Strange Brown Dots

[jfmnbpt]

I am experiencing a strange plant phenomenon and hopefully you can help. My location is NE Massachusetts. I have a gravel driveway bordered on the north & east with a stockade fence, and bordered on the south by my home (full length of the driveway). There is a four foot wide plant bed which runs along the entire foundation. Planted in this bed (in order): a 7’ arborvitae; evergreen bush; evergreen bush; evergreen bush; 7’ arborvitae. Some pachysandra ground cover. The rest covered in mulch.

The phenomenon: each August / September for the last three years, our vehicles become covered in small, brown, rigid, organic raised “dotsâ€

[The Helpful Gardener]

Moved this one as it hasn't anything to do with roses. It's the mulch. There has been a fungus that I've seen several times in poor quality mulch that when it spores, produces these small brown spots (happened to one of my customers who had a house with yellow siding; what a mess!). The cleaning regimen is a bear; no good way to get it off other than the elbow grease method you are already utilizing.

This is one of those times I might actually use a good fungicide on the mulch beds; the problem is that will work short term but leave the host site open once it washes out. If you've read this site at all you'll find I advocate organic biological counterculture; introducing a different (harmless) fungus or bacteria to colonize the area and attck the fungus. I would first try 1 cup of milk in a gallon of water and spray the mulch in the affected area, if that doesn't work I'd try neem oil (not a counterculture, but a harmless natural fungicide) and if that didn't work, Daconil, a fairly common, broad spectrum fungicide. If you continue to have problems after that, I'd contact my state extension service and see if they had regionally effective solutions.

Everywhere I've seen this has had a build up of old mulch that seems to have gone anaerobic; move the cars, rake it up to expose deeper layers, and then treat as above. THis is a real problemm and I wish I had more solid info but it seems to be a newer issue and there isn't a lot of info on this critter yet. Keep an eye here for more.

Newt and all; anyone else have any input for jfmnbpt?

Scott

[Newt]

Sounds like Artillery Fungus. What a mess it is! I've found a couple of sites, but not much help other than removing the mulch and disposing of it or using it far away from light colored houses and cars or spading it into the soil and wetting it. From the bottom of this site.
https://ohioline.osu.edu/hyg-fact/3000/3304.html

What to Do Once the Problems Occur

Sometimes very little can be done to control nuisance fungi other than to spade the mulch into the surface soil layer followed by soaking with water. Another option is to remove the mulch, place it in a heap after thorough wetting to allow for self-heating to occur (110-140 degrees F). This will kill nuisance fungi. If fresh dry mulch is placed on top of mulch colonized by nuisance fungi, the problems may occur again the following year or even earlier.

The best control strategy for homeowners and landscapers is to purchase composted products low in wood content. Fresh, finely ground woody products should be avoided for many reasons unless composted first. Coarse fresh woody products are much less likely to cause problems unless applied too deep. It is important to soak all mulches immediately after they have been applied. Generally, mulches should not be applied to a depth greater than two inches. Mulches and composts applied in this manner provide many types of beneficial effects rather than nuisance problems, or worse, plant diseases. Sour mulches should be avoided altogether.

Here's another site with more info.
https://www.personal.psu.edu/faculty/d/d/ddd2/artillery_fungus.html

Howard Garrett has some home made fungal treatments that might also help. I'm thinking that using Potassium bicarbonate might also be helpful.
https://www.dirtdoctor.com/view_question.php?id=204

The Ohio State Univ. site talks about the addition of urea in the form of poultry manure. Urea is a common human waste and can be collected in the bathroom or by sending a man to 'water the mulch' if privacy isn't an issue!
https://ohioline.osu.edu/hyg-fact/3000/3304.html

Mulch Type and Fresh versus Composted Mulch

The best way to avoid all these problems and bring about beneficial effects by mulching is to add nitrogen to woody and hardwood bark products followed by composting to lower the carbon to nitrogen ratio. Blending of grass clippings with wood wastes before composting is one way to achieve this. Addition of poultry manure or urea to supply 1.2 lbs. available nitrogen per cubic yard of material satisfies the nitrogen need also.

Wish I could be of more help here.
Newt

[The Helpful Gardener]

It is a growing issue and as someone who is a fan of mulch, one I hope continues to get good research like the stuff Newt has found here.

Remember, if the good guys already live there, no room at the in for bad fungus. Compost tea is our friend...

Scott