Diseases Of Holly Bushes: Pests And Diseases Damaging Holly Bushes
By: Nikki Tilley, Author of The Bulb-o-licious Garden
While holly bushes are common additions to the landscape and generally quite hardy, these attractive shrubs occasionally suffer from their share of holly bush diseases, pests and other problems.
Common Pests and Diseases Damaging Holly Bushes
For the most part hollies are extremely hardy, suffering from few pests or diseases. In fact, most problems that do occur are usually associated with other factors, such as environmental conditions. However, pests and diseases damaging holly bushes can happen so it’s important to become familiar with the most common ones for help in prevention as well as treatment.
Holly Tree Pests
Holly tree pests such as scale, mites, and holly leaf miner are the most commonly seen affecting hollies.
- Scale – While light infestations of scale can usually be controlled by hand, scale control for heavier infestations generally requires the use of horticultural oil. This is usually applied prior to new growth to kill both adults and their eggs.
- Mites – Spider mites are common causes of discoloration and speckling of holly foliage. While introducing natural predators,such as ladybugs into the landscape can help minimize their numbers, a nice healthy dose of soapy water or insecticidal soap sprayed regularly on plants can also help keep these pests at bay.
- Leaf Miner – The holly leaf miner can cause unsightly yellow to brown trails throughout the center of leaves. Infested foliage should be destroyed and treatment with a foliar insecticide is often required for leaf miner control.
Holly Tree Disease
Most diseases of holly can be attributed to fungus. The two most prevalent fungal holly tree diseases are tar spot and cankers.
- Tar Spot – Tar spot usually occurs with moist, cool springtime temperatures. This disease begins as small yellow spots on the leaves, which eventually become reddish brown to black in color and drop out, leaving holes in the foliage. Always remove and destroy infected foliage.
- Canker – Cankers, another holly tree disease, produce sunken areas on the stems, which eventually die out. Pruning out infected branches is usually necessary in order to save the plant.
Improving air circulation and keeping debris picked up is good for prevention in both cases.
Environmental Diseases of Holly
Sometimes a holly bush disease is due to environmental factors. Such is the case for problems like purple blotch, spine spot, holly scorch, and chlorosis.
- Purple Blotch – With purple blotch, leaves of holly become splotched with purple-looking spots, which are usually brought on by drought, plant injury, or nutritional deficiencies.
- Spine Spot – Spine spot is similar with gray spots edged with purple. This is most often caused by leaf punctures from other leaves.
- Scorch – Sometimes rapid temperature fluctuations in late winter can lead to browning of the leaves, or holly scorch. It is often helpful to provide shade to plants most susceptible.
- Chlorosis – Iron deficiency can lead to the holly bush disease, chlorosis. Symptoms include pale green to yellow leaves with dark green veins. Reducing pH levels in the soil or treating with supplemental iron-fortified fertilizer can usually alleviate the issue.
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Identifying Harmful Holly Tree Diseases
Identifying diseases that are harmful to a holly tree is important to a tree’s owner. Being able to identify the types of disease that may cause the tree to become damaged or suffer a premature death will help a holly tree owner apply a fix that will save the tree and prolong its life. Holly trees or shrubs are a common plant that produces holly leaves that are commonly found in homes during the Christmas holiday.
The types of diseases that are harmful to holly trees include tar spot, cankers, purple blotch, spine spot and chlorosis. Each of these diseases are discussed in further detail below.
Tar spot is a fungal infection that appears on the holly tree. They occur in the spring during periods when the weather is cool and moist. It appears as a yellowish spot on the leaves of the holly. The leaves that have tar spots will turn brown, black, and then eventually fall off.
Inspecting the leaves will reveal incidents of tar spots. When tar spots are noticed, those leaves should be removed immediately to prevent its spread to other leaves on the holly.
Cankers are also a fungal infection, affecting the stems of the leaves. Cankers cause spots on the stems, which undetected will cause the plant to die. Inspection will reveal cankers which are sunken in the stems of the holly. The stems should be cut out and removes from the holly tree immediately to prevent and spreading and further damage.
A purple blotch appears when a holly tree is injured, damaged or if it is dry and without nutrients. Purple blotches appear on the leaves of the holly and, as the name indicates, are purple. Removing affected leaves will eliminate the spread of this disease.
Spine spot occurs when the leaves of the holy perforate. As you should know, the leaves of the holly are sharp and pointy so a perforation will cause them to not grow properly. Spine spot appears to be similar to purple blotch except that the leaves turn gray with a purple ring.
Perforated leaves of the holly that develop spine spot, as with other infected leaves, should be removed from the holly tree.
A holly tree that is iron deficient will develop a condition known as chlorosis. The leaves of the holly appear yellow or pale green with deep green veins. Iron deficiency occurs when the pH balance of the soil is out of balancing. An additive to balance the pH level of the tree’s soil will correct this condition and stop the spread of chlorosis.
Regular and periodic inspection of the leaves and stems of the holly tree will reveal any of these diseases. You should maintain a list of the commonly occurring holly tree diseases and their appearance to identify them and address infections.
Provide the best care you can for your holly plants. Though hollies are known for their resilience, they are not immune to disease. Healthy plants can better fend off disease and spring back to wellness, particularly when compared to stressed, weakened plants. Grow hollies in full sunlight to partial shade. Maintain moist, well-drained soil, rich in organic content. Lay a 1- to 2-inch layer of organic mulch, such as pine needles or wood chips, over soil without pressing it against holly trunks. Mulch aids in moisture conservation while deterring weed growth.
Dead Leaves May Not Mean The Branch Is Dead
However, don't rush to prune out branches because they may not really be dead. Plants may exhibit discolored leaves but still have live buds. Once the ground thaws and the shrub can absorb water through its roots, it may recover. One way to tell whether a branch is alive is to gently scratch a small nick in the bark with your thumbnail. If you see a green layer beneath the outer bark, the branch still is alive. Although it may drop its damaged leaves, it will flush new ones in the spring.
If you do have sections of dead branches, you should prune them out. Hollies are very tolerant of being pruned and will often re-sprout even if they are cut to the ground. Many people do not prune their hollies as they like the symmetrical shape they naturally assume. However, they tolerate pruning very well. Wait to prune your holly until it begins to show new growth in the spring. At this point, you can prune out the dead tissue above the new, emerging leaves.
When to plant:
Plant during milder months of spring or fall to avoid heat or cold stress.
Where to plant:
Choose a sunny to lightly shaded site with fertile, well-draining soil that will stay evenly moist.
How to plant:
Dig a hole 2 to 3 times wider than the root ball and not quite as deep. Remove plant from container and gently tease out roots or slice the root ball in several places if potbound. Mix compost into the planting hole. If soil pH is alkaline or neutral, add bark, wood chips, or peat moss to the backfill to increase acidity. Place the plant in the hole so the top of the root ball is slightly above or level with the soil surface. Fill in the hole, tamp down soil around the base, and water well. Mulch with 2 to 3 inches of organic matter to conserve moisture and suppress weeds, but not not cover the top of the rootball.