Root-lesion nematodes, potassium deficiency, and prior cover crops as factors in apple replant disease
1989
Merwin, I.A. | Stiles, W.C.
Growth chamber evaluations of soil from an orchard replant site showed severe stunting of 'Northern Spy' apple (Malus domestica Borkh.) seedlings grown in field soil (FS) compared with pasteurized soil (PS) from the same site. The FS : PS seedling dry weight ratio of 0.44 indicated a serious replant problem. Leaf nutrient content was generally higher in PS than FS seedlings. Multiple-regression analysis indicated that leaf K and root-lesion nematode (Pratylenchus penetrans Filipjev) primary inoculum accounted for 75% of the variation in FS seedling dry weight. Apple seedling dry weight in FS was 97% of that in PS following a marigold (Tagetes patula L. cv. Sparky) cover crop, and 75% following oats (Avena sativa L. cv. Saia). Root-lesion nematodes were nearly eliminated from the plots with marigold. Other cover crops and weed-free fallow period were less effective in controlling apple replant disease and/or phytonematodes.
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