integrated pest management (IPM)

The 4 “E”s for Easy, Breezy, Beautiful Mosquito Source Reduction

Maryland Grows7 Comments

Imagine the perfect summer day. What are you doing? For most people reading this blog, I’m guessing it involves being outside in your yard—maybe working in the garden, reading in a hammock, or sharing an al fresco lunch with family and friends. Sounds idyllic! But, then, the dreaded whine, the too-slow slap, and the ensuing itchy bite left behind by a mosquito. On repeat. It’s enough to drive many of us indoors, even on the perfect summer day.

More mature readers may think to themselves “I don’t remember it being this bad when I was younger!” and you’re probably right. You are almost certainly being bitten by a relatively new invader called the Asian tiger mosquito (scientific name: Aedes albopictus) that was first observed in Maryland in 1987 and has adapted to thrive in urban and suburban areas. Named for its striped legs, the tiger mosquito is capable of spreading viruses such as dengue, West Nile, and zika. It is aggressive, and, unlike most other mosquito species that feed at dawn and dusk, it seeks its blood meals during the day.

mosquito larva
black and white mosquito is an Asian tiger mosquito
An Asian tiger mosquito (Aedes albopictus) larva [left] and female adult [right].
Photo credit: Ary Farajollahi, Bugwood.org

One survey found that the tiger mosquito’s biting rate is 10 times higher than what Virginia residents were able to tolerate. In another, 61% of residents surveyed in the Washington, DC area reported that being bothered by mosquitoes caused them to change their behavior to avoid taking walks, gardening, or participating in other outdoor activities. So, if you’re hiding inside on a sunny day, you’re not alone.

What to do? Avoid them? Deter them with citronella candles? Swat them one by one?

The most effective action you can take to reduce the mosquito population in your yard is to cut them off at the source—their larval habitat. After a protein-packed blood meal, female mosquitoes lay their eggs in water-holding containers. Once flooded, the eggs hatch into an aquatic larval stage; after roughly a week of feeding on microbes in the water, the larvae develop into pupae and then emerge in a couple of days as the adults you know and hate.

Aedes mosquito life cycle. Image credit: Centers for Disease Control and Prevention

If you’re committed and persistent in eradicating places for mosquitoes to breed, a practice known as source reduction, you can reduce the number of mosquitoes in your yard. For successful source reduction, follow the four “E”s:

Eliminate

The first step is to eliminate every water-holding container from your yard that you can. Throw away pieces of trash. Drill holes in the bottom of the tire swing. Store kids’ toys, wheelbarrows, watering cans, etc. in a shed or garage, under a deck, or on a covered porch. The tiger mosquito can breed in as little as one teaspoon of water, so be thorough in your search!

Exchange

Next, consider exchanging containers that cannot be eliminated. Swap an open rain barrel for one with a lid. Substitute corrugated extension spouts with splash guards, open chutes, or flat extensions at a downward angle. Trade lawn chairs with solid seats that allow water to pool with slatted chairs that do not.

Empty

Be vigilant about regularly emptying any water-holding containers that cannot be eliminated or exchanged—ideally twice but at least once weekly. Replace the water in pet bowls. Dump out flower pot saucers. Shake out tarps.

Emaciate

This one sounds weird, but stay with me. There may be standing water on your property that would be undesirable or impossible to eliminate, exchange, or empty, such as a bird bath, pond, or structural element (a common one I see in urban environments is the remainder of metal fence posts that were sawed off rather than torn out after the removal of a chain-link fence). For these sources, you can emaciate mosquito larvae with Bacillus thuringiensis subspecies israelensis, or bti for short; when larvae eat this normally soil-dwelling bacterium, the toxins released by the bti paralyze their gut, causing them to starve to death. A brutal way to go for mosquito, black fly, or fungus gnat larvae but harmless to other insects, pets, and people. Bti can be purchased online or
at most garden centers—a common brand to look for is Mosquito Dunk®.

Adhering to the four “E”s of source reduction can help prevent mosquito infestations on your property so you can enjoy those perfect summer days!

But what about mosquitoes on your neighbors’ properties?

Bonus action: Encourage

Encourage your neighbors to practice source reduction as well! Devoted source reduction in your own yard may not protect you if your neighbors are harboring abundant larval habitat. Tiger mosquitoes don’t tend to fly far, especially when resources are plentiful, but depending on how close you live to your neighbors, they may cross into your yard. Local mosquito populations are best controlled when the entire community participates.

Bonus bonus action: Entice

Want to do even more? Perhaps you’re feeling a little vengeful from summers past? Entice mosquitoes into a larval habitat trap. You can purchase or DIY something called a Gravid Aedes Trap, or GAT for short, that targets species in the Aedes genus, like the tiger mosquito. Standing water inside the trap encourages gravid, or pregnant, female mosquitoes to lay their eggs, but a mesh cover above the water prevents any mosquitoes in the next generation from escaping. The clear sides around the dark funnel top confuse the females who enter, making it likely they’ll be stuck, too—especially if you add sticky paper or cover the inner walls with cooking spray or oil to coat their wings. This makes the GAT a double-kill trap, affecting two mosquito generations at once. Just be sure to check the trap regularly to ensure that water is present but below the netting. University Park, MD created a community-wide mosquito control program in their town and created a helpful PDF document for GAT deployment.

a black plastic mosquito bucket with a clear plastic insert is used to kill mosquito larvae
Gravid Aedes Traps. Image credit: Biogents

By eliminating, exchanging, and emptying water-holding containers in your yard and emaciating mosquitoes in remaining larval habitat (plus encouraging your neighbors and enticing egg-laying female mosquitoes!), you can once again enjoy your summer outside. Easy, brEEzy, bEautiful, mosquito sourE rEduction. Happy mosquito hunting!

By Sarah Rothman, PhD Candidate in the University of Maryland Department of Environmental Science and Technology. Sarah is studying the relationship between non-native mosquitoes and plants across socioeconomic gradients. Learn about the EcoHealth lab at www.leisnham.org. After graduating, she hopes to work in the public sector conducting ecological research and outreach on topics related to invasive species, restoration, and environmental justice. 


Q&A: Natural Landscaping and Ticks

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Lone Star Tick “questing,” or trying to sense a host so it can climb aboard to bite. Photo: M. Talabac

Q:  I like the style of more natural gardens, letting leaf litter be my mulch, etc. I’m concerned about this encouraging ticks, though. Do I have to change how I garden?

A:  It’s a legitimate concern given the diseases ticks can harbor and transmit, but ticks can appear even in more manicured and minimally-vegetated landscapes, so I would rather reap the rewards of having a biodiverse and “wilder” garden than restrict myself and still wind up with hitchhikers when I go outside. Besides, some of that wildlife attracted by having a medley of native plants and leaf litter habitat may very well be killing some of those ticks. (Or doing the next best thing, eating their small-animal hosts that carry the pathogens we worry about.)

We at the Home and Garden Information Center (HGIC) are often asked about yard perimeter sprays and treatments for ticks, but pesticide use is not our suggested solution. Even when reasonably effective, these products are temporary measures and probably not substantially different in terms of efficacy than simply treating your own clothes or exposed skin with a tick repellent and/or doing a thorough body check once you’re back indoors.

Chemicals used to suppress tick populations (like for lawn applications) are non-selective and don’t impact only ticks. Their close relatives, spiders and any mites that aren’t plant pests (fun fact: some mites eat pests) are definitely worth having in our landscapes. They’re valued partners in natural pest management but can be equally vulnerable to the effects of sprays marketed for tick control. Some pesticide ingredients are even more broad-spectrum than this, potentially affecting ground-dwelling insects and other organisms. As with mosquito management, it’s more sustainable to use personal protection to avoid bites and to landscape in an eco-conscious way to make full use of any existing natural checks and balances that keep tick populations down.

By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.

Have a plant or insect question? The University of Maryland Extension has answers! Send your questions and photos to Ask Extension. Our horticulturists are available to answer your questions online, year-round. You can also connect with your local County/City Extension Office and Master Gardener local programs.

How to grow a healthy garden

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It’s easy to get overwhelmed by the sheer volume of gardening advice in books and websites. So I thought I’d simplify things by sharing my top 10 tips for keeping a garden healthy. 

Start with your soil. Healthy soil grows healthy plants. So get a soil test to know what you have and need.  

Add compost or other organic matter regularly to enliven the soil and keep the soil community happy. This intricate web of beneficial microbes, fungi, bacteria, worms, and more is crucial to healthy plants. 

Well-adapted native plants such as this white penstemon naturally resist pests and disease. Photo: Kathy Vesely

Minimize soil disturbance. Every time you turn the soil, you bring up weed seeds and wreak havoc on the soil community. So dig and till minimally.

Keep the soil covered with plants, an organic mulch, or cover crops. Bare soil invites weeds, encourages soil-borne disease, and promotes erosion. 

Put the right plant in the right place. Choose plants that suit the site whether it’s sunny or shady, wet or dry. This matchmaking helps plants not only survive but thrive.

Use native plants. These tough, well-adapted plants need less water and fertilizer. Since they co-evolved with native wildlife, they support pollinators and other native species best. 

Encourage beneficial insects. These are the good bugs that help control bad bugs. Nine out of ten insects are beneficial, naturally controlling the few true pests. Put them to work for you. 

How? Reduce or eliminate chemical pesticides which kill both good and bad bugs. Use organic products instead and try other controls like hand-picking or floating row covers.

Further, encourage beneficial insects by planting a wide variety of plants to provide food and shelter. Add a rock to a birdbath so insects can sip. 

Wait to cut back perennials and grasses until spring to give beneficial insects a safe place to overwinter. Many tuck into hollow stems or leaf litter.

Check your plants often. When you’re strolling, be patrolling. Look for spots, yellowing, or other changes that might be clues to a problem. Early detection makes fixes easier.

If you live in Washington County, Maryland, e-mail or call me if you need help identifying an insect or disease. Just send me a photo or bring me a sample. If you live in another area of Maryland, contact your county or city Extension office, or send your questions to Ask Extension.

Many problems are preventable. Honest. About 80% have cultural or environmental causes and aren’t due to pests or diseases. So there’s much we can do to prevent problems.

Water wisely. Water in the morning and avoid overhead watering. Leaves that are wet overnight tend to have fungal problems.

Removed diseased plants. Add compost which naturally suppresses some diseases. Space plants so air circulates. Cover bare soil so rain doesn’t splash fungal spores up onto plants.

At the end of the growing season, thoroughly clean up vegetable plant debris which can harbor harmful overwintering insects and disease.

There you have it, my top 10 tips for a healthy garden. When you work with nature, not against it, you naturally limit pests and diseases, grow more resilient plants, and build a healthier garden and community.

That’s a very good feeling indeed.

By Annette Cormany, Principal Agent Associate and Master Gardener Coordinator, Washington County, University of Maryland Extension. This article was previously published by Herald-Mail Media. Read more by Annette.

Spotted lanternfly: The latest invasive species spreading through the eastern U.S.

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A man is holding an adult spotted lanternfly to show its wings
Adult Spotted Lanternfly. Photo: M Raupp, UMD

¿Hablas español? Aquí esta una traducción: Mosca linterna con manchas: la especie invasora más reciente que se está extendiendo por el este de los Estados Unidos.

Spotted lanternfly (SLF), Lycorma delicatula (Hemiptera: Fulgoridae), is an invasive planthopper moving its way through the eastern U.S. SLF was first detected in the U.S. in 2014 in southeastern Pennsylvania. It is native to parts of Asia and believed to arrive as egg masses laid on landscaping stones shipped to PA. Despite quarantines and eradication efforts, SLF infestations have been confirmed in 12 states and detected in several others.

A map shows that spotted lanternfly is confirmed in 12 states in the northeast USA
Since spotted lanternfly was first detected in Pennsylvania in 2014, confirmed infestations are in 12 states as indicated by this map (as of June 30, 2022). Image: https://nysipm.cornell.edu/environment/invasive-species-exotic-pests/spotted-lanternfly/spotted-lanternfly-range-us/

As we look at the SLF distribution map, we can see that counties with infestations are hundreds of miles away from any other infestation. This is related to the fact that SLF are excellent hitchhikers, taking advantage of human-assisted transportation. Many infestations occur along major interstates and train lines. In addition, the nymphs are active walkers and adults are able to hop and fly to new host plants and locations. Researchers at Penn State found that some SLF nymphs travel as much as 213 feet, and adult flights ranged from 30 to 150 feet in their search to find suitable hosts.

In response to SLF’s impressive ability to disperse, states have implemented regulatory quarantines and permitting programs implemented through State Departments of Agriculture, which requests actions be taken by businesses and the public who travel in and out of SLF-infested areas.

What do we know about the life cycle of SLF?

The life cycle of SLF consists of one generation per year, with eggs (the overwintering stage) laid in the fall (September – November). Egg masses are laid on smooth surfaces such as tree branches, landscape stones, rocks, wood from decks or fencing, outdoor furniture and equipment, etc. Egg masses are covered with a mud-like substance likely for protection. The protective covering is gray when freshly laid and becomes brownish with age. The eggs hatch in the spring between 240 (usually early to mid-May) and 1100 (late June to early July) degree days (DDs).

Spotted lanternfly egg mass ona tree trunk
Freshly laid egg masses of spotted lanternfly are gray in color and camouflage well on tree branches and other structures. Photo: M.J. Raupp, UMD

There are 4 nymphal instars (immature stages). Newly hatched nymphs are small (~1/8”) and at each molt they somewhat double in size. The first three nymphal instars are black with white spots and the last nymphal instar is red with white spots and black stripes.

early instar spotted lanternflies
Early instar spotted lanternfly nymphs are often found on new growth of plants. Photo: PA Dept. of Agriculture
late instar spotted lanternfly nymph
Late instar (4th) nymphs are about ½” long, bright red with white spots and black stripes. Photo: D. Ludwick, Penn State Extension
Spotted lanternfly adult
The adult spotted lanternfly has beautiful coloration and is ~ 1 inch in length. Photo: M.J. Raupp, UMD

In PA, adults begin to emerge in July (50% adult emergence at ~ 1,100 DDs) and they remain active (feeding, excreting honeydew, mating, and laying eggs) until the first hard freeze, which kills them. Adults of this planthopper are beautiful and relatively large (~1”). Adults have black bodies and legs; their front wings are gray with black spots and the ends are black with gray veins. Their hindwings are red, black and white. When the adult spreads its wings, the bright red color is quite impressive. Nymphs and adults are robust jumpers and adults can also fly.

Why is SLF problematic?

SLF is a voracious feeder on over 70 different plant species, which include numerous economically-important plants such as grapevines, some herbaceous ornamental plants, fruit trees, numerous ornamental trees, and tree of heaven. It uses its piercing sucking mouthparts to remove phloem sap from its host plants. Hundreds to thousands of SLF individuals can sometimes be found on a single tree. Surprisingly, even at these high numbers, death of hosts is only known to occur on grapes and a few sapling trees, although branch dieback on trees has occurred. Further research is needed to determine the longer-term impact of the stress of so many SLF feeding on trees has on secondary problems.

In addition to damage to hosts from feeding, SLF is also considered a nuisance pest. SLF excretes large quantities of honeydew which drops down onto leaves, branches, tree bark, driveways, cars, and anything else that might be underneath an infested host. The honeydew also has its associated black sooty mold, which makes it more unsightly. On sunny days the honeydew can be seen “raining” down from SLF infested trees.

Abundant honeydew-/sooty mold-covered foliage may reduce photosynthesis and further stress trees. In addition, many bees, wasps, and other insects that feed on sweets are attracted to the sugar rich honeydew. Because densities of SLF are so high, the honeydew/sooty mold can be quite significant and impactful to homeowners and growers.

An impressive breadth of hosts

An interesting aspect of SLF’s ecology is that it changes the plants it feeds on as nymphs and adults develop over the season.

table showing host plants preferred by spotted lanternfly nymphs and adults
This table is a (non-extensive) representation of common host plants that spotted lanternfly feed on during the season. The table allows knowing when to start monitoring for activity of nymphs and adults, and what host plants they are likely to be on. It is recommended to always monitor for SLF infestations, since densities change over time both within the season and between years even on the same host plant. Tree of heaven, Ailanthus altissima, is an invasive tree and a highly preferred host. Information in this table is based on observations in Eastern Pennsylvania and may vary based on local conditions. Image: https://extension.psu.edu/spotted-lanternfly-management-guide.

How can SLF be managed?

Managing SLF is challenging, as is the case for many emerging, invasive species. It is unlikely you can stop it from coming onto your landscape or farm, and unlikely you can get rid of all of them. Given this, the goal is to reduce SLF populations to acceptable levels. Using an Integrated Pest Management (IPM) approach will result in the greatest success.

At this time, natural enemies are not reducing SLF populations. However, many generalist predators (spiders, assassin bugs, birds, etc.) are feeding on SLF, a parasitoid brought into this country years ago for spongy (formerly gypsy) moth control has been found attacking SLF, and two fungal pathogens were also identified, one of which (Beauveria bassiana) is commercially available. Further research is underway to identify measures to enhance the impact of these biological controls for SLF.

Cultural controls can be implemented. This includes destroying the overwintering egg masses, putting traps (circle or sticky traps) on trees to catch the nymphs and adults as they move up trees, and removing tree of heaven. Numerous studies have examined the efficacy of contact and systemic insecticides against SLF (see websites below).

We need you!

Please assist in tracking SLF to help slow the spread of SLF and improve its management. If you find SLF, please report it to your State Department of Agriculture or University Extension Service. In Maryland, report SLF at the MDA website (click on “Report Spotted lanternfly here”).

For more information

By Dr. Paula Shrewsbury, Professor and Extension Specialist in Ornamental and Turf IPM in the Department of Entomology at the University of Maryland

Q&A: Why do my cucumber and zucchini plants wilt?

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One Spotted and multiple Striped Cucumber Beetles, feeding on overripe pumpkin. Photo: Whitney Cranshaw, Colorado State University, Bugwood.org

Q: Last summer I had cucumbers and zucchini wilting and dying even though I’m pretty certain I didn’t have root rot or squash vine borer. What should I try this year so I can hopefully get a harvest?

A: Bacterial wilt disease, transmitted by cucumber beetles is the prime suspect for crop failure in this instance. Both of these garden pests – Striped Cucumber Beetle and Spotted Cucumber Beetle – are native to North America and can cause serious damage to vegetables in the squash/cucumber family, though they can also feed on unrelated fruits, vegetables, and ornamental plants.

Although their feeding causes direct plant damage, the main issue comes from their introduction of one or more plant pathogens. These beetles can transmit diseases like bacterial wilt and viruses, none of which are curable.

Delaying the planting of squash and cucumber transplants until mid-June may evade the host-seeking adults. Until they bloom, cover plants with insect netting or row cover (the former is ideal as it doesn’t trap heat). Bees will need to reach the flowers for pollination, but once the fruits start to develop, plants tend to be less susceptible to infection. Since more than one beetle generation can occur per year, clean-up veggie garden debris in autumn to deny remaining adults overwintering shelter.

For now, ‘County Fair’ is the only available variety resistant to bacterial wilt. This pickling cucumber is parthenocarpic– it produces mostly female flowers that don’t require pollination to set fruit. The Cucumber Beetles page at the Home & Garden Information Center has more information about these insects and their management.

By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun. Read more by Miri.

Send home gardening questions to Ask Extension at the Home & Garden Information Center

The more the merrier: community actions for pollinators

Maryland Grows2 Comments
bumble bee on a purple coneflower

Besides it being the month when summer starts, June is a great month because it is when Pollinator Week happens! 😊

Tagging along with that week, in today’s post I want to talk about some actions you can take with(in) your community to help pollinators! Because, if we want to help pollinators, a very valid and effective way to amplify your actions is to get others on board! Here, a non-extensive list of ideas.

1. Become a Bee City

Ask your City or Campus to become a certified Bee City or Bee Campus USA. Bee Cities and Campuses are certifications that cities and campuses across the USA can obtain if they implement a series of actions (“commitments”) established by the Xerces Society. Once these actions are done, the City or Campus in question becomes certified as a pollinator-friendly space. The types of actions outlined are really activities that lead to increasing education on pollinators and pollination, to improving pollinator habitat on the institution’s land, to promoting actions in the way that the institution functions that may allow for increasing pollinator support (see here for city commitments and here for campus commitments). Becoming a Bee City or Campus is not hard, and most institutions say yes if their members ask. If you think this is something you would like your City and/or Campus to do, reach out to your representatives or leadership and get them on board! And to have an idea of what cities and campuses are already involved, take a look at the Bee City USA affiliates.

Bee City USA logo
Bee Campus USA logo

2. Organize a Pollinator Week Event

Pollinator Week is a National event organized by the Pollinator Partnership and includes many possible actions that lead to increasing pollinator survival and/or awareness. This year, Pollinator Week will be happening June 20-26. One can participate in activities already organized by others, or one can propose and host an activity! If you would like to get together with your community and organize an event, do it, and then submit it to the Pollinator Week event list! That way, others will know about it and will participate as well! To submit (or participate in) an event, go to the bottom of the Pollinator Partnership page.

Pollinator Week, June 20-26, 2022 logo

3. Ask your city to host a No-Mow Month in early-spring

Early-spring pollinators emerge usually when very few plants are flowering, meaning that the early spring is a critical time for these pollinators. In human-occupied landscapes like cities or suburban areas, a lot of the landscape is occupied by lawns, which can provide some flowers early in the spring. No-Mow Month (usually April or May, depending on the city’s conditions) is an action that seeks to allow the availability of the early flowers in lawns so that local pollinators can survive during the early spring. Once other plants in the landscape start flowering (usually at the end of April in most of Maryland), the lawn can be mowed with this not negatively affecting pollinators.

It is important to note that this action is based on voluntary participation, meaning that participants opt-in (instead of being mandated to do it). This action has been shown to be effective in increasing pollinator diversity and abundance in regions where it is implemented, and is not associated with excessive lawn growth because it occurs so early in the season. Further, it can be strengthened with native plantings, which can boost its effects and also support local landscapers during the reduced-mow month. Localities where the action has been implemented tend to have high adoption rates, increased nature awareness, and willingness to further support biodiversity around homesteads, with no- to very-reduced vermin occurrence.

This action usually requires some temporal amendments to City Code (e.g., to ensure that participants will not be penalized if their lawns surpass the maximum allowed height during the no-mow month) so it needs approval by City Councils. Although this may sound really complicated, it is not, and several Cities in Maryland have implemented this program very successfully during the month of April (see here for College Park, MD, and here for Greenbelt, MD), following Appleton, WI’s trailblazing action. If you think this is something you would like to implement in your community, get in touch with these cities’ Bee City USA committees so they can share their expertise, and then contact your representatives to ask them to adopt this action where you live!

No Mow April Collage Park sign

4. Ask your community to establish pollinator-friendly plants and nesting resources

Communities can also support pollinators through the way they decide to landscape their land. Requesting your community leadership to implement pollinator-friendly gardens and offer nesting resources for pollinators (e.g., bee hotels, create small wild spaces) is a really good way to help pollinators at a larger scale. To do this, you can get in touch with you City/Town Horticulturist and/or Public Works people, and request this. If you would like to implement this in your neighborhood and on private land, you can coordinate with your neighbors and create plots of native plants or small nesting areas in everybody’s green spaces. A very effective way to do this in Maryland is by establishing a neighborhood Green Team. If you would like to know about how to do this, take a look at this page of recommended native plants and this list of native plants that do well in our area.

Chart listing easy-to-grow native plants that support pollinators

5. Ask you city/town/neighborhood to adopt an IPM plan

Although we tend to think about helping pollinators only by planting flowers and maybe creating nesting spaces, pollinators also can be helped by the way we manage our landscapes. For example, herbicides and pesticides can be sometimes very harmful to pollinators, or cutting plants at certain times of the year can really negatively affect them. Reducing the use of pesticides and herbicides, or changing the way we manage our own private land is one possibility. However, cities, towns, neighborhoods, schools, and campuses also manage their public lands! For that reason, they can also implement actions to manage spaces in ways that support pollinators.

chart explaining Integrated Pest Management in 5 steps

A very good way to institutionalize this is by requesting these institution to implement Integrated Pest Management (IPM) plans. IPM is a way of controlling pests and increasing “beneficial” organisms in a given space by means that reduce the use of pesticides and herbicides. These plans establish a framework that allows institutions to still control pests and diseases, while reducing the negative impacts on biodiversity that some conventional practices have. These plans can be very general or very specific, and if your institution does not have one, it may be time to ask them to implement one! To do this, get in touch with your institutional horticulturist or your government representative. Here are some examples: city, campus and school district plans.

By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

Managing Slugs in Crop Fields and Gardens

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¿Hablas español? Una traducción de este artículo se puede encontrar aquí.

Slugs are a common field crop and horticultural pest. Managing them is challenging because their damage is often confused with other pest damage, and pesticide options are few and expensive. Luckily, knowing what to look for and the growing practices that reduce slug damage helps reduce the problems with this pest.

What exactly are slugs?

Unlike most other plant-feeding pests found in fields or your garden, slugs are not insects. Instead, they are soft-bodied, legless mollusks that are covered in slimy mucus that they secrete and leave behind as a trail. Slugs dry out easily, so they prefer environments with lots of shade and moisture. Slugs feed on a wide variety of food sources, but when they eat plants they can cause a significant amount of damage making them the bane of many farmers and gardeners.

In our area, the most common slugs found in crop fields and gardens are:

  • Gray garden slugs – about 2 inches long when fully grown. Ranging from cream-colored with irregular gray spots to dark brown with dark spots.
  • Marsh slugs – Smaller, about 1 inch long. Tend to be dark.

Eggs of both species are small, clear, round, and gelatinous. They are usually laid in clusters under plant residues.

Images of two types of slugs: gray garden slug, marsh slug, slug eggs
A) A gray garden slug, B) two marsh slugs, and C) slug eggs under old soybean roots
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