AusBonsai

Is it just me or are there a lot of curl grubs around this year, although I haven't had that much experience in Qld after only moving here 7 months ago from Mt Gambier. While I did get some down there nowhere near as many as I have this Summer, I have been getting around 10 per pot and have lost 5 trees so far.

As most of my trees are in development I am using a premium potting mix, I will need to change to a more inorganic mix to try to address the grub issue. I think a 50/50 ratio may be my next move, as a totally inorganic mix I have read is more often used in the refinement stage.

I would be interested to hear from others who may have had similar issues and how they overcame them.

I've only ever had a problem one year when they affected a few trees. Fortunately I found them before the damage was fatal.

Look for soft, disturbed soil on the surface where they are digging underneath.

Systemic insecticide seems to be effective if you can get it.

shibui wrote: ↑February 14th, 2022, 8:07 pm I've only ever had a problem one year when they affected a few trees. Fortunately I found them before the damage was fatal.

Look for soft, disturbed soil on the surface where they are digging underneath.

Systemic insecticide seems to be effective if you can get it.

That is what I noticed and as the roots are eaten the tree loses stability as well as a obvious decline in health. With reduced root mass the potential for root rot increases as the same rate of watering can not be taken up by the remaining roots.
I have been busy with renovations over the last 6 weeks and have not as much time to check the trees properly,

I'm in Brisbane here, and have never had a problem with curl grubs in my own trees. Nursery trees arriving in organic mix yes, but never in my 75% inorganic mix. Increasing the % of inorganics is probably the best way to go; if you are losing trees, it is false economy to persist with commercial mixes, and insecticides should be a last resort.

Haven’t had any for quite a few years now. Think l might of solved my problem, added some diatomite generally about 15-20% of the mix. Has many benefits and one is that curl grubs do not like it upsets their digestive system. Also sprinkle some lawn grub granules on the surface and water it in, they come to the top very quickly and you just pick them and throw’em to the birds. This works well for my trees. Come repotting time you can see where the grub have been.
Cheers RodM

Redsonic wrote: ↑February 15th, 2022, 10:13 am I'm in Brisbane here, and have never had a problem with curl grubs in my own trees. Nursery trees arriving in organic mix yes, but never in my 75% inorganic mix. Increasing the % of inorganics is probably the best way to go; if you are losing trees, it is false economy to persist with commercial mixes, and insecticides should be a last resort.

Cost was not the reason for using the commercial mix, I have read that trees in development should use a organic mix. Most of my trees are in development. I thought that inorganic mix was for the refinement stage.

PWC wrote: ↑February 15th, 2022, 7:00 pm

Redsonic wrote: ↑February 15th, 2022, 10:13 am I'm in Brisbane here, and have never had a problem with curl grubs in my own trees. Nursery trees arriving in organic mix yes, but never in my 75% inorganic mix. Increasing the % of inorganics is probably the best way to go; if you are losing trees, it is false economy to persist with commercial mixes, and insecticides should be a last resort.

Cost was not the reason for using the commercial mix, I have read that trees in development should use a organic mix. Most of my trees are in development. I thought that inorganic mix was for the refinement stage.

all of my trees are in 100% inorganic mix and the day the come into my yard they get repotted regardless of a tree in Refinment or a seedling
I use inorganic because of Curl grubs years ago and have not seen one in 1 years

try adding 50% inorganics to your mix and you should only get a few if any going forward

ps. Inorganic mixes can be reused year after year and thus make a very cheap growing medium

Ken

For my trees in development I use a locally made mix that has lots of gritty particles in it. Its probably 70% aged pine bark, the rest is sharp sand, basalt, charcoal and coal ash. I have never seen a curl grub in this mix. I assume it is the grittiness that they don't like. Previous mixes weren't as gritty and I would occasionally find up to 20 in a 200mm pot.

There is no reason that developing trees need a different soil mix to older ones. Using one standard mix for all your trees simplifies watering and fertilising.