If you have blueberries that need mulching, that’s precisely where I’d put it.
I always use shredded paper as mulch. I recycles company’s shredded paper, It usually last for a year. It serve two purpose: recyle, keep recylable material away from landfield； keep the weeds down. The bounce I got is that I got ton of worms, The earth worm loves the paper. It does not look a nature color on the ground, heck, who said red mulch on the ground is nature?
Sawdust doesn’t really have much affect on acidifying soil. The difference in soft and hardwood is a higher concentration of ash in the latter, in other words it has more overall mineral content. Both will likely decompose into something sweet but soft wood leaves less.
That sawdust or pine needles meaningfully acidify soil is one of those gardener’s folk tales, but if I have a choice, I will use pine wood mulch or needles for blueberries over hardwood mulch anyway, however slight the difference.
It is commonly found in apples (we just had an outbreak-people died) and melons, raw fruits and vegetables. I would not take contaminated wood lightly. The disease can be fatal. It would be extremely fool hardy to expose your fruits and vegetables to listeria. I have grown it many times. It’s not an easy death either.
Drew (BSMT, ASCP)
I think the excess vigor from too much mulch is a little like “too much rain”. An east coast problem, which is somewhat like a first world problem.
I get my wood chips for free at the transfer station. I bet that’s true a lot of places. Failing that, there’s usually a materials place that has bins of gravel or mulch for prices that are at least better than the Home Depot. You can inspect the stuff and pass if you suspect treated wood is in there.
I need to be a little more careful with watering. It’s easy to get complacent in a dry climate and assume its wet under there. When the summer is in full swing I need to quit watering the surface and jam the hose in there and not waste any precious gallons on the mulch itself.
Lol. I don’t sell apples, so there 
Seriously though, I don’t use pallet wood chips (only arborist chips) but E. coli and Listeria are in the soil. Maybe you and Patty could comment on this since you both are in the medical field, but my understanding is that in almost all cases (but not all) bacterial exposure, by ingestion, must exceed a certain threshold before disease occurs. There are a certain number of intestinal bacterial pathogens people are commonly exposed to, but when they surpass the threshold, they trump natural defenses of the body. At least I was told that’s the way the intestinal tract of a pig works. I was also told pigs and people have very similar digestive systems (a very humbling thought imo 
)
I haven’t read as much about the latest carmel apple poisoning, but I know with the cantaloupe poisoning, the lysteria was introduced to all the cantaloupes through contaminated wash water, then colonized and grew on the outside of the cantaloupes.
Like you I think food safety is a pretty big deal, which is why I will never fertilize my trees with manure, unless it’s had a lot of time to compost before the crop is harvested. Wood chips seem a fairly clean alternative to me. I just can’t see how they would be more prone to unusually high amounts of harmful bacteria than other organic materials commonly found in the garden (like leaf litter, grass clippings, etc.)
Drew, I would not say LIsteria is “commonly” found on or in anything. Thank goodness. It does rear its ugly head every now and then, though. And, the amount of Listeria on an exposed to air wooden pallet probably would not be at a quantity enough to be pathogenic (yes, it is a facultative anaerobe, but it is just not going to survive long on a dry surface of a wood pallet, and yes Olpea, you are correct in this assumption). Many of the cases of serious or fatal listeriosis are due to either being inoculated with a large dose of contaminated food (such as some of the listeriosis outbreaks with infected cheese products from Mexico), or an immuncompromised person becoming exposed. And, entering into the soil it has to compete with all the other soil microbes. It will be a battle of the dominant organisms, and I doubt Listeria would win that battle based on health soil microbiology. Listeria is definitely a nasty organism, but the deaths associated with listeriosis are nearly always with immuncompromised individuals (pregnant women, children/babies, elderly, those with chronic illnesses affecting the immune system, etc.), not healthy adults (very rarely does a healthy adult become deathly ill with listeriosis.) Plus, you’re apples aren’t going to come into contact with any Listeria in your mulch unless they’re on the ground. And then it would have to rain, and splash up on the apples sitting on contaminated mulch. The mulch would have to be really, really contaminated, and I just don’t see that happening. It is implausible. Technically possible but highly, highly implausible. I would much more worried about chemical toxins and heavy metals that could be in or on those pallets. That can get into the soil, stay in the soil, and be absorbed into the tree’s system and the fruit. That I would be more worried about, and why I would not use any mulch made from pallets from China.
The heavy metals would be a big deal to me. With agricultural arsenic showing up in American rice, and now arsenic in wine, and who knows what is on those pallets, I feel more than ever that chipped tree prunings and choppings are the way to go. Benefit outweighs risk by a lot, I think.
Ok the pallet industry is saying they are safe, but the CDC is telling a different story, wow amazing.
Listeria can only survive on porous surfaces, it would not survive on plastic, it is an anaerobe.
This is why they found so much inoculant on pallets.They are so porous.
I was looking at Web MD and the first listed sources of listeria is soil and fruit.
I would really like to know how it infected melons in 2012, 33 people died.
The Web MD advice said pregnant woman should not eat lunch meat unless cooked again.
Nothing unpasteurized. Luckily most people just get extremely sick and recover. But those over 60 tend to die, I’m 58.
We should all look for local sources for mulch and use that, which you guys have been doing.
I agree the danger is low but I think still there. I guess working with this stuff for years, I get very paranoid. I’m glad I’m retired. Every lesion, pimple, mark on me, I would wonder if I contaminated myself. Especially when I was doing research with HIV and the herpes virus. At the time we knew so little about HIV. It was not until 2008 that we actually isolated the virus. In 1981 we determined AIDS was from a virus, but it took a long time to confirm what virus. It’s an RNA virus, those are really old. We think the first viruses were RNA types. Virus and viroids are creepy things. Are they really alive? A human flu virus is composed of 90% human DNA, it takes some and leaves some with every infection.
What strange creatures.
So much for the antibacterial properties! In the links in my next post they mention that the bacterial counts in the wood go through the roof! Ha!
“There are more than one billion wood pallets used in the United States, so it’s critical to understand the role they play in outbreaks of food poisoning,” added Moore. "We also need an effective way to track and trace wood pallets in the supply chain so that FDA and USDA can identify the source of food contamination and quickly stop the spread of food borne illnesses.
Let the media wars begin!
No you’re right it is not! Again I’m a little too paranoid from working with this kind of stuff.
Although we should not ignore that they did find it on the pallets when tested. Luckily it’s not a spore forming type, else we would really have a problem!
Please look at these articles…
Absolutely, Drew. On a petri dish or agar medium, designed to be an optimal growing medium, you’re going to have maximum proliferation and maximum pathogenicity. In an absolutely hostile growing environment, all those wonderful soil microbes will crowd out or simply devour Listeria. Yes, a spore-forming organism is actually much more difficult to manage. I think of them as the “cockroaches” of the microbial world - spore-forming organisms will still be here (along with the cockroaches) after everything else is dead and gone 
Again, the dangerous chemicals and heavy metals that are used without discretion in China that have a long half-life (or no half-life at all) are much more disconcerting to me. I don’t want that in my soil, ground water, or up in my trees and fruit. Good articles, and worth reading. Also, a perfect example of why we should all wash our fruits and vegetables we buy from the store, even organic stuff. I have a very soft bristle brush and I use just plain old Dawn dishwashing detergent (NOT the anti-bacterial version, I never use any of that, it’s not healthy), and gently scrub all my veggies and fruits well. Especially fruits and veggies with uneven surfaces, like cantaloupes. Let them air-dry completely before you refrigerate. Clean your veggie drawers out once a month with the same detergent, and then rinse with a 1:10 bleach/water solution. You’ll never get sick from any contaminated fruits or veggies you have to buy. Another awesome reason we do what we all do - we know exactly what we’re putting on our crops.
I’m usually a reader not a poster, so I’ll try… Hoping to remember my agronomy classes from 30 yrs. ago on plant fiber and soil contact. Most plant fiber(wood chips, paper etc.) is in the 200/1 carbon/nitrogen ratio. To get optimal bacterial break down of plant fiber you need a 17/1 carbon/nitrogen. At the 17/1 either nitrate or ammonium ions are released and are plant available. Any higher ratios and nitrogen is removed from the soil til the 17/1 ratio is obtained. I’ve always added extra N in fertilizers when using a fiber mulch because of the tie up of N due to the low C/N ratio.
I’ve also hard that mulches under apples allow voles places to burrow against trees and possibly girdle them. Is that wrong or are you mulchers using product to eliminate voles?
No voles in S. California, fortunately. Instead, we deal with the horrid pocket gopher, which just popped up in my walk & pick orchard last night. Awoke this morning to find a dead gopher floating in the pool. If I don’t see further digging activity, I can assume my pool did the job (any number of dead rodent types are often found floating in my pool, one of the best rodent traps I have going in the yard.) What we do deal with, in regard to pests and mulch are snails and slugs, though. So, we have to watch for that and treat with iron phospate (Sluggo). And chikn, that’s why it’s not a bad idea to toss your grass cuttings down under your mulch as well, or, at the least on top. I can’t because my gardener uses his own mower, so he is constantly bringing in weed seeds, so don’t want to “seed” under my fruit trees. Bad enough trying to deal with that in my lawn. I don’t have room to buy my own mower right now, and have him use that, but it’s in the plans.
Chikn
I wrap my tree trunks with a somewhat loose sleeve of hardware cloth. Voles eat my tree trunks with or without mulch. They like figs the best, then have gone after Asian pears. Rabbits go after saplings, so they get the hardware cloth sleeve too.
My intent is for the mulch to last a couple of years. I prefer that it not break down too fast. But if it does, I’ll just add another layer.
On the nitrogen, for the smallest saplings I do use leaves or grass clippings, more nitrogen for faster growth. I also pee-cycle, but that is for a different thread with it’s own topic, I think. For more mature trees, I don’t want so much new growth, so not into adding much nitrogen for those.
My dog adds plenty of nitrogen to my trees. For a long time he was killing my blackberries, but now that the trees are bigger, he has gone to them.
I think they an handle the nitrogen better.
One thing kinda off subject that Patty brought up. She mentioned normal flora out competing listeria. I’m not disputing that at all, but it reminds me I often here organic growers say having all this microbial growth will eliminate pathogens. But nobody told the pathogens they are not normal flora, as they most certainly are and have their place too. They have a reason for being there, and no normal flora is going to push them around.
Brown rot is just like the honey badger, it just doesn’t care!
https://www.youtube.com/watch?v=4r7wHMg5Yjg
Drew, it’s not so much a matter of organisms like Listeria not being normal flora, but more a matter of checks and balances that occur is a healthy, diverse microbiosphere. There are lots of potentially pathogenic organisms down there in our soil, like Liseria. Don’t forget Clostridium botulinum and Clostridium tetani to name a couple very nasty bugs that natively live in our soils. But, that vast, healthy microbiosphere keeps them in check, and they stay at non-pathogenic levels unless that organism is suddenly thrust into a more condusive growing media (such as stepping on a dirty nail and having it drag C. tetani deep into your foot, where there is nothing to check its growth - now you’re dead unless you’ve had a recent tetanus booster shot). Think of pathogenicity as a matter of “opportunity and preparedness coming together”. Sort of like getting a yeast infection after a course of broad-spectrum antibiotics - the “preparedness” is that the yeast organism is always there, it’s part of your nomal flora. The “opportunity” in that the broad-spectrum antibiotics have wiped out all the other normal flora that would keep the yeast in check. Voila - yeast overgrowth and now you’ve got a secondary yeast infection. Does that make sense?? Another example I can give you here in my soil microbiosphere: Phytophthora. Normal soil organism here. But, when we do abnormal things in S. California (such as artificicially irrigate our crops), it grows wildly out of control, the other normal soil organisms cannot keep it in check, and it attacks the roots of many plants (each having their own sp-specific Phytophthora organism). So, my citrus suffer, my avocados suffer, my Pittosporum drop suddenly dead, etc. So, LIsteria is not going to proliferate in our soils from contaminated woodchips because the equation of “opportunity and preparedness” will not come together to make that happen, and have the bacterial count go up high enough to cause it to become pathogenic. There is “preparedness” in that it could be clinging to a piece of bark, but the “opportunity” is not there - not optimal growing conditions and the other soil microbes will simply out-compete it for space. Remember the Pauli Exclusion principle VERY loosely applied here: No two objects can occupy the same space at the same time. The other soil microbes will keep something like Listeria (and the C. species) in check, unless they can find their way into a more hospitable environment and proliferate to pathogenic quantities.
Okay, I think we’ve probably beat this poor horse to death, and completely taken over this message thread, lol! I promise to post more pics of my mulched trees, lol!
Yes we have over talked it, but I did bring up a new point. And I do disagree with you somewhat. Having healthy microorganisms in the soil can limit Phytophthora’s spread. But if you supply it with a bunch of dead plant material (dead roots due to overwatering), it is hard to stop. Normal flora help in providing an environment where roots do not die. But if they do and provide food for the fungus the normal flora cannot stop it. They only keep it in check by providing a healthy environment for roots, they do not directly keep it in check.
And as I said I do not disagree with your example with listeria. Fungi are terrible. Hard to stop in plants or people. Some of the pathogenic fungi I studied in school were very scary as to what can happen to a person. All the same 500 people a year die of listeria in the USA, and it may certainly have a lot to do with pallets.
I have a minor in microbiology, and have extensive training in virology, mycology, parasitology and pathology. I worked and did research for the Anatomy dept, and the Microbiology dept. at Michigan State University. I also was a Medical Technologist at Sparrow Hospital in Lansing MI. As far as fungi and bacteria I’m considered a professional expert.
I also disagree about listeria not proliferating in your environment. Your fruit and vegetables most certainly are susceptible to infection from listeria from wood pallets.
You say
"unless they can find their way into a more hospitable environment "
Yes, like your melons, if you grew them, and they were on chips from infected pallets.
Listeria infected fruit and food products are common I’m afraid.
Most sources turn out to be farms, or processing plants. it happens all the time.
1 in 4 people a year come down with a food born illness. Listeria is not that common around 3000 people a year get it. Other forms are a lot more common, but it happens. and one should be careful to avoid any potential contaimination, like infected pallets.
If I used those pallets, I would throw all my food grown near them out.
From the FDA
FDA identified the following factors as those that most likely contributed to the introduction, spread, and growth of Listeria monocytogenes in the cantaloupes:
Introduction:
There could have been low level sporadic Listeria monocytogenes in the field where the cantaloupe were grown
I wonder if they mulched with wood chips?? 33 people died from this outbreak.
After all the things I’ve seen spilled on pallets, listeria would be the least of my worries. I worked for years in the lawn care and sod business and the multitude of spilled chemicals on pallets is amazing. Roundup, 24-D, any insecticide/ fungicide combo, oil, grease you name it. Pallets are the last thing I want in my garden unless they are new. Tree company chips from down the road ok, no pallets. I don’t fear ag chemicals and use them in their time and place, but in time and in place. If I’m not mistaken, wash water without bleach is usually the villain.
@hoosierquilt I like your explanation of the balance of ‘normal flora’ . You also made me glad I got my tetanus booster last year.
Nobody has mentioned inoculating the wood mulch and trying to use mycelium to shift the balance towards favorable fungi.
I’m interested in using King Stropharia aka Stropharia rugosoannulata.
Has anybody tried inoculating wood mulch around fruit trees?
Another benefit is the mycelium locks all the wood chips together so they do not blow or wash in a storm.
@Chikn I agree about nasty pallets, some truck company depots never get empty to clean floors, and some truck trailer floors are super nasty even food trucks.