Apex37
Chumono
This kinda just appeared over the past couple days and I have no idea what this is but it’s all over my Chinese Elm. We’ve been getting a lot of rain so I’d be surprised if it’s aphids, but looks similar.
What is this all over my Chinese Elm?
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Looks like you have an infestation of White Prunicola Scale.
Some scale insects are easier to manage than others. This is one of the tougher ones. This pest will have three generations each year. By the time the end of the season rolls around, your tree or shrub could be completely infested. This may even happen in areas of the plant where you’ve not noticed this pest before. White Prunicola Scale is often mis-identified and treatment ignored for a number of years. When this happens, there will be so much scale encrusting the branches that it can almost appear like someone had slathered it on with a brush.
This insect is built for survival. As they develop this crusty shell, it makes them easier to shelter themselves from not only natural predators but also makes it difficult to get insecticides to this pest. This makes it increasingly difficult for scale control. Managing White Prunicola Scale is possible, but it requires frequent inspection and a little extra effort to remove pests.
Some scale insects are easier to manage than others. This is one of the tougher ones. This pest will have three generations each year. By the time the end of the season rolls around, your tree or shrub could be completely infested. This may even happen in areas of the plant where you’ve not noticed this pest before. White Prunicola Scale is often mis-identified and treatment ignored for a number of years. When this happens, there will be so much scale encrusting the branches that it can almost appear like someone had slathered it on with a brush.
This insect is built for survival. As they develop this crusty shell, it makes them easier to shelter themselves from not only natural predators but also makes it difficult to get insecticides to this pest. This makes it increasingly difficult for scale control. Managing White Prunicola Scale is possible, but it requires frequent inspection and a little extra effort to remove pests.
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Apex37
Chumono
My first time dealing with any scale. I sprayed it down with some insecticide and gonna treat with a systemic too. I’m waking up early tomorrow to scrub it down with soap water and then treat any areas that doesn’t clear out with q-tip and alcohol.
Brian Van Fleet
Pretty Fly for a Bonsai Guy
Agreed, scale. This one is nasty, as these are the eggs I believe. Manually scrub off what you can and use rubbing alcohol or Malathion to reduce the numbers, then be vigilant and repeat. Here is what happened to one of my trees with what appears to be the same type.
nebaribonsai.wordpress.com
Wanna see something nasty?
Me neither, but nevertheless, I noticed some white flecks on this trident early in the spring. They didn’t come off easily, and weren’t moving either, so I just kind of ignored them. 3/…
nebaribonsai.wordpress.com
AJL
Chumono
Mike Corazzi
Masterpiece
Systemic treatment !!!
Apex37
Chumono
Well the soap water/toothbrush treatment did nothing. Q-tips and alcohol is working a lot better, but man this thing is INFESTED. Definitely a learning experience here. I’ve been more lax on my insecticide treatment this year trying to go a more “natural” approach. Gonna probably be two days of q-tipping every nook and cranny. I treated it with some Bonide Systemic Insecticide and spraying with some Malathion.
Apex37
Chumono
Also, thank you all for your help on this, seriously. I’m definitely gonna be QT’ing the tree and watching it. Might as well treat all the trees with systemic as well just in case.
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rockm
Spuds Moyogi
Sk
Skip the spray. It is ineffective on scale unless you catch the precise moment when the larvae are in their "crawler" stage That lasts a VERY short time. Systemics for such a heavy infestation, physical removal of the scale are the combination that will be most effective. I would also keep this tree well away from any others in your collection for a while.
+1 on the advice on this thread to move to physical removal. I had a very bad infestation of scale on a Juniper last year. Insecticides were not effective. I spent probably about 4 hours going through every branch and every needle with an old used nylon bristled toothbruth. I made two passes on the tree and it significantly reduced the scale, but did not eliminate it. I expect to repeat that cleanup this upcoming season.
Mike Corazzi
Masterpiece
I use this on ALL the trees.
www.bonsainut.com
I have ONE flowering crabapple that I post a sign for that says
"Bees, STAY AWAY !"
Truth is, we get very few bees. Undoubtedly from neighbors who have ignored Rachel Carson.
NO MORE APHIDS !!!..... or SCALE !!!
It's the time of year again for the pesties. I've been regularly recommending this product in various threads here when I see them. I'm putting this one here in General Discussion and then I can just link it when someone is having a bug problem. I started using this 3 years ago. Since that...
I have ONE flowering crabapple that I post a sign for that says
"Bees, STAY AWAY !"
Truth is, we get very few bees. Undoubtedly from neighbors who have ignored Rachel Carson.
Leo in N E Illinois
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Bee safety and systemic pesticides depends primarily on when you apply the pesticides. It is mandatory that you read the pesticide label and follow the application recommendations there. The label instructions trump any of my suggestions.
Bees are primarily attracted to trees and shrubs in FLOWER, apply systemic pesticides after flowering or remove flower buds if applying before flowering. The scale insects will eventually kill your tree, removing flower buds will not harm your tree, skipping a season of flowering is not a big deal.
Applying a systemic pesticide to a tree or shrub that is not in flower presents a much lower risk to bees. Bees are generally not attracted to plants that are not flowering. A systemic on a non-flowering or out of flower tree or shrub is not a great risk.
Spray your foliage and soil surface. Do not spray to the point of run off. Or if you do have run off, make sure the run off does not flow into areas of flowering plants. For example, if your lawn has a lot of white clover, bees will frequent your lawn, avoid spraying your trees where the run off will flow into the white clover in your lawn. This helps improve the bee safety of using systemics.
Imidacloprid is a very effective systemic, but it must be used with caution.
Bees are primarily attracted to trees and shrubs in FLOWER, apply systemic pesticides after flowering or remove flower buds if applying before flowering. The scale insects will eventually kill your tree, removing flower buds will not harm your tree, skipping a season of flowering is not a big deal.
Applying a systemic pesticide to a tree or shrub that is not in flower presents a much lower risk to bees. Bees are generally not attracted to plants that are not flowering. A systemic on a non-flowering or out of flower tree or shrub is not a great risk.
Spray your foliage and soil surface. Do not spray to the point of run off. Or if you do have run off, make sure the run off does not flow into areas of flowering plants. For example, if your lawn has a lot of white clover, bees will frequent your lawn, avoid spraying your trees where the run off will flow into the white clover in your lawn. This helps improve the bee safety of using systemics.
Imidacloprid is a very effective systemic, but it must be used with caution.
Apex37
Chumono
Well I’ve spent 2 days and about 7 hours total cleaning this tree top to bottom. 
I got some firm bristled toothbrushes and insecticidal soap and scrubbed it down, went back over with q-tip and 91% alcohol, and toothpick where I could that needed it. I feel like at this point I’m having a hard time differentiating scale from the white of bark of the tree or possible soap residue. Can anyone take a look at these photos and tell me if you can see any definitive scale? I feel like it looks better in person, but I know I’m probably missing some and will end up needing to make another pass at some point. I treated it with some imidacloprid systemic a few days ago as well.
I got some firm bristled toothbrushes and insecticidal soap and scrubbed it down, went back over with q-tip and 91% alcohol, and toothpick where I could that needed it. I feel like at this point I’m having a hard time differentiating scale from the white of bark of the tree or possible soap residue. Can anyone take a look at these photos and tell me if you can see any definitive scale? I feel like it looks better in person, but I know I’m probably missing some and will end up needing to make another pass at some point. I treated it with some imidacloprid systemic a few days ago as well.
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Leo in N E Illinois
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@Apex37
You have done a textbook perfect job of cleaning the scale off this tree. Well done. Unfortunately there are likely a few eggs left behind that you can not see, and might have missed. Or there might be a few adults or eggs hidden in the soil. So a repeat will be needed at an interval short enough to kill any new crawlers that have hatched out from eggs, but before these crawlers have matured into egg laying adults. You will have to repeat at least 2 additional times at some interval. The work of repeat cleanings like this is the reason so many people recommend systemic sprays, where a single application is often sufficient. But you did a great job, so let us figure out how frequently you need to repeat this procedure to eliminate this particular scale insect.
I looked at the Maryland extension website posted by @AJL , on pruniosa scale, the good news is that the cycle time between generations is fairly long, 1637 degree days base 50 degrees F. What this means is a "generation" as far as pest management is concerned requires accumulating 1637 hours above 50 F. But the higher the temperature, the quicker the accumulation. the formula Maryland extension service used is Daily DD50 = Ave. Daily Temp. – Base Temp
You are in Texas, if your average temperature for 24 hours is 80 degrees F, it means daily you would accumulate 30 degree days (base 50 F) per 80F average day. This would mean the scale insect would produce a new generation in 54 days. This is quite slow compared to many pests we encounter in bonsai, and is good news. You will need to repeat the cleaning procedure you did at some frequency less than 54 days if your temperatures average 80 degrees.
Just based on the 54 days per generation for 80 F weather, I would suggest repeating the process you just did once every 30 days to once every 40 days, two more times, and that should completely eliminate the scale from your tree.
The thought process of looking at the life cycle of the pest and then using a treatment at a frequency that is frequent enough that the pest does not have time for the next generation to mature enough to lay the next batch of eggs is called "integrated pest management". It minimizes effort needed to put into pest control. And if one were to use chemicals, by using chemicals on such a schedule overall lessens the likelihood of developing a resistant population of insect.
You have done a textbook perfect job of cleaning the scale off this tree. Well done. Unfortunately there are likely a few eggs left behind that you can not see, and might have missed. Or there might be a few adults or eggs hidden in the soil. So a repeat will be needed at an interval short enough to kill any new crawlers that have hatched out from eggs, but before these crawlers have matured into egg laying adults. You will have to repeat at least 2 additional times at some interval. The work of repeat cleanings like this is the reason so many people recommend systemic sprays, where a single application is often sufficient. But you did a great job, so let us figure out how frequently you need to repeat this procedure to eliminate this particular scale insect.
I looked at the Maryland extension website posted by @AJL , on pruniosa scale, the good news is that the cycle time between generations is fairly long, 1637 degree days base 50 degrees F. What this means is a "generation" as far as pest management is concerned requires accumulating 1637 hours above 50 F. But the higher the temperature, the quicker the accumulation. the formula Maryland extension service used is Daily DD50 = Ave. Daily Temp. – Base Temp
You are in Texas, if your average temperature for 24 hours is 80 degrees F, it means daily you would accumulate 30 degree days (base 50 F) per 80F average day. This would mean the scale insect would produce a new generation in 54 days. This is quite slow compared to many pests we encounter in bonsai, and is good news. You will need to repeat the cleaning procedure you did at some frequency less than 54 days if your temperatures average 80 degrees.
Just based on the 54 days per generation for 80 F weather, I would suggest repeating the process you just did once every 30 days to once every 40 days, two more times, and that should completely eliminate the scale from your tree.
The thought process of looking at the life cycle of the pest and then using a treatment at a frequency that is frequent enough that the pest does not have time for the next generation to mature enough to lay the next batch of eggs is called "integrated pest management". It minimizes effort needed to put into pest control. And if one were to use chemicals, by using chemicals on such a schedule overall lessens the likelihood of developing a resistant population of insect.
Leo in N E Illinois
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Where I first had to think about life cycles and temperature was when I had a large orchid collection and would end up with mealy bug infestations. Then the generation time was about 14 days at household temperatures. So I would end up spraying every 7 to 10 days.
Then when I was part owner of a blueberry farm, we had to deal with spotted wing fruit fly (SWD). Here, because it was a fruit crop, and our main customer wanted organic, no spray at all fruit, we had to simply pick what we could before the bugs got bad, the leave the rest to rot in the field. Thankfully we had an early variety of blueberry, so we did get a small but profitable crop. AND, being the smooth talker I was, I got the university interested in using our fields for research on SWD, and they paid us for the to allow them to come in and "experiment" in our fields that were planted with late fruiting varieties. So we kept about one acre of berries to harvest for fruit and 14 acres were leased to the University for bug research. It worked out okay. Sold the farm when COVID put an end to the bug research money coming in.
Oh, spotted wing fruit fly has about a 4 day from egg to adult laying eggs cycle. And the adults will live for 2 to 4 weeks laying eggs every day after about the 4th day. This is "base 50F" So you can see how lucky you are having an insect with a much longer life cycle.
Then when I was part owner of a blueberry farm, we had to deal with spotted wing fruit fly (SWD). Here, because it was a fruit crop, and our main customer wanted organic, no spray at all fruit, we had to simply pick what we could before the bugs got bad, the leave the rest to rot in the field. Thankfully we had an early variety of blueberry, so we did get a small but profitable crop. AND, being the smooth talker I was, I got the university interested in using our fields for research on SWD, and they paid us for the to allow them to come in and "experiment" in our fields that were planted with late fruiting varieties. So we kept about one acre of berries to harvest for fruit and 14 acres were leased to the University for bug research. It worked out okay. Sold the farm when COVID put an end to the bug research money coming in.
Oh, spotted wing fruit fly has about a 4 day from egg to adult laying eggs cycle. And the adults will live for 2 to 4 weeks laying eggs every day after about the 4th day. This is "base 50F" So you can see how lucky you are having an insect with a much longer life cycle.
Apex37
Chumono
@Leo in N E Illinois thank you as always for providing your expertise and sharing your experiences. This is the nicest tree in my collection, so I definitely want to be proactive with it and make sure this doesn’t become a recurring problem. Do you have a systemic spray you recommend? I plan to be proactive and using neem oil spray on all my plants this winter as I’ve never been very good with preventative pest control during the winter, which obviously helps come spring and summer once the pests can become a real problem.
Leo in N E Illinois
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I hesitate to recommend to anyone a specific pesticide, because doing so can potentially open me up to liability. You really need to read labels, either at your local garden center, or on line at some place like
Most Big Box garden centers carry Bonide products. Bonide makes a systemic called Disystox. - look at that one, read the label, if you think you can handle it safely, it should work well as a systemic.
If you don't want to use Disystox. Go to
www.Hummert.com
Which i where I get my pesticides. Explore what options they have. Read, they have a number of good options.
If you have a large collection of plants, more than 100. I suggest putting them all in one room, and then using a single "flea and tick bomb" as recommended for killing fleas in your house. Use the bomb that says good for 7 months. It contains juvenile growth hormone disruptors, and will have long lasting pest control for your trees. Much easier to use than spraying under every leaf for several hundred plants. I've used it on my orchid collection a number of times.
Note: with the flea and tick bomb, do not point the spray directly at your trees. the spray can burn leaves. Set the bomb on an elevated table, or post or or shelf, above the trees. So the fog can diffuse around them freely without "wetting" the leaves.
Most Big Box garden centers carry Bonide products. Bonide makes a systemic called Disystox. - look at that one, read the label, if you think you can handle it safely, it should work well as a systemic.
If you don't want to use Disystox. Go to
www.Hummert.com
Which i where I get my pesticides. Explore what options they have. Read, they have a number of good options.
If you have a large collection of plants, more than 100. I suggest putting them all in one room, and then using a single "flea and tick bomb" as recommended for killing fleas in your house. Use the bomb that says good for 7 months. It contains juvenile growth hormone disruptors, and will have long lasting pest control for your trees. Much easier to use than spraying under every leaf for several hundred plants. I've used it on my orchid collection a number of times.
Note: with the flea and tick bomb, do not point the spray directly at your trees. the spray can burn leaves. Set the bomb on an elevated table, or post or or shelf, above the trees. So the fog can diffuse around them freely without "wetting" the leaves.
