Mercedes Campos

Use of arthropods for the evaluation of the olive‐orchard management regimes

Abstract  1 The presence and abundance of arthropods were compared in three olive orchards under organic, integrated and conventional management regimes. In each olive orchard, trees were sampled in the canopy by beating branches and soil arthropods by placing pitfall traps. Contrary to expectations, the highest abundance of arthropods occurred in the integrated management orchard. The most abundant groups were Formicidae and the species Euphyllura olivinae (Homoptera: Psyllidae).

Dynamics of the predatory arthropod community in Spanish olive groves

1 A survey of the predatory fauna of olive pests, particularly the olive moth, Prays oleae, was undertaken in Granada, Spain, from May to September 1994–95.

Qualitative aspects of myrmecocenosis (Hym., Formicidae) in olive orchards with different agricultural management in Spain

A study has been made of the presence of ants in 60 olive trees in each of three orchards under different agricultural management in the province of Granada (southern Spain), during the months of May, July and September 1997, using both observational methods as well as the collection of specimens from the soil and trunk and the tree canopy. A total of 18 species of ants were identified, 16 of which were present in the orchard of Arenales, four in Colomera 1, and nine in Colomera 2. The number of species varies over the survey, being greatest before the flowering of the trees, this period coinciding with the lowest temperatures. The species Tapinoma nigerrimum (Nylander) was the only species present in all the samplings of the olive orchards, and the other common species in the three zones proved to be: Messor barbarus (L. 1767), Tetramorium semilaeve André and Plagiolepis pygmaea (Latr.). Most of the species found made their nests in the soil under the tree canopy, and only four species nested exclusively in open areas. Ten species foraged in the tree and seven foraged in groups. The three olive orchards were similar in phenology, temperature and humidity, and therefore the differences in the myrmecofauna at the different sites were attributed to agricultural practices at each site.

Long-term study on the evaluation of yield and economic losses caused by Prays oleae Bern. in the olive crop of Granada (southern Spain)

Abstract A 28-year study (1970–1997) of olive trees grown in Granada (southern Spain) has revealed the levels of attack by the olive moth (Prays oleae Bern.), as well as the beneficial action of oophagous predators (Chrysopidae). On the basis of the results, the damage caused by the moth has been divided into three categories, and the yield and economic losses have been evaluated. When the final attack is ‘high’ (more than 40% fruit fall), which occurs approximately one in every three years, the necessity of control methods against the pest should be considered.

Is ground cover vegetation an effective biological control enhancement strategy against olive pests

Ground cover vegetation is often added or allowed to generate to promote conservation biological control, especially in perennial crops. Nevertheless, there is inconsistent evidence of its effectiveness, with studies reporting positive, nil or negative effects on pest control. This might arise from differences between studies at the local scale (e.g. orchard management and land use history), the landscape context (e.g. presence of patches of natural or semi-natural vegetation near the focal orchard), or regional factors, particularly climate in the year of the study. Here we present the findings from a long-term regional monitoring program conducted on four pest species (Bactrocera oleae, Prays oleae, Euphyllura olivina, Saissetia oleae) in 2,528 olive groves in Andalusia (Spain) from 2006 to 2012. Generalized linear mixed effect models were used to analyze the effect of ground cover on different response variables related to pest abundance, while accounting for variability at the local, landscape and regional scales. There were small and inconsistent effects of ground cover on the abundance of pests whilst local, landscape and regional variability explained a large proportion of the variability in pest response variables. This highlights the importance of local and landscape-related variables in biological control and the potential effects that might emerge from their interaction with practices, such as groundcover vegetation, implemented to promote natural enemy activity. The study points to perennial vegetation close to the focal crop as a promising alternative strategy for conservation biological control that should receive more attention.

What is consuming Prays oleae (Bernard) (Lep.: Yponomeutidae) and when: a serological solution?

Abstract Over 10 000 predatory arthropods were collected from two olive orchards, and tested in a serological bioassay for olive moth, Prays oleae (Bernard), predation. The highest number of natural enemies tested positive during the flower generation, when the pest is most vulnerable. No consumption of P. oleae was detected once the larvae penetrated the olive fruit. Drought affected development of flowers and fruit, so reducing the pest and natural enemy population. Site differences affected the relative importance of the different predatory groups. Ants were the most commonly found predators, followed by Heteroptera and Coleoptera. Secondary predation and scavenging may have yielded false positives among the ELISA results.

Potential effects of various ant species on green lacewing, Chrysoperla carnea (Stephens) (Neuropt., Chrysopidae) egg numbers

Abstract: Chrysoperla carnea (Stephens) is an important egg predator of the olive moth, Prays oleae (Bernard). Its eggs are laid on pedicels, which are likely to provide some protection against predators and parasitoids. Ants figure prominently in the insect fauna of olive orchards. Six of the most common species in Granada were tested both in the laboratory and the field to establish their effect on chrysopid egg numbers. Crematogaster scutellaris Ol. and Tapinoma nigerrimum Nyl. were the most effective predators of chrysopid eggs with probably the latter being the most damaging due to both its large nest size and its activity. Plagiolepis pygmaea (Latr.), Camponotus micans Nyl. and Camponotus foreli Em. proved to be the least efficient predators. Formica subrufa Roger was intermediate in terms of its ability to eat lacewing eggs but a small sample prevents any firm conclusions from being drawn.

Evaluation of the effect on arthropod populations by using deltamethrin to control Phloeotribus scarabaeoides Bern. (Coleoptera: Scolytidae) in olive orchards

Field tests were made for the control of an olive insect pest, the olive bark beetle, Phloeotribus scarabaeoides (Col: Scolytidae), using the pyrethroid insecticide deltamethrin (D) and this insecticide combined with ethylene (D+E), an attractant of the olive bark beetle. The tests were run in olive orchards in the provinces of Granada and Jaén (Andalusia, southern Spain), treating several olive rows so as to create a barrier effect to control the pest attack. The main objective was to evaluate the arthropod fauna affected by these treatments. The different taxa captured have been separated in three different trophic groups: parasitoids, predators and phytophagous. A knock-down effect was found during the first dates in all the functional groups in all cases. The results showed the following trend in arthropod abundance: D+E>D>C. This trend was significant (p<0.05) for predators and phytophagous insects in both zones. The parasitoids of Prays oleae (Lep.: Plutellidae), a major olive pest, were most affected by the treatments, together with several groups of predators such as ants, cantharids, coccinellids and mirids. Data from the captures show the need to determine the optimum time for insecticide application in order to minimise its effect on beneficial insect populations.

Development of a monitoring trap for the olive fly, Dacus oleae (Gmelin) (Diptera: Tephritidae), using a component of its sex pheromone as lure.

A major component of the sex pheromone of Dacus oleae (Gmel.) has recently been identified as a spiroacetal. The use of this compound as a lure for use in the development of a monitoring trap for that species is described. Polyethylene vials gave a slower release rate of the spiroacetal than rubber septa or microfibres, but even in polyethylene vials a loading in excess of 10 mg was required (optimum 20 to 25 mg) to obtain catches in delta traps which were comparable with those in unbaited vertical yellow sticky traps. In studies in an olive grove near Granada, Spain, a 25-mg spiroacetal lure used with a vertical yellow trap gave catches of males of D. oleae which were four times as great as those in delta traps with the same lure or in unbaited yellow traps. The height of the trap had no apparent effect on catch. Previously recorded components of the sex pheromone did not prove to be effective when combined with the spiroacetal. Combined monitoring of Prays oleae (Bern.) and D. oleae , using their respective pheromones in the same trap, appears to be feasible with delta traps.

Effectiveness of deltamethrin for protecting olives from attack by the beetle Phloeotribus scarabaeoides (Scolytidae)

Deltamethrin, a pyrethroid insecticide, was tested in both the laboratory and the field, with the aim of controlling the olive bark beetle, Phloeotribus scarabaeoides (Bernard), in living olive trees. In the laboratory, bark beetle adults were exposed to olive twigs treated with different concentrations of deltamethrin. Among these concentrations, dosage at 0.05% produced 100% mortality in the scolytids after 13 weeks. This dosage of deltamethrin, applied in the field, protected olive trees from scolytid attack during the whole emergence period.