Do Marigolds Attract Whiteflies?

Preventive Control

• Provide consistent care to your marigolds to ensure the growth of healthy plants and increase their ability to ward off pest infestations. Grow marigolds in areas of the home garden that offer full sunlight. For successful growth, maintain moist, well-drained soil high in organic content; marigolds tolerate most soil types as well as acid or alkaline conditions. Plant marigolds that perform best in your region. For example, French marigolds (Tagetes patula) thrive in all U.S. Department of Agriculture plant hardiness zones while Mt. Lemon marigold (Tagetes lemmonii) grows best in USDA zones 8 through 11.

Pest

• In addition to a variety of other insect pests, marigolds attract whiteflies. These pests are tiny flies with yellow bodies; however, the coverage their white wings provides makes them look white. You will typically see them gathering on the undersides of leaves where they feed by sucking out plant tissue fluid. Whiteflies measure approximately 1/10 to 1/16 inch in length and look like small flies or moths. They are most active during daylight hours in warm weather.

Effects

• When whitefly infestations are left untreated and/or populations become large, they may result in extensive damage. Due to whitefly feeding and removal of fluids, your marigolds may experience yellowing leaves that wither and often fall early. Stunted or poor growth may occur along with diminished health. In addition, as whiteflies feed, they release a sticky, sweet substance called honeydew. The substance drips onto plant parts and the ground below; where the honeydew falls, a black-hued fungal growth called sooty mold often develops. The fungus does not directly harm the plant but may block out sunlight.

Control

• Because insecticides may lead to greater problems, avoid chemical control. Depend more on cultural and biological measures instead. Begin by releasing natural enemies such as lacewings and minute pirate bugs that kill whiteflies without harming your plant. Remove and destroy heavily infested plant parts to control the population. In extreme situations, apply insecticidal soap to the plant. Mix concentrated insecticidal soap with water in a sprayer for application. Follow the product's directions, which will instruct you to use 2-1/2 to 5 tablespoons of concentrated soap per 1 gallon of water. Fully saturate the entire plant and repeat application once weekly until the infestation is under control and according to the specific instructions on the insecticidal soap label. Sooty mold will diminish and go away on its own once the whiteflies are under control.