage weeds, insects and diseases, and organic farming requires the reduction of external and off-farm inputs and elimination of synthetic pesticides and fertilizers and other materials, such as hormones and antibiotics. Numerous studies and reports have shown that organic produce is significantly more nutritious than conventionally farmed produce. Here are some tips to get you started on farming organically. Make a plan for your farm! Think about what crops you are going to grow, how you are going to rotate them, what fertilizers to use, and how to keep pests away. Don't use any synthetic poisons to keep away pests. These poisons are harmful to people and our planet! The three parts of Pest Management are prevention, monitoring, and controlling.

To supply your plants with good nutrition, use a soil building program in addition to foliar feeding. Fertility management can be used to deter specific pests. There are, also, good insects that can keep away harmful pests. Other simple things that can go a long way are: good field and orchard hygiene (cleaning up fallen fruit and prunings and using soil inoculants to help break down crop residues, etc.); planting pest and disease resistant varieties, in season; timing planting to outrun or otherwise avoid heavy infestations; interplanting with appropriate companion plants or trap crops; watering properly to avoid stressing plants, etc.
''Monitoring'' Regularly monitoring your plants will help ensure that you know if you have a pest infestation, and, if you do, its level. To help, use tools like pheromone traps, sweep nets, and insect vacuums.

''Controls'' The most natural pest controls are, of course, the physical ones like fences, barriers, traps, etc. After that, the options include beneficial and biological organisms, mineral-based insecticides, oils, botanical insecticides and fungicides.

Crop rotation refers to the sequence of crops and cover crops grown on a specific field. Particular sequences confer particular benefits to long and short-term soil fertility, and to pest management.

Grow different crops on the same piece of land. While conventional farming consists of mass production of a single crop in a single location, organic farming calls for multiple crops in the same space. Agricultural biodiversity has been proven by the science of agroecology to have many benefits. Planting a variety of vegetable crops supports a wider range of beneficial insects, soil microorganisms, and other factors that add up to overall farm health, but managing the balance requires expertise and close attention.

Use natural fertilizers. Natural fertilization is crucial to organic farming. This different from conventional farming, as conventional farms often use synthetic fertilizers that can be harmful to health. Natural fertilizers also make the soil healthier, which can result is better produce. The most common natural fertilizer is manure.
Composting stabilizes the nutrients in manure, builds populations of beneficial organisms, and has a highly beneficial effect on soils and crops. Compost can be produced on-farm by a number of means.

There are other forms of natural fertilizer such as bone meal, blood meal, etc. *The mixed vegetable organic market garden is often associated with fresh, locally-grown produce, farmers' markets and the like, and this type of farm is often under 10 acres. Farming at this scale is generally labor-intensive, involving more manual labor and less mechanization. The type of crop also determines size: organic grain farms often involve much larger area. Larger organic farms tend to use methods and equipment similar to conventional farms, centered around the tractor.