Question regarding needle tip browning

[casun]

I have two Ponderosa Pine seedlings and two Sugar Pine seedlings. One of the Ponderosa Pine seedlings is in a colander and the other is in a one gallon nursery pot. Same for the Sugar Pines (one in a colander; one in a one gallon nursery pot). All four seedlings are in identical soil - pumice, lava, akadama. The needle tips are browning on both seedlings in the one gallon nursery pots. Basically no needle tip browning in the colanders.

Question: What is causing the needle tip browning? Are the nursery pots retaining too much moisture?

Sugar Pine in the colander:


Sugar Pine in the one gallon nursery pot:


Ponderosa Pine in the one gallon nursery pot:


Ponderosa Pine in the colander:

 

[Bonsai Nut]

How long have you had the trees? Did you move them into the nursery pots and colanders at the same time?

I wish you luck with your sugar pines. I was unable to keep them in Southern California because I couldn't give them enough cold.

 

[casun]

All four were planted into their respective containers on the same day in late July.

Thank you for wishing me luck with the Sugar Pines. I’ll probably have the same trouble you had, so I’ll probably learn that lesson the hard way.

 

[clem]

I'm not woried about your needle symptoms. It could be a water issue (excess)? I advise you to protect your pines from excessive rain, to let the soil surface dry out in a ventilated greenhouse

Considering the period of the year (winter), and the lesions on the needles, it's probably not a fungus attack.

From Ryan Neil teaching, i know this regarding needle "yellowing/bands/brown points" :
If it touches all the tree like your "sugar Pine in the one gallon nursery pot" it's probably a root issue affecting all the foliage
If it touches only a few branches, it's probably a local issue : fungus/insects/weak branch/local damage

Here's an interesting pic from Michael Hagedorn's blog ->

 

[Clicio]

Usually yellowing or brownish tips are a symptom of overwatering.

 

[casun]

Thank you clem and Clicio. The water excess photo most closely resembles what is happening to the two seedlings in one gallon nursery pots, so it does seem like it’s being caused by too much moisture. If true, it’s surprising that there’s that much of a difference between the colander and nursery pot. Glad I did this container test. I’m also noticing other signs of healthier growth in the trees in colanders versus nursery pots. Advantage colander.