Butterfly Bush is one of the easier ornamental shrubs to grow in the home garden. The flowering season is long in most gardening zones and will attract loads of beneficial pollinators and insects to help create a healthy ecosystem in the garden. Butterfly bush, Buddleia spp, are not typically bothered by pests, but if the shrub is grown in poor conditions or becomes weak from a disease, it can be easily infested with a range of harmful pests. The good news is that often simple mechanical or cultural techniques can be used to stop an infestation and help your Butterfly Bush recover.
Common Butterfly Bush Pests
Earwigs
Damage from Earwigs, Forficula auricularia, is generally minimal on Butterfly Bush and is most often noticed on the leaves as ragged holes or partially chewed margins. In fact, Earwigs are one of the most beneficial insects for decomposing plant debris and keeping other damaging pests such as nematodes and aphids in check. Earwigs are nocturnal beetles that have pinchers on their rear ends that can deliver a sharp pinch if disturbed. During the day, Earwigs hide under pieces of bark, logs, or in weedy areas to stay cool and safe. One way to tell if the pest eating your Butterfly Bush leaves is indeed an Earwig is to place a rolled-up piece of corrugated cardboard near your shrub in the evening. Unroll the cardboard the next morning and inspect the nooks and crannies for Earwigs hiding out.
Treating Earwigs on Butterfly Bush
If the damage from Earwigs worsens, there are ways to keep this hybrid pest/beneficial insect in check. Manually picking Earwigs off plants and disposing of them in a bucket of soapy water is an easy way to keep populations low. The best time to do this task is at dusk before the sun goes down completely.
Leaving out a rolled-up piece of corrugated cardboard is also a great way to collect them overnight and dispose of them in the morning. For this to be effective, do not skip a day. If the cardboard is left for more than a few nights, the Earwigs will actually use it as a home and start to lay the next generation.
Using shallow beer or fish oil traps is a great way to collect many Earwigs in a night. Shallow tuna cans full of your liquid of choice attract the Earwigs and drown them. Diatomaceous Earth sprinkled around the base of your plants also is a great way to control Earwigs. This treatment is most effective during dry periods and must be reapplied after heavy rains. The diatoms are microscopic but extremely sharp and leave deep cuts in the exoskeleton of the beetle, resulting in death after a few days.
Preventing Earwigs on Butterfly Bush
There is only one beneficial predator of Earwigs and that is the Tachinid fly, Diptera spp. Fortunately, these flies are easy to attract to your garden just by planting their favorite nectar plants, alyssum, fennel, dill, and calendula. Other ways to keep Earwigs under control are by keeping garden beds free of damp debris for the Earwigs to hide under. Damp areas along the foundations of houses or retaining walls are a favorite daytime refuge for Earwigs to hide. Using rock and gravel as a barrier between the foundation and the garden instead of just mulch will keep these areas drier.
Blackfly
Blackfly is a type of sapsucking aphid. These pests live on the host plant, extracting sap from the leaves, stems, and any other soft tissue of the plant. Blackfly can produce many generations of offspring in a short period of time; left untreated, this pest can cause a plant to die. Blackflies can fly between plants and quickly spread. After a time, the blackfly will exude a sticky honeydew on the surface of the remaining leaves and nearby hard surfaces. This ‘honeydew’ attracts sooty mold spores and ants in large numbers. A secondary infestation of ants is difficult to get rid of because they will act as protectors and defend the blackfly who are providing food for them in the form of the honeydew.
Treating Blackfly on Butterfly Bush
Treating a plant for Blackfly is much easier in the early stages of an infestation. Hosing shrubs off with a strong stream of water is often the best treatment. This removes the Blackfly from the plant and drowns them. This may need to be repeated once a week until the insects disappear.
Using insecticides, even insecticidal soaps on Butterfly Bush is not recommended. These shrubs attract butterflies, hummingbirds, and bees in great numbers. Even the most ‘organic’ insecticide could have adverse effects on beneficial insects. Beneficial insects such as lacewings, lady beetles, and syrphid flies will keep Blackfly and other sapsucking insects in check. Attract these “good” insects by providing shelter over winter, planting plenty of annual flowers such as zinnia, cosmos, and alyssum for nectar, and only using insecticides and other chemicals in the garden when absolutely necessary.
Butterfly Bush will rapidly recover once the Blackfly has been treated. Any damaged areas of the shrub should be pruned out to clean the plant up for the rest of the season. Because most Buddleias tolerate hard pruning early in the spring and bloom on new wood, your shrub should fully regain its strength to bloom heavily the following year.
Preventing Blackfly on Butterfly Bush
Blackfly outbreaks often are a result of over-fertilizing with a high nitrogen feed. Butterfly Bush needs little in the way of nutrients when it is planted in average garden soil. Only use a fertilizer with a balanced ratio of NPK (5-5-5 is ideal) if the shrub begins to show signs of slow or sparse growth.
Buddleia Budworm
Budworm is the larvae of the Brown Moth, Pyramidobela angelarum, and has a very short, but destructive life cycle. The adult moth lays its eggs at the base of the flower and leaf buds. As the young larvae hatch, they eat the flowers and are completely hidden until there is not much left of the flower itself.
Leaves can also be affected and are used as protection for the caterpillars who often spin cottony webs around the curled leaves. The leaves will appear distorted and twisted, sometimes turning yellow. Outbreaks can be quite large if not controlled quickly. There can be many generations of Budworms in a single growing season and they can affect the overall flowering rate and growth of the Butterfly Bush.
Treating Buddleia Budworm on Butterfly Bush
Budworm can seem like one of the most difficult pests to treat on Butterfly Bush. The larvae eat until they get so heavy that they fall off the shrub and onto the ground. They will then dig in and quickly pupate to the adult moth to begin the whole process over. Late in the growing season, the last generation of adults will lay eggs that overwinter easily.
The best treatment is to prune your Buddleia spp. hard in the early spring, cutting back to 6-10 inches from the ground. This will get rid of any overwintered eggs and greatly reduce an early infestation. Throw any prunings in the trash if you have had problems with Budworm to keep them from spreading to other ornamental plants.
Because Butterfly Bush attracts many beneficial insects, using any chemical insecticides is not recommended. Bt (Bacillus thuringiensis) is only effective for a short period of time. It is safe to use around bees and butterflies, but it quickly breaks down when used in full sun locations where Butterfly Bush grows. Small numbers of the Budworms can be manually picked off and destroyed in a bucket of soapy water. The best time to harvest Buddleia Budworms is at dusk as they begin to forage.
Extremely heavy infestations can be controlled by cutting the bush down to 2-3 feet from the ground and spraying the remaining canopy with an insecticide that is OMRI certified. Dead Bug Brew is a good spray that contains the active ingredient Spinosad. Always follow the label directions and only spray at the end of the day before sunset. This is to ensure that any local honeybee populations have returned to their hive for the night and will not be affected.
Preventing Buddleia Budworm on Butterfly Bush
Frequent monitoring of your ornamental plants is a good way to catch any infestations early. Early detection gives your plants a better chance of surviving with little damage. Cut out affected stems or branches early and throw them in the trash. Do not compost any plant parts that may be harboring Budworm eggs. Cutting back Butterfly Bush hard in the spring will help to control populations on the shrub while rejuvenating its growth.
Japanese Beetles
Japanese Beetles really like your ornamental plants and can seem to show up out of nowhere just as the flowers are at their peak. So frustrating, but their timing is very predictable from year to year in parts of the United States plagued by these flashy metallic green and copper garden foes. From the end of June through to the first weeks in August, adult Japanese Beetles are hard at work feasting on flowers and leaves of at least 300 varieties of ornamental and edible plants. They are also laying many generations of eggs that hatch into grubs in well-manicured lawns across most states east of the Rocky Mountains.
Skeletonized leaves and ragged flower petals are the telltale damage left behind as they go from plant to plant. Mature trees and shrubs are much more likely to recover without any lasting issues. Perennials and annuals can be decimated in days with no chance of photosynthesizing enough to survive the rest of the growing season. Butterfly Bush that is planted in the best location possible with full sun and well-draining soil may be healthy enough to put on growth before the fall and the dormant winter period.
Image by Smurphy Pix
Treating Japanese Beetles on Butterfly Bush
Treating Japanese Beetles successfully and with as few chemicals in the garden as possible is fully dependent on the timing of treatments. By far the best way to reduce Japanese Beetles is to control the grubs that they lay in the grass. These grubs eat on grass roots for 9 months of the year in warmer locations and are a captive audience with no way of flying.
An application of beneficial bacteria spores is perfect to kill off the grubs and reduce the number of adults emerging in the summer. Milky Spore is a bacteria that only targets the grub of Japanese Beetles. The Milky Spore kills the grub and releases more spores into the soil. For this treatment to be beneficial, it must be applied before the soil temperature falls in the autumn. Soil temperatures need to be above 60 degrees F to keep the spores active. The powder should be watered in to wash the bacteria deeper in the soil. Always follow the manufacturer's instructions for the best results.
Pheromone-baited traps for Japanese Beetles do a great job of attracting all of the beetles in an area. Make sure to place the traps as far away from the plants you want to protect as your property allows and empty or replace the traps on a regular basis throughout the season.
Preventing Japanese Beetles on Butterfly Bush
Japanese Beetles are an invasive pest that is very difficult to fully get under control. They have the ability to fly and will fly some distance to find a suitable plant to dine on. Even if you have completely overcome the problem of grubs in your lawn, do not be surprised to see adults in the yard in areas of high concentration such as the East Coast and most of the states east of the Mississippi River.
Protectant repellents will need to be reapplied after watering or heavy rain, but they may be useful for protecting an area with many susceptible plants. Floating covers such as insect netting or lightweight horticultural fabric are best used for specific treasured plants and edible crops. These covers need to be placed over the plants well before the first beetle hatches.
Twospotted Spider Mites
Red Spider Mites are a common pest for gardeners that grow in hot and dry climates. They are more likely to attack plants weakened from underwatering or previous infestations. The undersides of leaves may have webbing and spider mites or the bodies of dead mites. Look for stippling of the leaves, which affects the plant's ability to photosynthesize over time. Regular inspection of plants during hot, dry weather will allow you to stop an infestation quickly with hopefully little damage to the Butterfly Bush.
Treating Twospotted Spider Mites on Butterfly Bush
Spider Mites have many natural predators that normally keep populations in balance. Overuse of broad-spectrum insecticides that kill both beneficial and invasive insects can disrupt that balance, leading to uncontrolled outbreaks. Encourage lacewings, lady beetles, minute pirate bugs, and predatory mites to your garden by growing their favorite nectar plants (alyssum, chervil, calendula, carrots) and providing a habitat for them to overwinter from year to year.
Large outbreaks of Twospotted Spider Mites can be controlled by spraying insecticidal soaps or oils at the proper time of day and following the manufacturer's directions. Any damaged portions of the shrub can be cut back to healthy wood and allowed to regrow without applying fertilizer. Overfertilizing causes dense, juicy growth, attracting more Spider Mites.
Preventing Twospotted Spider Mites on Butterfly Bush
The best way to prevent infestation is to resist the urge to overfertilize Butterfly Bush and to ensure that the shrub is not stressed by lack of water when the hot and dry weather of summer arrives. Healthy plants are much better equipped to fend off mites and large infestations. Check often for signs of Spider Mites to control any outbreaks early.
Nematodes
Soil Nematodes are more common in coastal, sandy soils. The microscopic worm lives in the soil and will attack the roots of a Buddleia shrub. Shrubs that are affected by Nematodes will have stunted-looking foliage and/or flowers. Another common symptom is drooping foliage. Watering does not revive the plant and can lead to further stress and injury to the roots. Nematodes injure the root system, allowing secondary infections by fungus or bacteria, which will eventually kill the plant completely.
Treating Nematode on Butterfly Bush
Nematodes are plant specific and do not spread to other plants. If other ornamental plants are showing similar signs to your Butterfly Bush, another pest or disease may be affecting your garden. Unfortunately, there are no Nematode controls registered for home garden use. The only means of treating Nematodes is by trying to grow your plants as healthy as possible from the start.
Plant Buddleia in full sun with well-draining soil. Mulch annually to keep the soil moderately fertilized and weed-free. Water Butterfly Bush regularly during periods of drought. Do not allow outbreaks of other pests or diseases to weaken the plant. If Nematodes have been a problem in the past, either choose plants that are naturally resistant or grow your Butterfly Bush in a large container where the soil can be controlled.
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Author Robbin Small - Published 5-30-2023 |