Leaves on bush bean mottling, turning yellow, falling off - Ask Extension
The leaves on our bush beans are mottling, turning yellow and falling off. Cause? Solutions?
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Leaves on bush bean mottling, turning yellow, falling off #877614
Asked July 17, 2024, 12:21 PM EDT
The leaves on our bush beans are mottling, turning yellow and falling off. Cause? Solutions?
Denver County Colorado
Expert Response
It is not possible to give a definitive diagnosis from your description alone. If you are able to send in some pictures that would be helpful. Please send a couple well-focused up close pictures of the mottling on the leaves and a couple well-focused pictures of a whole plant. Even better, you can also take some of the leaves to a diagnostic lab to get a definitive diagnosis. In the Denver area you can go to the CSU Spur extension lab: https://agsci.colostate.edu/agbio/plantclinic/
Here are some possible causes you can explore if the above options don't work for you:
Rust: This could appear as brownish red spots on the leaves. They can be surrounded by a yellow halo. Severely affected leaves can look yellow with brownish red mottling and eventually drop. Management includes watering at the base of the plant in the morning to prevent spores from spreading and to remove all fallen leaves. Seal in a garbage bag and dispose. Avoid over fertilizing with high nitrogen fertilizers. Do not plant beans in the same location for two years after this one.
Anthracnose: Please take a look at this information from the University of California https://ipm.ucanr.edu/agriculture/dry-beans/bean-anthracnose/#gsc.tab=0
Bacterial Blight: Please take a look at this information from the University of Californiahttps://ipm.ucanr.edu/agriculture/dry-beans/common-bacterial-blight/#gsc.tab=0 and this information on bacterial diseases from CSU: https://extension.colostate.edu/topic-areas/agriculture/bacterial-diseases-of-beans-2-913/
Viral Diseases: This information from University of Connecticut describes a couple viruses that can cause mottling on bean plants: https://ipm.cahnr.uconn.edu/bean-viruses/
Angular Leaf Spot: Gray or brown spots on leaves that look more angular/square than circular. More likely to cause defoliation in humid climates. Collect fallen leaves and seal in garbage bag and dispose. Do not plant beans in the same location for three years after this one. Can treat with specific fungicides.
Here are some possible causes you can explore if the above options don't work for you:
Rust: This could appear as brownish red spots on the leaves. They can be surrounded by a yellow halo. Severely affected leaves can look yellow with brownish red mottling and eventually drop. Management includes watering at the base of the plant in the morning to prevent spores from spreading and to remove all fallen leaves. Seal in a garbage bag and dispose. Avoid over fertilizing with high nitrogen fertilizers. Do not plant beans in the same location for two years after this one.
Anthracnose: Please take a look at this information from the University of California https://ipm.ucanr.edu/agriculture/dry-beans/bean-anthracnose/#gsc.tab=0
Bacterial Blight: Please take a look at this information from the University of Californiahttps://ipm.ucanr.edu/agriculture/dry-beans/common-bacterial-blight/#gsc.tab=0 and this information on bacterial diseases from CSU: https://extension.colostate.edu/topic-areas/agriculture/bacterial-diseases-of-beans-2-913/
Viral Diseases: This information from University of Connecticut describes a couple viruses that can cause mottling on bean plants: https://ipm.cahnr.uconn.edu/bean-viruses/
Angular Leaf Spot: Gray or brown spots on leaves that look more angular/square than circular. More likely to cause defoliation in humid climates. Collect fallen leaves and seal in garbage bag and dispose. Do not plant beans in the same location for three years after this one. Can treat with specific fungicides.
I have attached photos of the bean plants. The mottling seems limited to a few plants in our home and a few plants in our community garden, rather than spreading to all plants.
Alan
On 07/18/2024 1:10 PM MDT Ask Extension <<personal data hidden>> wrote:
Alan,
Thanks for the additional photo's. Here is some additional information:
This appears to be a leaf blight, most likely bacterial leaf blight. It is a fairly common disease on beans. Frequent watering which wets the leaves can increase the severity of the disease. We can't do much to control the weather, but we can manage irrigation by using drip irrigation rather than overhead sprinklers. This can reduce infection. Crop rotation is a good management strategy too - i.e. don't plant beans in the same place next year. As for the infected plants, they may survive but yield will most likely be reduced.
Here is some good information on leaf blight in beans. http://pnwhandbooks.org/plantdisease/bean-all-phaseolus-vulgaris-common-bacterial-blight-common-blig…
Thanks for the additional photo's. Here is some additional information:
This appears to be a leaf blight, most likely bacterial leaf blight. It is a fairly common disease on beans. Frequent watering which wets the leaves can increase the severity of the disease. We can't do much to control the weather, but we can manage irrigation by using drip irrigation rather than overhead sprinklers. This can reduce infection. Crop rotation is a good management strategy too - i.e. don't plant beans in the same place next year. As for the infected plants, they may survive but yield will most likely be reduced.
Here is some good information on leaf blight in beans. http://pnwhandbooks.org/plantdisease/bean-all-phaseolus-vulgaris-common-bacterial-blight-common-blig…
