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JOURNAL OF SCIENCE OF HNUE Chemical and Biological Sci., 2014, Vol. 59, No. 9, pp. 81-87 This paper is available online at http://stdb.hnue.edu.vn FLUCTUATION IN SPECIES COMPOSITION OF PREDATORS (NATURAL ENEMIES) OF DIEN GRAPEFRUIT TREE INSECT PESTS IN BAC TU LIEM, HANOI Bui Minh Hong Faculty of Biology, Hanoi National University of Education Abstract. The article presents the first study of the most complete composition of natural enemies of Dien grapefruit tree. Fluctuation in specie component of predators (natural enemies) of Dien grapefruit tree insect pests differed over the months of this investigation with Coleoptera species being most prevalent with 7 species, accounting for 38.89% of the total species and Hymenoptera species numbering 5, accounting for 27.78%. The numbers of species of natural enemies of Dien grapefruit tree insect pests differed over the months of this survey: Species composition of natural enemies of Dien grapefruit tree insect pests was highest at 18 species in September when 100% of the natural enemies of Dien grapefruit tree insect pest species of our list were found. In June 2013, and in January 2014, 17 species were found, in July 16 species were found, in June 15 species were found, in December 14 species were found, in October 13 species were found and in November only 11 species were found. Keywords: Predators of Dien grapefruit tree insect pests, Bac Tu Liem, Hanoi. 1. Introduction Natural enemies have an important role to play in the control of pest populations. The use of natural enemies in insect control reduces the need for other plant protection products thereby lowering the cost to farmers. Moreover, the use of natural insect enemies helps protect the environment and reduce both producer’s and consumer’s expose to harmful chemicals. To develop sustainable agriculture, the use of natural enemies to control insect pests is essential [5, 6]. A great number of insect species are natural enemies of Dien grapefruit tree insect pests but the use of pesticides has eliminated or reduced the populations of many species Received November 4, 2014. Accepted December 2, 2014. Contact Bui Minh Hong, e-mail address: bui_minhhong@yahoo.com 81 Bui Minh Hong of these natural enemies. A close look at the species composition of the natural enemies of Dien grapefruit tree insect pests in Bac Tu Liem, Hanoi, was needed which could lead to the establishment of a practical and scientific proposal to make use of insect which will prey on Dien grapefruit tree insect pests. This paper presents the first study of the most complete composition of natural enemies of Dien grapefruit tree and the change in composition of insect species which prey on the insect pests of Dien grapefruit trees in Bac Tu Liem, Hanoi. This is followed by a proposal on how to best make use of insect species which are the natural enemies Dien grapefruit tree insect pests. 2. Content 2.1. Study sites and methods 2.1.1. Study sites - This study of the natural enemies of Dien grapefruit tree insect pests was conducted in in the Phu Dien Communes of Bac Tu Liem in Hanoi. - Sample analysis was conducted in the laboratory of the Zoology Department, Faculty of Biology, Hanoi National University of Education. 2.1.2. Methods * Methods used to determine the species composition of natural enemies of Dien grapefruit tree insect pests We determined the species composition of the natural enemies using the method of the Institute of Plant Protection (2000) [4] as follows: Insect species of natural enemies of Dien grapefruit tree pests were collected once every seven days. In each study area, a field was selected which is representative for the area for investigation. In each plot, five points investigated diagonal, each of 5 trees. When carrying out the survey, we first made a visual observation of the natural enemies in Dien grapefruit tree insect pests and their activities. Samples were later collected using tennis rackets and by hand. Specimens that we managed to catch in this way were photographed, measured, examined in terms of morphology description, taking photos and identified according to scientific name. * Method for the type of sample To identify specimens collected, we used the classification system of Ann E. Hajek (2004) and Charles A. Triplehorn and Norman Johnson (2005) [1, 2]. In addition, we used the description, photos and drawings of the authors, Nguyen Van Dinh, Ha Quang Hung, Nguyen Thi Thu Cuc and Pham Van Lam (2012) [3]. Samples were classified following the system of Charles A. Triplehorn and Norman Johnson (2005) [2]. 82 Fluctuation in species composition of predators (natural enemies) of Dien grapefruit tree... 2.2. Research results and discussion 2.2.1. Species composition of natural enemies of Dien grapefruit tree insect pests in Bac Tu Liem, Hanoi The results of this investigation into the species composition of natural enemies of Dien grapefruit tree insect pests at selected study sites are presented in Table 1. Table 1. Species composition of natural enemies of Dien grapefruit tree insect pests in Bac Tu Liem, Hanoi No. Scientific name Order Family 1 Micraspis discolor (Fabricius, 1798) Coleoptera Coccinellidae 2 Menochilus sexmaculatus (Fabricius, 1781) Coleoptera Coccinellidae 3 Lemnia biplagiata (Swartz, 1808) Coleoptera Coccinellidae 4 Coccinella transversalis (Fabricius, 1781) Coleoptera Coccinellidae 5 Harmonia octomaculata (Fabricius, 1781) Coleoptera Coccinellidae 6 Chilocorus nigritus (Fabricius, 1798) Coleoptera Coccinellidae 7 Coccinella 7- punctata (Linnaeus, 1758) Coleoptera Coccinellidae 8 Sycanus falleni (Stal, 1863) Hemiptera Reduviidae 9 Camponotus vagus (Scopoli, 1763) Hymenoptera Formicidae 10 Dolichoderus thoracicus (Smith,1860) Hymenoptera Formicidae 11 Oecophylla smaragdina (Fabricius, 1775) Hymenoptera Formicidae 12 Vespa affinis (Linnaeus, 1764) Hymenoptera Vespidae 13 Batozonellus sp. Hymenoptera Pompilidae 14 Syrphus ribesii (Linnaeus, 1758) Diptera Syrphidae 15 Episyrphus balteatus (De Geer, 1776) Diptera Syrphidae 16 Ischnura senegalensis (Rambur, 1842) Odonata Coenagrionidae 17 Anaciaeschna sp. Odonata Aeshnidae 18 Mantis religiosa (Linnaeus, 1758) Mantodea Mantidae Insect species which are natural enemies of Dien grapefruit tree insect pests were identified as being of 18 species, 9 families and 6 orders (Coleoptera, Hemiptera, Hymenoptera, Ondonata, Diptera and Mantodea). To determine the number of species and the proportion of each to the entire population of the natural enemies of Dien grapefruit tree insect pests at the study sites, we analyzed the samples that we collected. The results are shown in Table 2. Hymenoptera have 3 families, accounted for 33.33 % of total families. Three families of Hymenoptera were: Formicidae, Vespidae, Pompilidae with 5 species collected, accounted for 27.78% of total species, in which Formicidae has the most species number with 3 species. 83 Bui Minh Hong Table 2. The number of taxa and proportion of each taxa of natural enemies of Dien grapefruit tree insect pests in Bac Tu Liem, Hanoi Family Species No. Order Number Percentage of Number Percentage of of family family (%) of species species (%) 1 Coleoptera 1 11.11 7 38.89 2 Diptera 1 11.11 2 11.11 3 Hymenoptera 3 33.33 5 27.78 4 Hemiptera 1 11.11 1 5.56 5 Ondonata 2 22.22 2 11.11 6 Mantodea 1 11.11 1 5.56 Total 9 100 18 100 Of the Coleoptera order, insects of one family, Coccinellidae, and 7 species were found. These 7 species accounted for 38.89 % of the species of all orders. More individual insects of the Coleoptera order were found than any other. Of the Coccinellidae family, 7 species were found of the Formicidae family, 3 species were found, and of the Syrphidae family, 2 species were found. Of the families Aeshnidae, Pompilidae, Coenagrionidae, Mantidae, Reduviidae and Vespidae, a fewer number of species were found. Of the Hymeniptera order, three families were found: Pompilidae, Formicidae, Vespidae, with 33.33% of all families being of the Vespidae family. Of the order Ondonata, 2 families were collected, this being 22.22 % of all families. Of the orders Coleoptera, Diptera, Hemiptera and Mantodea, 1 family of each was found, which totals 11.11% of all families. Individual insect numbers of the orders Hemiptera and Mantodea were the lowest. There was a high abundance (high encounter frequency) of the families Coccinellidae, Syrphidae and Formicidae. The Coccinellidae were most prevalent with Menochilus sexmaculatus, which accounted for 38.89 % of all insects collected. With percentage abundance was 27.78% (with natural enemies on Dien grapefruit leaves as Vespa affinis, Batozonelluss sp.). 2.2.2. Fluctuation of species composition of natural enemies of Dien grapefruit tree insect pests by month during the investigation in Bac Tu Liem, Hanoi The composition and abundance of natural enemy species of Dien grapefruit tree insect pests differed over the months of the investigation, these numbers reflecting the growth stage of the Dien grapefruit crop (Table 3). From June 2013 to January 2014, we collected 18 species of natural enemies of Dien grapefruit tree insect pests, all of which varied in abundance but which were most 84 Fluctuation in species composition of predators (natural enemies) of Dien grapefruit tree... prevalent in July, August and September 2013, and in January 2014. The species of Coccinidae were observed in all of the months of the investigation and were most prevalent from July to late September and in January at which time Micraspis discolor, Menochilus sexmaculatus and Coccinella 7- punctata had the highest densities and encounter frequencies. The encounter frequencies dropped from mid-November to December. Oecophylla smaragdina appeared from June to October in 2013 and in January 2014 with high frequency, and in September and December with low frequency. The species Camponotus vagus, Dolichoderus thoracicus appeared from November to December with ‘average’ frequency, in June to October with high frequency. Vespa affinis and Batozonellus sp. appeared from September to August with high frequency and December to not see this species of out. During the Dien grapefruit growing season in Bac Tu Liem, Hanoi, from 2013 to January in 2014, we collected 18 species of natural enemies of insect pests. The species varied in number and distribution month to month (Table 3). June: 15 species were collected. Four species appeared at a frequency much greater than 75%, 8 species appeared at a frequency of 25% - 75% less and 3 species appeared at a frequency of less than 25%. July: 16 species were collected 7 of which appeared at a frequency much greater than 75%, 7 species appeared at a frequency of 25% - 75% and 2 species appeared at a frequency of less than 25%. August: 17 species were collected, 10 of which appeared at a frequency much greater than 75%, 6 species appeared at a frequency of 25% - 75% and 1 species appeared at a frequency of less than 25%. September: 18 species were collected, 9 of which appeared at a frequency much greater than 75%, 6 species appeared at a frequency of 25% - 75% and 3 species appeared at a frequency of less than 25%. October: 13 species were collected. Two species appeared at a frequency much greater than 75%, 7 species appeared at a frequency of 25% - 75% and 4 species appeared at a frequency of less than 25%. November: 11 species were collected, none of the species appearing at a frequency greater than 75%, 5 species appeared at a frequency of 25% - 75%, and 6 species appeared at a frequency of less than 25%. December: 14 species were collected, none of which appeared at a frequency greater than 75%, 5 species appeared at a frequency of 25% - 75% and 9 species appeared at a frequency of less than 25%. 85 Bui Minh Hong Table 3. Fluctuation in species composition of natural enemies of Dien grapefruit tree insect pests in Bac Tu Liem, Hanoi The level of encounter frequency through the months 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Ischnura senegalensis Episyrphus balteatus Syrphus ribesii Batozonellus sp. Vespa affinis Oecophylla smaragdina Dolichoderus thoracicus Camponotus vagus Sycanus falleni Coccinella 7-punctata Chilocorus nigritus Harmonia octomaculata Coccinella transversalis Lemnia biplagiata Menochilus sexmaculatus Micraspis discolor Odonata Odonata Diptera Diptera Hymenoptera Hymenoptera Hymenoptera Hymenoptera Hymenoptera Hemiptera Coleoptera Coleoptera Coleoptera Coleoptera Coleoptera Coleoptera Coleoptera Mantidae Aeshnidae Coenagrionidae Syrphidae Syrphidae Pompilidae Vespidae Formicidae Formicidae Formicidae Reduviidae Coccinellidae Coccinellidae Coccinellidae Coccinellidae Coccinellidae Coccinellidae Coccinellidae ++ ++ + ++ ++ - + + - ++ 6 +++ ++ +++ +++ ++ ++ +++ +++ ++ ++ +++ +++ - +++ +++ +++ ++ ++ + ++ +++ - ++ + - ++ 7 +++ +++ +++ ++ + +++ +++ +++ +++ +++ ++ ++ +++ ++ ++ - ++ +++ 8 +++ ++ +++ + ++ +++ +++ +++ +++ +++ + +++ ++ ++ ++ ++ + +++ 9 ++ ++ ++ + + ++ ++ +++ +++ ++ - + - - + - - ++ 10 + ++ ++ - - + + ++ ++ ++ - + - - + - - + 11 + ++ + - - ++ + ++ ++ ++ - + + + + + - + 12 ++ ++ ++ ++ + ++ ++ +++ +++ ++ - +++ ++ ++ ++ ++ ++ +++ 1/2014 Family 16 Anaciaeschna sp. Mantodea Order 17 Mantis religiosa No. Scientific name 18 Total 15 16 17 18 13 11 14 17 Notes: +: Low encounter frequency (less than 25% total of encounters), ++: moderately common (25 - 75% total of encounters), +++: very common (≥ 75% total of encounters) 86 Fluctuation in species composition of predators (natural enemies) of Dien grapefruit tree... 3. Conclusion 1-Eighteen species of natural enemies of Dien grapefruit tree insect pests were identified belonging to 9 families and 6 orders: Coleoptera, Hemiptera, Hymenoptera, Ondonata, Diptera and Mantodea. Coleoptera were most prevalent in number of species with 7 species accounting for 38.89% of total species. The number of Hemiptera and Mantodea species was the least with one species each. 2-Of the 18 families of natural enemies of Dien grapefruit tree insect pests, 3 families were of the order Hymenoptera, accounting for 33.33% of total families. Two families were of the Ondonata accounting for 22.22%. Of the orders Coleoptera, Hemiptera, Mantodea and Diptera, 1 family of each was found, accounting for 11.11% each. 3-The species composition of natural enemies of Dien grapefruit insect pests varied over the months. I In August and January 17 species were found and in June 16 species were found. December of 14 species and October of 13 species and November of 11 species. REFERENCES [1] Ann E. Hajek, 2004. Natural enemies an introduction to biological control. Printed in the United Kingdom by Lightning source UK Ltd. 133362 UK 00002b/1-12A, p. 372. [2] Charles A. Triplehorn and Norman F. Johnson, 2005. Borror and DeLong’s Introduction to the Study of Insects, 7th edition (Thomas books/Cole, 2005) - A Classic textbook in North America. [3] Nguyen Van Dinh, Ha Quang Hung, Nguyen Thi Thu Cuc, Pham Van Lam, 2012. Insects pest and harmful animals agriculture in Vietnam. Agriculture Publishing House in Hanoi, p. 679. [4] Institute of Plant Protection, 2000. Research methods in plant protection. Agriculture Publishing House in Hanoi. [5] Waterhouse D. F., 1998. Biological Control of Insect Pests: Southeast Asian Prospects. ACIAR Monograph No. 51, ACIAR Canberra, Australia. [6] Waterhouse D. F and D. P. A Sands, 2001. Classical biological control of arthopods in Austrlia. ACIAR Monograph No. 77, ACIAR (Australian Centrer for International Agricultural Research), Canberra, Australia. 87