Shrivel: please cast your experienced eye

[tom1999]

Hi.

I have 6 seedlings, now 4 weeks old. This is my first, rookie, grow.

4 seedlings look healthy and strong. 2 have developed a worrying shrivel.

My research would indicate the following possible causes.
- I have got the watering wrong? I don't think I have under-watered. The soil is very free draining.
- I have over fertilised - I have only watered with a very dilute Miracle Grow solution after the 2nd week. Might the potting mix be too rich for sensitive seedlings?
- Light is too strong - Envirogrow 2 T5 tubes - around 8 inches above. 18 on, 6 off.
- Too hot? 27 Centigrade max.
- Wind burn. From a small USB fan?? The other seedlings are thriving.
- Pest?
- root rot from over watering? All the other plants have been treated equally and are thriving.

Anything obvious I am missing - your wisdom/appraisal would be appreciated.

Thanks in advance,

T

------

What Strain is it? Mango Kush
Is it Indica, Sativa or Hybrid? Hybrid - more Sativa?
How Many Plants? 2 affected, 4 thriving.
Is it in Vegetative or Flowering Stage? Veg.
If in Vegetative Stage... How Long? 4 weeks
If in Flowering Stage... How Long? n/a
Indoor or Outdoor? Indoor
Soil or Hydro? Soil
If Soil... What is in your Mix? Commercial high quality potting mix.
If Soil... What Size Pot? 4 inch seedling
Size (Wattage) of Light? How Many? 2 or 4 tube T5 Fluoro
Is it Air Cooled? Yes - small PC case fan to extract cabinet air + small oscillating fan inside to stir airflow.
Temperature of Room/Cabinet? 22 - 28 C
RH of Room/Cabinet? ~60%
PH of Medium or Reservoir? Not measured
Any Pests? None seen
How Often are you Watering? once every 48 hours during first 3 weeks, have reduced after week 3 (am I over watering?)
Type and Strength of Fertilizers used? Very dilute Miracle grow
Size or Square Footage of Room? 20 inches x 40 inches, 40 inches height.

 

[Carcass]

Welcome to 420,tom1999

You've definitely got something different going on...

Do a google image search for "Hemp Russet Mites" and see what you think
Aculops Cannabicola is the scientific name-symptoms match what you've got going on.

 

[GreenStart2019]

Unfortunately that does look very very very similar to mites of some sort.

Look into neem oil it's a powerful natural insecticide and fungiside.

But that does look pretty advanced , when did you start noticing it.

**I am new myself just stating what I have researched

 

[Carcass]

You'll need a loupe or microscope to see them-they're about 1/4 the size of a spider mite,and spider mites are pretty darn small...

 

[tom1999]

Update.

Thanks for the Russet / Broad mite heads up. I looked at web pages on the subject and indeed the leaf pattern is strikingly similar to what I am seeing in my grow cabinet.

I called the local grow shop and they commented it was very rare but very serious if I have an infestation. They also suggested the jeweller's loupe to inspect, before doing anything further.

As luck would have it I have a good microscope - so pulled both suspect leaves and some OK leaves to compare.

I used both 40x and 100x magnification to go over the leaves. It was a tense and fascinating moment - Anyone seen the microscope scene from the 1971 movie The Andromeda Strain - I was there! Poor phone images were captured to share here.

I immediately found these suspicious outlines, but they were solitary on the leaves I examined - no others were found.

All other leaves were clear and looked vibrant! Hairs, veins. It is a view to get you close to your plants!

In summary - I could see no sign of anything untoward on any of the leaves. No populations of mites of any sizes, no egg clusters.

So - from the leaf shrivelling alone, other web pages indicate Russet Mites. But none found.

Is this a "monitor over the next few days" situation? Should I be thinking about predatory mites, precautionary spraying?

Thanks for your attention and inputs so far - it is much appreciated.

T

 

[tom1999]

But that does look pretty advanced , when did you start noticing it.

Started noticing it around 2 weeks ago.

 

[Carcass]

Wow,definitely not a mite infestation-I really don't know what to tell you,then-
it doesn't look to me to be nute related,but I'm no expert...maybe @Emilya could take a peek and see what she thinks...then you and I can both learn something.
Sorry I can't personally be more help....this seems like a real odd one...

 

[Emilya Green]

look at this critter... this well fed critter that looks like a cow. That pretty well describes a mite... they just eat and eat and eat and eat...
You definitely have a very severe infestation and I would move to your highest defense alert. It is time to fight back strongly or lose the crop, and if you don't wipe them out, any other crop you bring into this space.

 

[Carcass]

Interesting-I thought he'd see a crapload of them under the microscope.
The symptoms match an infestation,I just thought they'd be crawling all over the place.
Thanks Emilya-what's it take to get rid of them?

 

[Emilya Green]

Thanks Emilya-what's it take to get rid of them?

a flamethrower...

we have some sponsors that offer less dramatic methods.

 

[tom1999]

Thanks all for your inputs so far.

I snipped several more leaves today to see if I could spot anything else unwanted. I also took a pinch of the soil to inspect of anything lurking there.

Again, at 40x magnification - all looked very healthy. No sign of a single mite or eggs on leaf or soil..

I will be re-potting into larger pots in the next 48 hours - will examine roots for health, vigor and consistency between good and bad plants.

I am back on plain water - no feed or nutes. The new soil should provide everything for another week or so.

Will take stock and see what comes. I'll also clean out the grow cab to ensure best environment. (already pretty clean).

Thanks again - will report back with any changes.

 

[Carcass]

Good deal,Tom,I hope you get it cleared up-if not there's various choices of cannabis friendly miticides you can apply to the plants as a next step.