Types of Garden Enemies
Fig. 1
White oaks may presist for a few years with branches dying. All species of oaks are susceptible. Infection is through wounds and root grafts. The means of long-distance spread is not yet known, but spores could be carried by birds and insects. There is no control as yet beyond the drastic procedure of removing all oaks within 50 feet of trees dying with the disease in an attempt to prevent infection through roots.

TOMATO WILT {Fusarium oxysporum f. lycopersici).
In some areas this is our most damaging tomato disease. Leaves of seedlings curve downward, wilt and die. On older plants the wilt often appears as the fruits mature, with lower leaves turning yellow, often on only one side of the stem. The fungus lives in the soil, enters through roots, and produces a toxin which turns the vascular system dark brown.

Control. Wilt-resistant strains include highly resistant Pan American, moderately resistant Marglobe and Rutgers, Southland, Jefferson.

VERTICILLIUM WILT {Verticillium albo-atrum).
This wilt is widespread, affecting maple, elm, fruit trees, monkshood, chrysanthemum, dahlia, and other herbaceous perennials; tomato, eggplant, and other vegetables; strawberries, raspberries, and other bush fruits; and roses. Lower leaves turn yellow and die, turning brown or black. Plants are stunted, and if you cut across the stem you can see blackened vessels; annuals are killed; perennials sometimes recover. Maples are very susceptible, and often there is sudden wilting of one side of the tree in midsummer, sapwood of the infected side having greenish streaks.

Control. It is sometimes possible to prune out affected maple limbs and save the tree, helping it along with a soluble nitrogenous fertilizer, but in most cases plants die eventually. Do not transfer plants from any area where wilt has appeared.




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