In a previous piece I fingered the flea beetles as the biggest pest in my garden. I mentioned how we control them using natural means. About a week after posting that article, as if in response, the slugs arrived to stake their claim as the worst pest ever. The flea beetles were soon forgotten. The slugs were legion, and they were ravenous. They enjoyed some of my beloved tomatoes, especially the fruit if they could find an opening in the skin. But they didn’t like all tomatoes. They didn’t touch the Juliets, but I had to wipe them off the Brandywines and Black Krims. Pepper flowers disappeared overnight. They nibbled on the strawberries – the fruit but not the leaves. They stripped the leaves from some types of potatoes, but not others. They chewed on the beet leaves. I transplanted 2 salvia from the front yard to the back, and the plants disappeared in hours, as did one of the two newly planted delphiniums.
The terrible roar of a million slugs at their dinner should have been deafening, like a jet at take-off. But it was a quiet carnage, happening under cover of darkness.
So why such an outbreak? What happened to my natural allies in the air and in the soil? And what could I do about it now? So much for the natural balance in my eco-garden, I feared.
Our natural allies – the slug predators like toads, beetles, birds, and centipedes - were dragging their feet. Immediate human intervention was required, or this year’s crop would be decimated. Of course, we did not choose a chemical response. Commercial slug bait is hazardous to kids and pets, probably to birds, soil, and karma too.
First, we got some cheap beer, found some bowls and trays, and placed the beer and bowls around the garden every evening. Slugs love beer, or more accurately the yeast in beer. They partied hard every night, but the hangover was fatal. In the morning, we put masses of the critters in a pail of soapy water to stew for the day (i.e. make sure they were really dead, and not just passed out). Then they went on the compost as a good source of nitrogen and other nutrients for the friendly microbe herd there to devour. We soon bought yeast to put out with water and save a little money on beer.
I also sprinkled diatomaceous earth around the plants most susceptible to slug attack, in theory to irritate and cut their bodies as they slid over the jagged particles, but rain quickly washed the DE away.
I never tried laying copper strips around the garden. The theory is that the copper shocks the slugs when they travel over it, a sensation they apparently find unpleasant. That would have taken a lot of copper in our case – wasteful and unnecessary I think.
Garlic pepper tea used as a spray over the plants on which slugs feed is said to be a great deterrent. I didn’t try that – too many plants, too little time, too many beneficial insects driven away. Something more certain was required.
We have planks in the vegetable garden for walking. We turned these over one sunny day to find the slugs snoring in their beds, as thick and numerous as cooked macaroni at a buffet. These were easily scooped into the soapy water, or crushed underfoot or by back of shovel. We also found them sleeping in the space between the garden’s wooden edge and the soil, and under thick mats of the oregano hedging the garden.
The number of slugs soon dwindled, the serious damage stopped, and most of the crop was saved. So how and why did so many arrive this year in the first place?
Reports talk about the eggs coming in with the bedding plants. This may be so, but once here, they need the right conditions. The outbreak coincided with rainy and humid weather in July. Slugs like rainy and humid weather.
They also like a cool shady place to sleep and lay their eggs. They found that here in our intensively planted and mulched yard. Some conventional gardeners insist that all fallen leaves and other debris be cleaned away and put in the garbage every fall. But from an ecological point of view, that is wasteful and contrary to the health of the garden, and particularly the fertility of its soil. The mulch and intensive planting shade is home to the slugs but also to the insects that will eat the slugs – the ground and rove beetles, and the centipedes. I found centipedes wherever I found slugs. They are eating the slug eggs, which is good news for next season. The beetles are common here but apparently more shy than the centipedes, because I didn’t see many enjoying a meal of fresh slug. However, they apparently dine at night, and I am confident they are eating their share.
So why not just bare the garden of mulch and debris, and plant sparsely so the slugs won’t find a home? Well, the mulch and plant debris are good for the soil – its temperature, moisture level, structure, and longer term fertility. It is home to predators that the garden needs, like beetles and centipedes. Earthworms eat the mulch and debris and convert them into incredibly fertile poop. Intensive planting is a good use of space, prevents weed competition, and, in healthy soil, results in bigger and better yields.
All considered, the solution to the slug problem is not bare soil and sparse plantings. This was an exceptional year, weather wise, with perfect slug conditions. They have laid their eggs, but so have our friends the predators, which are always slow to respond, but extremely effective once they arrive. The predators will dine on eggs this fall, and be hungry for more next year. Even if the perfect weather conditions repeat, the slugs won’t have a chance because the predator population will be ready.
As will the gardeners. Starting early in the spring, bowls of beer will be put out in the evening, and examined in the morning. The planks and any other hiding places will be turned over every day. The sleepers found there will be composted, transformed by microbes into plant nutrients, and returned to the garden – to feed the plants, rather than feed on them.