Many homeowners enjoy growing phalaenopsis orchids as houseplants. These plants are relatively healthy and resistant to many insects. However, phalaenopsis orchids are susceptible to sucking pests such as spider mites, mealybugs and aphids. These pests feed on the foliage of orchids, causing poor health and appearance in the host plant.
Spider mites are not actual bugs, but are members of the Arachnid family and common pests of orchids. The twospotted spider mite, false spider mite and red spider mite are all known to infest orchids. Spider mites are very small and are hard to see without a magnifying glass. Hot, dry weather conditions are favourable for spider mite development. Mealybugs are white and woolly insects that often found on the undersides of orchid leaves. These insects are covered with a white, waxy coating that resembles finely ground cornmeal. Aphids also feed on orchid leaves and cause reduced vigour in phalaenopsis orchids. Aphids are tiny, pear-shaped insects that congregate on the undersides of orchid leaves and feed on the foliage.
Orchids infested with sucking pests such as spider mites, mealybugs and aphids may develop speckled or flecked leaves, yellow leaves or leaf bronzing. Some insects, such as aphids, carry damaging viruses to infested plants. Orchids infested with sucking pests may also suffer from leaf curling, distorted leaves and grey sooty mould. Gray sooty mould is caused by the excretion of honeydew, which is a direct result of plant sap ingestion. Honeydew lands onto the orchid leaves, stems and flowers and causes grey sooty mould fungi to stick to it. This condition is not especially harmful to orchid health, but causes them to become unattractive and messy.
When infestations of sucking pests are light, they can be removed by placing a cotton swab soaked in alcohol on the insect. Keeping your orchid healthy and stress-free may also help reduce insect infestations. Drought stress is a common cause of insect infestations in many houseplants. Spraying your orchid with a strong jet of water can reduce insects by knocking them from orchid leaves. Repeat this process two or three times weekly for continued control.
Horticultural oils are often used to treat sucking insects on orchids. These products work by coating insects and causing them to suffocate and die. Apply horticultural oils to orchids thoroughly, as these products must come into contact with insects to be effective. Oil products may also help reduce grey sooty mould by loosening it and making it easier to remove. Insecticidal soaps or homemade soap solutions are often effective in controlling insects on orchids. To make your own soap solution, combine 1 tablespoon liquid dish soap with 1 gallon of water and apply it to your plant. Always test soap solutions on a small area of your plant before applying it all over to avoid adverse effects. Some plants are very sensitive to soap solutions. If no adverse effects are visible within seven days, it is safe to apply to the entire plant.