Snail Damage Research Articles

Distinguishing between Epipactis leptochila (Narrow-lipped Helleborine), Epipactis helleborine (Broad-leaved Helleborine) and their putative hybrid, Epipactis x stephensonii at the Warburg reserve, Oxfordshire

A drought in May 2020 curtailed snail damage to a population of Epipactis leptochila (Godfrey) Godfrey (Narrow-lipped Helleborine) such that in July there were 33 flowering plants in an area well known for this species at the Warburg nature reserve in Oxfordshire (v.c.23). Despite growing in a heavily-shaded area under beech, the typical habitat of E. leptochila, some of these plants were actually E. helleborine L. (Crantz) (Broad-leaved Helleborine) based on recognized distinguishing characteristics. We took morphological measurements (19 floral characters and 10 vegetative characters) for all the flowering plants present and were able to confirm by statistical analysis our initial species identifications. We were able also to discriminate between the species reasonably accurately using leaf characters alone, such as leaf colour, leaf length to width ratios and the angle of turn of the bottom three leaves. Using the outcomes from this analysis we were able to make predictions about the identity of most of the 82 non-flowering plants present. There were 4 plants that defied clear initial allocation to one or the other species and were suspected to be the hybrid E. x stephensonii Godfrey. Statistical analysis confirmed that these plants were indeed distinguishable from either parent, and most characters were intermediate to some degree between the two. The morphology of these putative hybrids is described pending molecular confirmation of their identity.

Sectorial land snail damage to the lichen Argopsis friesiana could be explained by metabolite profiles

Notodiscus hookeri is the only native land snail of the sub-Antarctic present in Crozet Archipelago. Two shell ecophenotypes co-exist on Possession Island and feed exclusively on lichens [1] that are symbiotic organisms widely distributed in sub-Antarctic islands. To improve our understanding of lichen-snail trophic interactions, the endemic tripartite lichen Argopsis friesiana was selected. The snail belonging to the organic ecophenotype occurs sympatrically with A. friesiana. Profiling and quantification of the major secondary metabolites in the whole lichen were carried out by LC-DAD-MS. Two main compounds were identified, the depside atranorin (8.2 mg g-1 DM) and the depsidone argopsin. Besides, a screening of primary metabolites was carried out to determine which compounds could be useful for the snail energetic demands. Glutamate, glutamine, gamma-aminobutyric acid and alpha-alanine were the main amino acids found in the lichen in low concentrations (0.4 mg·g-1 DM). Carbohydrates, including arabitol (10.2 mg g-1), mannitol (4.0.10-4 mg g-1) and sucrose (3.0.10-4 mg g-1), were also identified. In cultivation, N. hookeri snails were fed with fructified thalli of A. friesiana. Snails (n = 20) ate the podetia cortex and phyllocladia but they clearly avoided apothecia, the reproductive organs. This sectorial damage of the lichen by the snail suggested a differential distribution of the metabolites. Therefore, a profiling of secondary compounds was performed by Direct Analysis in Real Time – Mass Spectroscopy (DART-MS) [2] on each morphological part of the lichen (phyllocladia, apothecia, podetia and cephalodia). The identification and distribution of secondary metabolites, fatty acids, amino acids and carbohydrates should help us to determine whether metabolites affect snail feeding choice and which of them could be involved.

Feeding strategies of the giant African snailAchatina fulicaon papaya in Samoa

The giant African snail (Achatina fulica) is a widely introduced invasive land snail species, and is considered an important agricultural pest in several regions of the world including in the south Pacific. In Samoa, A. fulica is a major pest that feeds on various crops of economic importance, including papaya. This study investigated the feeding strategies of A. fulica and the damage caused to papaya through field and laboratory trials in Samoa. Unripe mature fruits were sampled to assess snail damage. Results showed heavy snail infestation; on average more than two snails were recovered per papaya tree. The mean number of snails per plant decreased with the height of the plant. Snails inflicted primary damage through feeding that led to abrasions on more than 80% of fruits and indirectly caused fungal contamination through their faeces (93%) and slimy marks. Snail feeding damage induced premature ripening of papaya fruits. In the host choice tests, the snails preferred to feed on papaya than tomatoes; however, they showed equal preference to papaya and cabbage in the field trails. Smaller snails were voracious and ate more papaya leaves per unit of body weight compared with larger snails. Snails were found to be good climbers, and 60% of the snails released near the papaya tree trunk were able to reach the papaya fruits on the tree. However, climbing was less prevalent on wet/rainy days.

Effects of silicon soil amendments and nitrogen fertilizer on apple snail (Ampullariidae) damage to rice seedlings

This study examines the potential for silicon soil amendments and nitrogen to reduce apple snail, Pomacea canaliculata Lamarck, damage to rice (Oryza sativa L.) seedlings. A rate of 75 kg/ha of nitrogen applied as (NH4)2SO4 to rice (cv IR64 and cv YTH183) seedbeds increased seedling biomass, allowing the seedlings to gain critical stem thickness and avoid snail herbivory. These seedlings remained relatively large after exposure to snails in pot experiments, mainly because of faster growth rates, but also due to lower damage from snails to >21 day-old IR64 seedlings. Silicon applied as Na2O3Si·9H20 alone (without nitrogen) reduced seedling growth compared to control seedlings. When nitrogen and silicon were applied together, the addition of silicon resulted in reduced seedling growth in YTH183 compared to seedlings treated with nitrogen alone. However, the same effect was not noted for IR64 seedlings, indicating clear variety-specific responses to seedbed inputs. Regardless of variety, silicon-treated seedlings that were transplanted to snail-infested pots at 21 days after seeding (DAS) had lower biomass than seedlings without silicon despite silicon-treated IR64 seedlings having less snail damage than untreated controls. From an experiment conducted in snail-infested ponds, we found no difference between snail damage to silicon (SiO2)-treated and control cv IR50 seedlings. Although we did not determine silicon levels in plant tissues, our results indicate that the effects of silicon soil amendments are largely insufficient to reduce the impact of apple snails to young rice seedlings (≤21 DAS).

Evaluation of changes in activity of glutamate dehydrogenase and glucose serum levels in rats exposed to Parathion

The golden apple snail Pomacea canaliculata (Lamarck) is a recently introduced rice pest in Asia. Its management is based on preventative and corrective methods emphasizing cultural and mechanical practices, with molluscicide as a measure of last resort. 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. Drainage immobilizes snails. More preventative measures should be undertaken in high-risk (⩾ 2 snails m−2) than in low-risk (< 2 snails m−2) 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). 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 0.5 kg a.i. ha−1, which most farmers cannot afford.

Induced twining in Ipomoea purpurea (L.) Roth.: response threshold and induction by volatiles and snail damage

El trepado en algunas Convolvulaceae puede ser inducido por el dano foliar y por la aplicacion de acido jasmonico. Esta respuesta inducida se cree que reduce la probabilidad de dano futuro a las hojas y esta limitada por la sequia. Se ha detectado esta respuesta en la familia Convolvulaceae usando dano artificial. Los mecanismos y las implicancias ecologicas de esta respuesta aun se desconocen. En este trabajo, se evaluo si la induccion de trepado requiere un nivel umbral de dano y si se puede inducir por volatiles y/o por dano por caracoles. Se realizaron tres experimentos independientes donde se registro la induccion de trepado en Ipomoea purpurea (Convolvulaceae) aplicando diferentes niveles de dano (0, 1, 5, 10 perforaciones a las hojas), volatiles (hojas molidas) y dano natural por caracoles. Las plantas expuestas a los dos mas altos niveles de dano artificial se enroscaron mas rapido que las expuestas a los dos niveles menores de dano. Las plantas expuestas a hojas molidas (volatiles) se enroscaron mas rapido que las plantas control. Finalmente, el trepado se indujo con el dano por caracoles, siendo mas rapido que en las plantas no danadas. La mayoria de los rasgos de crecimiento no se alteraron en ningun tratamiento. El trepado en I. purpurea puede ser inducido por dano artificial o natural, como tambien por volatiles emitididos por hojas danadas de plantas vecinas, convirtiendo la induccion de trepado en una respuesta inducida ecologicamente relevante.

Seedling broadcasting as a potential method to reduce apple snail damage to rice

Exotic apple snails (Pomacea spp.) are a major threat to the productivity and profitability of rice farming globally. Cultural methods that are applicable to traditional rice transplanting are often successful in reducing snail damage to rice. However, high labor and irrigation costs associated with transplanting highlight the need to develop modern rice crop establishment methods to replace traditional, labor-intensive methods. This study examined four broad categories of rice crop establishment for their vulnerability to apple snail damage. Seedlings from dapog nurseries and wet-direct seeding were highly vulnerable to damage and produced no grain in snail-infested ponds in the Philippines. Rice transplanted from dry bed nurseries at 21 days after sowing (DAS) had high mortality (85%) and consequently low yields. In contrast, seedling broadcasting (21 DAS) significantly reduced rice vulnerability (22% seedling mortality) to snail damage compared to all other methods and resulted in the highest grain yields per plot in our experiments. We attribute lower vulnerability to snail damage and successful stand development to reduced transplanting shock at the time of seedling broadcasting and to the generally good condition of seedlings even after 21 days in polyvinyl chloride trays. We suggest that seedling broadcasting be considered as a crop establishment method with potential to sustainably manage apple snails in irrigated rice.

Reducing seed-densities in rice seedbeds improves the cultural control of apple snail damage

Several cultural methods are known to reduce the densities of exotic apple snails (Pomacea spp.) and the damage they cause to rice in Asia. However, one aspect of seedling production – seedbed seed-density – has been largely overlooked and could compromise popular cultural control methods such as delayed transplanting. We conducted experiments to examine the effects of seedbed seed-density on hill survival in snail-infested paddy fields in the Philippines and to examine the interactions between seedbed seed-density and other cultural methods (delayed transplanting, 3 seedlings per hill and hand-picking). Seedbed seed-density determined seedling weight and stem thickness at the time of transplanting. Hill survival was highest where cultural methods (delayed transplanting and 3 seedlings per hill) were combined with low seed-density seedbeds (60–120 g m−2). Furthermore, reduced seedbed seed-density was directly related to increased hill biomass in field plots 32 days after transplanting. Hand-picking of snails together with delayed transplanting and 3 seedlings per hill eliminated hill mortality due to snail herbivory. Farmers adopting cultural snail control methods, but without adhering to low seedbed seed-densities risk increased losses due to snails because of poor quality seedlings. We suggest that seedbed seed-densities should not exceed 120 g m−2 with better results at even lower densities.

The biological control of Pomacea canaliculata population by rice-duck mutualism in paddy fields

Duck has been used as a non-chemical control method against Pomacea canaliculata Lamarck, but little is known about its principles that underlie the control of snail populations. An indoor experiment was initially used to observe the predation potential of ducks, followed by replicated field trials. In the indoor studies, ducks effectively preyed on juvenile snails, but had a weak predatory effect on large snails and egg clusters. In the field, application of a rice-duck mutualism system significantly reduced the numbers of snails (especially number of immature individuals), number of snail egg clusters and snail damage to rice plants. The controlling effect was longer and more stable than the chemical application, resulting in a better yield than with the pentachlorophenol sodium and tea seed powder treatment. Our experimental results also suggested that the snail age structure in the rice-duck mutualism plots was shifted towards older snails by ducks preying, indicating a trend towards population decline, and ducks caused snails to oviposit on sites not ideal for hatchling establishment. Throughout the studies, it is suggested that a rice-duck mutualism system could be used for controlling P. canaliculata in organic rice production.

벼 생육시기별 왕우렁이의 벼 섭식량 및 피해해석

왕우렁이는 일본으로부터 식용목적으로 1983년에 국내로 도입되었으나, 현재는 우리나라 벼 담수직파재배지에서 피해가 나타나고 있는 실정이다. 따라서 본 연구는 왕우렁이에 대한 온도 및 벼 생육시기별 섭식량과 피해정도를 구명하여 효율적인 관리대책 수립을 위한 자료로 활용하고자 수행하였다. 온도별(<TEX>$l5{\sim}35^{\circ}C$</TEX>) 왕우렁이 벼 섭식량은 <TEX>$30^{\circ}C$</TEX>에서 가장 많았으며, <TEX>$30^{\circ}C$</TEX>에서 왕우렁이 크기별 벼 섭식량은 왕우렁이 유체(각고 15 mm)와 성체(각고 30 mm 이상)는 출아 직후, 1엽, 3엽, 및 5엽의 벼를 1 일 동안각각 19.0/79.8, 11.0/54.5, 5.5/18.5 및 0.0/2.0개를 섭식하였다. 왕우렁이는 먹이 습성상 벼가 어린 유묘기(5엽 이하)에 피해를 많이 주는 것으로 조사되었다. 벼 생육시기별 왕우렁이 성체(각고 25mm 이상) 접종밀도를 달리하여 피해정도를 조사한 결과 벼 출아 직후에서 10 <TEX>$m^2$</TEX>당 왕우렁이 개체수가 10마리 일 때 수량감소가 16%로 피해가 가장 심하였다. The golden apple snail was introduced to the Korea from Japan as a potential food for people in 1983. It is one of the pests of direct-seeded rice in korea. This study was conducted to investigate rice(Oriza sativa) consumption and the extent of damage by the golden apple snail(Pomacea canaliculata) in direct-sown paddy fields. Food consumption of the golden apple snail was highest at <TEX>$30^{\circ}C$</TEX>. When the emergence of the 1st, 3rd, and 5th leave of rice supplied food, the consumption of young(shell height 15mm) and adult golden apple snail(over shell height 30mm) at <TEX>$30^{\circ}C$</TEX> were 19.0/79.8, 11.0/54.5, 5.5/18.5, and 0.0/2.0 individuals, respectively. Young rice seedings(before 5th leaves of rice) are very susceptible to golden apple snail damage because the young, tender leaves and stems favor the snail's feeding habits. The field experiment with four treatments (0, 2, 5 and 10 individuals respectively per 10 <TEX>$m^2$</TEX>) was carried out. The most serious yield loss was 16% from the plot with 10 adults released at emergency stage of rice.

Strategies for Controlling the Apple Snail Pomacea canaliculata (Lamarck) (Gastropoda: Ampullariidae) in Japanese Direct-Sown Paddy Fields

The apple snail Pomacea canaliculata becomes a much more serious pest in direct-sown rice fields than in transplanted fields. In south Japan, it represents an important constraint on the implementation of direct seeding. Described here are possible measures to control the snails and suggestions for its management in Japanese direct-sown rice fields. Crop rotation with upland crops is a practical way with the lowest extra cost. The apple snails were often not eradicated by growing an upland crop in the previous summer. However, snail densities always decreased below the control threshold in direct-sown fields (0.5 snails/m 2 ). Longer drainage period after sowing greatly reduced snail damage. Thus, draining fields for 10 to 20 days after sowing is a basic practice to control snails in direct seeding. Tillage and puddling have a function to crush snails and, thus, reduce snail densities. Intensive tillage, in which a field with compacted hard soil is tilled shallow with faster cultivator rotation, achieved higher snail mortality. It is recommended to lower the risk of snail damage after unexpected heavy rain. An application of bait type metaldehyde showed enough control effects to avoid rice damage by snails even in heavy rain conditions. The stable effects seemed to be due to the active ingredient in the bait type which is dissolved slowly. Improving techniques for weeding and for draining fields effectively are necessary for better snail management in direct seeding.

Differential land snail damage to selected species of the lichen genus Peltigera

The intensity of grazing of two land snails, Cantareus aspersa and Limax sp., on three epigaeic species of Peltigera with ( P. horizontalis, P. neckeri) and without ( P. praetextata) secondary compounds, were studied in the field in three transects of 2×50 m along an altitudinal gradient in the surroundings of Pistoia (Tuscany, Italy). The results were confirmed by laboratory experiments and were carried also out on a further species lacking lichen compounds ( P. degenii), showing that land snails definitely prefer thalli lacking lichen secondary compounds. Damage intensity is correlated to the thallus size of the lichens.

Damage potential of the golden apple snail Pomacea canaliculata (Lamarck) in irrigated rice and its control by cultural approaches

The damage caused by the golden apple snail in rice seedlings of various ages was assessed for different pest densities and water depth regimes. The experiments involved randomized complete-block and split-split plot designs with three replications. Water depth accounted for a higher proportion of the damage than seedlings' age and pest densities. At a water depth of >5.0 cm, direct-seeded rice and transplanted 21-, 30- and 40-day-old seedlings incurred damage of 100, 89.2, 59.7 and 46%, respectively. The susceptibility to snail damage decreased as seedling age increased. At a water depth of 5.0 cm, the pest caused insignificant damage to the 30- and 40-day-old seedlings. The same result occurred in direct-seeded rice and 21-day-old seedlings when the water was drained to a saturated soil moisture condition. Limited moisture conditions immobilized and prevented the pest from causing severe damage. This treatment reduced damage significantly, even when the pest density was five snails m−2. Dry direct seeding, which used a minimal amount of water in the early stages of growth, received 0% damage. Direct seeding with field draining to a saturated soil moisture condition, dry direct seeding, and transplanted 30- and 40-day-old seedlings with a water depth of 5.0 cm were tolerant to snail attack. The agronomic performance of these planting methods was not significantly different from conventional practices. The damage potential of the golden apple snail in rice depends on water depth >seedling age >pest density, in decreasing order.

Effect of seedling age and seedling number per hill on snail damage in irrigated rice

Rice ( Oryza sativa L.) seedlings are often destroyed by golden apple snail ( Pomacea canaliculata Lamarck) after transplanting. Two field experiments were conducted to determine the effects of seedling age and seedling number per hill on snail damage, plant growth, and grain yield. The first experiment was unsprayed (snail-infested experiment) while the second experiment was sprayed with molluscicide to control snails (snail-free experiment). Increasing seedling age from 2 to 5 weeks resulted in significant reductions in snail damage in terms of missing hills. Increasing seedling number per hill from 1 to 8, 6, 4, and 2 for 2, 3, 4, and 5 week-old seedlings, respectively, also reduced snail damage significantly. In the snail-free experiment, grain yield was not affected significantly when seedling age was increased from 2 to 5 weeks. Increasing seedling number per hill decreased or increased grain yield depending on the season and seedling age. In general, transplanting 4–5 week-old seedlings at one seedling per hill or increasing the number seedlings per hill reduced snail damage in terms of missing hills and minimized yield losses from the snail damage.

Golden apple snail damage in Philippine Seed Board rice varieties

Golden apple snail damage in Philippine Seed Board rice varieties

Preference and Feeding Behavior of Apple Snail, (Pomacea canaliculata), for Fruits and Vegetables.

To pursue the possibility of controlling apple snail damage on rice seedlings, the preferences and feeding behavior of the apple snail, under the use of fruits and vegetables as attractants in rice fields, were investigated. The apple snails showed higher preferences for specific fruits and vegetables, such as melons, watermelons, lettuce, eggplants, and tomatoes than for rice seedlings. Many more apple snails were observed adhering to and feeding on those fruits and vegetables than on rice seedlings when the seedlings, fruits and vegetables were simultaneously placed in one container. Most apple snails found their preferred food directly, or they moved to it after leaving unpreferred food within six hours. Moreover, the apple snails stayed on melons and eggplants for clearly a longer time period than on rice seedlings. Therefore it is suggested that vegetables in rice fields would attract the apple snails and may contribute to reduce apple snail damage on rice seedlings.

落水管理とメタアルデヒド剤によるスクミリンゴガイの直播水稲の食害防止

The effect of a combination of drainage and methaldehyde on feeding damage to directseeded rice by the golden apple snail, Pomacea canaliculata (Lamarck), was tested under conditions of high snail density and heavy rainfall. A 10-day drainage immediately following the wet seeding and subsequent 11-day low-level water management was successful in suppressing the snail damage below an acceptable injury level when methaldehyde granules (10%) were applied at a rate of 4 kg/10 a, 4 days and 10 days after sowing. The analysis of the results of methaldehyde application revealed that the success was due mainly to its effect as feeding arrestant.

Effect of Snail (Helix aspersa) Damage on Botrytis Gray Mold Caused byBotrytis cinereain Kiwifruit

In three (1994) and two (1995) kiwifruit vineyards in the coastal area of California (San Luis Obispo County), the incidence of fruit with all sepals removed by the common brown garden snail (Helix aspersa) ranged from 11 to 35% in 1994 and 2 to 15% in 1995. Partially damaged fruit with fewer than three sepals per fruit ranged from 7 to 20% in 1994 and 3 to 5% in 1995. Swollen tissues associated with healing developed around the receptacle (stem end) from which sepals had been removed by snails. In a 3-year study, kiwifruit with and without characteristic damage (full removal of sepals) by snails were harvested from two vineyards and stored in controlled-atmosphere (CA) cold (-0.5°C) storage. After 3- to 5-month storage, fruit with snail damage consistently had more Botrytis gray mold than fruit not damaged by snails (P < 0.01). In separate studies, kiwifruit caged with snails developed more gray mold than fruit caged without snails after 3 to 5 months in CA storage in 1994 but not in 1993. In two vineyards, removal of sepals by hand did not consistently increase gray mold in CA storage. More viable propagules of Botrytis cinerea and other mycoflora were recovered from fruit that had snail slime than fruit without slime (P < 0.05). Although snail slime did not affect the germination of B. cinerea conidia on a nutrient-rich medium (acidified potato-dextrose agar), snail slime increased germination of B. cinerea conidia on a nutrient-poor medium (acidified water agarose) to more than 50% compared with 1 to 2% germination without slime after incubation at 21°C for 22 h. These results suggest that wounds caused by snails eating the sepals around the receptacle area of kiwifruit and (or) stimulation of conidial germination by snail slime may lead to more infections by B. cinerea.

Management of the golden apple snail Pomacea canaliculata (Lamarck) in rice

The golden apple snail Pomacea canaliculata (Lamarck) is a recently introduced rice pest in Asia. Its management is based on preventative and corrective methods emphasizing cultural and mechanical practices, with molluscicide as a measure of last resort. 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. Drainage immobilizes snails. More preventative measures should be undertaken in high-risk (⩾ 2 snails m −2) than in low-risk (< 2 snails m −2) 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). 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 0.5 kg a.i. ha −1, which most farmers cannot afford.

Survey of snails on citrus in the Riverland of South Australia

A survey of snails and snail damage to 95 blocks of citrus in the Riverland of South Australia was made during 1974 and 1975. The owners of each block were interviewed to determine the cultural practices used and to find out if control measures were applied. An examination of the orchard was made to determine the amount of snail damage to the crop and the species of snails present. The European brown snail Helix aspersa (Muller) was the only species causing significant damage. Snail damage was most severe on orchards irrigated by overhead sprinklers, less severe where undertree sprinklers were used, and rarely a problem on furrow irrigated orchards (P &lt; 0.01). Cultivation did not significantly affect the snail problem. In 1974 an estimated 43 per cent of orchards either had more than 10 per cent crop damage or were sprayed to control snails. In 1975 there were an estimated 9 per cent of orchards affected to that extent.