Bromeliad Pests – Spider Mites

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Care and Culture, Growing Indoors, Growing Outdoors, Insects

Perhaps the most dreaded pests of houseplants, spider mites are not true insects, but are more closely related to spiders and ticks. Spider mites damage plants by piercing the leaves with needle-sharp mouth-parts and then sucking out plant juices.

Description: Perhaps the most dreaded pests of houseplants, spider mites are not true insects, but are more closely related to spiders and ticks. Spider mites damage plants by piercing the leaves with needle-sharp mouthparts and then sucking out plant juices. They congregate on the undersides of plant leaves, where they may not be seen until the plant is seriously infested. Mite-laden leaves may show numerous yellow pinpricks, or they may be dry and limp while still green. Left uncontrolled, spider mites can kill their first victim and then spread to other nearby plants.

Spider mites cannot hurt people or pets, however, because they are so very tiny. Most adults are only 1/50 in (.05cm) long, so you would need a 15X magnifying glass to see them. Under magnification, spider mites may be green, yellow, red, black, or colorless. Without a magnifying glass, you can usually see faint silky webbing on the undersides of badly infested leaves. Also, if you tap or brush the underside of an infested leaf over a white piece of paper, you may be able to see miniscule moving dots.

Control: Spider mites usually gain entry to homes and offices on new plants, so it’s always a good idea to keep new plants isolated from others for a couple of weeks. In dish gardens, sometimes one plant will have spider mites, but the others will be okay. This is usually because the infested plant was stressed in some way, which left it easy prey for the mites. Weak plants have more problems with spider mites than healthy ones.

Early detection is a challenge, but light infestations of spider mites are much easier to treat than severe ones. Spider mites multiply rapidly, with eggs hatching only 3 days after they are laid. A complete life cycle, from egg to egg-lying adult, can pass in only 2 weeks. Very dry conditions encourage spider mites, so they are often seen in winter, when plants struggle in dry, heated rooms. Misting plants regularly or setting them on beds of pebbles that are kept damp helps to prevent problems with spider mites.

How you control spider mites depends on the size and value of the affected plant, and how much you want to keep it. Small, inexpensive plants that have come into your life casually are best disposed of, because in the time it takes to bring the mites under control they could spread to more significant houseplants. However, if only some parts of the plants are infested, promptly clip them off and dispose of them in a sealed plastic bag. Then treat the remainder of the plant with insecticidal soap. Repeat at least twice at 5-day intervals to make sure you kill new mites that hatch from eggs hidden in leaf crevices or beneath bits of webbing.

Do not attempt to control spider mites with pesticides. They often do not work, and mites rapidly become resistant to them. If you gave a very large collection of houseplants that are affected by spider mites, you might consider releasing beneficial mite predators to bring spider mites under control. This solution is often used in greenhouses, and it is very effective.