Resistance of potato genotypes (Solanum spp.) to aphids (Homoptera: Aphididae) and the influence on parasitoids

The resistance of potato genotypes to the aphids Myzus persicae (Sulz.), Macrosiphum euphorbiae (Thomas) and Aphis gossypii (Glover) and the influence of these genotypes on parasitoids were evaluated in field conditions, in 1996 and 1997, in Jaboticabal, SP. The genotypes planted in the first year were: Achat, Baronesa, Bintje, BR-2, Contenda, Monalisa, N 140-201 and NYL 235-4, distributed in a randomized block design with four replications. Two surveys were made at the 70th and the 85th day after planting, by counting the number of aphids/leaf and calculating the proportion of parasited aphids, in the upper, medium and low thirds of the plant. In 1997 the same genotypes were planted (except for N 140-201), with surveys at the 72th and the 80th day a.p. The genotype NYL 235-4 was susceptible to M. euphorbiae, under the medium infestations of 2.90 (1996) and 1.19 aphids/leaf (1997); among the commercial cultivars, Baronesa was one of the least attacked by M. persicae (0.12 and 0.10 aphids/leaf in 1996 and 1997), while BR-2 was very susceptible (1.10 and 0.66 aphids/leaf). The largest population of the aphids was found in the medium and low parts of the plants; a higher number of aphids attacked by Aphidius ervi Hal. and Diaretiella rapae (McIntosh) was observed in NYL 235-4, in which there was a larger infestation of aphids, with parasitism varying from 15 to 36%.

Insecta; Aphis gossypii; Macrosiphum euphorbiae; Myzus persicae; biological control