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Chances are pretty good that at some point in time your plants will be subjected to insect damage. The mealybug is one pest that I am well acquainted with, as are my plants.
Although you may see adults crawling about, normally you won't notice much of an issue until the appearance of cotton-looking substances on the leaves, stems, or bark. These cottony masses serve as protection for the adult female mealybug's eggs.
Once the eggs hatch, the nymphs, also known as crawlers, will position themselves in ideal locations, protect themselves with a waxy coat and, using their piercing stylets, begin to suck the sap life out of leaves and stems. In exchange, they deposit saliva that is toxic to the plant and which will ultimately lead to the plant's demise (McCormick, 2019).
And, as if that weren't enough, these pests resort to leaving a trail of honeydew in their wake, the sweetness of which attracts ants. The ants return the favor by doing their best to protect their benefactors. Not to mention that the honeydew is a breeding ground for sooty mold, which will limit the amount of sunlight the plant can take in for the purpose of photosynthesis. A lot is going on in this scenario with the plant paying the ultimate price if control measures are not in place.
Online sources offer preventative and remedial recommendations for the control of mealybugs, a number of which are presented below. As you will note, not all are considered eco-friendly.
1. Inspect your plants before purchase. Oftentimes, we end up bringing mealybugs and other pests home with the plant. Make certain you are purchasing one that is healthy and free of pests.
2. When selecting plants, ensure they are the right ones for the location you have planned for them. Even healthy plants can be attacked by pests. However, those that become weakened because their needs are not being met offer an even greater invitation to mealybugs and other pests.
3. For light infestations, try a burst of water to dislodge the unwanted pests, keeping in mind you may also be dislodging beneficial insects.
4. Dab a cotton ball with 70 percent isopropyl alcohol and gently remove the unwanted pests by hand. Avoid spraying alcohol directly on leaves as it can cause leaf damage.
5. If you see evidence of mealybug predators, such as parasitic wasps, lacewings, midges, spiders or black ladybugs, also known as mealybug destroyers, consider leaving the plant alone. You can be assured that these good bugs are taking care of business.
6. Avoid using products that are not intended for use on plants. Although some online do-it-yourself sites suggest dish soap and other such detergents as remedies, you are encouraged to steer away from their use as they will harm beneficial insects. Additionally, "Dish soap products, designed to remove tough grease and oils, may be particularly damaging to a plant's waxy cuticle because they contain synthetic detergents and other potentially phytotoxic chemicals." (Borden & Dale, 2019, p. 4).
7. Avoid the use of broad-spectrum insecticides as these will kill the good along with the not-so-good bugs. Following label directions, consider less toxic measures, such as insecticidal soaps, to address the situation. Soaps and other contact remedies are effective against nymphs before they have had the chance to settle in for feeding. You can also consider horticultural oils as a remedy for all stages of mealybug development (Buss & Turner, 2004).
8. If you see ants along with the mealybugs, consider placing ant traps in the vicinity, keeping in mind that the ants are there to work against you and for the pests.
While the great majority of insects are beneficial, the mealybug is one of the more bothersome ones. However, they can be controlled with a little due diligence on our part and so all is not lost.
Happy gardening!
Janetta Fox is a Lee County Master Gardener volunteer and member of the Garden Club of Cape Coral.
Sources:
n Borden, M. A. & Dale, A.G. (July, 2019). Managing plant pests with soaps. UF/IFAS Extension. Retrieved from https://edis.ifas.ufl.edu/pdf/IN/IN124800.pdf
n Buss, E. A. & Turner, J. C. (February, 2004). Scale insects and mealybugs on ornamental plants. Retrieved from UF/IFAS Extension. Retrieved from https://ufdc.ufl.edu/IR00002883/00001
n McCormick, K. (June, 2019). Questions from the plant clinic: mealybugs. UF/IFAS BLOGS. Retrieved from http://blogs.ifas.ufl.edu/seminoleco/2019/06/14/mealybugs/