Abstract
Numerous species of the family Chrysopidae, commonly found in agroecosystems, whose larvae predate on several pests of economic importance, are regarded as biological control agents. Their abundance and diversity are influenced by vegetation cover, although little is known about the effects of semi-natural habitats on their populations. The objective of this study is to gain a better understanding of the relationship between the trees in semi-natural habitats adjacent to olive groves, juvenile stages of the family Chrysopidae and factors influencing their population decline, which is crucial for an effective habitat management program aimed at conserving these important predators. Using cardboard band traps (eight per tree), the juvenile stages were collected from 25 almond, oak, olive and pine trees over a one-year sampling period. The population decline was caused by parasitoids (26.5%), predators (5.1%) and unknown factors (13.2%). In addition, chrysopids established in olive trees showed the lowest rate of parasitism. We identified ten chrysopid species that emerged from the juveniles collected from almond, oak, olive and pine trees, with a predominance of Pseudomallada prasinus. The chrysopid–parasitoid complex was composed of five species; Baryscapus impeditus (Eulophidae), which was the most abundant, was preferentially associated with Chrysopa pallens, Chrysoperla lucasina and Chrysoperla mediterranea.
Highlights
Of the many families of the Order Neuroptera, Chrysopidae attracted the most attention as compared to Coniopterygidae and Hemerobiidae [1], as numerous species belonging to the Chrysopidae family are regarded as biological control agents given their potential impact on pest populations in crops [2,3,4,5,6]
This study provides an insight into the abundance of chrysopid populations in olive groves, as well as almond, oak and pine trees adjacent to the crop, in addition to population decline factors
We have demonstrated that chrysopid abundance in almond and oak tree species in the arboreal stratum adjacent to olive groves is comparable to that in olive trees
Summary
Of the many families of the Order Neuroptera, Chrysopidae attracted the most attention as compared to Coniopterygidae and Hemerobiidae [1], as numerous species belonging to the Chrysopidae family are regarded as biological control agents given their potential impact on pest populations in crops [2,3,4,5,6]. Chrysoperla carnea (Stephens, 1836) sensu lato, which has been reared and released in crops around the world [8,9,10,11], is the species most commonly used in agricultural biological control programs [12]. There is evidence that C. carnea is a complex of at least 21 cryptic species [1,13,14]. Some species are well defined with respect to morphological characteristics, habitats, courtship songs and molecular techniques, their taxonomy has not been fully
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