Cotoneaster new growth issues

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Hprelude
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Cotoneaster new growth issues

Post by Hprelude »

Hi everyone

My cotoneaster tree has been suffering over the last year. The leaves and new growth have white spots and it’s colour looks very bad. I’ve attached photos of the leaves which better describes the issue.

I’ve used confidor and Yates rose gun to control the insect and pests however the tree is still unwell. I’ve also pruned the tree back as much as I can to remove all the ill growth.

Wondering if anyone has had this issue?

Thank you in advanced.
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Phil Rabl
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Re: Cotoneaster new growth issues

Post by Phil Rabl »

I have been growing Cotoneaster as bonsai in Canberra for years. Mine (which I believe to be C. glaucophylus) have a different leaf to yours. I have not had the symptoms you describe, but they certainly do shed their old and damaged leaves. The second photo shows a lot of new growth so I would be pretty confident the tree is OK. On pruning, the species I have can take massive pruning. They shoot back readily from old wood. Some of mine had become too tall so I gave the a big 'rejuvenation' prune over winter and they are all growing back strongly. A few years ago I defoliated one in July as an experiment and it grew new leaves as soon as the growing season began in Spring. They are tough. There is still 6 weeks of warm weather to come (probably more in Melbourne) so, I wouldn't hesitate to cut off any damaged or diseased leaves. I am sure it will grow new ones before winter sets in.
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Re: Cotoneaster new growth issues

Post by shibui »

The leaf symptoms look a lot like azaleas with azalea lace bug. I am not sure if azalea lace bug also feeds on cotoneaster but it could be another similar sucking bug.
The problem is that the older leaves have been damaged. They don't get better when you wipe out the bugs but new leaves should be OK if you are on top of the problem.

Another possibility is nutrient deficiency. Do you know the pH of the soil and water you use? What fertilizer regime has the tree had?
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Hprelude
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Re: Cotoneaster new growth issues

Post by Hprelude »

Hi Phil Rabi, I did remove most of the damaged and diseased leaves however the new leaves develop the same issue. At first the leave are very green and then develop little white spots. This photo shows how bad the some leaves are. I will now remove the damage and diseased leaves to see how the new growth develops. PS. your Cotoneaster is a fantastic looking tree.

Hi Shibui, it does look like the new leaves are developing the same problems but Ill remove the bad leaves shortly and see if it improves in a few weeks. I don't know the pH level of the soil, I was very close to purchasing a Gardman soil pH level meter at bunnings last weekend. Maybe Ill purchase one this weekend, unless the one that you push into the soil is not recommended?

I was using Powerfeed citrus and fruit liquid fertilizer every two weeks (although I missed a fortnights in between over the past 8 months) and now Ive switched to the Osmocote fruit, citrus, trees and shrubs controlled release fertilizer.
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juan73870
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Re: Cotoneaster new growth issues

Post by juan73870 »

Hprelude, I'm pretty certain what you have there is spider mites. I've experienced these on the same cotoneaster and they are difficult to see and very difficult to eradicate. I'm almost 100 percent sure that is what you've got here.
Isolate the plant away from other plants, spray neme oil liberally onto the back side of all of the leaves every second or third day for a couple of weeks.
Hope this helps. 🙂
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Re: Cotoneaster new growth issues

Post by shibui »

Your fert program sounds good so probably rule out nutrient deficiency unless the soil pH is way off. I am told the push in soil pH meters are notorious for being way inaccurate. I use the powder test kits because they are usually much better.
Juan has probably solved the problem for us. Mites are not insects so they are not affected by most insecticides. You need to use a miticide to control them. I have not used neem on mites. There are some other effective miticides but check that the label lists spider mite as a target species because many insecticides infer they treat but actually don't. I have found spider mites quite difficult to get rid of. All leaf surfaces must be sprayed, especially underneath. You will probably need to repeat spray every week or so for a while to catch the new ones that hatch out.

Spider mites are usually much worse in protected locations, especially indoors. I assume you are keeping the tree outside somewhere?
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Re: Cotoneaster new growth issues

Post by greg27 »

I've also had success with neem oil (Eco Neem from the big green shed) on spider mites. It's often suggested that neem oil doesn't harm bees but there's now some research which contradicts this, so it's best sprayed at or after dusk.

I've found it's best to spray the plant again after 10 days or so just to make sure you've got them all.
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Re: Cotoneaster new growth issues

Post by juan73870 »

Also, Phil Rabl, the trunk on your cotoneaster is a beauty! Beautiful little tree :clap:
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Hprelude
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Re: Cotoneaster new growth issues

Post by Hprelude »

Hi Juan73870, thanks for your reply.

Ok that would make sense why the insecticides do not work. Ive looked online at bunnings and they have a Eco-Organic Garden Eco-Neem Concentrate, ill read the label when I'm there to make sure it will get rid of spider mites. The tree was near another, but i have now isolated it. I also pruned the tree quite a bit.

Thanks Shibui, I will purchase the soil ph kit as well rather than the push in soil ph meter. Ill test the soil is weekend and let you know what the results show. Yes I keep the tree outside always but its previous location wasnt ideal. Not enough sun and too close to other trees. I have since moved them to a better spot and the tree seems to be improving. Although I've had the mites issue for the last 9 months.

Thanks Greg, good to know. I will use it after dusk :)
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