Our rainy spring weather has been great for our gardens – but may also have encouraged some unwelcome garden visitors, including snails and slugs.
To control snails, slugs and other pests, the University of California recommends that homeowners follow the Integrated Pest Management (IPM) process. IPM is a strategy that focuses on long-term prevention of pests by utilizing cultural, biological, mechanical and physical controls. With IPM, pesticides (chemical control) are used only as a last resort, and when pesticides are used, they are applied in ways that minimize harm to nontarget organisms, humans, pets, and the environment.
Mechanical or physical controls kill a pest directly or block a pest from an area experiencing damage. In the case of snails and slugs, handpicking is an effective mechanical control if it is done on a regular basis. They can be searched out after dark with a flashlight and then either crushed in place or picked up with rubber gloves. Once they have been picked up, they can be placed in a bag and thrown away in the trash, or placed in a bucket of soapy water and disposed of in a compost pile after they are dead. Alternatively, if you are lucky enough to know someone with pet turtles, you can give your snails and slugs to them (as long as they are healthy) -- most turtle owners are happy to receive these pests, which add protein to the turtle diet. Those with backyard chickens may be similarly appreciative, as chickens, too, eat snails.
Copper flashing or copper foil can be used as a physical barrier for slugs and snails. It is believed that copper is an effective barrier because it reacts with the slime of these pests, causing a disruption in their nervous system that is similar to an electric shock. These barriers should be at least four inches wide with the bottom buried in the soil to prevent slugs from crawling under them. Dry ashes or other abrasives such as diatomaceous earth can also be used as barriers for slugs and snails. Such abrasives should be piled about one inch high and 3 inches wide to be effective. However, these materials lose their deterrent value if they become damp, making them not very useful in most garden situations. Another drawback of wood ashes is that they are quite alkaline and can have a detrimental effect on soil pH.
Slug and snail baits can be applied as a last resort, but are most effective if used in conjunction with the IPM methods described above. There are other effective baits, but baits containing iron phosphate are the only ones that are safe for children, domestic animals, birds, fish and other wildlife. Iron phosphate baits are sold under many trade names including Sluggo and Escar-Go. The bait should be placed in moist areas that snails or slugs are likely to frequent. Timing is also important. If the weather is very hot, dry, or cold, baiting will have a limited effectiveness because slugs and snails are least active during these times. Take advantage of snail and slug habits by irrigating before baiting and scattering the bait in the late afternoon or evening.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.
- Author: Annie Sicotte, UCCE Master Gardener
Flowers and veggies lingered in my garden this year, encouraged by the mild autumn weather. Then came the holidays, followed by rain. So much for Fall garden tasks and cleanup chores. Between rainstorms in January, I walked around the garden amazed at how quickly the ground turned from golden fall leaves to a green carpet. As the summer garden died back, weeds took advantage of less competition and filled in the open spaces. They grew from seeds that blew in, were dropped by birds, or were stored in the soil “seed bank' from previous plants that went to seed – just waiting for the right conditions to germinate. Constantly moist soil and cool weather allow seedlings to get their roots established before the soil dries out.
Those beds of weeds are often ignored until Spring weather urges us to get our summer garden started. By then, the weeds are lush and well-rooted. “Weeding” becomes an unpleasant, daunting task if we wait.
Since weeds rob plants of nutrients and provide habitat for unwanted pests, it is important to control them early while they are still small. Although pulling weeds seems like a no-brainer, there is a definite way to do it efficiently. Grab a knee pad, hand hoe, Hori-Hori or trowel, and a big bucket. Kneel at the open edge of a bed and work on the weeds closest to you. Gently pull the largest weeds, lifting the root with a Hori-Hori or trowel. Next, with your fingers, pinch the base of an individual plant and “pluck” the weed out. This loosens the soil around it. making the next plant easier to pull. Gently shake the soil off the roots back into the bed before putting the weed in your bucket. Now, give the cleared area a shallow scuffle with the hand hoe to dislodge small seedlings. Don't dig weeds with a spade or disturb the soil deeper than an inch. This is hard on the soil structure and brings more weed seeds to the surface. Don't get anxious. If you try to grab and pull large handfuls, it only breaks off the leafy tops, which soon regrow from the leftover roots. It's better to do a smaller area thoroughly. Finally, add a 1” layer of weed free compost to the cleared area. This prevents light from germinating new seedlings.
Pulling weeds will give you a chance to appreciate the abundance of slugs and snails as well! It always catches me off guard to see how early the eggs begin to hatch. These voracious tiny babies are everywhere I look. Weeds, as it turns out, are a perfect hiding place to avoid predators. Tucked under the flat rosette of Shepherd's Purse or in the axis of an Asparagus leaf, slugs can eat and grow and not be found. Removing the weeds will greatly reduce their hiding places, as will removing last season's straw mulch and keeping the grass short around the garden beds… But slimy things are persistent in coastal gardens.
The undersides of wilted summer foliage keep snails happy and dry until tastier foliage emerges. They do serve a function, of course. Slowly, they help the decomposition of plant material. Summer plants that have been left to rot give slugs and snails an easy dinner. As I clean the debris and cut back the plants, I have found tiny little snails by the hundreds this year. Cleaning the beds reduces snails, but it also redirects them to the fresh new growth of healthy plants. Although I would love to just leave them for natural predators, there aren't enough birds, snakes, opossums, or other critters to make a dent in this year's bumper crop of mollusks.
There are no sure-fire exterminators for slugs and snails in the home garden. Environmentally concerned gardeners use Iron Phosphate baits like Sluggo with some success. But even the heavy-duty snail baits- the ones that contain Metaldehyde or Carbaryl (that also harms worms, reptiles, birds and some mammals) - only work on the snails that come in contact with the chemical. Many of the small hatchlings emerge and head for a sheltered place above the ground. You'll find them hiding in the tender tops of plants, under the lips of flowerpots, or behind shrub foliage where their ‘foot' never touches the ground. In the cool, damp air of night, they glide from their perch to devour prized plants – which seem to be their favorites. Controlling them becomes a bit more problematic and requires a combination of approaches.
I hesitate to share that hunting slimy slugs and snails has become a bit of a questionably sane, definitely weird obsession for me. You won't find me excited by a dish of beer with a few drunken snails in it. Instead, I clean, prune, plot, bait, consider the possibility of becoming an Escargot farmer, and then become the Human Predator. (That's right - it's my Super- Power. ) To tackle the problem, I put on the garb of a crazed gardener - a bright LED headlamp, rubber gloves, a container of soapy water - and head into the night garden to make my rounds. As I examine each plant, turning over leaves to check bothsides, I pluck my slow-moving prey and pop it into the container, where it sinks to its demise. It's not a pretty sight. But there are just SO many snails!
As the nights go by and the population dwindles, I marvel at the impact I can have on a single population of slugs and snails. Yes, that's right, “a single population” because there will be more eggs hatching. A single snail can lay 6 batches of eggs in a year with up to 80 eggs each. That's 480 eggs for every snail! It's never-ending. But I'm doing my part.
So, I encourage you to get a head start on the weeding and garden cleanup this year. Keep that cool fashion-statement headlamp handy, and just ignore the neighbors' comments about your new nighttime gardening chore. For what it's worth, I can vouch for your sanity.
For additional information about Integrated Pest Management (IPM), including weeds and mollusks, Check out the University of California website https://ipm.ucanr.edu/PMG/menu.homegarden.html?src=302-www&fr=3723
For help identifying and controlling weeds, https://ipm.ucanr.edu/PMG/weeds_intro.html
For more on slugs and snails, https://ipm.ucanr.edu/PMG/PESTNOTES/pn7427.html
All photos are courtesy of the author, Annie Sicotte, and are used with permission.
- Author: Jeannette Warnert
A collection of small raised beds decorated with colorful scarecrows, quaint décor and several rabbit topiaries make up Mr. McGregor's Garden, but this one doesn't have mischievous Peter Rabbit nibbling on the fruit and vegetables. The main problem appears to be snails. Last fall, dozens of garden snails were found feeding on the leaves of napa cabbage, cauliflower, kohlrabi and broccoli plants.
The Master Gardeners have been searching for organic solutions to the problem. Picking them off one by one has been the first line of defense. The Farmers Almanac suggests spreading crushed egg shells to deter snails from garden beds, and we tried it. However, the UC Integrated Pest Management program reports that egg shells are an ineffective deterrent, and we have seen little improvement.
Another solution available to Fresno County gardeners are decollate snails. Decollates are small, thin, tapered and easy to distinguish from the familiar larger, rounded brown garden snails. The decollate is native to North Africa and the Mediterranean region. It was accidentally introduced to Southern California in the 1960s, and has since helped manage snails in gardens and agricultural settings throughout Southern California and parts of the San Joaquin Valley. It is legal to purchase and release decollates only in the California counties of Fresno, Imperial, Kern, Los Angeles, Madera, Orange, Riverside, Santa Barbara, San Bernardino, San Diego, Tulare and Ventura. Because of its potential adverse impact on certain endangered and native mollusks, they should not be used in any other places in the state. Even in counties were decollate snails are permitted, they should not be introduced in or near natural areas because of the potential danger to native snails.
“Literature says it takes four to eight years for decollate snails to control brown snails, but my experience is they'll clean them out in a year,” Woods said.
The decollates are easy to find throughout Woods' front and back yards, under rocks and plants and nestled in plant litter. In February, Woods donated about 30 decollate snails to the Master Gardener's Children's Garden. The decollates were dispersed among strawberry and vegetable plants. While not a scientific trial, our experiment may lead to fewer snail and slug pests and less leaf damage in the coming years.
More information:
Visit the UC Master Gardeners Children's Garden in the Garden of the Sun, 1750 Winery Ave., Fresno. Hours: 9 to 11 a.m. Monday, Wednesday and Friday.
How to manage snails and slugs, UC IPM
UC IPM Natural Enemies Gallery, decollate snails
Identify snail damage, UC IPM (YouTube video)
Citrus trees need care throughout the year, including cultural practices to keep trees healthy and pest management. During the fall season, several pests can attack citrus trees in many California regions.
Brown Rot
Monitor for this disease by checking for damaged fruit on your tree, as well as fruit in storage. Sometimes affected fruit develops a pungent odor and can ruin fruit held in storage. See the UC IPM web page on Brown Rot to learn more.
If you see what look like small “tunnels” on your citrus tree leaves, your tree might have citrus leafminer. The adult stage of this pest is a small, light colored moth; the larval stage feeds and develops inside the leaves of young citrus and other closely related plants.
Citrus leafminer rarely causes problems for mature trees, however, it can seriously damage very young trees. Read the UC IPM Pest Notes: Citrus Leafminer for recommendations for prevention or management.
Snails and Slugs
Asian Citrus Psyllid and Huanglongbing
You may have heard of the Asian citrus psyllid (ACP) and the deadly disease huanglongbing (also called citrus greening) that has been featured in the news. This disease doesn't pose a threat to humans or animals, but is deadly to citrus trees. Once a tree develops huanglongbing, there is no cure, so for this disease prevention is key.
UC IPM Web Site
For information on managing other citrus pests in the garden, see the UC IPM webpage on Pests in Gardens and Landscapes: Citrus.
- Author: Ben Faber
Slugs and snails, destructors of crops and gardens,
could be
controlled by bread dough
CORVALLIS, Ore. – New research from Oregon State University Extension Service found slugs and snails are strongly attracted to bread dough, a discovery that could lead to better ways of controlling these serious pests of agriculture, nurseries and home gardens.
Since the beginning of recorded history, slugs have ravaged crops and today are responsible for billions of dollars in damage – including between $60-$100 million to Oregon's valuable grass seed industry alone, according to Rory Mc Donnell, associate professor and Extension gastropod specialist.
“Damage to grass seed is a major issue,” said Mc Donnell, who collaborated with scientists from other states on a study that was published in a special issue of Insects that focuses on slugs and snails. “But that's just one crop. It's mind boggling when you think about it. A huge array of crops is affected. They even take out specialty crops like mint. Many times, I've seen farmers lose an entire crop.”
Currently, nurseries, farmers and home gardeners use commercial baits like metaldehyde, iron phosphate or sodium ferric EDTA to control slugs and snails. These molluscicides are relatively expensive, can be toxic to non-targets and work with varying degrees of success, Mc Donnell said. Given its simplicity, low cost and the ready availability of its ingredients, bread dough has potential not only for crop protection in the United States but also for developing countries where access to pesticides is limited by cost. A dry formulation would likely have an indefinite shelf life and be easy to ship. It can be used to attract the slugs to a trap, where they will die, or to attract them to a molluscicides.
“Bread dough is a nontoxic, generic and effective tool that could be used in the detection and management of gastropods worldwide,” Mc Donnell said. “It represents a tool to aid in managing pest gastropod infestations, either using baited traps or in attract-and-kill approaches. It could also be incorporated into existing baits to improve their attractiveness.”
Of the 28 exotic or non-native slug and snail species in Oregon two are particularly troublesome – European brown garden snails (Cornu aspersum) and gray field slugs (Deroceras reticulatum), which plague nurseries and feed on hundreds of important crops with significant financial cost. If European brown garden snails are found in shipments of Oregon nursery plants at ports of entry in other states, the items are either shipped back or treated in place, Mc Donnell said. Either way it's expensive.
“With worldwide trade and travel, we are getting a homogenization of slugs and snails on planet Earth because of the widespread introduction of species,” Mc Donnell said. “This is not just a modern phenomenon. Slugs and snails have been traveling with humans for thousands of years. But it's getting more severe because of purposeful introductions, global trade, intensification of agriculture and development of new crops.”
Mc Donnell and his collaborators haven't determined yet why bread dough – a simple mixture of flour, water and yeast – attracts slugs and snails, but theorize that it is the fermentation process that draws them. They used a range of food in addition to bread dough to determine which would be the most attractive bait, including beer, cucumber, lettuce, strawberries, citrus, tomatoes, hostas and Marmite (a yeast-based food product popular in Great Britain).
“We gave them a choice of food and they consistently went for the bread dough,” Mc Donnell said. “They really, really like it. They went bonkers for it. Bread dough outperformed everything.”
In one instance, over 18,000 snails were trapped in 48 hours, according to Mc Donnell. The research revealed the bread dough can be effective in the field in Oregon for at least eight days.
“It has something we call ‘good field life,'” Mc Donnell said. “That's really, really important. If it worked for 12 hours, that would be good, but eight days gives a much bigger window for use.”
The project was a collaboration between Mc Donnell and his team; Robin Veasey and Jocelyn Millar, University of California at Riverside; Arnold Hara, University of Hawaii at Hilo; Amy Roda, U.S. Department of Agriculture, Miami; Gary Adams, U.S. Department of Agriculture, Billings, Mont.; and Ian Foley, Montana Department of Agriculture. This work was supported by funding from the U.S. Department of Agriculture under the Plant Protection Act Section 7721.