Help me save my tomatoes!

Asked April 5, 2013, 2:11 PM EDT

Hello! I have tomato plants that I grew from seeds awhile back, and are various sizes, from 6 inches to 3 feet tall now. Many have yellow blossoms, and I am really excited to have tomatoes that I grew myself thriving in my southern window!

HOWEVER, I have FLIES, and LOTS of them! I have literally spent hours reading everything available to me on the net and on your site before writing, and I am more confused than ever. I think I might have 2 different kinds of flies, since the symptoms are so diverse. Can you help me identify them all, and get rid of them in the least toxic way? Here is what I see...

1. Even when I let the plants dry out to the point of wilting, as soon as I water, little black flies that look like fruitflies fly out from and around the soil and water, as if to play & thank me. That is when I thought they were fungus gnats. (and still do), but they do not seem to diminish even when I almost kill the plant by not watering in hopes that they would die instead.

2. Now I also notice now that there are clusters of little light spots that are alive, and now hatching on leaves! YUCK! They seem to congregate together in a colony on a few leaves of choice, and when I pick off the leaf they are on, they seem too dumb to care much and do not try to get away. This made me think they are aphids, since they are cogregating and hatching on leaves and not in the soil or on the stems. ??

3. There is a white "dandruff" directly under the leaves they are on, and it is all over the plant below those leaves, on the soil, and all over the table. It does not seem to be sticky like I see described in other places. What the heck is this?

4. The last symptom is that they DO congregate on the WINDOWS when the sun comes out, and occasionally commit suicide in my morning coffee. But these files do not seem too interested in my compost bin over at the sink, so I am pretty sure they are not fruitflies, although they look like them. I have aphids, fungus gnats, or BOTH? How do I safely and effectively get RID of them?? I read on your site that insecticidal soaps can be too harsh, but there is nothing that tells me what kind I CAN use, or what soap to make it with. How about a recipe? Several other things on the net say to mix garlic juice, cayenne pepper extract, or even a splash of rubbing alcohol with the soap as well. I am so confused! :(

When I took these puzzle pieces to Home Depot for help, they didn't seem to have much in the way of helpful info, or safe pesticides for edible plants. I was sold a pretty toxic looking bottle of junk called, "copper fungicide". I used it once awhile back, but I am afraid it will make the tomatoes poison, and I am not even sure which kind of flies I have, or if it worked. There has got to be a better way.

I plan to put these tomatoes outside in patio pots as soon as the frost danger has passed. I need to repot them ASAP now, as they are too crowded. I was going to treat them and repot them at the same time, so I need advice ASAP.

I am new at this, and need to call in the expert BIG I am turning to YOU! I am attaching pics below. Could not get shots of the adult flies that go up and down the window, but they are a nuisance as well. PLEASE HELP! Thank you SOOOO much! :)


Lisah Brown

Boulder County Colorado

1 Response

Hello Lisah, It sounds like you have fungus gnats and after consulting with the the extension office entomologist we believe the other insect is a winged aphid. It can be difficult to diagnose by photos, so if you would like to come in for a definitive identification we could confirm that for you. To make this diagnosis the fee would be $7 and could take up to 10 days. Normally we recommend putting the insect in rubbing alcohol, but due to the fragile nature of the wings I would recommend placing a leaf with the insects in a plastic ziploc bag. We believe the "dandruff" you are seeing is from the aphids molting. The aphids could have come in on another plant brought in from the outdoors if you might have brought anything else in, as they overwinter. I have attached a fact sheet and some other information on aphid control. I would also recommend crushing them or washing them off, being careful not to overwater your plants, which would increase the fungus gnat issue. The fungus gnats have come from your soil. Too much water can cause overpopulation of these insects. I have also included a fact sheet on these insects which recommends control. Thanks, Zoey