Effects of Apple Rootstocks and Nematicides on Pratylenchus penetrans Populations and Apple Tree Growth

Abstract

Abstract ‘Rogers Red McIntosh’ (Malus domestica Borkh.) on Mailing Merton (MM)111, MM 106, Mailing (M) 26 and M 7a were planted within an old apple orchard site. The trees were trickle-irrigated and the sandy soil was treated with the nematicides Telone (C-17), Vorlex, or Nemacur 3. In 1984, data were collected from trees excavated at 50, 100, and 156 days after planting and from permanent trees in 1985 from plots treated with nematicides prior to planting. The numbers of Pratylenchus penetrans [(Cobb) Filipjev & Schuurmans-Stekhoven] in soil and rootstocks from nematicide treatments and controls were well below reported damage levels and not considered a problem on this test site. M 111 and MM 106 roots and ‘McIntosh’ scion growth were superior to M 26 and M 7a counterparts regardless of soil treatment in 1984, while only the scions on MM 111 were larger than those on M 26 in 1985. ‘McIntosh’ scions grew 36% larger on Telone C-17-treated soil and 19% larger on Vorlex-treated soil than on untreated soil. Leaf and soil analyses showed no interaction with rootstocks and minor differences between soil treatments in both years. A soil replant bioassay revealed disease factor(s), including P. penetrans, present in untreated soil.