Early roothealth management

With the discovery of the soil fumigant 1,3-dichloropropene, 1,2-dichloro-propane, (DD mixture) pineapple nematodes were easily and economically controlled during the early stages of pineapple plant growth (Carter, 1943; Keetch, 1979; Johnson and Feldmesser, 1987; Caswell and Apt, 1989). Today, early nematode control is accomplished by clean fallow, preplant soil fumigation with dichloropropene at 224-336 l ha-1 (Fig. 9.17 ) and postplant application of an approved nematocide (e.g. fenamiphos and oxamyl) by broadcast sprays or drip irrigation (Fig. 9.18;

Rohrbach and Apt, 1986; Caswell et al, 1990). Effective soil fumigation requires good plant-residue management and soil preparation (Fig. 9.19). The discovery and use of the inexpensive DD control may have affected the development of other methods of nematode management for pineapple, such as cover crops, crop rotation and hostplant resistance. Crop rotations and resistance have been examined but not researched in depth or used (Caswell and Apt, 1989; Caswell et al., 1990). The root-knot, reniform and root-lesion nematodes have relatively large host ranges. Thus, crop rotations are of value only if crop susceptibilities are known.

Root rots are controlled by improving soil water management, including raised beds, deep cultivation and improving surface-water drainage. The fungicide fosetyl aluminium has shown good control of P. cinnamomi root rot (Rohrbach and Schenck, 1985). The soil fumigant mixture of DD (Telone) was shown to reduce root rot caused by P. arrhenomanes (Anderson, 1966).

Mealybug wilt is readily managed by controlling ants, which tend and protect mealybugs, with an approved insecticide bait (e.g. hydramethylnon) (Rohrbach et al.,

Fig. 9.17. Nematode control using preplant soil fumigation under plastic mulch.
Fruit Trees Irrigation Cover Roots
Fig. 9.18. Postplant drip irrigation and application of postplant nematocides.

1988). The use of bait stations in an IPM approach increases the efficiency of insecticide use and reduces environmental impacts (G. Taniguchi, personal communication).

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