Tiny "Bags" Hang on Branches due to Bagworms
Small spindle-shaped bags hanging like Christmas ornaments from juniper branches are bagworm cases. Each case is woven of silk and bits of needles, and houses a caterpillar. Dark brown with white or yellow heads, these bagworms carry their bags with them as they feed. They can kill a tree if left uncontrolled. A fully developed bag is about two inches long and protects up to 1000 eggs over the winter, which hatch out the following spring. During the winter, handpick any bags within reach from the shrubs and burn them. In the late spring and early summer, after the caterpillars have emerged, spray juniper foliage with Bt (Bacillus thuringiensis) just as the young caterpillars begin to eat the leaves. Repeat every 10 days through mid-July so that as many as possible ingest the bacteria as they eat, sicken and die. An alternative control is to spray foliage with a neem insecticide 2 or 3 times every 10 days while caterpillars are active. It acts as an anti-feedant and a repellant. For more information see the file on Controlling Caterpillars
Leaves Distorted and Yellowed means Mites
In very severe infestations these tiny (1/50 inch long) green, yellow, or red spider mites cover juniper leaves with fine silken webbing. The foliage (needles) turns yellow. Spray affected shrubs in the early morning with a forceful water spray to knock the mites from leaf undersides. Repeat the water spray daily for 3 days. If that doesn't do the job, spray mites with insecticidal soap every 3 to 5 days for two weeks. For more information see the file on Controlling Mites
Leaves And Twigs Webbed Together caused by Webworms
Juniper webworms are 1/2 inch long and brown, with longitudinal reddish brown stripes. The adult females, moths with 3/5-inch wingspans, appear in June and lay eggs that hatch in 2 weeks. The pests winter over in the immature larval stage. Webworms spin webbed nests that enclose juniper leaves and eventually kill them. Handpick as many of these nests as possible and destroy them. Spray juniper foliage with Bt (Bacillus thuringiensis) when the worms begin to feed on it. Repeat sprays at weekly intervals for 3 weeks or if it rains soon after it is applied. Worms that ingest Bt will soon stop eating and will die within a day or two. An alternative is to spray a neem insecticide on juniper needles 2 or 3 times at 10-day intervals until the worms are gone. For more information see the file on Controlling Caterpillars
Foliage Curls, Turns Yellow indicates Aphids.
Check juniper stems and needles for small groups of soft-bodied, pear-shaped, reddish-brown insects a little bigger than the head of a pin. These are aphids, which suck sap from leaves and stems of junipers, causing the needles to yellow. These insects also secrete sticky "honeydew" on the foliage that coats it. It encourages sooty mold fungus, which then coats the leaves in black. Combat light infestations of aphids, by spraying the undersides of the leaves vigorously with water 3 times, once every other day, in the early morning. Spray them with insecticidal soap every 2 to 3 days if they congregate in great numbers. A "light” horticultural oil spray on juniper foliage in early spring suffocates over wintering eggs. If aphids persist in spite of the insecticidal soap, spray juniper foliage with a neem insecticide 2 or 3 times at 10-day intervals instead. For more information see the files on Controlling Aphids
Small Bumps On Leaves And Twigs caused by Juniper Scale
Scale insects form groups of small bumps or blister-like outgrowths on stems and leaves. These are waxy shells that protect the insect feeding beneath. Early in the season they are white, then they dull to gray, then black, and are about 1/10 to 2/5 inch in diameter. Scale insects usually appear on juniper twigs, where they join branches, or close to growing tips. They cause needles to turn yellow, and secrete honeydew, which covers leaves and encourages sooty mold. Spray juniper foliage with light ("superior") horticultural oil to smother scale insects. Sprayed in early spring before new growth begins, it will kill over wintering eggs. For more information see the file on Controlling Scale
Leaf Tips Die due to Midges
Tiny yellow maggots of a small fly, the juniper midge, cause blisters at needle bases and kills leaf tips. Control midges by picking off and destroying the infested twigs. Spray the whole shrub with insecticidal soap. Spray shrubs with light ("superior") horticultural oil in early spring to kill over wintering eggs.
Branch Tips Turn Brown And Die Back means Blight
A blight disease caused by a fungus causes juniper branch tips to turn brown then die back until the entire branch or even the entire shrub is killed. Shrubs over 5 years old are usually not seriously affected. Avoid this disease by planting resistant juniper varieties such as Spiny Greek juniper or Hill juniper. In late winter, prune and burn affected twigs and branches. For more information see the file on Controlling Fungal Disease
Galls On Leaves; Branch Tips Die Back because of Rust.
A disfiguring disease caused by the cedar apple rust fungus sometimes covers juniper branches with bright orange galls. These swellings, an inch or more in diameter, appear on junipers that are near infected apple or crabapple trees (the disease needs both junipers and apple trees to complete its life cycle). Leaves are infected during the summer, and by the following June they develop green swellings. By fall, the swellings have turned into chocolate-brown circular galls. The next spring the galls form many long, yellow to orange "horns", especially during warm, rainy weather.
Spores released from these horns infect apple leaves, which fall prematurely. Infected juniper branch tips die, but the shrubs are usually not seriously affected. Prune out galls in early April before the horns develop. On apple trees, as many as six sprays of wettable sulfur at 10 day intervals are needed to obtain control. Begin when leaves first emerge. Plant varieties that are resistant such as: Columnar, Chinese (Pfizer), Prostrate or Andorra junipers. For more information see the file on Controlling Fungal Disease
Foliage Burned indicates Dog Urine.
Dog urine discolors leaves and even kills juniper branches, particularly of low growing types. Spray vulnerable foliage with an anti-transpirant to provide some protection. Screen the affected shrubs or spray their leaves with an aerosol pet repellent. For more information see the file Dealing With Dogs and Cats
Bark of Stems and Roots Gnawed due to Rodent Injury.
Small rodents, such as mice, sometimes gnaw bark off juniper stems and trunks in the winter, causing injury that allows disease organisms to invade. Rake mulch away from shrub bases until the ground freezes hard to deny a cozy winter cover to these pests. Repel them by wrapping shrub stem bases with guards of 1/4-inch hardware cloth. For more information see the files Dealing With Mice and Dealing With Voles