Types of Garden Enemies
WHITE-MARKED TUSSOCK MOTH (Hemerocampa leucostigmd).
This is a pest of city shade trees, particularly sycamores, but also destructive in some orchards, with foliage skeletonized and fruit scarred. The caterpillars are pale yellow with red head, a pencil tuft of black hair projecting from either side of the head and from the tail, and four tufts of white hairs along the back (Figure 40B). Female moths do not fly; they lay eggs in masses, covered with hardened white froth, on trunks, branches, and dead leaves.

Control. Egg masses can be daubed with creosote and trees sprayed with lead arsenate or DDT. There are many parasites so that outbreaks are seldom serious for more than a season or two at a time.

NEMATODES
Nematodes are eel worms or roundworms; they live in moist soil water or in decaying organic matter, and some become parasitic on plants. They are so small they have to be seen under a microscope. They move through the soil with a threshing motion but rarely make more than a few inches a year, being spread to greater distances in irrigation water, on tools, or with infested plants. In some nematodes both males and females are wormlike, in others the female is pear-shaped and the male long and narrow. Some live inside plant galls, and others live outside roots while feeding on them, sucking out plant sap through a hollow spear.

CHRYSANTHEMUM LEAF NEMATODE (Aphelenchoides ritzema-bosi),
one of the worst problems in growing chrysanthemums in home gardens. The nemas winter in the soil and in crown of old plants. If spring divisions are made by cutting up the old crown, then the nematodes go along, but if new plants are made by rooting tip cuttings taken from apparently healthy new shoots, then new plantings may be safe. Nematodes swim up the stem in wet weather and into the leaves, causing a wedge-shaped browning between the veins followed by the leaves turning entirely brown and hanging down along the stem. Infestation starts with the lowest leaves and progresses upward.

Fig. 41

Control. Avoid overhead watering; use a mulch to keep nematodes from being splashed up from soil in rains. Parathion gives good control as a foliage spray, but for home gardeners treating soil with sodium selenate is probably preferable, using it in a solution that will give exactly 54 gram of the chemical to a square foot of soil.

MEADOW NEMATODES (Pratylenchus spp.).
These are ecto-parasites feeding on and mutilating roots from the outside and not causing galls. On boxwood they destroy much of the root system but often leave a sort of witches' broom of fine feeding roots near the surface, put out by the plant to compensate for the loss of other roots.




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