Egyptian Journal of Biological Pest Control, 22(1), 2012, 1-3 Parasitism of the Sunn Pest, Eurygaster integriceps Puton (Heteroptera: Scutelleridae) with Hexamermis eurygasteri Tarla, Poinar and Tarla (Nematoda: Mermithidae)Gülcan Tarla * , Şener Tarla * , Mahmut İslamoğlu ** and Gürhan Gün *** * Uşak University, Vocationa l High School, Department of Organic Agriculture Program, 64800 Sivaslı, Uşak - Turkey,[email protected]
** Plant Protection Research Institute, P.O. Box 21, 01321, Yüreğir, Adana - Turkey *** Hanyolu Elementary School, Hanyolu village, 31040 Antakya, Hatay - Turkey( Received: November 17, 2011 and Accepted: December 9, 2011 ) ABSTRACT The present study evaluates the infection rates of the nematode species, Hexamermis eurygasteri Tarla, Poinar andTarla (Nematoda: Mermithidae) on the overwintering generation population densities of the Sunn pest (SP), Eurygaster integriceps Puton under natural conditions in 2008 and 2009. Parasitism rates were 13.8 and 16.0% for females and 7.5and 7.1% for males in 2008 and 2009, respectively. Parasitized SP contained an average of 4.7.±0.79 nematodes. In asample of 26 parasitized SP, 15.4% contained single worm, 34.6% contained three worms and 30.8% contained five or more worms. The mean body length of juvenile obtained from SP measured 9.0 ± 0.65 cm. H. eurygasteri is animportant natural mortality factor of SP in overwintering areas at Gaziantep Province, Turkey. Obtained results showedthat this parasitic nematode has the potential as biological control agent for SP management. Key words: Eurygaster , Hexamermis , Mermithidae, parasitic nematodes, Sunn pest, Turkey. INTRODUCTION The Sunn pest (SP), Eurygaster integriceps Puton (Heteroptera: Scutelleridae), is an economicinsect pest of great importance on wheat in the NorthAfrica, throughout the Middle East and West toCentral Asia and parts of Russia (Critchley, 1998and Tarla and Kornoşor, 2009). Both nymphs and adults of SP cause damage to plants through feedingon leaves, stems, and grains of cereals. Wheat couldn’t be valid for export in case of the sucking rates in grains above 2%. The economic loss canreach up to 100%, if control measures are notimplemented (Kivan and Kiliç, 2006).The SP is univoltine and as adults spend, at leastnine months of their life in the soil (at about 0-5 cmdepth) and under plant leaves litter on the mountainsaround wheat fields during hibernation andaestivation. When soil surface temperature reaches15°C, overwintering adults start to migrate to cerealfields. From mid-October until late March or April,the SP passes through a further inactive periodat overwintering areas (Brown, 1965). Duringthis period, various natural enemies andentomopathogenic diseases may play an importantrole in reducing populations of SP. The infection of E. integriceps with a mermithid was found out whileconducting a field survey in overwintering areas inthe province of Gaziantep in Turkey in 2008. As aresult of the later studies conducted on this subject,the nematode was classified as belonging to genus Hexamermis Steiner, 1924, as a new species and itwas identified as Hexamermis eurygasteri by Tarla et al. (2011). The Mermithidae is a family of nematodes that parasitizes several species of insects,spiders, leeches, crustaceans, nematodes, and other invertebrates throughout the world (Nickle, 1972).This family has the potential to reduce populationsof many agricultural insect pests. Species of thegenera Agamermis, Geomermis, Hexamermis, Limnomermis, Mermis, Ovamermis, Pentatomermis, and Romanomermis have been found parasitizing awide range of insects of economic importance(Rahaman, et al ., 2000). Very few studies dealt withthe mermithids/SP relationship in overwinteringareas of the pest. While, there are many researchstudies about the nematode parasitization in someother insect species. Earlier reports of mermithidsattacking SP were made by Memişoğlu and Özer (1994) in Turkey; however, the determinedmermithids were not identified at that time. Themermithid species were reported on some insectsspecies from Turkey (Yaman et al ., 2002; Mennanand Ertürk, 2006 and Yaman et. al ., 2009).Entomophilic nematodes have great potential to beused as biological control agents against agriculturalinsect pests (Welch, 1965; Poinar, 1971; Nickle,1972, Petersen and Willis, 1972 and Grewal et al. ,2006).This study aimed to determine the infection ratesof SP with the parasitic nematode, H. eurygasteri during 2008-2009 and to detect its potential capacityas a biological control agent for SP management. MATERIALS AND METHODS Before SP migration to cereal fields, many adultswere collected from overwintering areas at Gaziantep Province of Sofdağı in Turkey in 1 st week of January, 2008 and in 3 rd week of January, 2009.Collected samples were transferred to the laboratoryin refrigerated boxes. In the first year, the adults 2 were counted, sexed (58 females and 40 males in thefirst year and 119 females and 88 males in thesecond year), killed in ethyl alcohol (70%), and thendissected in distilled water, under a stereomicroscope, searching for the presence of mermithids. Finding of parasitic nematodes in theinsect bodies was recorded and rate of infection wascalculated individually in females and males of theSP in 2008-2009. In addition, percentages of thecases of SP adults containing single, three, five or more nematode worms were also counted.In the second year, to estimate infection rates of SP, the bugs collected from overwintering areaswere fed on wheat plants and the post-parasitic juvenile nematodes were obtained, according to themethod described by Tarla et al. (2011). DuringMarch, 2009, a total of 207 individuals of theoverwintering adults of SP were handpicked fromoverwintering areas and transferred to thelaboratory. Collected adults were placed close to theroots of wheat plants, sown in plastic rearing cupsfilled with moist soils and covered with organdycloth tops. The rearing cups were kept at roomtemperature of 20-27 °C. Every four to five days, the plants were removed from the rearing cups and newwheat plants were replaced. After emergence of the juveniles from the infected SPs, the nematodesmigrate into the moist soil. They were carefullyremoved from the soil and fixed in 3% formalin and processed to glycerin for observation andmeasurement. The mean body lengths of 23 juvenilesamples were measured by using a stereomicroscope. RESULTS AND DISCUSSION The SP adults collected from overwintering areaswere found to be parasitized by a mermithid species.After preliminary morphological inspection of themermithid juveniles, the species was identified asgenus Hexamermis Steiner, 1924. This genus wasredefined according to Rubsov (1978). Hernández-Crespo and Santiago-Alvarez, (1997) reported thatthe post-parasitic juveniles of Hexamermis differ from Agamermis Cobb, Steiner and Christie, 1923 by the tail tip appendage, which always preservedafter final molt. Generally the description of thisgenus is based on post-parasitic juveniles.Obtained data of the nematode parasitism rates inSP females and males at Gaziantep Province inTurkey are given in Table (1). The parasitism rate inmales was significantly lower than that in females in both years. Choo and Kaya (1990) stated that themajority of adults (90.4%) of the brown planthopper (BPH), Nilaparvata lugens (Stal)(Homoptera: Delphacidae) were females from thefield. They determined that collected few males(n = 28) were not parasitized by Agamermis unka Kaburaki and Imamura (Nematoda: Mermithidae),however, 48.2% of the females (n = 398) were parasitized. When BPH nymphs were exposed to the pre-parasitized individuals in the laboratory, 39% of the females and 4.5% of the brachypterous maleswere parasitized and the parasitism data obtainedunder field conditions showed similar trends and thereason(s) for these differences in parasitism wasreported as unknown (Choo et al., 1995).The nematodes were observed in the bodies of dissected E. integriceps (Fig. 1). Parasitized SPscontained an average of 4.7±0.79 (n = 26)nematodes. Most individuals contained three parasites, but some contained several. Adults of SPdied soon after emergence of the nematodes fromtheir bodies. To determine infectivity rate, a sampleof 26 parasitized SP was dissected, 15.4% was foundwith single worms, 34.6% with three worms and30.8% with five or more worms. 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