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"Small Head" Disease? Cannabis Virus? any feedback?

Hi all,

Looking for any grower feedback on the below, seeing something we have not seen before.

Have a large greenhouse facility in CA. Automated light dep.
Bays of 500+ plants in each bay.

Plants look healthy in propagation, mom appear healthy.
Aprox 3 weeks into flower bud heads appear stunted, leaves closest to buds are yellowed, rest of leaves on plant look healthy but small.

Plant will continue to grow through harvest but buds are very small, leaves are brittle, almost zero trichomes, no smell, not sticky at all.

Maybe 10-20 plants out of 550 exhibit the issue, but increasing number. Plants right next to them are healthy and vigorous, climate is the same, feed is identical (coming from automated fertigator feeding entire bay at a time). Issue crosses strains so its not genetics.

Best guess at this point is infected mom and issue is being spread by cross contamination in propagation (scalpels etc) when taking clones.

Anyone seen anything like this? stumped everyone so far.

Thanks for any feedback.


@cellis @URBorganic @ethan @ryan1 @botanyunlimited @Cody @Pharmboy @tamarindotradingco @mwmzx6 @JoeGrow @ralpht @Dsolomon @milessadowsky @Alfro_EndoFarms @casey @caseyrootz

Does anyone notice what is wrong by the description and pictures?

Wow, looks like Tobacco Mosaic Virus. I think there is a simple test for it now. @Hunter, have you seen references for TMV testing?

There are some old protocols from Paul Eckl and Bob Olgovie that they commissioned from I think Pen State. For test and control.

One strange contol method involves heat. You would have to look up citrus production. You heat the plant up, killing the virus but not the plant.

Do you notice clubbing on any other areas?

Anyone else notice anything?


One othe thing could this be Fusarium? It also causes a clubbing, in some ornamentals.

You could sacrifice a couple plants and use a fungicide not labeled for Cannabis. Remove them from the greenhouse, don’t risk cross contamination. There are a couple systemic fungicide that control fusarium well in other crops.


Thank you for your feedback, @ethan!

Soil drench cal / mag
Royal knight posidean
It’s locked up. Not producing what the plant needs. During flower the plant
needs to breath the most. It’s the most stressful time. Need to check EC
and Balance.

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And flush to knock EC and salinity. Knock sodium off soil colloids. Cal/
mag/ potassium (volcanic ash) flush it and then flush w regular water. Too
far for a foliar. Need to rotate drenches.


before using any pesticides. Take it to a lab. Get it identified. So we know what the issue can be. my history tells me that if any plant is under stress. A pest of any kind will attack. Fungal, insect, root rot. Stress can come in several ways. Get it identified and try organic cultural practices first


You’d have to do genetic testing on the “infected” plants and look for signs of the virus. Because TMV can evolve and vary based on the host species, it would have to be compared to known strains. That said, TMV is common enough that people know about it, so most labs that serve horticulture would be able to test for its presence. Basically, you need a genetic test to confirm it’s TMV.

That said, what I’ve typically read about TMV is it primarily causes stunted growth, “clubbing” of leaves, yellowing of leaves, which matches @graham’s description. I don’t know how it affects reproductive tissue in cannabis, partially because each strain of TMV acts slightly differently.

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TMV in lots of plants prevents flowering. In ameranth flowers are almost completely absent. Harry Laudens walking stick, a filbert, it causes a twisting of the stem and sterility. They bread the filbert and introduce TMV into the seedlings.

Let me see if there is an ELSA test for TMV

TMV testing strips

University of Massachusetts

I wish we had testing kits when I was younger. Would have saved lots of time


Thanks a lot for all the great feedback… much appreciated community…In answer to some of the questions and additional pictures:

Older leaves look healthy, the further from the flowers the better they look few more photos:

Lower leaves:

Same plant at the flowers:

Also noticing on the plants that are having issues various deformations, 3 fingered leaves, leaves with curls etc.


What are those light colored splotches on the lower leaves in this picture and, why the hell is there one on the schedule 80 pvc just above the pot?

Also, have you pulled one out and looked at the roots?


You’re growing in large soil pots. How much nutrients, and how often?

Root zone development is super important for healthy plants and I’m of the belief (as Claude Bernard, Florence Nightingale and others), that there are no bad organisms - since they are pleomorphic - only bad conditions.

Fix the conditions and you’ll fix the problems. That you only have a few specimens exhibiting the problem is telling, imho.


bad conditions. ipm . something is off with the foundation. I think ??

We believe that a serious Fusarium virus is attacking our property. The lab tests from dirty business soils should be here Monday. If so the symptoms you are having do not match ours. I would guess that it is Tobacco mosaic or another systemic plant disease. Has anyone treated or successfully harvest a heavily infested Fusarium crop that you know of?


Do you have pictures? Fusarium is a systematic fungus. I do not know any fungicide labeled for cannabis.

With some pictures I will look to see what other growers around the world are doing for control.


heritage is a systemic and mycobutanil also known as eagle. the spray apples and everything else we eat. Its a last case scenario. I really feel if we monitor and do the right ipm with consistent management you can salvage

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Have you already 'scoped for broad mites? You can’t find them with a hand lense, you need at least 60x to spot them. It only takes a few per leaf to start showing symptoms. Once there are 10-20 per leaf growth stops. The first sign is usually prematurely browning pistils and new growth becomes pale. Leaf contorting, russeting, clawing comes next. I use my bench top scope I purchased to look at compost tea. I alternate using the light on the scope as well as a halogen lamp as close as possible to the sample.


Preventing a problem like Fusarium is preferable to fighting one. Dos (David #2) at Cultivation Gear is a definite believer in an ounce of prevention. For Fusarium, as well as other problems like Pythium, he would recommend a Trichoderma inoculation of the root zone. RootShield Plus is his favorite and the wettable powder works well in most situations It has 2 strains of Trichoderma, which are aggressive colonizers of the root zone. There are also some EPA registered plant extracts which will boost a plant’s defense mechanisms. Dos is available to help at (815) 301-4941. He would be better able to help on specific issues than I would.


@JoeGrow I couldn’t have said it better myself.

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