Slugs-Snails: About/Control Methods

Snails on Lily Leaf
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Introduction

Understanding Slugs Snails

In order to keep slugs snails under control (not exterminate because they are beneficial too!) it would be best to understand the critter first…”who, what, when, and why” sort of thing and what makes it tick. During the last thirty plus years in the landscape pest control business, I found it best to understand just what you are dealing with and maybe there are alternative measures to take. Rather than “nuking” a yard with pesticides or poison slug bait.

Why is this disease or insect attacking only this cultivar or particular plant? Can the environment or other situations where the plant is located be changed? Can a ph level of a certain plant be adjusted. Therefore creating a healthier plant so insects or diseases won’t attack it. Can the plant be moved to a different location? Is the plant in the right location, i.e. shade, sun? In other words, what alternatives are there to help control or alleviate a problem?

Why Slug Snail Control is Important

Slugs snails are probably the most destructive pests in the garden. That is why slug snail control is so important. Especially for Calla lilies, Lilies, vegetables, and much more!

They are nocturnal feeders and before you know it, your veggie starts or that prize calla lily or lily plant Aunt Edna gave you is GONE! As a result, for effective slug snail control management, check for activity in the evening hours. They not only feed on lush green foliage of low lying and slow growing vegetables and landscape plants, but also feed below ground on roots. However, they are also beneficial in the fact they will feed on decaying material above and below ground. But, unfortunately, they prefer the lush “green” stuff.

I have tested all methods and treatments mentioned below (and then some). Plus being in the pest control business for the past 30 plus years and treating them for my clients. Therefore, I will share with you, in this article, the best slug snail control methods I have found for keeping these awful pests out of my callas, lilies, and garden.

About Slugs Snails

Slugs are simply snails (mollusks) without shells. These slimy creatures live in and on the ground. And have big appetites for a wide variety of plants found around the landscape or gardens. Young seedling plants are eaten as well as mature plants. They frequently cause damage to greenhouse, garden plants. And may be especially injurious in mushroom houses. Occasionally, they may congregate in large numbers in basements, on walls, doorways, and along walkways. Making these areas unsightly. Slugs may be found when the ground thaws in the spring until it freezes in the fall. Wet conditions are ideal for slug development.

The rasping mouth parts of slugs and snails are directed downward so that food can be taken from the surface over which they travel. Snails chew the edges of foliage and open the holes that slugs have made. The slugs’ mouth parts scrape away and puncture the surface of foliage causing the most damage.

Slug Mouth
Slug Mouth

Description of Slugs Snails

Slugs

Probably the best description of a slug is that it is a snail without a shell. They vary in size depending upon the species and measure from 1/4 to seven inches long.

A way to check on slug snail activity during the day, is to look for their slime trails. They secrete a characteristic slime (mucus) which they leave behind as they move around. These slime trails are silvery in appearance upon drying. And is a common diagnostic character used to identify the presence of slugs.

The color of slugs also varies with species, ranging from a dark black-brown to an orange color. When an actual slug is found their soft slimy bodies and extensible eye stalks give the creature its characteristic appearance.

The most common slugs found in landscapes are the gray garden slug, the leopard slug, and the dusky slug.

The gray garden slug is the most common and is generally a mottled gray to black in color. It is usually less than one inch long.

The leopard slug is the largest, commonly reaching four to five inches in length. It has characteristic black spots on its upper surface.

The dusky slug is intermediate in size, being one to three inches long, and can range from a gray to a bright orange in color.

The rate of growth of immature slugs depends mostly on the type and amount of food available. Dry conditions usually result in a loss of weight which is regained rapidly when moist conditions return.

In a temperate climate, slugs usually live one year outdoors. In greenhouses, many adult slugs may live for more than one year.

Gray Garden Slug on Leaf
Gray Garden Slug
Leopard Slug
Leopard Slug
Dusky Slug
Dusky Slug

Life Cycle: Slugs Snails

Slug Snail Eggs

All slugs snails lay eggs. Each species requires a different length of time for the development of its’ eggs and the maturing young. Snails are born with their shell. The number of eggs laid by slugs or snails may be up to 100, but average 20 to 30. Young adult slugs – snails lay fewer eggs.

Eggs appear as perfectly round gelatinous spheres filled with a watery substance. They range in size from 1/8 to 1/4 inch in diameter. They are usually colorless, often reflecting the color of their surroundings. But they may become cloudy just before hatching. Baby slugs/snails resemble adults but are smaller and may not be as fully colored.

When Slug Snail Eggs Are Laid

Though slug and snail eggs may be found outdoors during any month of the year, most are laid in the spring and early summer. Most species over winter as adults or nearly mature young. in the spring, eggs are laid in mid-summer. Therefore, making possible a second generation. Mating usually takes place from August until mid-October. Eggs can be laid from 30-40 days after a successful mating.

Snail Eggs
Snail Eggs
Slug Eggs
Slug Eggs

Where Slug Snail Eggs are Laid

Eggs are generally laid on or near the soil surface. However, they are deposited in places of concealment. Such as underneath mulch, rocks, flower pots, trash, and boards. Particularly preferred spots where the nature of the cover keeps the surroundings relatively cool and moist.

Temperature

The minimum temperature at which egg development will take place varies with each species of slugs or snails. However, it is in the general range of 32 to 42 degrees F. as long as 100 days may be required for the eggs to develop. At higher temperatures, development is usually completed in ten days to three weeks.

After Slugs Snails Hatch

As soon as slugs snails hatch, they are active and begin to feed or crawl if the temperature and humidity are right. Slugs snails are mainly nocturnal and remain motionless, concealed until nightfall provides conditions for activity.

The rate of growth of immature eggs depends mostly on the type and amount of food available. Dry conditions result in a loss of weight which is regained rapidly when moist conditions return.

In a temperate climate, slugs/snails usually live one year outdoors. In greenhouses, many adult slugs/ snails may live for more than a year.

Slug Snail Management

Management

Good slug snail control methods and slug snail control management program relies on a combination of methods: eliminating shelters, creating unfavorable conditions, destroying existing colonies.

Environment

Slug snail control starts with managing their habits/environment. You can easily start eliminating these habitats by clearing boards, stones, decaying yard debris, weedy areas around tree trunks, low growing leafy branches, and dense ground covers. This allows fewer snails and slugs to survive, and those remaining congregate in the last few shelters where they can more easily be located and removed.

Slugs and snails like shaded, moist environments and feed on decaying plant or wood material and in that sense are beneficial until the new Spring growth of succulent garden plants begin. Then they become unwanted, and destructive.

Breeding Grounds

Compost piles are ideal breeding grounds for slugs and snails, especially slugs. Effectively removing them could be a chore (to say the least). Destroy slugs in these areas before new growth appears on succulent plants in the Spring by keeping the pile as dry as possible, using beer traps, nematodes (microscopic eelworms), or other methods we will discuss later.

Compost Pile

Slug Snail Control Methods

Natural Predators

Vertebrate predators of snails and slugs include shrews, mice, squirrels, and other small mammals; salamanders, toads and turtles, including the uncommon Blandings Turtle Emydoidea blandingii; and birds, especially ground-foragers such as quail, thrushes, ducks, chickens, grouse, blackbirds, and wild turkey.

Natural predators work very well for slug snail control.  However, it takes great numbers for this slug snail control method to satisfactorily work. In other words, if you live in an area that has a good number of natural predators, and will not eat your prize vegetables, lily plants, etc.. Therefore, this is the best method of slug snail control.  If not, read on…

Non Predator Control

Organic slug bait is best, especially for large areas! 

There are a great deal of slug snail control methods. Some of the more popular ones are:

  • Beer traps
  • Smooth metal deterrents such as copper (too expensive)
  • Hand picking (too much time)
  • Lures and traps (do not last long but very effective)
  • Metaldehyde-based chemical products poison bait (too dangerous but very effective)
  • Organic baits made from Iron Phosphate
  • Decollate predatory snails (they can take a long time to decrease the harmful snail population and will eat succulent plants, too)
  • Scratchy things such as sandpaper, cinders, wood ashes, diatomaceous earth, sand, and using plant repellents.
  • Mixing mint or sage in your mulch will repel slugs and snails.
Slug or Snail Damage
Slug or Snail Damage
Slugs on Orange
Slugs on Orange Trap

Of the above mentioned slug snail control methods, I prefer organic slug bait (Iron Phosphate) in combination with the steps I have listed below. Organic slug bait works quite well for me because it is fast, we have to treat a larger area than most, it’s safe for all, and even adds natural fertilizer!  However, you have to apply it every three to four weeks during Spring, late Summer, and through out the Fall months for effective slug snail control.

Summary

All the above mentioned slug snail control methods work quite well, but we need something that will get rid of slugs and snails for a bit of time so we can enjoy other activities, too. I have tried all of the above mentioned control methods and after many years of combating theses destructive garden pests, I prefer to use a combination of slug snail control methods.

Phase 1

Organic Slug Bait

As soon as temperatures warm, I will treat areas where I know there will be a problem. This means treating 100% of my garden area, lily bulb plantings, compost piles, lawns, etc.

Combination Methods

Search out and destroy as many eggs and adults as I can find. Since slugs feed nocturnally, there will be some late night searches. However, if stumbling around with a flashlight is a bridge too far, look for slugs and their eggs during the day in the drainage holes of pots, beneath stones, and hunkered in long grass. If they evade your efforts, set traps.

On a small scale, a classic that works brilliantly for hard-to-find small ground-dwelling slugs is to place the scooped out half-shells of grapefruits or oranges near the crowns of vulnerable plants. Come dawn, the slugs make for the damp yellow domes, as they love to chew the pith inside.

Slugs also make a beeline for cardboard. Lay a sheet on the ground among long grass. Check your traps daily.

Nematodes

Again, this control method works well on a small scale control effort: I will either purchase nematodes or make my own and place the nematodes in the garden soil. This is really the best and safest method for slug snail control. You will get six weeks of control.

Slug Nematode
Slug Nematode

Phase 2

Repeat Treatments

In about 4 weeks, eggs you miss or invading slugs-snails from surrounding areas not previously treated will begin to appear. Retreat with above mentioned methods: nematodes, combined with organic Iron Phosphate bait (aka Sluggo or Escar-Go), orange/grapefruit traps, crushed egg shells, etc. Place methods around the plants you wish to protect. Keep a vigilant eye out for signs of re-appearing slugs-snail. Retreat as needed.

During the Autumn months, repeat treatment of Phase 1 for even better control the following Spring.

Reference:
Ohio State University Fact Sheet HYG-2010-95

Photos Courtesy of Ohio State University, Wikipedia

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