Need help: Fungus Problems?

Question: I have an issue in the yard of the home we bought in May 2023. Over the last year we have personally installed new pollinator flower beds to cover much of the grassy areas. Since late June, about 75% of the yard has been taken over by what seems to be a fungal disease and I can't control with neem or copper fungicides. I will attach additional images once my post is approved.

responder: The Question Asker Replied September 20, 2024, 11:20 AM EDT
response: Additional images are below:

responder: The Question Asker Replied September 20, 2024, 11:21 AM EDT

responder: The Question Asker Replied September 20, 2024, 11:22 AM EDT

responder: The Question Asker Replied September 20, 2024, 11:22 AM EDT

responder: An Ask Extension Expert Replied September 20, 2024, 5:03 PM EDT
response: Hi Sarah, thanks for the question.  Looking at the pictures, it really doesn't seem to be a fungal problem.  Most fungi are usually specific to a certain family of plants.  Although there are generalist diseases, in your case it appears that everything is affected.  Some post emergent broadleaf herbicides can persist in the soil for a while.  Mulches can be contaminated or toxic. Salt can be a problem by the street or driveway causing yellowing or burned leaf margins. Since this appears to be universal in your landscape and you feel confident in your watering and planting, a pH or nutrient issue could be to blame.  A soil test (Home | MSU Soil Test) could validate this. Take a look at the different sections that have the problem and try to determine what they may have in common.   Are there certain plants that are unaffected?  If so, what plants are affected and what is not?  Do any of the plants show abnormal growth?  What type of soil do you have (sand, clay, loam)? Did you amend the soil in any way?  I believe we can solve this mystery! I look forward to your response.

responder: The Question Asker Replied September 20, 2024, 8:28 PM EDT
response: Thank you for your response. I would say 2/3 of the plants are affected - and that is plants in all beds, across the yard - not just on area. We did not amend the soil at all when moving in, and I know the previous owners chemically treated the lawn. We do not. I killed grass to make way for beds using newspaper and cardboard, covered in mulch. whatever is affecting plants is NOT affecting the azalea, roses, holly, lavender, heuchera, bluebells, phlox, or delphinium. Our soil is fairly sandy in general. I was thinking of cutting all affected plants to the ground (except the tree), and moving the mulch back from around the base. Would that make sense? I can also have the MSU soil test done.

responder: The Question Asker Replied September 21, 2024, 10:11 AM EDT
response: Just another note: I noticed this morning that there are several plants also dying in an area of the yard/a different flower bed that is not covered by mulch/is mostly rocks. These are largely succulents but have the same brown leaf/yellow leaf/wilting problem.

responder: An Ask Extension Expert Replied September 23, 2024, 9:05 AM EDT
response: Hi Sarah, Thanks for the additional information.  Looking at the plants that are not affected did not show a significant trend, although, there are several of the plans like a lower (acidic) pH. Data shows your county was ~25% below normal in rainfall.  How are your irrigating? This could indicate that there may be a problem with water. One problem with the cardboard is that it can inhibit infiltration of air and water in the soil beneath.   Even though the top of the soil seems wet, further down it may be too dry preventing good deep root development.  Tree roots can also compete for moisture.   What trees do you have? Dig a few test holes at least 6 inches deep a to see what the lower soil is like. Cutting the plants back may not be a good idea since any green leaves are supply the energy for the plant.  Since you have sandy soils, there is a good chance that you may have a nutrient issue. Many sandy soils are potassium shy.  Potassium helps regulate water in the plant. Have you done any fertilization?  The soil test can be a real help here.  One last item, have you seen any unusual growth such as curling, stunting, etc.?  I look forward to your response.