Question
I work in a retail garden centre that gets its plants from growers in either florida or southern ontario. Over the past two months we have experienced an out burst of mealy bug. We had a professional come in and spray about a month ago, then two weeks later we used an insecticidal soap ourselves, but they have come back again. What causes them, and what should we stop or start doing to erradicate the problem. We water usually once a week for 8"pots and the smaller ones get water usually ever other day depending on the size of the pot. The concrete floor is watered daily as we are in southern ontario and the garden center is very dry.
any help is appreciated!

Answer
Hi Andrea,

The difficulty with treating mealybugs is that there is always more to deal with than meets the eye. Young mealybugs lack the telltale cotton-like protective coating and they are skillful at hiding in nooks and crannies where leaves and stems join.

The key to successfully eradicating these creatures is to spray the ones that are out of sight. That means that whatever treatment you select, you must get complete coverage, to the drip point, of all leaf and stem surfaces. If you miss a few, they will live to breed another day. In addition, it means that every new plant that enters your garden centre should be carefully inspected or treated first.

Undoubtedly, the mealybugs came in on some of the plants that you purchased. Once the infested plants are in an enclosed space, it is very easy for them to spread. They are more likely to attack plants that are under stress, although even healthy plants can be vulnerable. So keep your plants healthy by providing good light and proper water.

Quality foliage growers take precautions to ensure that there are no pests on their plants when they are shipped. Discount growers often cut corners on effective pest prevention programs. So it is important to know your growers.

I am not familiar with Canadian pesticide regulations, although I believe they are more stringent than in the US. The best pesticide teatment for mealybug is Imidacloprid (Trade name Merit or Marathon). If you can legally obtain and use it, that is what I recommend.

The best non-pesticide, non-toxic treatment for mealybug is called Brand X Foliage Cleaner (Yes, that's for real). It is available through Southwest Plantscape Products in California (ftp://ftp.southwestplantscape.com/Brandx.pdf). Their phone is 1-800-333-7977. It is a silicon-based product so it is very slippery. Its ability to penetrate is probably the key to its effectiveness because it gets into the tiny crevices that other sprays miss.

You may want to try spraying with rubbing alcohol. Mix 1 part alcohol with 8 to 10 parts of water. Be sure to spray all leaf and stem surfaces thoroughly. It is also best if you repeat this treatment again in 5 to 7 days to catch any crawlers that you missed the first time. After that, you should check your plant weekly to see if they return. This may not be a good option if you have a lot of plants in your garden centre.

Never spray in direct sunlight or when temperatures are above 75 degrees. It is also advisable to test any spray on a few leaves as a test before you spray the entire plant. Wait a few days following the test to see if there is any negative reaction to the spray.

For the future, carefully inspect or treat any new plants before you bring them into your centre.

Good luck and please let me know if any of this is unclear or if you have any additional questions.

Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

You can E-mail me directly at: [email protected]

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