Alguns fatores que influenciam populaçoes de afídeos em mimoseira (Citrus reticulata B.)e macieira (Pyrus malus L.)com referencia especial aos inimigos naturais

Abstract

Abstract: Weekly counts were made of aphids and their natural enemies occurring in seven tangerine and four apple trees in an orchard in Curitiba, Parana - between April 1973 and March 1974. Aphid populations were related to the number of new shoots in each tree, the natural enemies and meteorological data. . Four species of aphids occurred in the tangerine trees, including Toxoptera citricida (Kirk.), the most abundant, and Aulacorthum Tsolani (Kalt.) Uroleucon sp., not previously recorded on citrus in Brazil; aphid populations were highest from June September. In the apple trees, Aphis spiraecola Patch, wee abundant, principally during November and December; small colonies of Eriosoma lanigerum (Hausm) also occurred. Aphid populations were found to be directly dependant on the number of young shoots per tree; rain and temperature were not found to be important in limiting aphid numbers. Coccinellidae, Syrphidae, Hemerobiidae and Chrysopidae were found preying on aphids and Lysaphidius platensis (Brethes) (Hym., Aphidiidae) parasitised both T. citricida and A. spiraecola. Larvae of Coccinellidae were most abundant in citrus in november and in apple trees during December and February. Scymnus spp., Pullus sp., Hyp eraspis sp. Pentilia sp., Cycloneda sanguinea (L.), Coccinellina pulchella, (Klug) Delphastus argentinicus Nunenm, and Zagreus bimaculatus (Muls.) were 9 found in both citrus and apple trees, the two latter being recorded as aphid predators for the first time in Brazil. Pullus limbaticollis Muls. was found only in citrus and Psyllobora sp. only in apple trees. Scymnus spp,were the most common of the aphid predators, adults occurring in citrus the whole year. Syrphidae were most abundant in citrus trees during August and in apple trees in December and February. Larvae of Syrphus phaeostigma (Wied.), Pseudodorus clavatus (Fabr.), Ocyptamus gastrostactus (Wied.), Allograpta exotica (Wied.) and Allograpta sp. occurred in citrus trees, but only P. clavatus and 0. gas tros tactus were found.in apple trees. S. phaeostigma has not previously been cited as an aphidophagous species, nor as occurring in Brazil. Some larvae of Hemerobiidae were found throughout the year in both citrus and apple trees; Hemerobiidae have not previously been recorded in Brazil as aphid predators. Larvae of Chrysopidae were found between January and April in low numbers, only in citrus. Effectiveness of the predators was reduced by ants which attended the aphids-in both citrus and apple trees, and by micrchymenopterous parasite; Laboratory tests showed that at 249 c, adults of C. sanguinea consumed an average of 32 T. citricida or 29 A. spiraecola per day compared with 30 and 26 consumed by C. pulchella; similarly larvae of C. sanguinea consumed more aphids than did larvae of C. pulchella.