Several of my Alocasias have fungus gnats. With other plants I always just sprayed a solution containing pyrethins, but am a little reluctant to do so with these guys. Earlier in the year, I discovered a minor red spider mite population on 3 of my Alocasias. Without thinking, I sprayed them with pyrethins. Big boo boo. It burned the heck out of most of leaves. My poor Colocasia had all of it's leaves burned, but has since recovered nicely. So, how do I get rid of these pesky gnats without burning my plants? Other plants that live by are small musas, night blooming jasmine, and prayer plants, which also have fungus gnats. Any advice on this matter would be very much appreciated.
--Emily
Alocasias and fungus gnats. How do I deal with them?
Emily, read this thread and see if it helps.
http://davesgarden.com/forums/t/375818/
Kay
This message was edited Dec 12, 2004 3:57 PM
On another forum someone recommended spreading horticultural cornmeal over the top of pots to control fungus gnats. I asked if regular cornmeal would work, but he never answered. I haven't tried it yet.
Diatomaceous earth sprinkled on the top should work. You can make a drench of a few drops of tea tree oil in 8 oz water and drench the soil. You can buy the Bt variety israliensis to kill fungus gnats. It's the same Bt that is in mosquito dunks.
I read the thread Kay posted the link to and just about fell out of my chair! I had no idea the "larval form" of these pests munched on roots of my beloved plants! I ran to the kitchen and sprayed the soil of many plants with a spray containing pyrethins. My Alocasias will have to wait until I can get to the nursery next weekend. Oh, I also spent the next hour airing out my house trying to rid the air of the fumes from that pungent spray.
Pyrethrins sure do stink, but so do most other insecticides. Be careful using any pesticide on alocasia, because the leaves spot easily.
A sprinkle of a systemic insecticide will get rid of those pesky knats. It also helps to rough up the top layer of soil so it does not stay as damp. I used the Diatomaceous earth outside to control slugs, but, never thought about using it inside! Great idea!
Mel
I used Scanmask and it worked REALLY well. I just posted a thread in the Garden foes forum if you want to read it. I used it on sensitive plants and there were no problems.