What is causing this ?

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What is causing this ?

Post by Zencitizen »

Is this caused by pests, under-watering or over-watering?
Some of the foliage looks healthy, some foliage has turned brown (and then become green again past the brown), and most recently I've noticed they have started to become this colour.
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Re: What is causing this ?

Post by shibui »

Could be a number of things.
A couple of pests can make tips die. Check for tiny scale insects. Harder to find mites because they are even smaller but look for very fine webs among the affected foliage or tap the branch above a sheet of white paper and look closely for tiny moving creatures on the paper.

Given that it happened before then recovered I would guess more likely to be a watering issue. Shimpaku do not like wet feet but also do not like being dry, even for a day. Is it possible the pot got dry recently?

Have you moved the plant recently? Pics do not show overall tree so it is hard to guess if this is localized to lower branches or all over or just on the outside. Sunburn normally affects upper and outer branches and often just the sunny side.

What sort of potting mix is the tree planted in?
How often are you watering?, How much each time?
Where does it live? - facing north, outside, inside, under cover, on the ground, bench, etc
Sometimes the clues lie in things around rather than just in the symptoms. The more info you can give, even stuff that may not seem relevant, the more likely we can diagnose accurately.
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Re: What is causing this ?

Post by Zencitizen »

It's kept outdoors, I had an erratic water schedule because of work but it's now automated, 3x day for 6min w/ sprayers, doesn't get rain water.

Soil is 25% pumice, 75% Debco Bonsai Soil Mix.

I use Seasol occasionally.

Roots looked very healthy during repot (white inside when cut not black).

I did spray with pesticide (Pest Oil) a couple weeks ago to kill juniper scale (at night). I have noticed some webbing, but the Pest Oil should deal with that as well right? I am hesitant to apply more pest oil in case that's the problem

It's located on my balcony, NW facing, sub-tropics so it can be quite sunny and warm.

My guess is it dried out so that's why I've got the sprinklers going a lot now to see if that fixes the problem. If it continues I guess it means it's due to something else.
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Re: What is causing this ?

Post by shibui »

Outdoors is good.
Automated watering should be fine provided you have matched water cycles to weather. It is easy to keep the soil too wet or too dry so keep checking soil moisture levels. 3 x a day seems to be a lot but other factors like soil type and local weather play a big part. Even the tiny pots here manage with 2x water each day.
Seasol occasionally does NOT sound like an adequate diet. With regular watering nutrients get washed out of the pots quickly. Most experienced growers I know are fertilizing every 2-3 weeks to maintain good growth and healthy plants.
Seasol is not sold as a fertilizer. Check the label - it is marketed as a soil conditioner because nutrient levels are relatively low and variable depending on the time of year and source of the raw seaweed. Many growers still use seasol but in conjunction with a real fertilizer with known nutrient levels. I'd be looking to supplement your seasol with Powerfeed or another complete fertilizer.

I just checked and Yates says that pestoil should also control mites but they are notoriously hard to kill so check regularly to see if there are any signs.

The signs are consistent with a dry spell but don't go overboard with water now. Too much of a good thing can be just as bad as too little. Give it a few weeks at the new settings and see what happens.
Trimming off the damaged foliage would not usually cause any problems for the tree and may help you monitor whether the issue has gone or not.
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Re: What is causing this ?

Post by Zencitizen »

Thanks for the reply and advice,

Just to clarify the Debco Bonsai soil mix comes with Osmocote controlled release fertiliser included in it, so I am hoping that feeds it adequately.

I have some Powerfeed available to use and also some more Osmocote I could sprinkle on top but am wary of over fertilising so I have left it as is for the moment.

The soils seem to drain well with the mix and it can really heat up here so I'm hoping the 3x day works well. I've set it up to run at 5:45am, 9:15am, and 2pm. I could maybe remove the water at 9:15am but I'm concerned it would dry up in the middle of the day.
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Re: What is causing this ?

Post by shibui »

Re fert: You are correct to be wary of over fertilizing. It is not common but can occur if someone gets too heavy handed.

Most commercial potting mix comes with the bare minimum of fertilizer that the makers can get away with and still claim the standard ticks. The fert is one of the expensive components so they make better profit when using the minimum.
Osmocote also comes in a range of release times. The potting mix standard says the fert should supply nutrients for 3 months after that it is up to the grower.
I just checked the Debco site and found that bonsai mix has 6 month of fert so more than the min but still not a full year's supply of nutrients and if the tree has been in the pot for more than a year what will supply nutrients?

I also add a controlled release fert to my potting mix but use a higher amount and use a 12 month release formulation. The controlled release provides a constant background level of fert but it is still low level given that we water bonsai pots so much. I supplement the controlled release with regular applications of liquid feed (usually Thrive or Powerfeed but any brand will do) and occasional applications of solid pellet organic fertilizer on the surface of the pots. I have never experienced damage from too much fert but I do see signs of nutrient deficiency, usually in trees that have not been repotted recently, if I neglect the supplemental fert.

Re watering: Watering bonsai is one of the difficult aspects of bonsai culture. We use small pots with minimum soil so water becomes critical. Every situation is different so requires different schedules and your situation is very different from mine so If your watering schedule appears to be doing the job leave it as is for now but be aware that too much water can be just as bad as not enough. It certainly takes longer to kill a plant but can still do so. Just do regular checks on soil moisture whenever you are able to monitor that the soil gets to slightly dry just before watering occurs.

Good luck with the bonsai journey. I hope you will update in a few months to let us know how the tree is growing.
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Re: What is causing this ?

Post by dansai »

Shibui has offered some great and detailed advice that has covered many things. As to the original issue I would say underwater most likely. Junipers can take weeks to show signs after an event, like breaking branch during wiring or drying out too much. A watering system can be a useful tool, but it hard to ensure its doing its job and watering the right amount. 3 x a day seems like a lot. weather also has a big effect on watering. An overcast and cool day means plants may only need water once a day, or maybe not any if during the winter months. A warm windy day can dry them out in a couple of hours.

You also haven't put you location in your profile. Even just a general one is helpful for others to tailor advice. Far North Queensland has very different growing conditions to Sydney, Tasmania and Broken Hill.
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Re: What is causing this ?

Post by Zencitizen »

So in the last few days have noticed this has spread quickly to some of my other junipers which definitely have not been under watered and were previously very healthy, I've also noticed these black spore like area's.

After some more research I'm thinking it's Phomopsis (Juniper tip blight). It's been quite humid and warm here in SE QLD with the recent storms.

I've applied Mancozeb to all my junipers and will go through tomorrow and cut out the infected area's. I've also reduced the watering to 2x day.
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Re: What is causing this ?

Post by Zencitizen »

Update:

I think this was definitely Juniper Blight, the combination of sprinklers & humid weather spread it through my junipers extremely quickly.

What has stopped it spreading further is:

1) I started watering in the early morning only.
2) Spraying with Mancozeb Plus every 7 days (I’ve now swapped to Liquid Copper as I don’t like the residue from Mancozeb + and health concerns).
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