White powder / crust on Juniper leaves

[Eetyaj]

Hi everyone,

I'm new to Bonsai and recently got a Chinese Juniper. I live in the tropics and I keep the plant on my outdoor balcony, with it getting a good few hours of direct morning / noon sunshine. I water the roots and mist every day. I had rarely applied insecticide.

About 3 weeks ago I noticed white powdery flakes on the leaves and, on one of the lower twigs beneath a leaf pad, it was almost a hard crust. Some insecticide (bottle label read synthetic pyrethoid) and selective pruning at the bonsai nursery got rid of them after a few days.

Now, the white powdery flakes seem to have come back, although in lesser amounts. I attach a few pictures here and would be grateful if someone could tell me if this is indeed scale insect or something else. I had read that Junipers may produce a natural resin that forms white flakes like this.

The plant seems otherwise healthy to my untrained eyes, with light green growing tips and little evidence of other stress such as browning tips or excessive needle foliage.

Should I be worried, or just keep up my daily care regime, apply some insecticide and wait for it to go away ?

As I'm new to this, any comments would be most welcome!

Thank you!
Justin

 

[Stan Kengai]

This is definitely scale. As with most pest, one application of pesticide is not enough. You have to spray at least twice, a week apart, to kill any eggs that have hatched because pesticides typically don't kill eggs.

On a side note, this plant should not be kept inside. I assume that it is because pest activity this time of year in most temperate part of the country are minimal.

 

[Eetyaj]

Hi Stan,

Thank you very much! If you don't mind, I have a few related queries please.

Is there a way of getting rid of scale without using too much insecticide ?

Also, I had read that if the affected area is small, using a toothpick or something similar to pick off the white flakes before applying insecticide will help. Is that right ?

Finally, as for future prevention, what sort of environment encourages scale ? Is it humidity, a lack of sunlight and /or inadequate ventilation ? I had wondered if my action of misting the tree everyday despite it being quite humid and rainy here, as it's monsoon season, contributed to the scale growth.

Thanks again for your patience and for your advice !

Justin

 

[Dav4]

You can use a Q-tip dipped in rubbing alcohol to kill the individual scale insects. Some sort of horticultural oil/dormant oil application would help with more wide spread infestations.

 

[skrit]

The most common comment on the board for new members is "fill in your location on your profile" so that we know a bit more specifically than 'the tropics' where you're at and what environment you're in.

Juniper's aren't really tropical plants and probably won't benefit from misting at all. I'm not sure if it's causing your infestation, but it's needless.
Regarding the scale, I agree with Stan, you have to spray at least twice, a week to 10 days apart, possibly a third time to be safe. Make sure you spray everywhere, undersides of branches, etc. Horticultural Oil or Insecticidal Soap should be all you really need. Try to save chemicals for a last resort.

 

[Eetyaj]

Thanks everyone.

I am currently living in Singapore, 25 - 30 degrees Celsius most days. Although, during monsoon season which just ended, it can rain several days in a row with no sight of the sun. That's why I asked if humidity encourages scale growth.

I've stopped daily misting, other than it being a little therapeutic, I suppose it doesn't really benefit the tree !

I will also look into the horticultural oil and insecticidal soap, as well as rubbing alcohol soaked cotton buds. I was only given synthetic pyrethroid from the local nursery, so I've been using that, although I'm quite averse to using strong chemicals too, especially with a young baby around.

Will the scale drop off on its own after repeated treatment ? So far, after two applications in a week, it doesn't look like it's spreading and white flakes do appear to be fewer in number. I will definitely spray again in a few days.

Thanks again everyone.

 

[Brian Van Fleet]

Juniper's aren't really tropical plants and probably won't benefit from misting at all.

Can you explain why you recommend against misting junipers? Has misting caused problems for your junipers?

 

[Giga]

Just ensure this is actually scale
http://bonsaitonight.com/2014/12/12/white-spots-on-western-juniper/

I have a common juniper(forgot the variety) that does the same thing as the link above.

FYI, juniper's get a lot of their strength from their foliage. Please check your facts before you say them so matter a fact. Maybe your just misinformed BUT junipers benefit greatly from misting. After collecting a new juniper with few roots you can "help" them along with proper protection and misting, and foliage feeding. Granted I'm unsure of your climate as I don't have exp. in the tropics, but even all the advice you get make sure you fact check it by good research. A lot comes with exp. and learning experiences( like this one) but when someone come off as so matter a factly, make sure it is a fact.

Just to prove a point
https://peterteabonsai.wordpress.com/2014/04/03/utah-juniper-aka-big-sexy/

 

[skrit]

My sincere apologies all around, I retract my statement regarding misting. It came more from 'internet learning' than experience, which I think we can all agree can be misleading or down right wrong sometimes. I agree that my statement came off reading like a 'fact', and for that I also apologize. Part of the reason that I made the statement was that based on Eetyaj's apparent location (tropics) and season (monsoon), I presumed that the environment was probably already quite high humidity and that added misting would be redundant.

Thank you for correcting my misunderstanding!

I think something that is still missing from this thread is an answer to one of the original questions:
What sort of environment encourages scale? Is it humidity, a lack of sunlight and/or inadequate ventilation?

(Note: I only have two junipers and thankfully have not had any issues with scale or other pests yet.)

 

[Giga]

Dr google has an answer

http://www2.ca.uky.edu/entomology/entfacts/ef429.asp

 

[Eetyaj]

Thank you for clarifying.

And yes, I had looked at the bonsaitonight site before which is why I posted my pics above to ask if it's scale or resin. To my untrained eye, they both look the same. My tree is Chinese Juniper though and not Western Juniper so perhaps I am being too optimistic in hoping that what I've got is resin and not scale!

It's been over a week and I've applied insecticide thrice in that time. I will keep monitoring it and hope it doesn't spread. The good news I think is that the white flakes have always been dry. I've not encountered the liquid mush described in your link as live scale.

Fingers crossed !

 

[crust]

I am NOT on your juniper leaves.

 

[M. Frary]

I am NOT on your juniper leaves.

Saw crust in the post title and clicked on to see what you had going now. But then I realized.......