Figure 1. Symptoms of replant disease. A, and B, mildly stunted and vigorous growth of peach trees in non-fumigated and methyl bromide fumigated plots, respectively, near Parlier, CA; C, decline and death of almond trees on non-fumigated soil (foreground) and adequate growth on chloropicrin-fumigated soil (background) near Chico CA.
Figure 2. Micro plots being used to determine effects of pre-plant cover crop rotations and fallowing at the USDA-ARS research center near Parlier, summer 2002.
Figure 3. Effect of soil history (year planted and previous crop) and pre-plant fumigation on severity of root discoloration symptom (associated with replant disease) on Nemaguard peach, Experiment 2, greenhouse. Soil was collected from the indicated sources, fumigated in a sealed container (MB, 0.3 g/liter soil) or left non-fumigated, placed in pots, and planted to Nemaguard peach seedlings in the greenhouse. Three months after transplanting, roots of the plants were washed free from soil and assessed for severity of replant disease symptoms.
Figure 4. Effect of soil history (year planted and previous crop) and pre-plant fumigation treatment on severity of root discoloration symptom (associated with replant disease) on Nemaguard peach, Experiment 3, greenhouse. Soil was collected from the indicated sources, fumigated in a sealed container (MB, 0.3 g/liter soil) or left non-fumigated, placed in pots, and planted to Nemaguard peach seedlings in the greenhouse. Three months after transplanting, roots of the plants were washed free from soil and assessed for severity of replant disease symptoms.
Figure 5. Effect of soil history (previous crop) and pre-plant fumigation treatment on severity of root discoloration symptom (associated with replant disease) on Carignane grape cuttings, Experiments 2 and 3 combined, greenhouse. Soil was collected from the indicated sources, fumigated in a sealed container (MB, 0.3 g/liter soil) or left non-fumigated, placed in pots, and planted to the grape cuttings in the greenhouse. Three months after transplanting, roots of the plants were washed free from soil and assessed for severity of replant disease symptoms.
Figure 6. Effect of soil history (previous crop) and pre-plant fumigation treatment on severity of root discoloration symptom (associated with replant disease) on Carignane grape seedlings, Experiment 3, greenhouse (Carignane seedlings were included in addition to Carignane cuttings in Experiment 3 only). Soil was collected from the indicated sources, fumigated in a sealed container (MB, 0.3 g/liter soil) or left non-fumigated, placed in pots, and planted to the grape seedlings in the greenhouse. Three months after transplanting, roots of the seedlings were washed free from soil and assessed for severity of replant disease symptoms.
Figure 7. Effect of soil history (year planted and previous crop) and pre-plant fumigation treatment on weight of Nemaguard peach seedlings, Experiment 2, greenhouse. Soil was collected from the indicated sources, fumigated in a sealed container (MB, 0.3 g/liter soil) or left non-fumigated, placed in pots, and planted to Nemaguard peach seedlings in the greenhouse. Three months after transplanting, roots of the plants were washed free from soil and the fresh weight of roots plus shoots was determined for each plant.
Figure 8. Effect of soil history (year planted and previous crop) and pre-plant fumigation treatment on weight of Nemaguard peach seedlings, Experiment 3, greenhouse. Soil was collected from the indicated sources, fumigated in a sealed container (MB, 0.3 g/liter soil) or left non-fumigated, placed in pots, and planted to Nemaguard peach seedlings in the greenhouse. Three months after transplanting, roots of the plants were washed free from soil and the weight of roots plus shoots was determined for each plant.
Figure 9. Effect of pre-plant fumigation treatment on weight of Carignane grape cuttings. Soil was collected from the indicated sources, fumigated in a sealed container (MB, 0.3 g/liter soil) or left non-fumigated, placed in pots, and planted with the grape cuttings in a greenhouse. Three months after transplanting, roots of the plants were washed free from soil and the weight of roots plus shoots was determined for each plant.
Figure 10. Experimental tree sites prepared for pre-plant fumigation (and non-fumigated control) treatments, fall 2002, near Chico, CA
Figure 11. Experimental pre-plant fumigation of tree sites in Chico-area orchard
Figure 12. Symptoms associated with replant disease (RD) on roots in greenhouse tests. A, Root discoloration resulting from cortex necrosis on Nemaguard peach roots grown for 3 months in non-fumigated soil from an RD-affected orchard (left), compared to healthy roots grown in the same soil after fumigation (right). B, closeup of roots with cortex necrosis (left) and healthy roots (right).
Figure 13. Use of coring tool to extract known volumes of Nemaguard peach root systems from Parlier micro plots after removal of shoots.
Figure 14. Response of Nemaguard peach plants to pre-plant treatments in one of the Parlier micro plot experiments. The microplots were filled with soil from an orchard affected by replant disease, fumigated on 4/30/02, and planted with 4-inch-tall peach seedlings on 6/3/02. The photos, from one representative block, were taken 8/12/02.
Figure 15. Washing of Nemaguard peach root samples from Parlier mircro plots (left), and appearance of representative roots from a non-fumigated plot (center) and a pre-plant chloropicrin-fumigated plot (right).
Figure 16. Effects of dilution with UC mix potting soil on growth and root health of Nemaguard peach seedlings in non-fumigated and fumigated soil from a Parlier RD site. The seedlings were grown for 3 months in 500-ml volumes of the mixtures in cone pots in a greenhouse before measurement of A, weight of plant tops; B, shoot height; C, root weight; and D, root health. Minimum signficant differences are according to the Waller-Duncan k ratio test.
Figure 17. Effects of fumigated and non-fumigated soil volume ratios in combination with UC mix on A, shoot weight, B, shoot height, C, root weight, and D, severity of root discoloration of Nemaguard peach seedlings grown in a greenhouse. Minimum signficant differences are according to the Waller-Duncan k ratio test.