Ahhh The spring mushroom crop. The beautiful caps emerging in bounty from logs as the humidity and temperature rises. This is one of the most delicious of spring scenes, especially knowing that in a few short days after seeing the pins form you'll have these flavorful caps sitting on your plate with fresh asparagus or other spring vegetables.
Enter slugs. Over the last few years slugs have become a terrible nuisance for us up here in Northern Wisconsin. We've had an impressive influx of rainy days, and with the increase in rain came an increase in the slug population. While the mosquitos take the cake in the most irritating of spring creatures, the slugs are a very, very near second. In 2019 and 2020 we lost 90% (I did not mistype) of our spring mushrooms crop to slugs. (Yeah yeah we know they have to eat too, but couldn't they eat the mosquitos?) Slugs have a tendency to eat their way through mushrooms in such a way that not much of the mushroom can be salvaged, leaving behind a sinister trail of slime.
It took two full crops, but eventually we here at F&F became frustrated enough to start trialing some shiitake-slug-protection methods. While there are multiple chemical barriers that you can use, we prefer to stay away from chemicals whenever possible. If you are looking to simplify and use a chemical we would suggest Sluggo. Sluggo is listed as an organic-production slug preventative and can say from experience that it does a good job of keeping the slugs at bay. But we like to make things a little more work-intensive here so we created a slug barrier using fruiting blankets and pallets. Here were the methods we tried:
Method 1:Logs on a pallet, covered with a fruiting blanket
Result:It was a fine try, but ineffective. The slugs were able to crawl (slither?) up the pallet onto the logs and feast.
Method 2:Lay a fruiting-blanket on the ground, place the pallet of logs on top of blanket, and then cover with another blanket.
Result: Progress! With the ground cover there was a marked decrease in slug activity. We found one slug on the entire stack of logs. However, we did find that while we did get rid of the slugs, the mice found fodder with the mushrooms taking bite sized pieces out of the cap (as seen above in the third photo). Fortunately, mice tend to tire of shiitake quickly and often times move onto other treats.
Slug damage is most often seen in the spring of the year.
A shiitake mushroom with slug damage.
A shiitake mushroom with mouse damage.
This is not to say that we have found the one and only slug prevention method. There are several other methods that we have heard of, though have not attempted. These include using copper wire or copper mesh below your logs. Laying copper wire or mesh down underneath your logs creates a field that deters the slugs. The only downside of this method is finding affordable copper if you are growing on a large scale. A similar method is to place your logs on a surface that slugs do not like to cross, such as a gravel pad. However, most gravel or pavement pads do not have adequate shade. Another method mention is.... ducks. Yes the animals. If you have a duck you're in luck! Ducks love to eat slugs and will handily take care of your problem- and plus, eggs!