Articles by Jim Gainan

As published in the Billings Gazette

Gardening Today: Houseplant Pests

Insects and Related Pests of House Plants

Minute, soft-bodied insects (1/8"), easily recognized by their pearlike body shape. Most species are green; however, some are brown, reddish or black. Adults may be winged or wingless. They cluster on undersides of leaves, buds and othe rtender plant parts. Damage is caused by sucking plant juices, causing poor growth and distorted leaves. Aphids secrete honeydew on which a black, sooty mold may develop.
How to control aphids: Use Dexol Systemic House Plant Insecticide or Malation.

Fungus Gnats
Adults (1/8") often seen flying over soil in pots. Rather feeble flyers and usually stay near soil surface or under leaves of plants. Adults do not cause damage, but can be a nuisance. Larvae, white with shiny, black head capsule, feed on decaying organic matter. Under certain conditions, some species larvae feed on root hairs or roots of seedlings.
How to control fungus gnat larvae: Drench soil with 2% Diazinon water emulsion. Apply granules to the soil as a systemic using DiSyston, Diatomaceous Earth or Dexol Systemic Houst Plant Insecticide and Tender Leaft Plant Insect Spray.

Soft-bodied, scale-like insects (3/16"), covered by a white, cottony wax layer which extends out from the body as short filaments. Damage is caused by sucking plant sap which causes plants to become stunted and distorted, or eventually die. These insects secrete honeydew on which a black, sooty mold may develop.
How to control mealybugs: Dip or spray plants using Diazinon. To ensure wetting of mealybugs, add mild household detergent (not soap) at a rate of 1/2 teaspoon per gallon of water with solution. Dexol Systemic House Plant Insecticide.

Adult scales are protected by a black, brown or tan hard covering. Immature scales or crawlers emerge from eggs deposited under the female's protective scale. Once crawlers establish a feeding site, they begin to secrete the hardened covering over their body. Scale damage is caused by sucking plant sap which will greatly reduce the vigor as populations build. These insects secrete honeydew on which a black, sooty mold may develop.
How to control scales: Same as for mealybugs.

Spider Mites
Very minute spider-like mites barely seen with the naked eye. Found most often within silky webbing on underside of leaf. All stages remove sap (usually feeding on underside of leaves). Feeding injury shows up first as pale, yellowish blotches on leaves which cause foliage to have a speckled appearance. Heavy infestations will cause leaf distortion, wilting and stunting of the plant.
How to control spider mites: Dexol Red Spider & Mite Killer or Isotox.

Cyclamen Mites
Adult mites are too small to be seen with the naked eye. Adults are amber or tan-colored and semitransparent while the young stages are white. They are found mostly in protected places on young, tender leaves (such as violet centers), buds and flowers. Damage, caused by removal of plant sap, will result in leaves becoming twisted, curled and brittle. Buds may become deformed and have a streaked and blotchy appearance. Blackening of injured leaves, buds and flowers is common.
How to control cyclamen mites: House plants lightly infested can be immersed, pot and all, for 15 minutes in water at 110 degrees Farenheit. Or, use Dexol Red Spider & Mite Killer.

Very small, cream to dark brown winged insects. Immature forms are wingless. If disturbed, adults fly readily. Damage results in the leaf survaces becoming whitened and speckled. Leaf tips wither, curl up and die. Buds will fail to open normally.
How to control thrips: Same as for aphids.

Adults (1/16") are snow-white in color with four wings and resemble a small moth. Both adults and larvae cause damage by sucking sap from the foliage. Infested leaves yellow and may drop off. These insects secrete honeydew on which sooty mold may develop.
How to control whiteflies: Dexol Whitefly & Mealybug Spray, Dexol Tender Leaf Plant Insect Spray, Dexol Systemic Houst Plant Insecticide.