Pests

What to Know Before Applying Pesticides in Your Garden

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a man inside of a hardware store reading a pesticide label
Before using a pesticide, read the label. Photo: Oregon Department of Agriculture, CC.

You have a pest problem in your garden – maybe it is hungry insects feeding on your vegetables, or stubborn weeds taking over your flower patch, or fungal diseases killing your lawn. You might consider using pesticides (which include insecticides, herbicides, and fungicides), especially if the problem seems widespread or severe. How do you choose the right pesticides and apply them correctly to support a healthy and thriving garden? How do you ensure your food plants remain safe for consumption and adverse impacts on beneficial species and soil health remain minimal?

Choosing the right pesticide

Home gardeners can generally choose between two types of pesticides: general use pesticides and minimum risk pesticides. Both pesticide types come with labels that explain how to safely handle, use, and dispose of the products. The labels of general use pesticides are reviewed by the Environmental Protection Agency (EPA) and will have an EPA registration number (highlighted by the blue rectangle on Figure 1), typically on the back panel. The labels of minimum risk pesticides are less extensive and are not reviewed by the EPA as they pose minimal risks to humans and the environment. Since these labels lack an EPA registration number, you can verify the product’s authenticity by contacting the Maryland Department of Agriculture’s State Chemist Section (410-841-2721). Alternatively, you can check out this list of approved minimum risk pesticide substances (PDF).

an example of a pesticide label for Houseplant and Garden Insect Killer
Figure 1: First representative label (back panel)

Regardless of the pesticide type, it is important to select a pesticide that has a narrow activity range. If your pest is an insect, you would ideally want a pesticide that targets insects. It would be even better if you could narrow down your insect pest – is it a caterpillar, beetle, or aphid? Some pesticides are more effective against certain pest insects (for example, see the product in Figure 2) and are therefore less likely to harm non-target insects. If you are unable to identify your pest, you can submit questions and photos to the University of Maryland’s Ask Extension service. Ask Extension will help identify the pest and recommend a course of action. 

Another important criterion for pesticide selection is human safety, which can be determined from the signal words on the front panel of the label (see the purple rectangle highlighted in Figure 2). Danger signifies high toxicity, warning signifies moderate toxicity, and caution signifies low toxicity. A pesticide that is virtually non-toxic may have no signal word. Ease of use and application frequency can also help make your choice, as it may not always be feasible to measure and mix or frequently apply the product. This information is typically part of the section on directions for use, often found by peeling open the entire label (see the black rectangle highlighted in Figure 1).

a sample label from a biological insecticide called Monterey B.t. - the caution word on the label is highlighted
Figure 2: Second representative label (front panel)

What else to look for on the pesticide label

Labels also include the following information on the front panel (see Figure 2): product brand name, ingredients, and the statement “Keep out of reach of children”. Other information found typically on the back panel (see Figure 1, which includes the label peel) are precautionary and other hazard statements, first aid, and storage and disposal sections. It is important to read all these sections properly, including the entirety of the directions for use, prior to the use of the pesticide. 

  • The precautionary statement typically includes personal protective equipment that needs to be worn during pesticide applications (for example, full-length clothes, gloves, and eye protection) and informs the period of time during which one must not enter or come into contact with the treated area. The signal words are repeated in this section. 
  • Hazard statements warn of potential hazards to the environment, including soil, water, air, wildlife, and nontarget plants. An example warning statement is “This product is highly toxic to bees”. This section may also include possible fire, chemical, or explosion hazards posed by the product.
  • First aid section recommends steps to be taken in case of accidental exposure or poisoning. The instructions vary in accordance with the route of pesticide exposure (swallowing, inhaling, contact, and eye), and include statements like “sip a glass of water if able to swallow”, and “take off contaminated clothing and rinse skin with water for 15-20 minutes”. Often, there is information on who to contact in case of a medical emergency. If you need to visit an emergency health provider, remember to take the pesticide label with you. 
  • Storage and disposal section provides information on how to store the product (for example, “store in the original container in a cool and dry place” and “protect from freezing”) and dispose of it (for example, “triple rinse the empty container” or “place the empty container in the trash”). The Maryland Department of Agriculture has often had an annual program where one could recycle an empty pesticide container for free. If you would like to dispose of unused pesticides, follow the instructions in the disposal section. Never dispose of pesticides down any indoor or outdoor drain. Many Maryland counties offer options to safely recycle or dispose of household hazardous waste, including lawn and garden pesticides. Current or retired farmers and producers can also avail of a free pesticide disposal program offered by the Maryland Department of Agriculture.
  • Directions of use section instructs how to properly use the product. This section typically includes a description of intended uses, mixing and application methods, use rates, and sites where the product may be used. It can also include application restrictions – this consists of statements like “do not apply if rain is predicted within the next 48 hours” or “do not apply when bees are actively foraging”. In many labels, application restrictions are also found within the hazard statements section. 

Why is it important to follow the label?

A pesticide is any substance that prevents, destroys, repels, or mitigates pests. Thus, by nature, pesticides negatively impact living organisms. Federal law states that the EPA must ensure that pesticides entering the marketplace do not cause “unreasonable adverse effects to humans or the environment”. To carry out this mandate, the EPA assesses a variety of factors, including data on the pesticide’s chemistry, human health effects, environmental effects, etc. These data help inform the label language ̶ if the label is appropriately followed, the pesticide product should not cause unreasonable adverse effects to humans or the environment. For example, if a pesticide is highly toxic to fish, the hazard statement of the label would include a sentence like “Do not allow pesticide to enter or run off into storm drains, drainage ditches, gutters, or surface waters”. Applicators can be protected from unreasonable adverse effects by complying with precautionary statements like “Avoid contact with eyes” and “Wear chemical-resistant gloves”. Pesticide use/application rates are set to prevent hazardous quantities from entering the environment, including the infested plants you would like to consume. 

Given the label’s critical role in minimizing a pesticide’s negative impacts, it is little wonder that the label is the law. Remember, if you use pesticides improperly, you are legally responsible for any consequences that may occur!

References:

U.S. Environmental Protection Agency. Label Review Manual. https://www.epa.gov/pesticide-registration/label-review-manual

American Association of Pesticide Control Officials. FIFRA Minimum Risk Pesticides – 25(b) Product Label Guidance. https://aapco.files.wordpress.com/2018/03/fifra-minimum-risk-pesticides-label-guidance-3-12.pdf

By Niranjana Krishnan, Assistant Professor, Department of Entomology, and Maryland Pesticide Safety Education Program Coordinator

Q&A: When Will Spotted Lanternfly Eggs Hatch?

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Spotted Lanternflies are black with white spots when they first hatch
Immature Spotted Lanterflies are black with white spots when they first hatch in mid-April to May. Photo: Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org

Q: When will Spotted Lanternfly eggs hatch? We’ve had such warm spells this season that I worry it’ll be early.

A: Spotted Lanternfly (SLF) egg hatch, like the activity of many insects, is greatly dependent on temperature. Predictions for egg hatch in an average year begin around mid-April but can continue into May, so while it may not be early per se at this point, it still will be soon. As such, this is your last opportunity to be vigilant for egg masses to squish before the active, hopping, hard-to-catch juveniles appear.

Don’t panic – juveniles cause little plant damage to gardens when young – but eliminate any egg masses within reach if possible because this is a serious agricultural pest (vineyards, mainly) and it might help you avoid an inundation of nuisance lanternflies later. To be fair, many eggs are laid high in tree canopies, making them inaccessible, but others can be laid on piles of stone, fencing, car hubcaps, grills, outdoor furniture, honey bee hive boxes, and so on.

Gray patches that look like dried mud are Spotted Lanternfly egg masses
Spotted Lanternfly egg masses on wood. Photo: Emelie Swackhamer, Penn State University, Bugwood.org

Be advised that the quarantine zones in Maryland have recently been expanded, and records indicate that the abundance of this pest has grown in our central counties. Check our Spotted Lanternfly web page and information updated on the Maryland Department of Agriculture website for more details. An MDA entomologist presented a refresher webinar about SLF this past winter, which you can find on the UMDHGIC YouTube channel as “Spotted Lanternfly Update from MDA.”

Spotted Lanternfly webinar (1 hour, 11 minutes)


If you haven’t seen Spotted Lanternflies in your neighborhoods yet, be prepared to see them in the next year or two as the population expands. I don’t want to scare you, just make you aware this will probably be something you’ll have to experience sooner or later, and I definitely discourage the use of any pesticide to combat this insect if its use can be avoided. Pesticides used to kill SLF have impacts on other insects and organisms and we don’t want to contribute to ecosystem damage by using them when the SLF damage done to most garden plants will be minimal.

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.

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.

Manage bagworms now so they don’t harm trees

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“Why are the pinecones on my tree moving?” a client asks.
“Because those aren’t pinecones, they’re bagworms,” I reply.  

Dangling from evergreens like teardrop-shaped Christmas tree ornaments, bagworms cause many a homeowner to scratch their head in wonder. Pinecones that dance?

Bagworms dangle from a juniper branch.
Credit: Erik Rebek, Bugwood

But the tell-tale thinning of trees that can follow is no laughing matter. Covered with bits of needles and leaves, the bags that give bagworms their name serve as protection for the caterpillars inside. Bagworm caterpillars are the juvenile form of a moth.  

That sounds innocent enough, but like all caterpillar-like insects, they are born hungry. Walking stomachs, they prowl among your trees, munching away to cause sometimes serious defoliation. They particularly enjoy evergreens such as arborvitae, cedars, junipers, and pines. But they will also dine on maples, locusts, lindens, and other deciduous trees.  

Eggs hatch out from bagworms’ bags in May. Tiny larvae spin an eighth-inch bag with bits of needles or leaves glued together with webbing. Like tiny backpackers, bagworms tote those bags around as they feed. As they grow, the bags get bigger and bigger and your tree foliage gets thinner and thinner.  

I don’t know if bagworms have an adventuresome streak, but they do a bit of hang-gliding. They spin a fine web and use the wind to glide to other trees in a stunt called “ballooning.” 

By August or September, the bags – and bagworms – are 1- to 2-inches long.  They stop wandering and feeding and tie up to a twig using tough silky threads. In late summer, they transform into moths. But get this, ladies, only the males have wings.  So the gals just hang out in their bags and wait for the boys to, um, visit. Post rendezvous, each female bagworm lays 200 to 1,000 eggs in its bag. Next spring, the eggs hatch to start the cycle over again.

Stopping that cycle is important and now is a crucial time. Mid-June to mid-July is the best time to treat trees with bagworms with a very effective organic control called Bt. A naturally occurring soil bacteria, Bt or Bacillus thuringiensis kills only small caterpillars. And guess what? Bagworms are just the right size right now.  Bt doesn’t harm humans or animals and is easy to find. It’s sold in hardware stores and garden centers under names like Dipel and Thuricide. Applying Bt is a do-it-yourself job if you can reach your trees with a sprayer. If not, call in a pro.

Even easier is picking off the bags if you have only a few bagworms. Snip them off with scissors or pruners, bag and trash them. Don’t leave them on the ground where the eggs can hatch. Since there can be as many as 1,000 eggs in each bag, removal is important. Get those bags gone. And gone before the eggs hatch in May.  

Tiny bagworms are hard to spot when they first appear in May on plants such as this Colorado blue spruce.
Credit:  Dave Lantz

Learn more about bagworms and see some great photos on the HGIC website.

You can beat bagworms and keep your trees safe. Fortunately, this is one insect for which there is an easy – and organic – fix.  So get out there and bag some bagworms.

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.

This article was previously published by Herald-Mail Media.

Spotted Lanternfly: A New Invasive Pest That is Too Close for Comfort

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spotted lanternfly adult
Spotted Lanterfly Adult. Photo: Pennsylvania Department of Agriculture, Bugwood.org

Spotted Lanternfly (Lycorma delicatula) is an insect native to China that was first detected in Southeastern Pennsylvania in September 2014.  It has spread fairly rapidly since then. There were recent finds in Delaware and New York. Both were dead individual adults.

spotted lanternfly quarantin map of pennsylvania november 2017
A quarantine is in place in several counties of Southeastern Pennsylvania to restrict the spread of Spotted Lanternfly. Source: Pennsylvania Department of Agriculture

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