ISHS Acta Horticulturae 442: III International Walnut Congress
THE CONTROL OF WALNUT APHID, CHROMAPHIS JUGLANDICOLA (HOMOPTERA: APHIDOIDEA) IN WALNUT ORCHARDS IN PORTUGAL. |
| Authors: | A. Cecilio, F. Ilharco |
| Keywords: | Trioxys pallidus, hyperparasitoids, predators |
| Abstract:
Chromaphis juglandicola (Kaltenbach) is the aphid species observed as a pest in walnut orchards in Portugal. The control of walnut aphid by chemical insecticides was not effective. Field studies of the walnut aphid and natural enemies (parasitoids and predators), were conducted at Alcobaça and Santarém region. Primary parasitism by Trioxys pallidus (Haliday) and hyperparasitism by Pachyneuron aphidis (Bouché), Asaphes suspensus (Nees), Syrphophagus aphidivorus (Mayr), and Alloxysta sp. were observed. Early and frequent insecticide applications were not associated to lower levels of aphids and can disrupt the presence of T. pallidus. The occurrence, early in the season of 50% hyperparasitism was associated with low numbers of mummies. The aphidophagous coccinelids observed in walnut orchards were Adalia decempunctata (L.) and Oenopia conglobata (L.). They can occur with low numbers of aphids per leaf (1 aphid per leaflet). The species of aphidophagous Syrphidae larvae collected on leaves with aphid populations were Meliscaeva auricollis (Meigen) and Syrphus sp: The Syrphidae larvae were observed in orchards with high levels of aphids (20 aphids per leaflet). Chrysopidae (eggs, larvae and adults) were also observed on the leaves. An economic threshold is proposed. | |
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