Question
Hi, I have a 4 ivy house plants and all four have this white fluffy stuff on the leaves.  I've noticed that it starts out on the leave and then it works its way down to the stalk and then the leaf turns yellow and it falls off.  When I go over to check them out little bugs like knats or something start flying.  Is this harmful are what can I do to get rid of this gunk that has begin to make my house plants ugly.

Answer
Hi Reshelle,

Apparently you have pretty serious infestations of both mealy bugs (the white fluffy stuff) and fungus gnats.

I have to tell you up front, that at this point these pests are difficult to eradicate and you plant has been weakened by them. Unless, you are particularly attached to your ivies, you might want to consider discarding them.

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.

You may want to try spraying with rubbing alcohol. Mix 1 part alcohol with 5 parts of water and a squirt of liquid soap. 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.

Adult fungus gnats fly around and are an annoyance, but they are not harmful to people. Each gnat lives for about 5 days. The trick is to get rid of the next generation - the gnat larvae that live in the top layer of the soil. The larvae feed on decaying organic matter. Decaying pine bark in potting mixes and decaying plants roots feed the larvae.

Try to keep the soil as dry as possible. Remove all loose soil from the surface and put a light layer of coarse coir (coconut husk) or sand or diatomaceous earth on the soil surface. These substances have sharp edges that carve up the larvae.

Another safe technique is to place ?inch slices of raw potato on the surface of the soil. After a day or so, discard the slices along with the larvae inside. Repeat this until there are no more larvae in the potato.

Detection trick: Add a little water to the soil and then look very closely for tiny fungus gnat larvae swimming in the water as it pools on the surface. You need good light and good eyes to see them. If you don't, then your plant is probably gnat free.

Prevention is often the best remedy. Use sterile potting mixes that are free of bark chips. The potting mix should have ample drainage material, such as perlite so that it drains well and allows the soil to dry out frequently. Fungus gnats can nearly always be traced back to overwatering and/or poor soil quality.

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

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