Arborvitae Diseases, Symptoms & Management – Bagworms, Spidermites & More!
- The oldest branchlets turn brown in autumn and fall off
- Branchlets rather than scale leaves are shed in autumn as a normal part of the plant development
Kabatina Twig Blight
- Tips of one-year-old branches die and turn brown or ash gray. These remain on the shrub for many months. Larger branches can be invaded and girdled. On the dead tissue where it meets the still-living wood, small, black, pimple-like fungal fruiting structures form. Microscopic examination reveals oval colorless spores.
- Prune and destroy infected twigs and branches. Both Kabatina and Phomopsis twig blight can occur on the same plant. Apply mancozeb to protect the foliage.
Pestalotiopsis Tip Blight
- Twig tips turn tan to brown in color and have black pimple-like fungal fruiting structures dotting their surface.
- Protect plants from winter injury, drought, and other stresses. Apply copper to protect foliage.
Phomopsis Twig Blight
- Tips of branches die and turn brown or ash-gray. These remain on the shrub for many months. Larger branches can be invaded and girdled. On the dead tissue where it meets the still-living wood, small, black, pimple-like fungal fruiting structures form.
- Prune and destroy infected twigs and branches. Both Kabatina and Phomopsis twig blight can occur on the same plant. Apply thiophanate methyl when new growth is present
Other Arborvitae Diseases, Pests, and Signs of Problems
- Bagworm is a type of moth whose caterpillars feed voraciously on Arborvitae leaves and twigs. Signs of bagworm include defoliation and characteristic 2″ long bags of tough silk that hang like an ornaments from the tree’s branches. A bagworm infestation can cause severe defoliation which can retard the growth of the tree and make the tree vulnerable to secondary pests.
Handpicking the bag cases from the trees in the Winter and Early Spring provides good control because you remove the eggs before they hatch. You may need to use a pair of hand pruners to cut the bag cases off of twigs to avoid damaging the plant – the silk these insects produce to tie the bag cases to twigs is surprisingly strong. Put the bag cases into a plastic bag, seal it up tightly, and send it out with the trash. If they have started to hatch and you miss some with the handpicking, you can spray to control the escapees. While they are still very small – under 1/2 inch – Bacillus thuringiensis provides good control. Otherwise Bayer Multi-Force Insect Killer, Bonide Caterpillar Killer (lambda-cyhalothrin), Pyrethrins plus piperonyl butoxide, and Captain Jacks Deadbug Brew (spinosad) are labeled to control bagworms on Spruce.
These pests can cause Arborvitae leaves to gray or brown. There’s a “white paper” test you need to perform, and it’s very simple. You go to one of your trees with a sheet of clean white paper and shake the tree above the sheet. Then you study it closely in bright light. What will be immediately obvious are small pieces of plant material on the paper, but upon closer inspection you may see some very small bugs. These aren’t Spider Mites – they’re just bugs. You have to look even closer – find the tiniest black specks you can see (and what you may think is part of the paper initially)…focus on these. Find two or three, and see if they start to move relative to each other. If you can find these – there are your Spider Mites. PureSpray Green is a very effective way to control Spider Mites on Arborvitae’s. This product controls all life stages of unwanted insects. Your Arborvitae’s “mite” have a problem. Buy PureSpray Green today and take Control!!
One cultural technique that helps keep mite populations in check is periodically syringing mite-prone plants with a forceful spray of water. This forceful spray not only knocks off and kills the spider mites, but also dislodges the webbing that collects dusts and deters the natural predators. It’s also important to keep plants from becoming drought stressed in hot weather. Plants under stress are more vulnerable to spider mite attack. If cultural controls don’t work, then pesticide sprays may be needed if significant damage is showing up on your plants. Since mites aren’t insects, most garden insecticides are not very effective. There are specific miticide chemicals for mite control, but they’re not readily available to home gardeners. Two options that are available are insecticidal soaps and horticultural oils. Insecticidal soaps are only moderately effective against mites. For best results good coverage to both the upper and lower leaf surfaces is essential. (Remember most mites are on the bottom of the leaves.) The soap is only effective on the mites that are contacted with the soap spray. Eggs are not harmed, so repeat applications are usually needed within seven to ten days in hot weather. Additional treatments may be needed. During the growing season horticultural oils may be applied at the summer rate… but be sure to check the label for any hot weather precautions. Horticultural oils may also be used on dormant plants in the spring at a dormant application rate for controlling overwintering adult mites and mite eggs.
Aphids suck the sap from the Arborvitae, slowing down the tree’s growth and can cause leaves to yellow, brown or wilt. PureSpray Green is very effective at eliminating insects, such as Aphids. Buy PureSpray Green Today!
The sooty, charcoal-smoky mold that can spread over an arborvitae tree is actually a fungus that attacks the leaves and branches of the tree. The fungus doesn’t have a parasitic relationship with the arborvitae it spreads over, getting its nourishment instead from insect honeydew secretions. The sooty mold is passed in the wind from tree to tree, in spore form, where it sticks to the insect secretions, germinates and strands outward. This coating of mold serves to block light from reaching the chlorophyll in the leaves, hampering the arborvitae’s ability to produce food for itself. PureSpray Green in an effective way to control Mold. Buy PureSpray Today
This is another type of fungus that takes the form of a dusty-looking white or gray film, which most often afflicts the leaves of the arborvitae. They begin as separate, circle-shaped white blotches and eventually expand and blend into neighboring spots of mildew infestation to form a blanket of mildew.
Ideal conditions for mildew to grow and thrive on arborvitaes are humid weather, cramped placement of plants and shade. As with sooty mold, powdery mildew steals nutrients from the tree until the tree finally weakens and dies from starvation and illness. PureSpray Green works like a chemical pesticide but without the harsh chemical. This concentrate makes up to 25 gallons of finished spray. Therefore, a little bit goes a long ways. Purchase PureSpray Green today and control Powdery Mildew before it is too late!
Cankers affect the bark of an Arborvitae and are characterized as dad spots on the bark of the tree, cause by bacteria or fungi. Cankers sometimes take root on Arborvitae tree bark after a gouge or other injury has taken place as a result of mechanical injury, giving canker-producing fungi an opening to infestation.
When canker diseases spread, they tend to kill off one distinct area of bark at a time. These are known as target-shaped cankers, specific areas that grow and lead to a massive canker-ridden area, actual under-the-bark wood decay and eventual tree death.
Diffuse cankers are more rapid and widespread from the outset, frequently overwhelming a tree’s self-defense mechanisms and making effective treatment difficult.
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