Sick houseplants do not always indicate a disease, sometimes insects are to blame. Although improper care causes similar damage to a plant, an insect's damage is distinct. Diagnoses of insect damage and identification of the insect responsible will dictate the control process and how to improve your houseplant's environment.
Catch pests early on to prevent the buildup of large populations. The University of Delaware Cooperative Extension suggests looking at the plant for sticky deposits on the leaves or the stem that cause mold. Plants that look off-color, have yellow specks on the leaves or holes in the foliage, and plants that droop often indicate insect infestation.
Insect Feeding Habits
Insects usually fall into two feeding types: those with chewing mandibles and those that suck juice out of the plant. Feeding habits help determine the insect type. Chewing insects include grasshoppers, beetles and caterpillars, while sucking insects include aphids, leaf hoppers and plant bugs. Chewing insects have jaws that chew like a pair of scissors, while sucking insects have a beak. Physical differentiation between insects may be difficult without a good knowledge of insect anatomy. Some university extension services will identify insects for you when provided a sample and a small fee. Chewing bugs usually require a stomach poison for chemical control, while sucker bugs usually require a contact or systemic insecticide.
The University of Minnesota Extension recommends using preventative techniques to control insect population on house plants. Washing the plant leaves regularly prevents the build up of dust and grime that weakens a plant's defense against bugs. Houseplants require inspection at every watering for insects. Look at both the top and the bottom of the leaf for signs of bugs or sticky residues from sucking bugs.
To remove insects from a houseplant without the use of chemicals, the University of Tennessee recommends washing the plant by hand with soapy water and a soft brush. Remove aphids and mealy bugs by hand or a pair of small tweezers. A cotton swab dipped in alcohol will kill individual bugs found on plant leaves.
According to the University of Tennessee, few insecticides are approved for use within the home. Ready-to-use sprays are available in pressurized cans that allow you to spot spray the house plant. Pump sprays are also available. Check the insecticide to ensure it is approved for indoor use and apply according to the instructions.