“I have tried growing gardenias, but they always die. When I pull them up there are white bugs all over the roots. What are these and how do I get rid of them?” Question from Sheila of Tampa, Florida.
Answer: There are several pests and diseases that will attack gardenia roots. I am glad that we narrowed yours down to root or ground mealybugs (Rhizoecus spp.) in our email communications. Here is a little more about these pests.
About Root Mealybugs
Root mealybugs also feed on the roots of African violets, grasses, palms, citrus, pineapple, mangoes, and other plants. The sucking insects suck the life out of the roots. This eventually will kill a plant. These pests will live for 27 to 57 days on a host plant, but cannot live off of a host for long. The females lay eggs and live young, called crawlers, hatch in just one day. Crawlers are microscopic but can travel several feet in search of a plant to feed on.
Root mealybugs are certainly a serious pest to manage, but there are some safe management practices that will enable you to get rid of them. Here are some cultural and organic treatment methods for their removal.
1. Remove all infected and surrounding plants and dispose of them far from the garden.
2. Do not replant gardenias where you had them previously planted without allowing the soil to remain unplanted for at least several weeks.
3. Check the roots of all new potted gardenia or other plants that you bring into the garden. Ants like to feed on the sugary dew created by mealybugs, so you will often see ants in infected pots or around infected plants.
Organic Treatment Methods
These pests are REALLY difficult to control, as you have already discovered. Here are some methods that are approved for organic gardening and have been shown to work. All products need to be applied as drenches.
1. Insecticidal soap drench: Apply insecticidal soap as a drench, being sure to apply enough to reach all of the infected plant’s roots. Be sure to follow the manufacturer’s recommendations.
2. Standard soap root drench for potted or uprooted specimens: Mix one teaspoon of Ivory liquid into 1 quart of water and drench the roots. This can kill the mealybugs at all stages. Repeat every couple of weeks until the problem appears to be gone.
2. Pyrethrin drench: Apply standard pyrethrin as a soil drench rather than a spray. Be sure to follow the manufacturer’s recommendations.
Some advocate digging up plants, treating their roots with a bowl/tub of drench, and replanting them elsewhere.
I hope that these tips help you tackle destructive root mealybugs.
Black Gold Horticulturist