Question
Hi Darlene,
Today I went to HD to buy an insect spray to kill these little flies which I am not sure if they are thrips or fungus gnat. I just was going to spray it to the soil, then I saw some kind of bug (I think there are a lot in the soil) which looks like caterpillar. They are about a half inch long with lots of legs and dark gray color. When I touch them, they curl up.
I do not know what they are. They can be the ones who are causing yellow leaves on my Diffenbachia (tropic snow). I had to cut at least 6 leaves.

So, what should I do? Should I repot my plant to get rid of thrips or fungus gants & bugs?

By the way, what are the differences between thrips and fungus gants?
Thanks
DERYA


Answer
Derya,

Thrips are described at ths site:
http://www.nysaes.cornell.edu/ent/hortcrops/english/thrips.html

Fungus gnats are described at this site:
http://ohioline.osu.edu/hyg-fact/2000/2114.html

You probably have fungus gnats because the soil is too moist and the catapilar is the larva of the gnat. They are attracted to the rotting roots of the plant like gnats are attracted to rotten fruits and vegetables on your counter. Let the plant dry out more between watering and they will disappear. This time of year it is easy to think spring is almost here and start watering a little more but the plant is still semi dormant and not growing. Keep the plant on the dry side until you see signs of growth. Pour off any excess water from the drain tray an hour after watering. Do not repot at least until April 15th, then put the plant back in the same pot, just remove it from the soil and mix the soil with more perlite 50/50 to make it drain better and repot it.  Good luck.

Darlene