Check Juniper Problems in Early Summer

Some gardeners simply call them all cedars, because some of the junipers we use in home landscapes are varieties selected from the Eastern Red Cedar, an evergreen plant common to fields and roadsides in Missouri and much of the eastern United States.

Not all junipers we use in the landscape are American. Some, such as the well-known Pfitzer, came from Oriental or European species. Whatever the variety origin of juniper most of them are subject to some of the same pests and diseases. The best known of these is the bagworm. While red cedars are among the most susceptible or ornamentals to be attacked by bagworms, many other plants may also be attacked by these ravenous feeders. Total defoliation of evergreens may result in the death of the plant or a portion of it.

The eggs, which remain in the bag, normally start to hatch out in late May or early June. They may move from plant to plant by spinning a long, silken thread and being carried by the wind. They promptly make a bag of needles or leaves and remain within it during their entire feeding time. They are easiest to kill while they are small in early to mid-June. Common garden insecticides such as carbaryl, diazinon, or malathion may be used for their control. The biological material used for cabbage worm control, Bacillus thuringiensis, has also been shown effective on bagworms. Be sure to use any of these materials carefully according to directions. Also check labels for any precautions.

Malathion can injure some junipers such as Canaerti, Sargent, or Burk. Mites are another common juniper problem. They are also known as spider mites or red spiders. They feed primarily on the undersides of needles or leaves, but they may be found throughout as they become more numerous. Small webs may sometimes be seen and foliage will become pale green and eventually may die as they increase. Mites may be present in spring, but do not normally do serious damage until hot dry weather arrives. Washing plants with a strong stream of water helps disrupt the pests, but serious infestations are best controlled with a material such as dicofol (Kelthane).

During hot, dry weather, frequent sprays may be necessary for control. While junipers are very durable plants, some environmental conditions may also cause problems. Coatings of ice on the branches during winter may cause partial or total death. Junipers need well-drained locations and plenty of sunlight. In wet spots or shady locations they are more subject to diseases. Probably the most damaging fungus disease of junipers in home landscapes is twig blight. When it attacks, the tips of twigs turn brown. Browning continues to move down the twig until an entire branch is killed out. If this disease is suspected, do not shear trees. The shears only spreads the fungus from infected twigs to the cut ends of healthy twigs.

Careful pruning to remove dead or dying twigs will slow spread. The use of Benlate in the fall and again at two-week intervals during the spring has been suggested as a control. Cedar-apple rust is another fungus disease found on junipers. In spring the ball-like galls it forms produce long, orange, jelly-like projections. While the disease occurs on apples, crab apples, hawthorns, and related plants as rust-colored spots on the leaves.

http://en.wikipedia.org/ wiki/Juniper