Understanding Magnolia Scale Insects and Their Impact

Magnolia scale insects are a type of sap-sucking insect that can cause significant harm to magnolia trees.

These insects are small, white, and oval-shaped, making them difficult to spot at first glance.

They feed on the sap of the tree, which can weaken the plant and make it more susceptible to disease and pests.

Magnolia scale insects can be found in many parts of the world, including North America, Europe, and Asia.

They tend to thrive in warm and humid environments, which is why they're often found in regions with mild winters and hot summers.

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Magnolia scale insects are small, soft-bodied insects that feed on the sap of magnolia trees. They are typically brown or gray in color and have a waxy or cottony coating on their bodies.

These insects can grow up to 1/4 inch in length and have a distinctive pear-shaped body. They have six legs and two antennae, but no wings.

Magnolia scale insects are usually found on the stems and branches of magnolia trees, particularly on the leaves and flowers. They are most active during the spring and summer months.

The female magnolia scale insect lays her eggs on the underside of the leaves or on the stems of the tree. The eggs hatch into tiny, wingless insects that feed on the sap of the tree.

The magnolia scale insect's feeding habits can cause damage to the tree's leaves and stems, leading to reduced growth and an increased risk of disease.

Magnolia scale insects are a pest of magnolia trees, and some varieties like saucer, star, and lily magnolias may be more heavily impacted.

In Kentucky, magnolia scales overwinter as dark-colored nymphs on the relatively new growth of their host tree. These immature scales resume feeding and continue to grow and mature in the spring.

The life cycle of magnolia scale insects is quite unique, with males emerging as small fly-like insects in late July or early August to mate with females, which then die.

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In Kentucky, Magnolia scales overwinter as dark colored nymphs on the relatively new growth of their host tree. This is a crucial survival strategy that helps them make it through the winter months.

These immature scales will resume feeding and continue to grow and mature in the spring. As they grow, they'll develop into their adult forms, which are characterized by their pink gnat-like appearance.

Males will complete their development into these adult forms and will then mate with females in the early summer. After mating, the males will perish.

Females will continue to feed and develop, eventually turning a noticeable purple-brown color in June and a yellow-brown color by July. They'll also produce eggs that hatch inside of them.

In July and August, the female's eggs will hatch and immature crawlers will emerge. These crawlers will begin searching for a spot to feed, and eventually, they'll settle down on young twigs to overwinter and start the cycle anew the next year.

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Magnolia trees are the primary hosts of magnolia scale, but some varieties are more susceptible to infestation than others.

Saucer magnolias, star magnolias, and lily magnolias are particularly vulnerable to the damage caused by magnolia scale.

These varieties often display more pronounced symptoms of infestation, such as yellowing leaves and stunted growth.

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If you catch the infestation in the initial, late summer crawler stage, blast the insects off with a sharp stream of water from the hose. Repeat as needed.

Crawlers are the most susceptible to control stage of a scale insect's life. To treat the crawlers, you should be monitoring for their emergence, which can be done by visually checking in late July through August for magnolia scale crawlers, or by placing pieces of black electrical tape near scale populations and monitoring the tape for the crawlers.

Horticultural oils kill crawlers by suffocation or after penetrating over-wintering stages of the insect. Insecticidal soaps are long chain fatty acids that kill susceptible insects through direct contact. Like horticultural oils, they require thorough coverage.

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If adult scale is detected, insecticides aren't very effective. Try scraping the insects off branches with a gloved hand or Popsicle stick. Adults cannot climb back on the tree.

Here are some options for scale insect crawler control:

Prevention is the best medicine – a healthy well-watered and well-maintained tree is less likely to develop a scale infestation.

Magnolia scales are known for producing large amounts of honeydew, a sugary liquid that can attract other insects and pests. This sticky substance can also recruit black sooty mold fungus, which can cover branches and the trunk.

Accumulations of honeydew can be shiny and sticky, making them difficult to clean. Heavy infestations can cause individual branches to die and even kill the tree itself.

Mature female magnolia scales can grow up to ½ inch in diameter and appear as large pink-orange or brown bumps on the tree. They often have a white waxy powder on their body.

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Males, on the other hand, resemble small pink gnat-like insects that can fly and mate with females.

Other signs of an infestation include ants, wasps, and other insects visiting the scales to consume the sugary feces. These insects can be more noticeable than the scale insects themselves.

Here's a breakdown of the potential damage caused by magnolia scales:

If you catch the infestation in the initial, late summer crawler stage, blast the insects off with a sharp stream of water from the hose. This can be repeated as needed.

Adult scale is detected by the presence of white shells, and insecticides aren't very effective in this stage.

Try scraping the insects off branches with a gloved hand or Popsicle stick. Adults cannot climb back on the tree.

If it's only a few branches, another option is to prune these branches off.

A systemic insecticide can be mixed with water and applied to the tree roots. However, it takes time for the insecticide to be absorbed and delivered to the insects.

You should apply systemic insecticides several weeks before the eggs hatch.

Multiple applications might be necessary to eradicate magnolia scales.

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Systemic insecticides like imidacloprid and dinotefuran can be used to control soft scale species like the magnolia scale.

An application of imidacloprid in May, after flower petals have fallen from the tree, will provide protection against magnolia scale insects.

Dinotefuran applications can be made in August to provide control the next year, giving you a head start on potential infestations.

Systemic insecticides are a great option for controlling soft scale species like the magnolia scale.

You can use imidacloprid, a systemic insecticide found in Bayer Tree & Shrub, for control.

Timing is everything when using imidacloprid, so apply it in May after flower petals have fallen from the tree.

Dinotefuran, found in Ortho Tree & Shrub, is another systemic insecticide option for controlling soft scale species.

To use dinotefuran effectively, apply it in August to provide control the next year.

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You can control magnolia scale with spray treatments, but timing is everything. Apply a product containing bifenthrin, carbaryl, cyfluthrin, horticultural oil, insecticidal soap, malathion, or permethrin in late August or early September, followed by a second treatment 10 to 14 days later.

For best results, choose a product that contains bifenthrin, carbaryl, or cyfluthrin. These are effective against magnolia scale and can be used in late August or early September.

Systemic insecticides, such as those containing imidacloprid, can also be effective in magnolia scale control. These must be drenched into the root zone in early May.

Dormant oils can be used for control, but must be applied in March, before buds open. This is a good option if you want to avoid using chemical insecticides.

Proper timing of the application of these products is critical. Apply spray treatments in late August or early September, and follow with a second treatment 10 to 14 days later.

To detect magnolia scale insects, you need a good quality magnifying glass, an essential tool for any gardener. This will help you closely observe your plants several times per week.

Early detection starts at the nursery. Bring your magnifying glass with you when purchasing a magnolia tree to ensure you are buying a pest-free plant. Nurseries do a good job of monitoring their plants, but they can miss some pests.

Closely observe your magnolia(s) before leaves bud in early spring. Females from the previous year are dead, and their white, waxy coating is gone, leaving them appearing dark tan. Nymphs that have overwintered will be visible through the magnifying glass.

Monitor your magnolia(s) weekly as temperatures warm. Overwintering nymphs will mature, females will lay eggs, and they will begin creating their white convex shells (visible to the naked eye).

Initial infestation will occur in late summer. Be on the lookout for pinhead-size, black to reddish insects in the crawler stage from August through October.

Here are some common signs of a magnolia scale infestation:

Magnolia scale insects are notorious for their ability to spread quickly, often traveling from tree to tree via birds, squirrels, and other small animals.

These insects can infest a wide range of magnolia species, from the popular Southern magnolia to the evergreen sweetbay magnolia.

Their impact is significant, as magnolia scale insects can reduce tree growth and cause leaf drop, ultimately affecting the tree's overall health and appearance.

A heavy infestation can also lead to the production of honeydew, a sweet, sticky substance that attracts ants and promotes the growth of sooty mold.

Infested trees may become more susceptible to disease and pests, creating a cycle of decline that can be challenging to break.

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