Chrysanthemums, often called mums, are a favorite in autumn gardens for their vibrant, late-season color. Like most garden plants, they can become a target for various insects that undermine their health and appearance. Understanding how to eliminate existing infestations and implement a strong preventative care routine is the most effective approach to maintaining healthy plants. This guide details the process of identifying, treating, and preventing the most common pests that affect these popular flowers.
Identifying the Most Common Chrysanthemum Pests
The first step in effective pest management is accurately determining which insect is causing the damage, as different pests require specific treatments. Chrysanthemums are most commonly afflicted by three types of tiny, sap-sucking insects that cause distinct symptoms. These insects feed by piercing the plant tissue and extracting vital fluids, which leads to distorted growth and discoloration.
Aphids are small, soft-bodied insects that frequently congregate in tight clusters on new shoots, buds, and the undersides of leaves. They can range in color from dark brown to black or greenish-black, depending on the species. A telltale sign of their presence is the sticky, sugary residue they excrete, known as honeydew, which often leads to the growth of a black, velvety layer called sooty mold.
Spider mites are not actually insects but are arachnids. These pests thrive in hot, dry conditions and are generally found feeding on the lower surfaces of the foliage. Their feeding creates a characteristic stippling pattern—tiny yellow or white spots—on the upper leaf surface, and heavy infestations may produce fine, silky webbing around the plant’s stems and leaves.
Thrips are slender, minute pests that cause visible damage in the form of silvery streaks or stippled, bleached patches across the leaves. They feed by rasping the plant surface and sucking the exuded sap, which can cause new leaves to become twisted or distorted. If thrips infest the developing flower buds, the blossoms may fail to open correctly or may emerge with brownish, withered edges and discolored petals.
Immediate Solutions for Active Infestations
Once an infestation is confirmed, begin with the least toxic methods, such as physical removal. A strong, focused jet of water, applied every two days, can physically dislodge many pests, particularly when sprayed directly onto the undersides of the leaves where they hide.
For areas with dense clusters of pests, especially on terminal growth or heavily damaged sections, pruning and destroying the affected plant material reduces the overall population. This prevents the pests from spreading to healthier parts of the chrysanthemum. Always dispose of infested clippings in the trash rather than placing them in a compost pile, where the pests could survive and re-emerge.
When physical removal is insufficient, organic treatments like insecticidal soap provide a low-toxicity solution. Insecticidal soap works strictly on contact by penetrating the insect’s outer layer, disrupting the cell membrane, and causing desiccation or suffocation. It is important to thoroughly coat the pests with the spray, which usually requires repeat applications every four to seven days until the infestation is controlled.
Neem oil is another widely used organic product that acts as a repellent, an anti-feedant, and an insect growth regulator, affecting the pest’s life cycle. Both insecticidal soap and neem oil should be applied in the early morning or late evening to prevent leaf burn, or phytotoxicity, which can occur when these products are exposed to direct, hot midday sun or temperatures above 90°F.
For severe or persistent infestations that do not respond to organic treatments, a targeted chemical insecticide may be necessary. Products containing pyrethrins, which are natural insecticides derived from a species of chrysanthemum, offer a fast-acting solution. Since pyrethrins are broad-spectrum, they should be used sparingly and only applied following the label instructions precisely, especially avoiding application during the day when beneficial pollinators are active.
Long-Term Strategies for Keeping Pests Away
Preventing future pest problems relies on optimizing the growing environment and maintaining plant health. Proper cultural practices begin with ensuring adequate air circulation around the plants by providing sufficient spacing between individual mums. Dense, humid conditions create an ideal environment for many pests and fungal diseases to flourish.
Watering techniques also play a role in prevention, as water stress can weaken a plant, making it a target for pests like spider mites. Using drip irrigation or watering the soil directly avoids wetting the foliage. Avoid over-fertilizing, particularly with high-nitrogen formulas, as excessive new growth can attract sap-sucking insects like aphids and mites.
Regular inspection involves frequently checking the plants, particularly the undersides of leaves and new growth areas. Early detection allows for the prompt, localized removal of small pest populations before they escalate into a full-blown infestation. Simultaneously, cleaning up all fallen leaves and dead plant debris eliminates overwintering sites for pests and disease spores.
Introducing beneficial insects into the garden is a natural way to establish long-term pest control. Lady beetles, or ladybugs, are voracious predators of aphids and other soft-bodied pests, providing continuous protection without chemical intervention. Companion planting can also be used as a preventative measure, such as planting chives nearby, which can help deter aphids with their strong scent.