Leaf spots - Ask Extension
Hello--can you tell me what I can do about this--see pictures--its a flowering crabapple and slowly dropping leaves all summer-- Thanks so much, Sue
Knowledgebase
Leaf spots #849328
Asked September 10, 2023, 3:00 PM EDT
Hello--can you tell me what I can do about this--see pictures--its a flowering crabapple and slowly dropping leaves all summer--
Thanks so much, Sue
Boulder County Colorado
Expert Response
Hi Susan,
Thank you for writing to CSU Extension with your question about a diagnosis for your flowering crabapple.
From your photo the possible problems could be apple scab, rust, chlorosis or powdery mildew. At first glance it might be scab, which is a fungal disease that results in leaf blotches, leaf yellowing and premature leaf drop. The fruit may develop dark, leathery spots that affect its ornamental value.
To determine your exact problem and get a more accurate diagnosis, you can bring a sample to the CSU Extension office in Longmont. Please also bring photos of the entire tree and the area surrounding it, as it may contribute to the current condition.
Our diagnostics team is in the office each Tuesday through September from 9:00 a.m. - noon.
When you arrive, the receptionist will ask you to fill out a questionnaire with details about your plant. The fee for diagnostics is $7.00 for Boulder County residents.
Finally, I have attached a link to a CSU publication on crabapple trees that you might find useful.
Flowering Crabapple Trees - 7.424 - Extension (colostate.edu)
Regards,
Colorado Master Gardener
CSU Extension Boulder County
Thank you for writing to CSU Extension with your question about a diagnosis for your flowering crabapple.
From your photo the possible problems could be apple scab, rust, chlorosis or powdery mildew. At first glance it might be scab, which is a fungal disease that results in leaf blotches, leaf yellowing and premature leaf drop. The fruit may develop dark, leathery spots that affect its ornamental value.
To determine your exact problem and get a more accurate diagnosis, you can bring a sample to the CSU Extension office in Longmont. Please also bring photos of the entire tree and the area surrounding it, as it may contribute to the current condition.
Our diagnostics team is in the office each Tuesday through September from 9:00 a.m. - noon.
When you arrive, the receptionist will ask you to fill out a questionnaire with details about your plant. The fee for diagnostics is $7.00 for Boulder County residents.
Finally, I have attached a link to a CSU publication on crabapple trees that you might find useful.
Flowering Crabapple Trees - 7.424 - Extension (colostate.edu)
Regards,
Colorado Master Gardener
CSU Extension Boulder County
I don’t think it’s rust chlorosis or powdery mildew. What can be done about apple scab? Thanks so much. I do not live near you to drive in for diagnostics—Thanks so much.
On Sep 11, 2023, at 10:43 AM, Ask Extension <<personal data hidden>> wrote:
Is there any other time than Tuesday I can come in? I work that day-thanks so much—Sue
On Sep 11, 2023, at 10:43 AM, Ask Extension <<personal data hidden>> wrote:
Hello Susan,
Unfortunately, without looking at a sample, we are unable to diagnose the problem, so although you may be correct that apple scab is the likely cause of problem, we cannot confirm this.
In addition to diagnostics at the CSU Extension office in Longmont, we can recommend taking samples to CSU Spur Soil Water and Plant Testing Lab located in Denver. Maybe that location is better for you? The information for this can be found here; Soil, Water and Plant Testing Laboratory - Soil Testing Lab (colostate.edu)
If you do decide to proceed as if apple scab may be your problem, I have included some information that you may consider for possible treatment. However, please keep in mind, that we are unable to confirm that your culprit is apple scab without seeing a sample.
Backyard Orchard: Apples and Pears - 2.800 - Extension (colostate.edu)
If you do decide to bring a sample to the Boulder County Extension Office, you can drop off a sample anytime, Monday through Friday, from 8 am to 4 pm. Our diagnostic team will take a look at the sample on Tuesday or Friday when they are in the office.
Regards,
Colorado Master Gardener
CSU Extension Boulder County
Unfortunately, without looking at a sample, we are unable to diagnose the problem, so although you may be correct that apple scab is the likely cause of problem, we cannot confirm this.
In addition to diagnostics at the CSU Extension office in Longmont, we can recommend taking samples to CSU Spur Soil Water and Plant Testing Lab located in Denver. Maybe that location is better for you? The information for this can be found here; Soil, Water and Plant Testing Laboratory - Soil Testing Lab (colostate.edu)
If you do decide to proceed as if apple scab may be your problem, I have included some information that you may consider for possible treatment. However, please keep in mind, that we are unable to confirm that your culprit is apple scab without seeing a sample.
Backyard Orchard: Apples and Pears - 2.800 - Extension (colostate.edu)
If you do decide to bring a sample to the Boulder County Extension Office, you can drop off a sample anytime, Monday through Friday, from 8 am to 4 pm. Our diagnostic team will take a look at the sample on Tuesday or Friday when they are in the office.
Regards,
Colorado Master Gardener
CSU Extension Boulder County
Susan,
You can drop a sample off Monday through Friday anytime between 8am and 4pm. But your sample will not be looked until the next Tuesday or Friday. (Our previous email was wrong in omitting Friday.) But this is only through the end of September, and is best to get it in as soon as possible.
You can drop a sample off Monday through Friday anytime between 8am and 4pm. But your sample will not be looked until the next Tuesday or Friday. (Our previous email was wrong in omitting Friday.) But this is only through the end of September, and is best to get it in as soon as possible.
Hi Sue,
I'm so sorry that our earlier unclear message to you caused you to take time off work. As I said in a previous message today, we are open to drop offs any weekday 8 to 4.
I was unable to determine the problem with your sample. Our more expert plant pathologist is at an off-site meeting today. It may extend into later days this week, but I've left him a note to look at it.
Karl -- Master gardener plant diagnostician
I'm so sorry that our earlier unclear message to you caused you to take time off work. As I said in a previous message today, we are open to drop offs any weekday 8 to 4.
I was unable to determine the problem with your sample. Our more expert plant pathologist is at an off-site meeting today. It may extend into later days this week, but I've left him a note to look at it.
Karl -- Master gardener plant diagnostician
