Dealing With Common Pests

Plant pests can enter your home on new houseplants that you have brought in. Open windows and doors also offer pests a route inside. But by giving your plants a quick health check every week, you should be able to keep most if not everything under control. Sometimes its as easy as just picking them off.

Aphids: Aphids are small, soft-bodied, pear-shaped insects about 1/16– to 1/8-inch long. They are usually green but may be pink, brown, black or yellow. Some aphids have a woolly or powdery appearance because of a waxy coat. Adults may or may not have wings.

 

Aphids are usually found feeding on new growth or the undersides of leaves. Some feed on roots. They suck plant sap, resulting in yellowing and misshapen leaves. In addition, growth may be stunted, and new buds deformed. As aphids feed, they excrete a sugary material, called honeydew, which makes leaves shiny and sticky. Sooty mold fungi may grow on the honeydew, producing unsightly dark splotches on the plant’s surfaces.

Control: With minor infestations, handpicking, spraying with water or wiping the insects with a cotton swab dipped in rubbing alcohol may be practical. Insecticidal soap spray may also be used. In most cases the treatment will have to be repeated multiple times. For houseplants that are taken outdoors, spray with insecticidal soap, or neem oil extract. 

Mealybugs: Mealybugs are small, pale insects, related to scales. They are about 1/8 to 1/4 inch long and move very sluggishly. The adult females cover themselves and their eggs with a white, waxy material, making them look cottony. Some have waxy filaments that extend beyond their bodies.

Nymphs (immature forms) hatch from the eggs. Once they begin to feed, the waxy coating starts to form. Nymphs look like adults only smaller. The wax on mealybugs helps repel pesticides and makes them somewhat difficult to control. Mealybugs are most commonly found on the lower surfaces of leaves and in leaf axils (where the leaf attaches to the stem). One species feeds on the roots. They suck plant sap, causing stunted and distorted growth and sometimes plant death. Like aphids, mealybugs excrete honeydew, providing the opportunity for growth of sooty mold fungi.

Control: Light infestations can be controlled by removing individual mealybugs by hand or by wiping each insect with a cotton swab dipped in rubbing alcohol. An insecticidal soap spray may also be used. With a heavy infestation, it may be necessary to discard the plant. For houseplants that are outdoors, spray with neem oil extract.

Spider Mites: Mites are not insects but are more closely related to spiders. Since they are extremely small, plant damage is typically the first sign of their presence. A silky web is often seen with heavier infestations.

Both spider mite adults and their immature forms damage plants by sucking plant sap. Damage includes light-colored speckling on the upper surface of leaves, and results in a plant with an overall faded look. If the mites are left unchecked, leaves become bronzed or yellowed, and the plant dies. Spider mites are usually more of a problem on house plants that remain indoors year round.

Control: Spray sturdy plants forcefully with water, including the undersides of leaves, to dislodge mites and break up their webs. Plants also can be sprayed with an insecticidal soap. For houseplants that are outdoors, spray with insecticidal soap, neem oil extract or an insecticide containing sulfur. It is often necessary to spray once a week for several weeks to control mites.

Whiteflies: Whiteflies are not true flies, but are more closely related to scales, mealybugs and aphids. They are very small about 1/10 to 1/16 -inch long. They have a powdery white appearance and resemble tiny moths. When at rest, the wings are held at an angle, roof-like over the body. The immature stage is scale-like and does not move.

Both the adults and their immature forms feed by sucking plant sap. The damage that they cause is similar to that caused by aphids. The infested plant may be stunted. Leaves turn yellow and die. Like aphids, whiteflies excrete honeydew, which makes leaves shiny and sticky and encourages the growth of sooty mold fungi. When plants that are infested with whiteflies are disturbed, the whiteflies flutter around for a while before settling again.

Control: Wash the plant. Spray the plant thoroughly with insecticidal soap, or neem oil extract, especially the lower leaf surfaces. 

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