Abstract
Ground-dwelling spider assemblages comprise one of the most representative predatory groups to be found in manycrops. There is some evidence of the role that ground-dwelling spiders play in controlling certain citrus pests; however, thereare almost no studies about the abundance and composition of this predatory group in citrus orchards. A three-year surveyconducted using pitfall traps in three citrus orchards in Eastern Spain yielded more than five-thousand ground-dwellingspiders belonging to more than 50 species and 20 families. Wandering families such as Lycosidae, Gnaphosidae andZodariidaewere the most numerous in terms of captures. The generalist predator Pardosa cribata Simon (Araneae: Lycosidae) was the most common species, representing a quarter of all captures, followed by Zodarion cesari Pekar. (Araneae: Zodariidae) and Trachyzelotes fuscipes (Koch) (Araneae: Gnaphosidae). Spiders were active throughout the year with a peak population in summer. The species abundance data for the three spider assemblages sampled fitted a log normal statistical model which is consistent with a well-established community. The presence of a cover crop provided higher abundance of alternative prey and consequently higher abundance and diversity of ground-dwelling spiders. This work demonstrates that the citrus-orchard ground harbours a diverse and abundant ground-dwelling spider fauna, which is also active throughout the year. A challenge for future studies will be to establish conservation management strategies for these predators, that will improve biological control of those citrus pests that inhabit or spend part of their life cycle on the orchard floor.
Highlights
Biological control has a long-standing tradition in citrus orchards, where many potential pests are kept under excellent or satisfactory natural control by either exotic or indigenous natural enemies (Jacas and Urbaneja, 2010)
A total of 5,116 adult spider specimens belonging to 51 species and 20 families were captured in 36 pitfall traps during the three-year study, in the three citrus orchards sampled (Table 1)
Despite many studies about ground-dwelling spiders have been conducted in several citrus regions worlwide (Mansour et al, 1982; Mansour and Whitecomb, 1986; Green, 1999; Benfatto and di Franco, 2002), there is a lack of studies assessing the importance of this predatory group as biological control agents in citrus agroecosystems
Summary
Biological control has a long-standing tradition in citrus orchards, where many potential pests are kept under excellent or satisfactory natural control by either exotic or indigenous natural enemies (Jacas and Urbaneja, 2010). Most of these examples refer to specific natural enemies that inhabit the canopy of this crop. Around 41,000 species have been described world-wide (Platnick, 2011) and this number is estimated to increase to 60,000-170,000 species (Coddington and Levi, 1991). They can be found in relatively high abundance in agroecosytems (Mansour et al, 1980; Oraze and Grigarick, 1989). All known spider species display predatory behaviour and are dominant insectivores in some agroecosystems (Thompson, 1984)
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