Abstract
The impact of agroecological weed management on predatory mites (Mesostigmata: Phytoseiidae) is more and more studied. Based on surveys carried out in two experimental sites in Tunisian citrus orchards, this study aims: (i) to compare Phytoseiidae communities on citrus trees and weeds, (ii) to determine dispersal between agrosystem compartments and (iii) to assess the impact of weed management on Phytoseiidae communities. Samples were collected on trees and weeds; dispersal between ground cover and trees was surveyed using traps along tree trunks. Euseius stipulatus and, to a lesser extend, Iphiseius degenerans were the main species on citrus trees. Phytoseiidae were observed in weeds, with diversity and densities varying according to plant species. Phytoseiidae species in weeds were globally similar to those observed on trees. Phytoseiidae were trapped along the trunk; however higher dispersal was observed from weeds to trees than from trees to weeds. In one survey, species moving up the trees were not the same as those present on trees. With respect to weed management strategies, it seems that ploughed plots favour Phytoseiidae mite dispersal from weeds to trees with consequent increases in densities on trees. This weeding strategy therefore requires more attention to determine how its schedule can enhance biological control.
Highlights
Biological control is a key crop protection strategy to limit pesticide use (Wilson and Huffaker 1976)
The present study focuses on the effect of weed management in citrus orchards on Phytoseiidae mite communities
Three Phytoseiidae species were found on citrus trees: Euseius stipulatus (Athias-Henriot), Neoseiulus californicus (McGregor) and Typhlodromus (Anthoseius) rhenanoides Athias-Henriot (Table 1); the most abundant was E. stipulatus whatever the weeding management
Summary
Biological control is a key crop protection strategy to limit pesticide use (Wilson and Huffaker 1976). The present study focuses on the effect of weed management in citrus orchards on Phytoseiidae mite communities. These biological agents are efficient predators in controlling phytophagous mites and small insects in various crops worldwide (McMurtry and Croft 1997; McMurtry et al 2013). Some other studies focus on the effect of plant management diversity within crops, i.e. weed management, on Phytoseiidae abundance and diversity (Rock and Yeargan 1973; Hislop and Prokopy 1981; Smith and Papacek 1991; Kreiter et al 1993; Liang and Huang 1994; Nyrop et al 1994; Stanyard et al 1997; GraftonCardwell et al 1999; Pereira et al 2006; AguilarFenollosa et al 2008, 2011; Mailloux et al 2010; De Villiers and Pringle 2011). Herbicide application has for instance been reported to increase dispersal of pest mites from weeds to trees because of habitat destruction (Flexner et al 1991; Kreiter et al 1991, 1993; Alston 1994; Hardman et al 2005, 2011)
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