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Malformed leaves on tomatoes each year #865192

Asked April 19, 2024, 10:27 PM EDT

Each year, my tomatoes and cucumbers, start strong, only to become stunted and malformed. They stay small and produce small and misshapen fruit. I was dismayed to see my tomatoes and squash starters in the basement are already getting the misshapen leaves, and seem stunted, considering I started the March 6 and have grow lights. I also have a fan on the plants most of the time trying to discourage these pests. I see some tiny black bugs, flying or crawling on the soil. I do not see any bugs on the plants, or on the mottled leaves, or under the curled leaves. What are these bugs? How do I have these bugs every year, even in the basement starts? How should I treat the seedlings? I have been in the habit of using Monterey garden insect spray ( active ingredient of Spinosad) the past few years, and that works for a few weeks, and then I have to reapply up to the maximum times. Is there any way to eradicate this pest so I don’t have to fight it year after year? Thank you for your help! Fjaere

Ramsey County Minnesota

Expert Response

The little flies you are seeing are from fungus gnats. Their presence usually means the soil is staying too wet and should be almost dry between waterings. I highly recommend an inexpensive soil moisture meter from a source like Amazon. The new soilless mixes can be difficult to manage. Each one has its own quirks. Curling leaves and stunted growth can also occur if plants get too much water. They can stop growing and be set back as much as 3 weeks. To kill fungus gnat larvae us BT. BT is non toxic and available at garden centers. BT won’t kill any of the larvae that hatched into flies but it does prevent flies.
Your plants will recover and if isn’t  as hot as last year they should grow well. Tomatoes will pause flowering if temps are over 85 F. 
Overwatering causes leaf curl just they way too little does because the roots are damaged and they can’t take up water. 
Thank you so much for your response. It is helpful to have a name for those little black bugs – – fungus gnats, and a suggestion for treatment.  I was able to capture a picture just now. Could you confirm that this picture is a fungus gnat?

I also looked deeper online, and the seedlings and my previous years’ tomato/pepper problems match the pictures of “mosaic virus.”   If that is the case, what would the treatment be?    In the meantime, I will start by decreasing soil moisture and treating for fungus gnats. Thank you!

Fjaere



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Fjaere Harder Nussbaum
(Pronounced fee-air-uh)
 




On Sat, Apr 20, 2024 at 12:30 PM Ask Extension <<personal data hidden>> wrote:
The Question Asker Replied April 20, 2024, 2:22 PM EDT
Sad, if they are suffering from mosaic virus the only thing to be done is to discard them and do not compost the plants.  Buying  seed from a reliable source and   sanitizing pots and using fresh potting soil will help. Eliminating the virus will require rigorous sanitation. 
https://extension.psu.edu/tobacco-mosaic-virus-tmv#:~:text=Managing%20TMV&text=Purchase%20virus%2Dfree%20plants.,symptoms%20and%20obtain%20a%20diagnosis.
I can confirm those are fungus gnats. Good luck, spring is coming.
Thank you so much for your help! I think the fungus gnats and over watering are a small problem, but that the virus is the bigger problem that keeps happening each year.  

 I am going to dispose of all my seeds and starts and sanitize vigorously.  I will either buy new starts or take a year off. 
Would letting the garden soil lay fallow for one year help?

Thank you!


Fjaere Harder Nussbaum
(Pronounced fee-air-uh)
 




On Sun, Apr 21, 2024 at 10:42 AM Ask Extension <<personal data hidden>> wrote:
The Question Asker Replied April 21, 2024, 6:46 PM EDT
A year may not be long enough for any residual plant debri to completely break down. Container planting may be best for this year.
https://extension.umn.edu/disease-management/tomato-viruses
https://www.apsnet.org/edcenter/disandpath/viral/pdlessons/Pages/TobaccoMosaic.aspx
I think that is the ticket! Or a community garden.  Thank you for all your help!

Fjaere Harder Nussbaum
(Pronounced fee-air-uh)
 




On Sun, Apr 21, 2024 at 6:07 PM Ask Extension <<personal data hidden>> wrote:
The Question Asker Replied April 21, 2024, 7:52 PM EDT
Yo are welcome, happy gardening.

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