Predacious mites in papaya (Carica papaya L.) orchards: in search of a biological control agent of phytophagous mite pests

Ácaros predadores em pomares de mamoeiro (Carica papaya L.): em busca de um agente de controle biológico de ácaros fitófagos

SCIENTIFIC NOTE

Predacious mites in papaya (Carica papaya L.) orchards: in search of a biological control agent of phytophagous mite pests

Ácaros predadores em pomares de mamoeiro (Carica papaya L.): em busca de um agente de controle biológico de ácaros fitófagos

Karin F.S. Collier^I; Jose O.G. de Lima^II; Gilberto S. Albuquerque^II

^IFundação Universidade Regional de Gurupi, Campus I, Al. Madrid, 545, Jardim Sevilha, Gurupi, TO, 77410-470 e-mail: [e-mail]

^IILaboratório de Proteção de Plantas, CCTA, Universidade Estadual do Norte Fluminense, Av. Alberto Lamego, 2000, Campos dos Goytacazes, RJ, 28013-600. E-mail: [e-mail], [e-mail]

ABSTRACT

This study was conducted to search for potential mite predators to control phytophagous mites in papaya orchards. Bimonthly surveys, from January 1999 to February 2000, were carried out in two orchards, one in Silva Jardim (RJ), where pests are naturally controlled, and one at Linhares (ES), where pests are chemically controlled. All mite species collected from buds, new leaves, old leaves, and floral buttons of papaya trees and from weed leaves were quantified and identified to at least family level. Despite the relatively diverse mite fauna, we found representatives of only one family of predacious mites, i.e. Phytoseiidae. Among these, Neoseiulus idaeus Denmark & Muma was the most abundant and frequent during all seasons in the Linhares orchard, coinciding mainly with the fluctuations in abundance of tetranychid mites. Such occurrence in a production system with large use of acaricides, together with its favorable biological traits reported in the literature, lead us to recommend this species as a good candidate for biological control of papaya mite pests, especially Tetranychus urticae Koch.

Key words: Acari, Phytoseiidae, Neoseiulus idaeus, biological control

RESUMO

Com o objetivo de selecionar ácaros predadores com potencial de controle de ácaros fitófagos do mamão, foram realizadas, de janeiro de 1999 a fevereiro de 2000, amostragens bimensais de ácaros em dois pomares, um orgânico (Silva Jardim, RJ) e outro com controle químico de pragas, doenças e invasoras (Linhares, ES). Todas as espécies presentes nas brotações laterais, folhas novas, folhas velhas e botões florais dos mamoeiros e nas folhas das plantas invasoras foram quantificadas e identificadas ao menos até família. Apesar da relativamente diversa fauna de ácaros, somente representantes de uma família de predadores, Phytoseiidae, foram encontrados. Dentre estes, Neoseiulus idaeus Denmark & Muma destacou-se por sua abundância e freqüência nas diferentes épocas do ano no pomar de Linhares, coincidindo principalmente com as flutuações na abundância dos tetraniquídeos. Tal ocorrência em um sistema de produção com grande emprego de acaricidas, aliada às características biológicas favoráveis dessa espécie, recomendam-na como candidata a agente de controle biológico de ácaros pragas do mamão, em especial Tetranychus urticae Koch.

Palavras-chave: Acari, Phytoseiidae, Neoseiulus idaeus, controle biológico

The broad mite, Polyphagotarsonemus latus (Banks) (Tarsonemidae) and some mites of the family Tetranychidae, especially the two-spotted spider mite, Tetranychus urticae Koch, are the main pests of papaya (Carica papaya L.) in Brazil (Flechtmann 1981, Santa-Cecília & Reis 1986). Broad mites attack mainly the terminal buds; severe infestations inhibit new stem growth, with consequent reduction in fruit production. Two-spotted spider mites feed more commonly on older leaves, which initially turn yellow on the upper side and silver on the lower side, followed by necrotic areas and eventually leaf drop. This damage directly influences photosynthesis and increases exposure to the sun, with negative consequences for fruit production and marketability. The broad mite reaches higher population densities in the wet season, whereas the two-spotted spider mite predominates in the dry season. For this reason, pesticide applications in papaya orchards occur year-round, with the well-known risks to the environment and human health (Marin et al. 1995).

A safe alternative to chemical control of phytophagous mites in papaya growing areas of Brazil is the use of predacious mites. Since the 1960s, biological control of phytophagous mites, mainly with phytoseiid mites, has been implemented worldwide in several crops, both in the field and in greenhouses (McMurtry 1983). In Brazil, for example, a program was successfully implemented in apple orchards to control phytophagous mites using the phytoseiid Neoseiulus californicus (McGregor) (Monteiro 1994). Other studies suggested the use of several predacious mite species for the integrated management of phytophagous mites in citrus orchards (Gondim et al. 1996; Reis & Alves 1997 a,b). To date, nothing is reported on the role of predacious mites in papaya orchards in Brazil, and this has hindered the development of biological control programs in this agroecosystem.

One of the prime requirements for a predacious mite to be selected as an efficient control agent is its adaptability to the prey's habitat (Jepson et al. 1975). Thus, it is recommended that any search for such agent should be first attempted in the agroecosystems where the pest is a problem (Rice et al. 1976, Ferla & Moraes 1998). With that in mind, we conducted a survey in two three-year old papaya orchards (cultivar Golden, group Solo), one cultivated under the organic system (i.e., without pesticides, in Silva Jardim, Rio de Janeiro State) and the other under the conventional system (i.e., with pesticides, in Linhares, Espírito Santo State), with 3 ha and 5 ha, respectively. Both orchards are located in Brazil's southeastern tropical coastal plain, a region with great insolation, annual average temperature between 21°C and 23°C, and more than 1200 mm of precipitation (Neto et al. 1983).

Bimonthly samplings on papaya trees and weeds were carried out from January 1999 to February 2000. On each sampling date, we randomly selected 10 sampling sites, and, in each site, five trees, totaling 50 trees per orchard. From each papaya tree we collected one new leaf (small and light green, from the apical region), one old leaf (completely expanded and intense green, from the lower part of the canopy), one lateral bud (counted as one leaf), and one flower, which, together, constituted one sample. Whenever possible, we also collected five weed plants from each site sampled. Weeds were sometimes absent because growers usually control them chemically to keep away aphids that may carry the papaya ringspot virus (Marin et al. 1995).

Each sample was put in a paper bag properly identified. All bags were placed in cooler boxes and transferred to the Laboratory of Plant Protection, at the Universidade Estadual do Norte Fluminense. The material sampled was inspected under a stereoscopic microscope. All mites found, independently of their role in the ecosystem, were counted and preserved in a mixture of ethyl alcohol, glacial acetic acid, glycerol, and sorbitol, in the proportion of 8:1:1:1 (Gutierrez 1985). Finally, they were mounted on slides in Hoyer's medium for further identification. Among the phytophagous mites, special attention was paid to the number of broad mites and tetranychid mites found per sampling date, in order to compare their fluctuations in abundance with those of the predacious mites.

Overall, we found a relatively low diversity of mites in both orchards (Table 1). Representatives of seven families were found in Silva Jardim (organic orchard) and six in Linhares (conventional orchard). Most families (Acaridae, Ascidae, Oribatidae, Phytoseiidae, and Tetranychidae) were represented in both places, but some were present only in one of the orchards (Laelapidae and Pyemotidae in Silva Jardim, Tarsonemidae in Linhares). This last result was very striking, because P. latus, the only tarsonemid in Linhares and the most abundant mite in this orchard, was completely absent from the organic orchard throughout the year. Tetranychids, on the other hand, were abundant in both orchards. The low incidence of mites on weeds, except for Tetranychus spp., may be explained, at least in part, by the herbicides periodically applied by the growers to control these plants, which turned this resource very unpredictable in time for phytophagous mites and, most importantly, for thir predators.

In terms of predacious mites, only one family, Phytoseiidae, was represented in both orchards (Tables 1 and 2). In the organic orchard, seven phytoseiid species were found; among these, Typhlodromalus limonicus (Garman & McGregor), T. peregrinus (Muma), T. manihoti (Moraes), and Amblyseius tamatavensis Blommers were the most abundant. However, the average number of mites of each species per sample (< 0.5) was relatively low (Table 2). Similarly, there was a relatively low incidence of phytophagous mites throughout the year. Besides the absence of the broad mite, the density of the tetranychids never reached levels of severe infestation (Fig.1A). Because there was no association between the population levels of tetranychids and predacious mites (Fig.1A,B), probably the phytoseiids found in this orchard, included in the category of generalist predators by McMurtry & Croft (1997), rely mainly on food sources other than the main pests of papaya.

In the conventional orchard, only four phytoseiid species were found, namely Typhlodromalus aripo DeLeon, T. limonicus, A. tamatavensis, and Neoseiulus idaeus Denmark & Muma, the latter being the dominant species; we found more than two N. idaeus individuals per sample (Table 2). Fluctuations in its abundance coincided with those of the tetranychids found in the orchard (Fig. 1A,B). In a recent review, McMurtry & Croft (1997) concluded that predacious mites relatively specialists, represented by the genera Neoseiulus (in part, including N. idaeus) and Galendromus, usually are dominant in highly disturbed agroecosystems, but less common in more natural ecosystems. Our findings support this notion — although completely absent in the organic papaya orchard, N. idaeus was the most abundant in the conventional orchard.

N. idaeus belongs to a group of selective predators of tetranychid mites, but its prey range is relatively broad within these web-producers (McMurtry & Croft, 1997). In their absence, N. idaeus can survive on plant exudates (Mégavand & Tanigoshi 1995) and possibly feed on mites of other families (McMurtry & Croft 1997). These characteristics, along with its ability to disperse and reproduce rapidly and its adaptability to changing conditions of agricultural systems, make N. idaeus a very strong candidate for biological control of mite pests of papaya, especially T. urticae. The year-round presence and abundance of N. idaeus in this chemically-controlled environment indicates that it may easily develop resistance to pesticides, which furthers its potential as a control agent in integrated pest management programs.

Acknowledgments

Thanks are due to Gilberto J. Moraes (ESALQ/USP), for his help on the identification of all mite species, to Ederaldo A. Silva, for his help in the field samplings, and to two anonymous reviewers, for their suggestions that improved this manuscript. We also thank the Fundação Estadual do Norte Fluminense for funding this research and for the scholarship to K.F.S. Collier. G.S. Albuquerque acknowledges the support of CNPq through its Scientific Productivity scholarship.

Literature Cited

Received 11/12/03. Accepted 28/10/04.

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Publication Dates

• Publication in this collection
  21 Mar 2005
• Date of issue
  Dec 2004

History

• Accepted
  28 Oct 2004
• Received
  11 Dec 2003