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  • Author or Editor: J. David Mackenzie x
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Susceptibility to woolly apple aphids (Eriosoma lanigerum Hausmn.) was evaluated on 391 Malus clones in a mature cultivar test orchard and on 164 clones in the greenhouse and nursery. A spray program based on Mesurol (4-methylthio-3,5-xylylmethyl-carbamate) resulted in increased aphid populations in the orchard and thereby enhanced identification of susceptible clones. Resistant cultivars included ‘Northern Spy’, several derivatives of ‘Northern Spy’, ‘Ivory’s Double Vigour’, ‘Kola’, Malus halliana Koehne, M. hupehensis (Pamp.) Rehd., M. X robusta (Carr.) Rehd. No. 5 (R5), and M. tschonoskii (Maxim.) Schneid. No evidence was seen that a biotype capable of colonizing ‘Northern Spy’ and its derivatives had arisen in New York.

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