Abdullah, M.

Idris, A. B.

Universiti Putra Malaysia Institutional Repository

PertanikaJ. Trap. Agric. Sci. 24(2): 165 - 166 (2001) ISS : 1511-3701© Universiti Putra Malaysia PressCOMMUNICATIONParasitism of Bradybaeneus similaris Ferussas (Gastropoda: Bradybaenidae) byMegaselia Scalaris Loew (Diptera: Phoridae): ANew RecordIDRIS, A.B. & M. ABDULLAHSchool of Environmental and Natural Resource SciencesFaculty of Sciences and TechnologyUnivesiti Kebangsaan Malaysia43600, Bangi, Selangor, MalaysiaThe Bradybaena similaris Ferussas, commonlycalled round snail, is a terresterial species, con-sidered as an oppurtinist pest in the trophiesespecially at altitude of over 1,000 meters abovesea level (Nor' Aini et al. 1995). The snails has apotential to become an important agriculturalpest especially on Brassica crops such as B.chinensis L. and B. juncea Cosson (Murali 1991;Ahmad and Ho 1980). Our field observationsshowed that damaged on growing cabbage by B.similaris was comparable to damage by larvae ofthe diamonback moth, Plutella xylostella L., themajor insect pest of cabbage.B. similaris are currently controlled by baitedmetaldehyde (Siputox) at 3% and 5%. However,evidence of increasing resistence of the snails tothis mulloscicide (Salmijah et al. 1996) is sup-ported by decreasing field efficacy of the baitedSiputox at 3% and increasing usage at 5% by thefarmers of Cameron Highlands. Laboratory stud-ies by Noran et al. (1992) showed that only 1.5%of B. similaris was killed by metaldehyde and thatthey were unaffected by bioinsecticide treatment,extract of Azadirachta indica leaves, which wastoxic to the aquatic snails Indoplanorbis exustus.Currently, there is no report of any effectivebiocontrol methods against it, but screening ofour laboratory cultured population revealed thatthe snails were parasitized by a dipteran fly,Megalasia scalaris Loew (Phoridae). In West Ma-laysia, Ahmad and Ho (1980) reported that thegiant African snail, Achatina fulica Ferussas(Achatinidae) were parasitized by the Phorids(Aphiochaeta scallaris loew and Spiniphora genetalisSchmitt), Ephydrid (Discomyza maculipenniswied)and Calliphorid (Sacrophaga dux Thoms). How-ever, there was no report on parasitism of B.similaris by any Dipteran parastoids. Therefore,this is a new record of dipteran parasitising B.similaris . The objective of this study was todetermine the percent parasitism of B. similarisby the phorid fly, M. scalaris, and the life cycle ofthe parasitoid.To measure parasitism rate of the snails byM. scalaris in the field, we collected 430 snailsfrom our randomly selected cabbage field in theCameron Highlands, Pahang, Malaysia. The snailswere then reared in four empty fish aquariums(20 em x 15 em x 30 em), fed fresh cabbage leafraised in the glass house and kept at laboratorycondition for at least 10 days. Number of deadsnails having the M. scalaris were recorded. Tomake sure those fly larvae were M. scalaris andfor easier identification we continued rearingthem on snails until hatched and emerged asadult flies. Mean percent parasitism was calcu-lated as the number of dead snails with flylarvae, divided by the total number of snailscollected x 100.To study the M. scalaris life cycle and para-sitism rate we used in the laboratory a total of 50snails and 10 female flies (collected from thesame field as above). Five snails and one femalefly (per replicate) were put in each plastic con-tainer (500 ml) for 2 days, after which the flywas taken out. Adult flies were fed with 20%sucrose solution wetted on the cotton wool andput in 5 em diameter petri dish placed in thesame plastic container. Number of snails with flyeggs were recorded and used in calculating thepercent parasitism. They were then kept in thesame container until the eggs hatched. Numberof larvae produced per snail was recorded. Lar-vae were transferred to petri dish (10 em diam-eter) half-filled with nutrient agar (3% Gelosenutritive + distilled water, w/v) as food and keptIDRIS, A.B & M. ABDULLAHuntil pupation. The pupae were placed in plasticcontainer similar to the above until adult emer-gence. A high humidity environment wasmaintained by placing wetted cotton wool insidethe container and covering its top with alu-minium foil. The emerged adults were alsoplaced in a similar type of container and fed asabove until they died. The time taken for larvaeto reach pupa stage, and number of pupaeformed, adult emerged and adult longevity (daysfrom the date of emergence until they died)were recorded. The experiment was arrangedfollowing a Complete Randomize Design with10 replicates.The rate of parasitism in field populationand laboratory reared B. similaris parasitized bythe phorid fly were 35.0 ± 4.3 and 55.0 ± 6.8respectively. On average, 28.8 larvae were pro-duced per parasitized snail. Some 85.9% (±9.5)larvae survived successfully to form pupae, andof this, 76.7% (± 8.6) managed to producehealthy adults. The time taken for eggs to hatch,larval development time (to form pupae), adultemergence and longevity were 2.2, 5.5, 11.2 and24.3 days respectively.Our results indicate that the fly has a poten-tial to be used in controlling the snail pestespecially in combination with other controllingmethods such as chemicals (molluscicides) andcultural methods as the field parasitism rate isrelatively low. An augmention of field popUla-tion of M. scalaris is possible because it is rela-tively easy to culture them in the laboratory. Inaddition, its host, B. similaris, for the mass rear-ing of the fly, the snails can be easily maintainedunder prolonged captivity compared with othersnails.The use of pesticides for controlling otherpests in the field may affect the role of M.scalaris as a biocontrol agent of B. similaris. Assuch, the cabbage growers should adopt judi-cious use of chemical pesticides. Study on thehost-parasite relationship between the snails andfly in the field should be conducted as the resultcould be used as an indicator as to the flypopulation that is affected by the heavy use ofpesticides. Study should also be initiated to de-termine the main hosts of M. scalaris and itsbiological aspects such as longevity and fecun-dity. Information on M. scalaris ecology andbiology is important because it could help us inaugmenting and conserving its natural popUla-tion that indirectly reduces pesticide depend-ence in controlling B. similaris.ACKNOWLEDGEMENTThe authors wish to thank Mrs Habibah Sebotfor technical assistance. This study is part of anin tegrated study on molluscan pests of agricul-tural importance, under IRPA No. 1-07-03-008and 09-02-0038 Programs.REFERENCESAHMAD, Y, and T.H.Ho. 1980. List of economicpests, host plants, parasites and predators inwest Malaysia. Min. Agric. BulL No. 153: 538pp.MURAU, P. 1991. Ekologi siput Bradybaena similarisdi kawasan pertanian Cameron Highlands.Bachelor Thesis, Universiti KebangsaanMalaysia. 99 pp.NORAN, A. M., M. Z. H. HANIZA, S. SALMIJAH, M.ABDULlAH, H. L. P. AzIMAHTOL and D. NOR'AINI. 1992. The effectiveness of metaldehydeversus cabaryl in controlling Bradybaenasimilaris. In Proceedings of the SeventeenthMalaysian Biochemical Society Conference, pp197-204. 23-24 Sept. 1992.NORAN, A. M., R. A. AHMAD and M. ZAID ISMAIL.1995. Molluscicidal efficacy of Azadirachtaindica extract. Mal. App. BioI. 24 (1): 29-34NOR'AINI, D., M. ABDULlAH, P. MURALI and M.SULAIMAN. 1995. Distribution and abundanceof round snails in the agriculture gardens ofCameron Highlands, Pahang. Mal. App. Bioi.24(2): 89-94.NOR'AINI, D., M. ABDULlAH and M. SULAIMAN.1995. Notes on some land mollusc atMalaysian Agricultural Park, Shah Alam,Selangor. Malaysian Applied Biology 24(2):101-104.SALMIJAH S., S. P. SAY, and M. ABDULLAH. 1996.Tolerance development in B. similaris to-wards metaldehayde. Seminar on Pesticidesin Agroenvironmental, Fate and Impact, 16pp. 12 August, 1996. University Malaya.Received: 27 February 2001Accepted: 13 June 2001166 PERTANIKAJ. TRap. AGRIe. SCI. VOL. 24 NO.2, 2001

Parasitism of bradybaeneus similaris ferussas (Gastropoda: Bradybaenidae) by megaselia scalaris loew (Diptera: Phoridae): A new record

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Parasitism of bradybaeneus similaris ferussas (Gastropoda: Bradybaenidae) by megaselia scalaris loew (Diptera: Phoridae): A new record

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