Abstract1 A survey of the predatory fauna of olive pests, particularly the olive moth, Prays oleae, was undertaken in Granada, Spain, from May to September 1994–95.2 At both experimental sites similar patterns of emergence were observed for all predatory species with peaks occurring in June, both in 1994 and 1995. More individuals and species were captured in the morning than in the evening.3 A weak inverse relationship existed between the mean monthly temperatures and the total number of predators caught.4 The number of predatory species and of individuals caught at both sites was, respectively, two and three times larger in 1994 than in 1995; This difference is assumed to have been due to the accumulated affect of 6 years of drought.5 Synchrony between P. oleae and predator phenology was suggested by the coincidental timing of peak predator numbers with the oviposition and subsequent emergence of the most vulnerable stage of the olive moth’s lifecycle, i.e. the flower generation.6 There were more individuals of ants caught, whilst more spider species were captured than all other groups; predatory Coleoptera and Heteroptera were poorly represented.7 Ants appeared to have a detrimental affect on the number of all other predators.
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 01. 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.
In the olive orchards of Granada, Spain, ants are one of the most abundant insect families. Two sites were compared in 1994 and 1995 – a commercial orchard and an abandoned one. In both, the temporal pattern of abundance and the ant species composition were similar. Drought affected captures between the years. The managed orchard had fewer species and was dominated by Tapinoma nigerrimum. Predation studies using enzyme‐linked immunosorbent assay (ELISA) showed that the maximum number of ants found to be test positive for olive moth, Prays oleae remains coincided with the moth's most vulnerable period. In the commercial orchard the most abundant ant species also had, by far, the highest number of positives for predation whereas at the abandoned site several species were of equal importance. Trophallaxis and scavenging are two particular traits of ants that may artificially inflate the ELISA results. However, as a basis for further study, ELISA can greatly assist the identification of ant species which warrant further research into their possible role against the olive moth.
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