Chrysanthemums (mums) are a favorite addition to gardens, providing vibrant color often late into the season. Growing these popular ornamentals sometimes involves managing various pests that can diminish the plant’s health and aesthetic appeal. Dealing with infestations requires a systematic approach, beginning with accurate identification and moving toward safe, effective removal. This guide outlines how to recognize common mum pests, employ physical removal techniques, utilize targeted organic controls, and establish long-term prevention practices.
Diagnosing the Problem: Common Pests on Mums
The first step in any management plan is correctly identifying the invading organism, as different pests require specific responses. Aphids are small, soft-bodied insects that cluster primarily on new growth, sucking the plant sap. They excrete a sticky, sugary residue called “honeydew,” which often leads to the growth of sooty mold.
Another common culprit is the two-spotted spider mite, Tetranychus urticae, which is an arachnid that thrives in hot, dry conditions. These nearly microscopic pests pierce plant cells to feed, causing fine yellow or white speckling on the leaves, known as stippling. Severe infestations show delicate, fine webbing draped across the foliage, particularly on the undersides of leaves where the mites congregate.
Thrips are slender, tiny insects that feed by rasping plant tissue, resulting in silvered streaks on the foliage and distorted flower heads. Small, black specks of their excrement on the leaves confirm their identity. Finally, certain fly larvae, known as leaf miners, tunnel between the upper and lower surfaces of the leaves, leaving behind distinctive, winding, pale trails or “mines.”
Immediate, Non-Invasive Removal Strategies
Once a pest is identified, the least disruptive control methods should be deployed first. A strong, forceful jet of water is effective for dislodging soft-bodied pests like aphids and spider mites. The water stream must be directed with precision, targeting the undersides of the leaves where these insects hide. This process should be repeated every few days to break the pests’ reproductive cycles.
For larger, more visible pests, such as caterpillars or slugs, manual removal is a practical solution. These can be picked off the plant by hand and dropped into a container of soapy water for disposal. This method is useful for localized, small-scale infestations.
Pruning is another important technique, involving the strategic removal of the most heavily infested plant parts. Any leaves or stems that are severely damaged, such as those covered in spider mite webbing or showing extensive leaf miner trails, should be cut off. Immediately dispose of this plant material in a sealed bag away from the garden to prevent pests from returning to the healthy mums.
Utilizing Targeted Organic and Biological Controls
When mechanical methods alone do not adequately reduce the pest population, targeted organic treatments offer a safe next step. Insecticidal soaps work by dissolving the protective outer layer of soft-bodied insects, causing dehydration. These products are contact killers and must directly coat the pest to be effective, necessitating thorough coverage of the entire plant, including the leaf undersides.
Horticultural oils, such as neem oil, function by smothering pests and their eggs, and also act as a repellent. Because oils and soaps can cause phytotoxicity (damage to the plant tissue), they should only be applied when temperatures are below 90°F and never in direct, intense mid-day sun. A small test application on a few leaves is advisable before treating the entire plant.
Introducing natural enemies provides a biological control method. Lady beetles and lacewings are predators that feed on aphids, thrips, and whiteflies. The release of predatory mites, such as Phytoseiulus persimilis, is effective for managing spider mite outbreaks. These beneficial insects should be released near the infested plants, preferably in the evening, to encourage them to settle and begin feeding.
Long-Term Cultural Practices for Prevention
The most sustainable approach to pest management involves promoting overall plant health to make mums less susceptible to attack. Proper plant spacing is important, as overcrowding reduces air circulation around the foliage. Good airflow helps leaves dry quickly, which reduces the moist conditions favored by pests and fungal diseases.
Careful attention to watering techniques also reduces pest issues. Mums should be watered at the base of the plant, rather than overhead, to keep the foliage dry. Watering early in the day allows moisture on the leaves to evaporate before evening, discouraging pest activity.
Soil health and nutrient management play a significant role in plant resistance. While adequate fertilization is necessary, over-fertilizing with nitrogen results in tender growth attractive to sucking pests like aphids and spider mites. Maintaining a balanced feeding schedule and removing weeds and dead plant debris eliminates potential hiding spots and breeding grounds for pests.