Ants as predators of the egg parasitoidTrichogramma cacoeciae(Hymenoptera: Trichogrammatidae) applied for biological control of the olive moth,Prays oleae(Lepidoptera: Plutellidae) in Portugal

Abstract

The detrimental effect of predators on Trichogramma cacoeciae March. releases to control the olive moth, Prays oleae Bern., in the Trás-os-Montes region (Northeast of Portugal), was evaluated during three releases against the flower generation of the pest in 2002. At 1 and 3 h and at 1, 3, 7 and 14 days after each release, 30 Trichogramma releasing cards were examined in the field and predators were collected and identified. Furthermore, at 1, 3, 7 and 14 days after each release, the percentage of egg predation on the cards was also determined. Formicidae were the most abundant group of predators at 99.1% of the total individuals collected. Ten species were identified, Camponotus aethiops, C. lateralis, C. piceus, C. truncatus, Crematogaster auberti, C. scutellaris, Lasius niger, Leptotorax angustulus, Plagiolephis pygmaea and Tapinoma nigerrimum. T. nigerrimum was the most abundant species, both in total numbers as well as in the number of occupied cards. One day after release, the percentage of predation was 24.0% in the first release, 59.4% in the second and 38.0% in the third. Three days after release, the percentage of predation varied from 60.2 to 83.4% during the three release events. Seven days after release, the percentage of predation increased to 97.8% of the total eggs on cards.

Evaluation of the effects, on canopy arthropods, of two agricultural management systems to control pests in olive groves from north-east of Portugal

“…P. mediterraneus was a common species in both organic and integrated olive groves (Santos et al, unpublished). Although ants are considered a key-group in olive grove (Morris et al, 1999;Pereira et al, 2004) namely as bioindicators of disturbances, the information concerning the effect of pesticides over this group is scarce. In olive grove, ant species nest in soil or in old olive trunks and climb to the canopy to eat insects and liquid sugars (Redolfi et al, 1999).…”

Towards sustainable control of Lepidopterous pests in olive cultivation

“…Egg predation was identified as an important mortality factor, especially for the carpophagous generation, destroying up to 67% of eggs deposited on the fruits. A careful study in Portugal examined the role of ants in egg predation, suggesting that egg predators belonging to Chrysopidae and Coccinellidae might be negatively influenced by the presence of ants, especially by the species Tapinoma nigerimum F. (see also Pereira et al 2004). This observation confirmed earlier results published by Morris et al (1998).…”

“…Observed parasitism of olive moth eggs on treated trees was below 30% and the achieved efficacy concerning pest control was far from sufficient in all countries. In Portugal, one factor partially responsible for the failure of releases was the occurrence of high predation by ants, which removed considerable amounts of released material shortly after installation in the field (Pereira et al 2004). In the last year of the project, we were able to solve this problem by using cardboard devices that wrapped up the releasing material completely, so that ants could not contact it with their antennae (Fig.…”

Short term response of ants to the removal of ground cover in organic olive orchards

“…Most species of ants build their nests in the ground either under the tree canopy or between the rows of olive trees, although some species such as Crematogaster scutellaris (Hymenoptera: Formicidae) build their nests under bark (Redolfi et al, 1999). Ants play an important role within the arthropod community in olive orchards as they consume larvae of pests, such as Prays oleae (Lepidoptera: Plutellidae) (Arambourg, 1986;Morris et al, 2002;Pereira et al, 2002), but can also have harmful effects on natural enemies because ants eat the eggs of the predator Chrysoperla carnea (Neuroptera: Chrysopidae) (Morris et al, 1998) and the parasitoid Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae) used for the biological control of Prays oleae (Pereira et al, 2004). According to Altieri (1999), the maintenance of the functional biodiversity in agroecosystems is a key ecological strategy for sustaining production.…”