Types of Garden Enemies
Fig. 60
WEATHER
Weather in its many manifestations, ice storms, heat, cold, drought, and floods, can certainly be classed as a garden enemy. Some of its effects are mechanical, as frost cracks in sudden cold or actual breaking of limbs in hurricanes or by ice or snow, but almost everything else boils down to a water relation.

We call the large brown areas that appear on rhododendron leaves in late winter or spring SUNBURN or windburn. The cells that are exposed to sun or wind lose water faster than it can be drawn up from the often frozen ground and so they collapse, turn brown, and. die. Fungi may appear in this spot secondarily, but this is primarily a physiological disease. It can be partially prevented by watering broad-leaved evergreens very thoroughly late in the fall and by using a windbreak for too exposed locations.

SCORCH
is the name for sudden death of foliage in summer heat, with large areas in the leaves tan or brown. Sugar maples are subject to scorch, reacting promptly when hot weather follows a period of cool cloudy weather. Again it is a case of cells collapsing before the water evaporated in the heat can be replaced from the roots. Copper beech is often damaged (Figure 60A). Scorch on horsechestnut looks like a leaf spot, but it lacks the black dots indicating fungus fruiting bodies.

BLOSSOM-END ROT
of tomato, also occurring on pepper, squash, and watermelon, certainly looks like a fungous disease, but it is caused by irregular water supply, drought following excessive rainfall. Tissues at the blossom end of the fruit shrink, and a dark leathery spot is formed that may include half the fruit. Avoid excessive nitrogen, provide balanced fertilizers, mulch to conserve moisture, water regularly in dry periods. Frost cracks can sometimes be avoided by letting roses and other shrubs harden of? early; do not feed after the middle of July; avoid excessive watering in late summer.

When ice freezes into boxwood stems, the bark may slough off very gradually with branches dying back for 2 years or more after the ice storm or sudden cold.

WEBWORMS
Webworms are caterpillars which feed inside foliage they web or tie together.

FALL WEBWORM (Hyphantria cunea).
This is not a pest of evergreens but appears on more than a hundred fruit and shade trees and shrubs. The webs resemble tent caterpillar nests but are more loosely woven and are at the ends of branches, often with several tied together, rather than back at the crotch.




      (c)2005, common-garden-pests.com