House Plants/Diffenbachia


Ii have a diffenbachia that recently seems to have become infested with gnats. As far as I can see they seem more attracted to the soil than the plant itself. What is the best way to get rid of them?  They seem to multiply very quickly!

Get to a local garden center/nursery and buy a safer soap pesticide (professionally formulated) and apply it as a soil drench...Read the directions on the label...It won't hurt the plant and will kill the gnat worms as the eggs hatch...Ask them how to apply a pesticide as a soil drench...Buy your products from them and they should be more than happy to help you.
They make yellow sticky plastic cards to put near plants to attract the adults...Ask them where you can buy some...
You could also sprinkle a teaspoon of turf lime over the soil to sweeten (raise the soil pH) of the soil...Wet acidic soils attract flies for breeding purposes...Gnats and other flies breed in wet soils...They reproduce by laying their eggs in the damp soil producing small white worms (fly/gnat maggots)
Watering this way will prevent it from happening again...Let your plants dry out sufficiently between waterings...Water by weight...Put a saucer under the pot...Water and let the plant sit in the excess water for 5-10 minutes...After that time pour off any excess water in the saucer...Pick up the pot...It should feel heavy...Don't water again until it feels considerably lighter in weight...The soil will be light in color/not dark and wet...Watering frequency depends on many factors (sun exposure, wind, day temps, etc.)...

Hope this helps...Let me know what you think...
Rick in southern NJ  

House Plants

All Answers

Answers by Expert:

Ask Experts


Richard Hern


I can answer many common garden center/greenhouse houseplant questions such as , proper care, propagation of, pest problems, identification, growing mediums, construction, etc. & many more..


I currently manage a private 16 acre estate. i am in charge of the general maintenance of buildings and i supervise the landscape maintenance staff. i teach landscape/horticulture evening classes for a community college in NJ. I taught landscape/horticultural classes for a NJ vocational high school for 5 years. prior to that I owned & operated a landscape/garden center facility for 20 + years. My experience is in commercial & residential sales & care of houseplants as well as landscaping.


BS degree in Zoology (Entomology)
Certified landscape/horticulture teacher NJ

©2017 All rights reserved.

[an error occurred while processing this directive]