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BACKGROUND Ambrosia artemisiifolia, an invasive weed in Europe and Asia, is highly toxic to the golden apple snail (GAS; Pomacea canaliculata) in laboratory tests. However, little is known about the chemical components of A. artemisiifolia associated with the molluscicidal activity or about its potential application for GAS control in rice fields. This study evaluated the molluscicidal activities of powders, methanol extracts, and individual compounds from A. artemisiifolia against GAS in rice fields and under laboratory conditions. RESULTS Ambrosia artemisiifolia powders did not negatively affect the growth and development of rice but they reduced damage to rice caused by GAS. Extracts had moderate acute toxicity but potent chronic toxicity. The 24-h 50% lethal concentration (LC50 ) of the extracts against GAS was 194.0 mg L-1 , while the weights, lengths and widths of GAS were significantly affected by exposure to a sublethal concentration (100 mg/mL). Psilostachyin, psilostachyin B, and axillaxin were identified as the most active molluscicide components in the aerial parts of A. artemisiifolia, and the 24-h LC50 values of these purified compounds were 15.9, 27.0, and 97.0 mg/L, respectively. CONCLUSION The results indicate that chemical compounds produced by A. artemisiifolia may be useful for population management of GAS in rice fields. © 2017 Society of Chemical Industry.

BACKGROUND Pueraria peduncularis (Grah. ex Benth.) Benth., which belongs to the Leguminosae family, exhibits resistance to many crop pests in agricultural production. Pomacea canaliculata is an important invasive snail in rice fields and causes severe yield losses. To evaluate the toxicity of P. peduncularis to P. canaliculata, in this study the molluscicidal activity of root extracts of P. peduncularis was tested against P. canaliculata; the active compounds were isolated, and the structures of these compounds were analysed using nuclear magnetic resonance (NMR) analysis and mass spectral analysis. RESULTS Our results showed that the molluscicidal activity of the root crude extract differed between P. canaliculata with different shell diameters after treatment for 72 h. The median lethal concentration (LC50) was 5.511 mg L−1 against snails of 1.5 ± 0.2 cm diameter and 12.383 mg L−1 against snails of 2.5 ± 0.2 cm diameter. Furthermore, two active ingredients isolated from root methanol extracts were identified as pedunsaponin A and pedunsaponin C. Both pedunsaponin A and pedunsaponin C showed strong molluscicidal activities, with LC50 values of 3.893 and 4.252 mg L−1, respectively, against snails with shell diameters of 1.5 ± 0.2 cm after treatment for 72 h. CONCLUSION Pueraria peduncularis extracts exhibit high molluscicidal activity and have great potential value for exploring a molluscicide to control Pomacea canaliculata. © 2016 Society of Chemical Industry

Exotic slugs have become serious pests of canola, at establishment, in Southern Australian high-rainfall cropping zones. Slugs were monitored using relatively inexpensive 300 mm x 300 mm terracotta tiles acting as refuges. An investigation was made of the effects of the time of application of chelated iron baits on the slug species Deroceras reticulatum Müller and Lehmannia nyctelia Bourguignat. Baits reduced the number of surface-active slug species. A single application at sowing provided greater efficacy than one application before sowing, and efficacy was comparable with that of two applications. Canola seedling densities showed a negative response to D. reticulatum numbers; the presence of even one individual per refuge trap reduced seedling numbers below optimum densities. Thistles and other vegetation were associated with increased numbers of slugs. European guidelines for slug monitoring and damage appear to be at least partly applicable to Australian conditions.

Slugs are major pests of many crops in the UK, including winter wheat, yet current methods of control are often unreliable. This study investigates the potential use of red clover, as an alternative food source, to reduce the amount of damage caused to winter wheat by the field slug, Deroceras reticulatum (Müller). Two laboratory-based studies, each conducted over a 7-day period, investigated the effects of red clover seedlings and commercial metaldehyde pellets on damage to winter wheat seeds and seedlings. The results indicate that metaldehyde applications, in the form of commercially available pellets, resulted in significantly greater protection to wheat seeds compared with red clover, whereas metaldehyde and red clover were equally as effective in reducing damage to wheat seedlings. A further laboratory experiment investigated the effect of two slug population densities (48 and 16 adults m(-2)) and high and low red clover seed rates (125% and 75% of a standard rate) on damage to wheat seeds. Results showed that, at the highest slug population density, red clover sown at 125% of the standard rate gave 99% protection to wheat seeds, compared with the 75% seed rate which gave 55%. At the lower slug population density, both seed rates of red clover resulted in similar levels of protection. Implications for the potential use of red clover as an alternative food source for reducing damage to winter wheat in field conditions are discussed.

The behavioural response of the slug Deroceras panormitanum (Lessona and Pollonera) and the snail Oxyloma pfeifferi (Rossmassler) to novel molluscicides was investigated in choice and no-choice experiments. Low-light video-recording in combination with automated tracking and event recording was used to identify the repellent and irritant effects of (1) cinnamamide, (2) copper ammonium carbonate, (3) a mulch, (4) a horticultural ground-cover matting impregnated with a copper formulation and (5) urea/formaldehyde. In the no-choice experiments the products had a stronger irritant effect on the snails than on the slugs. All products tested except the mulch significantly reduced the locomotor activity of both the slugs and snails. The most effective product, cinnamamide, reduced snail locomotor activity by 94% and track length by 96%. The overall repellent effect of the treatments in the choice experiments was stronger in the slugs; where presence, locomotor activity and track length in the treated area were significantly reduced by all products. The avoidance of treated areas exceeded 95% with the mulch (for slugs) and with copper ammonium carbonate (for snails).

The ram's horn snail (Planorbella trivolvis (Say)) is an intermediate host for a digenetic trematode (Bolbophorus confusus (Krause) Dubois) that has recently been discovered to be a significant problem in commercial channel catfish (Ictalurus punctatus Raf) production ponds in the Mississippi Delta region in the USA. In these catf ish ponds, the digenetic life cycle of this parasitic trematode involves two intermediate hosts, the ram's horn snail and the channel catfish, and the final host, the American white pelican (Pelecanus erythrorhynchos Gmelin). One approach to eradicate this problem is to disrupt the life cycle of the parasitic trematodes by eliminating the snails. During our search for natural-product-based molluscicides to control the snails in the catfish ponds, vulgarone B, isolated from the steam distillate of the aerial parts of the plant Artemisia douglasiana Besser (Asteraceae), was found to be active towards the snails with a LC50 of ca 24 µM. Channel catfish toxicity studies indicated a LC50 of ca 207 µM. Vulgarone B may be an environmentally acceptable alternative for snail control in aquaculture.  2004 Society of Chemical Industry

The effects of 350, 500 and 700 mg kg(-1) of crude extracts of neem, Azadirachta indica A Juss, on edible tropical land snails Archachatina marginata and Limicolaria aurora (Jay) were determined and compared with control using pawpaw, Carica papaya L as bait. Responses were measured through normal feeding, cessation of food intake, cessation of crawling, mucus secretion, lack of response to mechanical stimuli (mortality) and decomposition. Results showed no effects on the controls or snails exposed to neem seed oil extract. Crude extracts of bark, root and leaf of neem at 500 and 700 mg kg(-1) produced mortality after exposure for 48 h for L aurora and 72 h for A marginata.

Over two years, six consecutive field experiments were done in which the chemical molluscicide metaldehyde and the nematode biocontrol agent Phasmarhabditis hermaphrodita (Schneider) were applied at the standard field rates to replicated mini-plots successively planted with lettuce, Brussels sprouts, leaf beet and cabbage, to compare the effectiveness of different treatments in reducing slug damage to the crops. Soil samples from each plot were taken prior to the start of the experiments, and then monthly, to assess the populations of slugs, snails, earthworms, nematodes, acarids and collembolans. The experiments were done on the same site and each plot received the same treatment in the six experiments. The six treatments were: (1) untreated controls, (2) metaldehyde pellets, (3 and 4) nematodes applied to the planted area 3 days prior to planting without or with previous application of cow manure slurry, (5) nematodes applied to the area surrounding the planted area 3 days prior to planting, and (6) nematodes applied to the planted area once (only in the first of the six consecutive experiments). Only the metaldehyde treatment and the nematodes applied to the planted area at the beginning of each experiment without previous application of manure significantly reduced slug damage to the plants, and only metaldehyde reduced the number of slugs contaminating the harvested plants. The numbers of slugs, snails and earthworms in soil samples were compared among the six treatments tested: with respect to the untreated controls, the numbers of Deroceras reticulatum (Müller) were significantly affected only in the metaldehyde plots, and the numbers of Arion ater L only in the plots treated with nematodes applied to the planted area 3 days prior to planting without previous application of manure; numbers of snails (Ponentina ponentina (Morelet) and Oxychilus helveticus (Blum)) were not affected by the treatment. The total numbers of all earthworm species and of Lumbricus spp were unaffected by the treatment, but Dendrobaena spp increased significantly in the plots treated with manure. The numbers of nematodes, acarids and collembolans in soil samples were compared between the untreated controls and the treatments with nematodes applied 3 days prior to planting to the planted area or to the surrounding area, without previous application of manure: the treatment had a significant effect on the number of nematodes in soil samples, but acarids and collembolans were unaffected.

Slugs are major pests of oilseed rape that are poorly controlled by conventional bait pellets. A series of laboratory experiments investigated the potential of seed-dressings to control slug damage in this crop. Four compounds: metaldehyde, methiocarb, cinnamamide and 3,5-dimethoxycinnamic acid (DMCA) were tested at a range of doses for phytotoxicity and ability to reduce damage by Deroceras reticulatum (Müller). Metaldehyde and methiocarb were not phytotoxic at any doses, whereas all doses of cinnamamide and DMCA were. All compounds reduced slug damage, but metaldehyde and methiocarb consistently performed better than cinnamamide and DMCA. Metaldehyde and methiocarb seed-dressings were compared with baited pellets containing the same active ingredients at recommended field doses. The seed-dressings protected plants from damage by D reticulatum and Arion subfuscus (Draparnaud) as well as, or better than, baited pellets. We therefore recommend that metaldehyde and methiocarb should be field-tested as seed dressings to control slugs in oilseed rape.

The effects of combinations of plant-derived molluscicides with piperonyl butoxide (PB) or ENT 8184 (MGK-264) were studied on different enzyme activities and biogenic amine levels in the nervous tissue of Limnaea acuminata. 24-h in vivo exposure of the nervous tissue of L acuminata to 40% and 80% of the 24-h LC 50 of the plant-derived molluscicides Azadirachta indica oil, Allium sativum powder and oleoresin of Zingiber officinale rhizome and their active molluscicidal components azadirachtin, allicin and [6]-gingerol, alone or in combination (1+5) with PB or ENT 8184, caused a significant reduction in the activity of acetylcholinesterase, lactic dehydrogenase, acid and alkaline phosphatases and sodium-potassium ATPase. There was a significant increase in the activity of succinic dehydrogenase. In vivo exposure for 24h to sub-lethal concentrations of azadirachtin, allicin and [6]-gingerol, singly and with PB or ENT 8184, significantly altered the dopamine and 5-hydroxytryptamine levels in the nervous tissue of L acuminata. It is concluded that these active moieties singly or with PB or ENT 8184 adversely affect all known neurotransmission mechanisms in the snail, either separately or through a complex interaction between the different neurotransmitters.

The zebra mussel, Dreissena polymorpha Pallas, is a biofouling freshwater pest for which alternative control methods to the use of chlorine are sought. Metaldehyde, a molluscicide used primarily for control of terrestrial slugs, has also been shown to have efficacy and specificity in the control of aquatic snails. To test its potential for zebra mussel control, we investigated its effects on zebra mussel viability and on contractility of siphon/mantle muscle preparations in vitro. Metaldehyde caused zebra mussel mortality within 48 h at concentrations of approximately 0.1 and 0.2 g litre−1. The same concentrations of metaldehyde activated a complex, excitatory response in previously quiescent siphon/mantle preparations but did not modify the contractile responses of the preparations to acetylcholine. The relatively low level of toxicity of metaldehyde to zebra mussels, compared to its toxicity to snails and slugs, and the difficulty of applying this relatively insoluble molluscicide in the aqueous environment suggest that metaldehyde would not be an effective zebra mussel control agent. © 2000 Society of Chemical Industry

Two field experiments were done in which plots of oilseed rape, immediately adjacent to the field margin, were left untreated or treated with the slug-parasitic rhabditid nematode Phasmarhabditis hermaphrodita. Nematodes were applied at a rate of 3 × 10 9 ha -1 . Slug populations within plots were low and nematode application had little detectable effect on slug numbers, biomass or slug damage to the crop. There was a large snail community in the field margin in both experiments, but P hermaphrodita had no detectable effect on the abundance of any of the nine snail species recorded. The susceptibility of seven common hedgerow species (Monacha cantiana, Cepaea hortensis, Cepaea nemoralis, Pomatias elegans, Oxychilus helveticus, Clausilia bidentata and Discus rotundatus) to P hermaphrodita was tested in the laboratory. Snails were kept confined for three weeks on soil without nematodes, or with P hermaphrodita applied at the recommended application rate or five times this rate. Soil treatment with the recommended rate of nematodes caused significant mortality only for the snail M cantiana and the susceptible slug Deroceras reticulatum. Soil treatment with five times the recommended rate caused significant mortality of the slug D reticulatum and the snails M cantiana and C hortensis, but not any other species. Reasons why application of P. hermaphrodita to arable crops in Britain is unlikely to pose a substantial threat to non-target molluscs are discussed.

The molluscicidal activities of ten Baylis–Hillman adducts against Biomphalaria glabrata (Say) snails, the intermediate host of schistosomiasis, have been determined. Nine of these compounds showed significant molluscicidal activity against B. glabrata, falling below the threshold of 100 µg ml−1 set for potential molluscicidal activity by the World Health Organisation. Among these compounds, 3-hydroxy-2-methylene-3-(4-nitrophenyl)propanenitrile had the highest activity, with LC50 = 6.64 µg ml−1. Copyright © 2006 Society of Chemical Industry

The steam-distilled fraction of the aerial parts of Erigeron speciosus (Lindl) DC was tested for activity against strawberry plant pathogenic fungi Botrytis cinerea Pers ex Fr, Colletotrichum acutatum Simmonds, C fragariae Brooks, C gloeosporioides (Penz) Penz & Sacc, and the intermediate host snail Planobdella trivolvis that harbors the trematode, Bolbophorus confusus, that infests and causes severe infections in pond-raised catfish in the Mississippi Delta region of the USA. Bioautography on silica TLC plates demonstrated antifungal activity in the steam distillate. Preliminary bioassays of the steam distillate indicated the presence of phytochemicals toxic to P trivolvis. The bioactive compounds methyl 2Z, 8Z-deca-2,8-diene-4,6-diynoate and its 2E, 8E isomer were isolated by bioassay-guided fractionation and chromatographic techniques and identified by 1H NMR spectroscopy.

Nine known diterpene polyesters of segetanes, jatrophenes and paralianes have been isolated from the aerial parts of Euphorbia paralias L. The molluscicidal activity of isolated compounds was evaluated on Biomphalaria alexandrina (Ehrenberg). Paraliane diterpene, (2S,3S,4R,5R,6R,8R, 12S,13S,14R,15R)-5,8,14-triacetoxy-3-benzoyloxy-15-hydroxy-9-oxo-paraliane, was the most potent compound against the snail. Anti-feedant activity was tested by a conventional leaf disc method against third-instar larvae of Spodoptera littoralis (Boisd). Jatrophene diterpene, (2R,3R,4S,5R,7S,8R,13R, 15R)-2,3,5,7,15-pentaacetoxy-8-angeloyloxy-14,15-dioxojatropha-6(17)-11E-diene, had the highest anti-feedant activity among the compounds tested. © 2002 Society of Chemical Industry

A new series of 1,2,4-triazole derivatives and their corresponding carbamates have been synthesized and screened for their molluscicidal activity against two types of terrestrial snail, Helix aspersa and Theba pisana, by two methods of application, either as contact or as bran baits. Several of the tested compounds exhibited good molluscicidal activity, and T pisana was more sensitive than H aspersa. Substitution at the o- and/or p-positions of the phenyl ring with chlorine or bromine gave higher molluscicidal activity than the unsubstituted compound, with o,p-dichloro substitution being optimum. In addition, compounds containing two triazole moieties showed higher molluscicidal activity, particularly as stomach poisons, than the contact toxic effect of the corresponding compound with one triazole ring. In general, carbamate derivatives were more active than their corresponding 1,2,4-triazole derivatives.