Magnolias are cherished for their stunning, blooms and lush green foliage, but they can sometimes fall victim to a sneaky pest: magnolia scale. This pesky insect, often overlooked until the damage becomes apparent, can weaken these beautiful trees, causing stunted growth, yellowing leaves, and even dieback if left untreated. Magnolia scale is one of the largest soft scales in North America, primarily targeting magnolias like the Saucer, Star, and Cucumbertree varieties.
Telltale signs of an infestation include sticky, honeydew-like substances on the leaves or ground and the appearance of black sooty mold. Catching these signs early is crucial to maintaining the health of your magnolia. Fortunately, with the right approach and timely treatment, magnolia scale can be effectively managed, restoring the tree’s vitality. Understanding how to identify, treat, and prevent this pest ensures your magnolias remain healthy and vibrant, showcasing their full beauty throughout the seasons.
What is Magnolia Scale?
Magnolia scale is an insect that primarily targets magnolia trees, using its needle-like mouth to suck out the tree’s sweet sap. Scales weaken magnolia trees over time and also leave them susceptible to other problems.
Magnolia scales are a part of the group of “soft scales”, which means they do not have a shield to protect themselves. Soft scales produce honeydew, a sugar-rich liquid that’s produced by some insects after sucking liquid from trees.
The scale insects feed by attaching themselves to the tree and sucking out sap, which weakens the tree over time. As they feed, they excrete a sticky substance called honeydew, which can lead to the growth of black sooty mold on the tree’s leaves and surrounding surfaces. This not only makes the tree unsightly but also attracts other pests like ants and wasps. If left untreated, magnolia scale can cause significant damage, including stunted growth, yellowing leaves, and even branch dieback, ultimately compromising the health of the tree.
What does Magnolia Scale Look Like?
Magnolia scales are one of the largest scale species in North America, with mature females growing up to ½ an inch in diameter. They often appear as small, brown, or pinkish bumps on branches and stems, blending in with the tree’s bark, making them easy to overlook if you aren’t checking your magnolia regularly or know what to look for.
How Does Magnolia Scale Spread?
Magnolia scale can spread through both the purchase of infected trees and the movement of its mobile nymphs, known as crawlers. When buying magnolias, it’s crucial to inspect them closely, as scale can be difficult to detect. Scales often resemble bumpy bark but are actually tiny insects that can weaken a tree over several growing seasons. Use a magnifying glass to look for small bugs, unusual bumps on twigs, or sooty black residue on leaves and bark. Avoid purchasing trees with these signs, and be cautious if other magnolias at the nursery show evidence of scale.
Once a tree is infected, the scale will persist through multiple growing seasons. The life cycle begins with nymphs feeding on new growth in early spring. By early summer, males and females mate, and eggs hatch in July and August. These new nymphs then settle on the tree to survive through winter, continuing the cycle the following year. In addition to being spread by purchasing infected trees, the crawlers can move to other trees via wind, birds, or insects, making it vital to address infestations promptly to protect other magnolias in your landscape.
How To Treat Magnolia Scale
Magnolia scale can cause significant damage if left unchecked, but with the right approach, you can effectively manage and eliminate it. Early detection is key, so keep an eye out for the signs, like sticky honeydew and sooty mold. With timely intervention, you can protect your magnolias and keep them thriving for years to come.
Types of Magnolia Scale Treatment
There are several effective ways to treat magnolia scale, depending on the severity of the infestation and the time of year. These include:
- Horticultural Oil: Applying horticultural oil in late summer or early fall can smother the scale and their eggs, reducing the population.
- Insecticidal Soap: A safe and effective option for treating smaller infestations, insecticidal soap can be applied during the crawler stage when the young scales are most vulnerable.
- Systemic Insecticides: These are absorbed by the tree and target the scale from within, making them effective for larger infestations. They are best applied in early spring.
- Pruning: For heavily infested branches, pruning can help remove the worst-affected areas and prevent the spread of scale to other parts of the tree.
Each treatment option has its own benefits and timing, so it’s important to choose the right method based on your tree’s needs and the scale’s life cycle.
Chemical Sprays
Chemical sprays can be an effective method for controlling severe magnolia scale infestations, particularly when other treatments aren’t enough. Insecticides containing active ingredients like imidacloprid, dinotefuran, or acephate are commonly used. These chemicals are typically applied in early spring or late fall when the scales are most vulnerable.
It’s crucial to follow the manufacturer’s instructions carefully to ensure proper application and avoid harming beneficial insects. Because chemical sprays can affect the environment, they should be used as a last resort, especially in areas where beneficial insects and pollinators are active. Always consider less invasive methods first.
Insecticidal Soaps
Insecticidal soaps, similar to chemical sprays, are chemicals that kill scale through direct contact. Coverage with insecticidal soap is key to ensuring effectiveness. Soaps dissolve after they’re applied and leave no residue, so repeat applications may be required to be effective.
If scales crawl over one another in layers, insecticidal soaps will only reach the upper layers. Repeated applications may be required in order to kill all pests.
Insecticidal soaps can burn plant leaves, so it’s important to follow all directions and read all labels to ensure that your soap of choice is safe for your tree. It’s also important to ensure the soap you’ve selected is effective against scale.
Dormant Oil
Dormant oil is a highly effective, eco-friendly treatment for controlling magnolia scale during late winter or early spring. This horticultural oil smothers overwintering scale insects and their eggs, preventing damage when the growing season begins. It’s applied when the tree is dormant, ensuring the oil doesn’t harm the foliage. Thoroughly coating the branches and trunk is key, as scale insects often hide in crevices. Dormant oil is an excellent first line of defense, offering targeted pest control without harming beneficial insects.
One effective product is Bonide All Seasons Oil Spray, a horticultural-grade mineral oil that quickly reduces pest populations. Applying it in late winter or early spring helps bring infestations under control before the pests can spread, making it an essential tool in your pest management strategy.
Systemic Insecticides
Systemic insecticides are insecticides that are absorbed by plants through the roots. They are not sprayed on the plant, like horticultural oils or insecticidal soaps. Systemic insecticides make the tree toxic to insects feeding upon them and give the tree long-lasting protection. Because the insecticide needs to be absorbed into the tree to be effective, it needs time to work.
Soft scale species like magnolia scale respond well to systemic treatment. To treat this problem, look for insecticides that include an ingredient called Imidacloprid.
A great choice is Bonide Tree and Shrub Insect Control. This systemic insecticide is a strong product that’s effective at killing scale when applied according to directions, but it can take up to 30 days to get through the tree. Once in the tree’s system, Tree and Shrub Insect Control will stay in the tree’s system for one year, preventing further damage.
You’ll find that timing is important when applying this type of product. The best time to apply is in early spring through early fall. Don’t apply to the ground when it’s frozen. If the ground is really dry, water the tree the night before applying.
Manual Removal
Adult scales can be removed by hand, especially if they’re found on the tree in small numbers. Use a gloved hand or a popsicle stick to remove adult scale. After removal, dispose of the scale insects far from the tree to prevent re-infestation.
Scale can also be removed with a tool called a “scale scrubber,” which looks like a dish scrubber. To use a scale scrubber, gently scrub the affected branches to dislodge and remove the scales from the tree’s bark.
It’s important to note that adult female scales may already have nymphs hatching beneath them. If the scrubber is used during a time when nymphs are emerging, manual removal alone may not fully resolve the infestation. In such cases, combining manual removal with other treatments, like horticultural oil or systemic insecticides, is recommended for more comprehensive control. Regular monitoring is also essential to ensure the infestation doesn’t return.
Tropical and Subtropical Plants
Tropical and subtropical plants like hibiscus, bougainvillea, and banana plants are ill-suited for winter conditions. These plants need warmth and humidity, conditions that are impossible to maintain during winter without a controlled indoor environment. For these plants, it’s best to bring them indoors.
Pruning
If scale is only found on one or two small branches and has not yet spread to other parts of the tree, you may consider pruning to remove the problem. By cutting back and removing the most affected areas, you can reduce the scale population and prevent the infestation from spreading to healthier parts of the tree. Be sure to use clean, sharp pruning tools to make precise cuts, and dispose of the pruned branches away from your garden to avoid re-infestation. Regular pruning also promotes better air circulation and overall tree health, making your magnolia less susceptible to pests in the future.
Will Magnolia Scale Kill My Tree?
Magnolia scale can kill your tree if given enough time. Watch for signs of distress in your magnolia, including:
- Dieback. Once healthy branches may start to show signs of withering and dying.
- Sooty mold. Leaves and a portion of the trunk may become covered in black, sooty mold.
- Tree covered in strange bumps. Mature magnolia scale can turn colors that resemble the tree trunk. When this happens, you may not be able to tell you’re looking at scale. While the color may not stand out to you, the tree branches will be covered in bumps. Some branches may have bumps and others do not.
- White waxy coating. Eventually, scale develops a white waxy coating. This can look like mealy bugs, if you’re familiar with this problem. Not sure whether you’re seeing mealy bugs or scale? Take several pictures and bring them to the professionals at Platt Hill Nursery.
- Presence of many ants and wasps. Ants and wasps love honeydew! If your tree has a lot of honeydew on the branches, you may notice that your tree has become a center of activity for ants, bees, and wasps. Follow the trail of insects to see what they’re feeding on.
Scale can take several seasons to kill your magnolia. Unless it’s treated, do not assume that the scale died during the cold winter. Scale can survive on a magnolia tree and will come back in the spring, starting with young nymphs that are ready to grow and reproduce.
Is Magnolia Scale Harmful to Humans?
Magnolia scale is not harmful to humans, however, unhealthy trees can be a danger. A large tree with heavy branches can become weakened by scale. Weak branches can fall. This can damage property or even cause an injury. When handling infested branches or leaves, it’s still a good idea to wash your hands after gardening.
Protecting Your Magnolias for the Long Term
Magnolia scale can be a serious threat to the health and beauty of your magnolia trees, but with the right care and treatment, you can manage this pest effectively. Early detection, combined with appropriate treatments like horticultural oils, systemic insecticides, and manual removal, can keep your magnolias thriving.
At Platt Hill Nursery, we’re committed to helping you grow and maintain healthy, beautiful trees. We offer a selection of hardy magnolia varieties, including the stunning Royal Star and Ann magnolia trees. Magnolia trees make excellent accents or can become the crown jewel of your yard. With beautiful blossoms, these trees provide years of beauty and even fond memories of flowers in the springtime.
If you need further assistance with treating or preventing magnolia scale, our knowledgeable staff is here to guide you. Visit us today at our nursery locations in Bloomingdale or Carpentersville to find the perfect trees for your garden and get expert advice on keeping them healthy and pest-free.
