Major Gardenia Pests And Problems

For many gardeners, gardenias are typical flowering plants. They are well-liked because of the lovely blossoms and fragrances that they create.

Sadly, it might be challenging to maintain these plants. If one plant fails, a gardener might quit trying to raise any more because so many things can go wrong.

Nonetheless, there are straightforward solutions for the issues that arise when taking care of these plants.

Start scrolling if you’re a gardener who wants to learn how to raise these plants or if you want to attempt growing them again.

Gardenia Pests And Problems

Let’s take a look at some common gardenia pests and their related problems with gardenias.

1. Gardenia Pests

The pests that wreak havoc on gardenias are among their biggest issues. The following are some common pests (together with information on how to recognize and eliminate them):

A. Whiteflies

Unlike real flies, whiteflies are more closely related to scale insects, mealybugs, and aphids. They are quite tiny, measuring only 1/10 to 1/16 of an inch. They resemble tiny moths and are a powdered white color. The wings are kept over the body in a roof-like position when at rest. 

Unlike a scale, the immature stage is immobile. Whiteflies flutter quickly before settling back down when plants that are afflicted with them are disturbed.

Dialeurodes citri, a type of citrus whitefly, feeds by sucking plant sap in both its adult and immature forms. 

Similar to what aphids do, they also cause damage. The plant that has been infected can be stunted. The leaves deteriorate and perish. 

Whiteflies also secrete honeydew, which promotes the development of sooty mold fungus and makes leaves glossy and sticky.

Control

A. Remove infected leaves and any plants that are infested and treat the plants with Neem.

B. Insecticidal soap or horticultural oil sprays are effective against whiteflies, but the plant must be sprayed thoroughly so that the soap or oil contacts the insects on the underside of the leaves. 

Repeat spray three times at 5 to 7-day intervals. 

Note that foliar injury from soaps and oils may occur on plants under drought stress. So, water the plants well the day before spraying. Apply only the horticultural oils or insecticidal soaps if temperatures are below 90 °F, and apply it very late in the day to prevent foliar injury.

Apply horticultural oil sprays when there is no rainfall in the forecast for the next 24 hours.

C. If stronger insecticides become necessary, products containing pyrethrin, bifenthrin, cyfluthrin, permethrin, cyhalothrin, esfenvalerate, or acephate can be used. 

Acephate is a foliar systemic insecticide and may provide better control than other contact spray insecticides. Soil-applied insecticides, such as imidacloprid or dinotefuran, can give season-long control of whiteflies. 

These are applied as a soil drench or as granules, which are watered into the soil. Soil-applied insecticides are most effective if applied in spring as new growth appears.

B. Scale Insects

Due to their unique appearance, scales are frequently mistaken for either plant parts or disease organisms by gardeners. This is because scales are peculiar insects. 

Female adult scales are small, motionless, and lack any discernible legs. Depending on the species, they secrete a waxy covering with a wide range of shapes and colors. Mature males are often relatively tiny and equipped with wings that allow them to fly to locate females.

Scales feed on plants by piercing the leaf, stem, or branch with their mouthparts and sucking sap. Their feeding can weaken or kill branches. Heavily-infested gardenias are often stunted with small flowers and leaves. Leaves may yellow and drop early. Like aphids, soft scales excrete honeydew. Armored scales do not excrete honeydew. The growth of the sooty mold fungus on the honeydew results in leaves that are covered in dark fungal growth.

Adult scales are relatively well protected from traditional contact insecticides by their waxy covering. Their immature forms, called crawlers, are susceptible.

Control

A. Scale insects are typically kept in check by a variety of natural enemies, including ladybird beetles (ladybugs) and parasitic wasps. 

Light infestations can usually be treated by scraping the scale off or by cutting off and destroying the affected branches.

B. A great and effective product for controlling scale is horticultural oil. 

Horticultural oil is a safe alternative that is especially suitable for sensitive locations where humans will be present immediately after treatment. Oil sprays aid in the preservation of beneficial insect species because of their brief lasting effects. 

Oil sprays used in agriculture cause suffocation and death. Spray in the early spring to eradicate any adults, crawlers, or eggs that overwintered. When springtime new leaves begin to expand, repeat repeated spray applications. At least two further spring applications must be made at intervals of five to six weeks. Spray the plants liberally with oil so that it drips or “runs off” from the tops

Follow the label directions for mixing rates with water. Typically, a 1 or 2% mixture of horticultural oil is applied. On mature foliage, apply a 2% mixture spray (5 tablespoons of oil per gallon of water). During the spring, as new tender growth appears, apply 1% mixture spray (2½ tablespoons per gallon of water).

Insecticidal soap sprays work well to control soft-scale adults and crawlers. Like with a horticultural oil spray, spray soaps when temperatures are below 90 °F, and spray in the evening to reduce the drying time of the spray. Spray the plants thoroughly, so that the oil sprays drip or “run-off” from the upper and undersides of leaves, branches, and trunk. Follow the label directions for mixing and use.

In terms of traditional contact insecticides, only the crawler stage is susceptible. Recommended insecticides for use against crawlers include the following: acephate, permethrin, cyhalothrin, cyfluthrin, bifenthrin, and esfenvalerate. 

Apply these materials only when crawlers are present and repeat after 10 days.

Soil-applied insecticides can give season-long control of scale insects. Dinotefuran can control both soft and armored scales. This treatment is applied as a soil drench or as granules, which are then watered into the soil. 

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C. Aphids

Aphids have piercing mouthparts that are used for extracting plant sap. Gardenias are not severely harmed by low aphid populations, but aphid populations that are high enough to cause harm can swiftly build up. Their nutrition leads to twisted, deformed, and stunted growth. 

The quantity and quality of blooms might be decreased by severe infestations. Aphids excrete honeydew, a sticky liquid that frequently draws ants, while they feed. 

Moreover, honeydew encourages the development of ugly sooty mold fungi, which are dark in color, on the leaves.

Control

Aphids have several natural enemies, including parasitic wasps, ladybird beetles (ladybugs) and larvae, and green lacewing adults and larvae. Their natural enemies tend to keep aphid populations under control except in cool weather. Ants are sometimes present with aphid infestations which will protect them from their natural enemies. If ants are present, they should be controlled.

Aphids can be hosed off with a strong stream of water directed above and below the leaves. 

Spray frequently with water, repeating as needed, focusing on new growth. Gardenias can also be sprayed with insecticidal soap or horticultural oil to control aphids. Insecticidal soap or horticultural oil must be sprayed onto the aphids to be effective. 

Repeat spray three times at 5 to 7-day intervals. Foliar injury from soaps and oils may occur on plants under drought stress. Water the plants well the day before spraying. Only apply horticultural oils or insecticidal soaps if temperatures are below 90 °F, and apply very late in the day to prevent foliar injury.

Read Also: How to use Natural Vinegar Spray for Aphids

While higher toxicity insecticides are available, it is important to note that aphids are very difficult to control because they multiply so rapidly. Leaving even one aphid alive can quickly result in a population explosion. In addition, these insecticides kill the natural enemies of aphids.

If stronger insecticides are deemed necessary, the following are available in homeowner-size packaging. Sprays containing acephate, bifenthrin, cyfluthrin, permethrin, cyhalothrin, esfenvalerate, malathion, neem oil, or pyrethrin will control aphids. Soil drenches or granular applications of imidacloprid or dinotefuran will control aphids and last longer within the plant to prevent future infestations. See Table 1 for products containing these insecticides.

D. Thrips

Thrips are slender, dark-colored insects with fringed wings. Adults are less than 1/16 inch in length. To see these fast-moving pests, inspect new growth with a magnifying lens. Thrips are typically found on leaves and between flower petals. Both adults and nymphs (immature insect stages that resemble adults but smaller) feed by scraping surface cells to suck plant sap.

When thrips feed on flower buds, the flower may die without opening. With a light infestation, their feeding causes leaves to have silvery speckles or streaks. With severe infestations, flowers are stunted and distorted and may turn brown and die.

Thrips also feed on expanding leaves, which creates purplish-red spots on the undersurfaces and causes foliage to severely curl or roll, then drop prematurely.

As a result of their small size, thrips are difficult to detect before damage is obvious. 

Control

Several naturally-occurring enemies feed on thrips. Contact insecticides should be avoided as much as possible to prevent killing these beneficial insects, which reduce thrips populations. Grass and weeds in the area should be kept mowed or removed when possible.

If it becomes essential to spray an insecticide, the following are available in homeowner-size packaging: bifenthrin, cyfluthrin, cyhalothrin, permethrin, esfenvalerate, acephate, or spinosad. Spinosad and acephate are foliar, systemic spray insecticides that will better control thrips that are within flower buds than will contact insecticides. 

Spray when thrips are present and again in 7 to 10 days. Soil drenches or granular applications of dinotefuran or imidacloprid will give some thrips suppression. See Table 1 for specific products.

E. Spider Mites

Mites are not insects. They are more closely related to spiders, having eight legs as adults rather than six. Spider mites are extremely small (about 1/50-inch long) and are somewhat difficult to see on a plant without a magnifying lens.

One way to make them easier to detect is to hold a piece of white paper under a branch and then tap the branch sharply. If still not visible, wipe your hand over the paper. If mites are present, red streaks will be seen.

Two-spotted spider mites (Tetranychus urticae) are pests on gardenias in South Carolina. While these mites may be present throughout the growing season, their populations tend to reach damaging numbers during hot, dry weather.

Mites have piercing-sucking mouthparts. They suck plant sap, typically feeding on the lower surface of a leaf. Early damage is seen as yellow or white speckling on the leaf’s upper surface. The shape of new leaves may be distorted as a result of their feeding.

Fine webbing may be seen on the undersides of the leaves. With severe infestations, webbing may cover both sides of leaves as well as branches. Webbing can collect dust and debris and makes the plant appear untidy.

Control

Both beneficial insects, such as lacewings and lady beetles, and predatory mites prey on spider mites. Predatory mites are about the same size as spider mites but can be distinguished from spider mites by their long legs and the speed with which they move.

Several species of predatory mites, lacewings, and lady beetles are available commercially for use as biological control agents.

A strong spray of water is a non-chemical control option that removes eggs, larvae (six-legged immature stage), nymphs (eight-legged immature stage), and adult mites. Be sure to spray the lower surfaces of the leaves and repeat as needed.

This method is most effective with light infestations as seen with early detection. An important advantage of this control method is that populations of natural pest enemies are not harmed.

Insecticidal soaps and horticultural oils are effective to control options for spider mites and are essentially nontoxic to humans, wildlife, and pets, and only minimally toxic to beneficial predators.

When using these products, good coverage is critical to ensure contact with the pest, and reapplication may be needed as determined by follow-up monitoring for the pest.

Foliar injury from soaps and oils may occur on plants under drought stress. Water the plants well the day before spraying. Spray very late in the day, and do not spray with soaps or oils if the temperature exceeds 90 °F.

When growing gardenias, the use of broad-spectrum insecticides should be avoided as much as possible, as these products can kill off natural enemies that help keep spider mite populations in check. 

Also, avoid pesticides that claim to “suppress” mites as they tend to be weak miticides. When stronger chemical control is needed, the following insecticides/miticides are available in homeowner-size packaging: tau-fluvalinate or bifenthrin sprays. 

F. Mealy Bugs

Another gardenia pest is the mealybug. Mealybugs are the most common gardenia leaf pests you will see. They are white and found in masses along the leaves of the gardenia. They tend to hide along protected areas of the plant.

Control 

These can be treated by spraying the plant with a soap solution or using a fine horticultural oil sprayed on the tops and underside of the leaves and plant.

2. Yellow Leaves on Gardenia Plants

Yellow leaves are the second biggest ailment of gardenia plants. There are three things will cause yellow leaves on your plants to include:

A.  Cold Temperatures

Gardenia plants don’t like being outdoors in temperatures below 60 degrees Fahrenheit. If you live in a climate where temperatures dip in the evening or at other times of the year, consider keeping your plants in pots that can be moved indoors.

B. Drainage Problems

If their soil isn’t well-drained, their leaves will turn yellow rather quickly. To remedy this problem in potted plants, place the pots up on marble, so the pot base is never sitting in water. Plants in the ground may need to be moved when they are dormant.

C. Soil Problems

Add a soil acidifier or you can use azalea fertilizer, blueberry fertilizer, or MirAcid. Outdoor plants can benefit from pine bark mulch.

3. Gardenia Bloom Problems

Below are the problems that gardenias experience while blooming. They include:

A. Blooms won’t open 

Nothing can be more disappointing to a gardener than when spring arrives, and the gardenia blooms are hard and won’t open. 

This problem can be solved by doing the following:

A. Check the soil pH

It should be between 5.0 and 6.0 (slightly acidic). Adjust the soil if necessary.

B. Proper drainage 

Make sure your plant doesn’t have “wet feet.”

C. Temperature

These plants need warm temperatures to bloom. Bring your plants indoors if they are in pots when the temperatures dip below 60.

B. Bloom Drop

This usually happens when a plant is moved right before or when the plant is blooming. Plants should only be transplanted after they have bloomed for the season.

C. No Bloom

It happens when you prune a plant too late in the year. The best time to prune the plant is right after the blooms die for the season. 

Be sure to know what type of gardenia you have before you prune; some varieties bloom twice in a season.

FAQ

Conclusion

We hope that this article was helpful. For more enlightenment, do well to leave a comment in the comment section below.