Why Are My Phalaenopsis Leaves Deformed?

Sap-Feeding Aphids

• Aphids are small, soft-bodied, sap-feeding insects that wedge themselves between moth orchid leaves, tapping into the juices of leaves and buds from hidden spots. They often cling to the undersides of leaves, but sometimes invade buds or emerging leaves as well. Aphids feed in clusters and can cause serious deformity to leaves if they feed on them while they are still developing.

  Aphids are easy to treat once you've located them. Take your indoor orchid to the kitchen sink every day and wash off the aphids you find, being careful not to damage your plant's leaves. You can do the same with outdoor plants using a garden hose. Although your leaves may be deformed, if they are still green, leave them attached to the plant -- your orchid needs these leaves to produce food. Eventually, it will grow replacements.

Wax-Covered Mealybugs

• The pink to gray, segmented mealybug is another sap-feeding pest of moth orchids. Mealybugs are significantly more mobile than aphids and may feed on various parts of the plant, but primarily focus on stems and leaves. These bugs feed in groups, shedding their protective wax coating as they go -- the wax accumulations are often the first thing a plant owner notices. Like with aphids, young buds with mealybug damage may develop into seriously deformed leaves.

  Mealybugs are simple to control with weekly sprays of pre-mixed insecticidal soap. Make sure you get between leaves and spray until the mealybugs are no longer causing problems. Because most mealybug colonies are made up of multiple generations, you'll need to stay vigilant and check frequently for activity. Wash the wax from leaves to help keep track of mealybug movements.

Plant Viruses

• A variety of plant viruses attack moth orchids, and many can lie dormant for a long time before becoming obvious in your plant. Common leaf symptoms include white to yellow rings, yellow stripes, brown lesions and downward leaf curling that may be so severe that it looks like a deformity.

  Your plant can be tested for viruses at a certified lab, but it will be an expensive proposition. Many keepers quarantine virus-infected plants to protect others in their collection, along with practicing exceptionally good hygiene when working with the sick plants. Tools should be disinfected between plants with household disinfectant or a dedicated set of tools established for the sick plants. Plant viruses are currently incurable, but if your plant is still relatively healthy, there's no reason to trash an expensive specimen before it is spent.

Environmental Problems and Chemical Toxicity

• Sometimes, deformed leaves aren't caused by illness or pests, but can be a response to unfavorable environmental conditions. Moth orchids are much more flexible than other orchids, but still require relatively high humidity between 50 to 75 percent to be at their best. Without proper humidity, plant leaves and other tissues may emerge deformed. Place your plant on some rocks in a shallow pan filled with water to increase the humidity -- make sure the pot isn't in direct contact with the water because sitting in water is even worse for your orchid than low humidity.

  Rarely, when plants are treated for pests or disease, they have a poor reaction to the chemicals involved. Agrimycin is particularly damaging to moth orchids, although it is extremely effective at destroying Erwinia bacteria. Leaves and flowers may both be deformed after treatment. There's not a lot you can do about this sort of damage, but if you give your plant excellent care it will eventually grow new, healthy leaves. You should consider repotting your orchid if new growth continues to emerge damaged.