Populations, longevity, mortality and fecundity of Chrysoperla carnea (Neuroptera, Chrysopidae) from olive-orchards with different agricultural management systems

Abstract

The influence that different styles of olive-orchard management (conventional, integrated, and organic) exert on the predator Chrysoperla carnea has been studied to strengthen this insect’s role in the integrated management against pests. For this, the adult chrysopid populations were determined by McPhail traps, and laboratory examinations were made of certain biological characteristics of the first generation of adults captured in each of the olive orchards studied. The chrysopid populations increasing significantly during some months in the integrated and organic olive orchard. The most abundant species in all the zones was C. carnea, representing 95% of all captures in the conventional olive orchard. It was found that the larvae from the integrated olive orchard took longer to develop, while the pupae from the organic orchard evolved most rapidly to adulthood. The highest mortality rate was for larvae in the conventional olive orchard. The fecundity of the females from the organic orchards was significantly greater, presumably due to their greater longevity and shorter pre-oviposition period. These results can be used to improve conservation strategies and to increase C. carnea populations and their predatory activity.

Introduction

Natural enemies play an important role in agroecosystems, offering a valid alternative to, or integration with, other control methods (Salerno et al., 2002). Thus, the development of integrated management of pests seeks to increase natural control by the attraction and preservation of entomophagous arthropods (Szentkirályi, 2001). For this, it is fundamental to improve knowledge on the influence that different agricultural practices exert over such beneficial organisms.

Chrysoperla carnea Stephens is a widespread predator in agroecosystems, with great potential in integrated pest management (Hassan, 1974, Stelzl and Devetak, 1999, Duelli, 2001). In olive orchards, this insect is a major predator of two of the main phytophagous pests in this crop, Prays oleae Bernard (Lepidoptera, Plutellidae) with three generations and Saissetia oleae Olivier (Hemiptera, Coccidae) with one generation (Alrouedchi, 1980, Campos and Ramos, 1984, Sacchetti, 1990, Pantaleoni et al., 2001), and therefore it is of great importance to conserve and increase its populations (McEwen et al., 1994).

Many laboratory and semi-field studies have shown the sensitivity or tolerance of C. carnea to insecticides (New, 1975, Bigler, 1984, Grafton-Cardwell and Hoy, 1985a, Hassan et al., 1985, Vogt et al., 1992, Vogt, 1994, Elzen et al., 1998). In the olive orchard, the treatments applied reportedly diminished not only the effectiveness of its larvae against P. oleae (Ramos et al., 1978) and S. oleae (Delrio, 1983), but also the diversity of the species of chrysopids present (Pantaleoni and Curto, 1990, Ruano et al., 2001), and even the stability of forewing development in C. carnea adults (Lorenz, 2002). On the other hand, the beneficial effect of vegetation on the chrysopid populations has been shown in this crop as this insect lays its eggs on plants (Canard and Laudého, 1980, McEwen and Ruiz, 1994).

Currently, the integrated approach to olive-orchard management is being promoted because of the undesirable alterations that are becoming apparent with the growing indiscriminate use of chemical treatments (Heim, 1994, Cirio, 1997). In addition, organic management is growing in this culture due to market demand as well as environmental advantages (Civantos, 1999), reaching 17.8% of the total organic surface area of Spain (Alonso Mielgo, 2001).

Since agronomic factors incising C. carnea are numerous, the aim of the present work is to study the populations and behaviour of this chrysopid in olive orchards with different agricultural management systems.