When I read about organic gardening, I see a lot of references to neem oil. What is it, and how do I use it in my garden? -Sherry

Neem oil is made from the seeds of the neem tree (Azadirachta indica), which is native to India. Since ancient times, the neem tree has been prized as a sacred remedy and important ingredient in Ayurvedic medicine. In the garden, neem boasts a powerful insecticidal ingredient, azadirachtin, which makes it a great organic choice for controlling a variety of problems.

Uses for Neem Oil

Neem oil can be used to treat a number of garden ailments, including:

• Insects: Neem oil kills or repels many harmful insects and mites, including aphids, whiteflies, snails, nematodes, mealybugs, cabbage worms, gnats, moths, cockroaches, flies, termites, mosquitoes, and scale. It kills some bugs outright, attacks the larvae of others, and repels plant munchers with its bitter taste.
• Fungus: Neem oil is also effective in preventing fungal diseases such as black spot, anthracnose, rust, and mildew.
• Disease: As if that wasn’t enough, neem oil also battles viruses that can harm plants.

Advantages of Neem Oil

Neem oil is a popular choice in organic gardens because it is:

• Nontoxic: As long as it isn’t sprayed directly on them, neem oil is nontoxic to beneficial garden insects such as predatory wasps, honeybees, earthworms, ants, spiders, ladybugs, and adult butterflies. Neem oil is considered nontoxic to humans, birds, and other animals as well (see below) and can be used on fruits, vegetables, and flowering plants.
• Organic: Neem oil is plant based and easily available from organically grown neem trees.
• Biodegradable: Neem oil breaks down quickly and leaves no lasting residue.

How To Apply Neem Oil

Neem oil concentrate is usually mixed with water and sprayed on both sides of plant leaves. Because oil and water tend to separate, you’ll need to keep your solution well stirred. You can also mix it with insecticidal soap for a double whammy. Neem oil is bottled in different concentrations, so follow the instructions on the package to get the right proportions of oil to water.

Other Uses for Neem Oil

If you’re concerned about the safety of neem oil compared to other products in your garden, consider that neem is often used as an ingredient in:

• Cosmetics
• Shampoos (including pet shampoos for flea/tick control)
• Natural insect repellents
• Alternative medical remedies for antiseptic, antiviral, antifungal, and anti-inflammatory uses

The only health cautions for neem oil relate to actual consumption of the oil, and garden use does not appear to pose any known health hazards. As with any chemical—organic or synthetic—use neem oil only in moderation when needed, and wash all veggies and plants thoroughly before eating.

Further Information

• Material Fact Sheets: Neem (Cornell University)
• Azadirachta indica: One Tree’s Arsenal Against Pests (Colorado State)

Related posts:

• Organic Sources of Potassium for Your Lawn or Garden
• What Causes White Lines on Tomato Plants?
• Why Aren’t the Flowers in My Garden Blooming?

Wound paints and dressings claim to prevent rot and help trees heal from pruning wounds, but research suggests that they actually do more harm than good. When you cut off a tree limb, or the bark gets damaged, the tree never actually “heals.” Instead, it compartmentalizes the wounded area with a special type of calloused wood – like a scar – that keeps out bacteria and helps the rest of the tree recover.

Painting wound with wound paint or dressing can:

• Prevent the tree from forming calloused wood, which can keep the tree weaker.
• Seal in water, bacteria, fungi, and decay.
• Attract disease causing organisms that feed on the wound paint.
• Interfere with a natural recovery process that nature has taken eons to perfect!

To help keep your trees healthy when pruning:

• Prune in late winter while trees are dormant.
• Sterilize pruning shears and saws between cuts with rubbing alcohol or hydrogen peroxide.
• Target specific risks by treating wounds with an organic fungicide or insecticide.
• Make careful, clean pruning cuts just outside the branch collar, where the tree can most quickly heal.

There are a few devastating diseases, such as oak wilt, that are introduced through insects feeding off pruning cuts, then spread from tree to tree via the roots. Wound paint can reduce (but not eliminate) the risk of these infections, so some tree experts feel that the downside of wound paint is better than the risk of spreading this disease throughout a neighborhood.

Check to see if diseases are a problem in your area. If they are, follow the guidelines from your local extension service regarding the use of wound paint when pruning. In general, however, only use wound paint when absolutely necessary to prevent specific diseases.

Further Information

• The Myth of Wound Dressings (Washington State University)
• Should I Paint or Otherwise Treat Pruning Cuts? (extension.org)
• Wound Dressings (Shigo and Shortle, Journal of Arboriculture, 1983)
• Proper Pruning to Prevent Oak Wilt Infection (Texas Forest Service)
• When to Trim Trees and Shrubs

Related posts:

• How To Trim Large Tree Branches
• Sidewalk Damaged by Tree Roots
• How to Select the Right Tree for Your Yard

Is it safe to use pre-emergent herbicides (such as crabgrass preventer) around my established bulb beds? -Helen

The short answer is “sometimes,” because in gardening a simple question doesn’t always have a simple answer! Products that are labeled as “weed preventers” are usually pre-emergent herbicides, which work by stopping seeds from germinating, so it stands to reason that they shouldn’t affect established bulbs (especially dormant bulbs underground). However, that’s not always the case, as a product labeled “weed preventer” may have any number of active ingredients that affect weeds, seeds, and garden plants in different ways. Every product should be evaluated separately to make sure it’s safe.

Corn Gluten: The Organic Choice

Corn gluten meal is a popular organic choice for preventing weeds. Corn naturally produces a substance that suppresses the germination of competing seeds. In addition to its weed preventing properties, corn gluten is high in nitrogen and adds some organic matter to the soil – nature’s own “weed and feed!”

Sold under brand names such as Preen Organic Weed Preventer, corn gluten meal is considered safe for use around bulbs, shrubs, trees, and ornamental plants. In addition, it’s far less toxic than chemical herbicides.

Chemical Herbicides: Check the Label

As for commercial chemical weed preventers, you really need to read the label. Some are safe around all bulbs, some are safe only if you apply before the bulbs sprout, and others aren’t safe at all. Before applying, read the label (and do a little research) to make sure the product is safe.

Examples of common products include:

• Surflan AS is safe around bulbs according to the product label.
• Scotts Turfbuilder with Halts Crabgrass Preventer is considered safe as long as it is applied before bulbs sprout.
• Trifluralin, the active ingredient in Preen Garden Weed Preventer, is also listed as safe around bulbs.
• On the other hand, Preen Lawn Crabgrass Preventer, isn’t recommended for use around bulbs. In this case, the product label wasn’t clear, but the website had more info. Lawn weed products are designed for grasses only and aren’t always safe around ornamental plants, so be careful if you’ve got naturalized crocuses in your yard.

In general, I would use corn gluten meal (or just pull the weeds by hand), simply because I don’t want those other chemicals in my yard. Many chemical herbicides are known to be directly toxic to our health, not to mention deadly to the environment. I’d also focus on enriching the soil and strengthening the desirable plants, because unhealthy gardens are prime targets for pesky weeds.

Further Information

• How to Control Weeds in Your Lawn
• How to Control Crabgrass
• Applying ‘Weed and Feed’ Products to St. Augustine Grass
• How to Target Weeds in Your Yard (video)

Related posts:

• Applying ‘Weed and Feed’ Products to St. Augustine Grass
• How to Kill Weeds in a Gravel Driveway
• Advantages of Weed Barriers for Your Garden

My downstairs neighbors have been remodeling their condo, and my place has been overrun with silverfish. I’m desperate to get rid of them, but I don’t want to use toxic chemicals. Help! -Tina

Silverfish (Lespisma sacchrina) are nocturnal members of the insect order Thysanura that thrive in high humidity and warm temperatures. They can move very fast, making them hard to see, and live on a diet that includes starchy foods, paper, and fabric.

While they don’t bite, silverfish are a creepy nuisance that can be destructive to your belongings. The best way to get rid of silverfish is to attack them at the source; however, in your case it sounds like the source is going to be impossible to find! The good news is, you don’t have to reach for the highly toxic sprays; in fact, some of the less-toxic options are the most effective! Here are some things to try:

• Boric Acid: This is the most popular product for silverfish control, and compared to other products, boric acid is quite low on the toxicity scale. In fact, it has historically been used as a cleaning product. You can purchase boric acid powder to sprinkle in areas where silverfish are active. You can also find boric acid in ready-to-use products such as baits, wafers, and traps. Roach Ridd and Dekko Silverfish Paks are examples of products made with boric acid.
• Diatomaceous Earth: The tiny silicate shells of microscopic sea diatoms are lethal to many insects, penetrating their exoskeletons and dehydrating them. Sprinkle diatomaceous earth in crevices, but make sure pets and children cannot get close enough to breathe it.
• Pyrethrin: This is a chemical pesticide, but because it’s made from the seeds of the pyrethrum plant, it’s biodegradable and considered less toxic than others. It’s the active ingredient in many flea and tick pet collars. While no pesticide is completely safe, this might be a more attractive option than a harsher chemical. You can find pyrethrin sprays and powders at most garden centers, and you would apply it only in crevices and areas where the silverfish are active.
• Jar Traps: Make your own silverfish trap by covering the outside of a glass jar with masking tape (to help the critters crawl in), then put crackers or something starchy in the bottom of the jar as bait. The silverfish crawl in, but they can’t get out.

DIY silverfish control:

• Sticky traps: Make a paste of flour, water, and boric acid. Coat index cards with the paste, allow it to dry, and use as sticky traps.
• Baits: Sprinkle boric acid on and around a cracker, and place it as poison bait. Be sure to put it out of reach of children or pets! You can also do this with diatomaceous earth.
• Crevice sprays: Make a 5% solution of boric acid in water. Use a spray bottle or turkey baster to inject the spray into cracks and crevices. You can also spray the powder directly. This puts the treatment where you need it and reduces your exposure to the chemical.

Be sure to target:

• Boxes and file cabinets
• Insulation
• Baseboards
• Behind appliances
• Cabinet tops
• Light fixtures and behind electrical outlets
• Behind siding and within walls
• Holes where water pipes enter walls

To make your home less inviting to silverfish:

• Fix Damp Spots: Leaky pipes, water condensation, damp basements, and humidity provide an attractive environment for silverfish.
• Eliminate Food Sources : Silverfish eat starches and sugars found in paper, glue, book bindings, insulation, and cardboard boxes, and they usually hang out pretty close to their food source. Use airtight plastic storage bins for paper, and get rid of anything that you find full of silverfish.
• Vacuum Crevices: Silverfish hide and lay their eggs in cracks and crevices. Dispose of the vacuum cleaner bag in the trash outside so they can’t crawl out again.

Further Information

• Silverfish (AgriLIFE Extension, Texas A&M)
• How to Get Rid of Silverfish (howtogetridofstuff.com)
• Boric Acid (Al’s Home Improvement Center)
• Boric Acid, Borates, Borax (beyondpesticides.org)

Given the pattern, I really should have been prepared for anything from earthquakes to temporary paralysis. Nevertheless, I was rendered nearly speechless when I crawled under the Christmas tree to add water, and I found the floor underneath the tree littered with what appeared to be ticks. There were dozens of them. Meandering around, looking bewildered and hungry, slowly spreading out across the living room. Ticks . . . you gotta be kidding me!

I wish I had a photo to show you, but frankly I pulled out the vacuum cleaner faster than Wyatt Earp at the OK Corral. And then I reached for the tick spray and gave that tree the dose of a lifetime. In a couple of days, my house would be full-to-bursting with houseguests, and my organic sensibilities were overrun by the fear of spreading a little Lyme Disease with my Christmas cheer!

The next day—after one more pass with the vacuum—the problem seemed to be under control, but it was quite a while before I found the time to face (and to learn about) what had happened. I’d never heard of ticks being in a Christmas tree, but, as my life has proved over and over, anything’s possible.

Meet the Cinara Aphid

Before you become infected with my panic and throw your Christmas tree on the curb, I’d better hurry up and clue you in on the punch line – it turns out they weren’t ticks at all. In fact:

• Ticks don’t live in trees, and they don’t lay eggs in trees. They dehydrate too easily, so they stay closer to the moist ground. They aren’t found in Christmas trees, period.
• Ticks need live animal hosts, so it would be impossible for them to multiply and infest a tree without a food source. It doesn’t fit with their life cycle or habitat.
• Ticks spread by clinging to and falling off hosts – they don’t swarm or form colonies.

While tree growers look for infestation, it can be difficult to spot on a large farm.

So what CAN multiply and infest a tree? Cinara aphids, also known as Conifer aphids, that’s what. Here are a few facts about the little critters:

• They’re harmless. That’s right, harmless. They feed on trees, not animals, and they don’t bite or carry diseases. For us humans, they’re nothing more than a nuisance.
• As I can testify, they look almost exactly like ticks, with their brownish-black, flat, round bodies and short legs. The dead giveaway, though, is that Cinara aphids have only six legs, while ticks have eight. You can see what they look like at BugGuide.net.
• They even leave a purple-red smear when you smush them (believe me, I smushed plenty of them).
• They feed on trees and infest pines, firs, and other conifers, making Christmas trees vulnerable.
• They can infest only one tree in a large area, so the tree grower may not know about them.

Aphids are no match for the vacuum – just be sure to throw away the bag.

What If My Tree Has Aphids?

If you’re like me and unknowingly bought a Christmas tree infested with aphids, not to worry! It really isn’t that difficult to deal with them. Try these tips:

• Shake your tree before bringing it inside, to dislodge as many as possible. You can also rinse your tree with mild soapy water and allow it to dry outdoors. Aphids are soft-bodied insects that are easily washed away.
• If your tree is badly infested, don’t be afraid to take it back to the tree lot. The grower should identify and understand aphid infestation and exchange it for a healthy tree.
• Inspect trees before you buy them. Look along the tips of branches and also deep within the tree – the aphids move to more protected branches as the weather gets colder.
• Vacuum up any critters that make it onto your floor. I only found them right under the tree – they didn’t travel far, and most of them were dead or barely moving. They really were easy to control – my only panic was because I thought they were ticks!
• Don’t squish them – they’ll stain your carpet or floors.
• You can treat your tree using a room fogger or insecticidal soap, if you wish.

Further Information

• Cinara Aphids on Christmas Trees in North Carolina (NC State University)
• Rogues’ Gallery of Post-Harvest Pests (NC State University)
• Pests on Christmas Trees (NC Christmas Tree Association, PDF 144kb)
• Insect Pests on Christmas Trees (Iowa State University)
• Buy a Real Christmas Tree! (University of Florida)
• How to Select and Care For a Live Christmas Tree
• Christmas Tree FAQ

This year my garden was exposed to the late blight epidemic, and I lost most of my tomatoes. As I plan next year’s garden, what do I need to do to prevent another outbreak? -Karen

Late blight (Phytophthora infestans) is like the “flu” of vegetable gardens – it’s airborne, waterborne, and fast spreading, and it can wipe out tomato and potato crops in just a couple of weeks. Late blight generally comes in new waves every year, usually from:

• Infected transplants at garden centers.
• Infected potatoes that survive the winter underground.
• Cool, wet weather.

Unfortunately, even the most careful garden can be infected by spores blowing in from elsewhere, but following these tips can prevent bringing in (or harboring) the spores in your garden:

• Transmission: Late blight can only survive in living plant tissue – it doesn’t live in the soil, and it doesn’t live on seeds, tools, stakes, or cages. Make sure to harvest all your potatoes to prevent harboring the disease underground over the winter.
• Planting: Start your tomatoes from seed, to avoid buying infected transplants. If your potatoes were affected, start fresh this year with seed potatoes that are certified disease-free. Throw away any “volunteer” potato vines.



• Fungicides: Treating with fungicides can be used as a preventative measure on healthy plants, but late blight is not treatable once it strikes.
• Act Quickly: If you see signs of late blight, pull and throw away the affected plants immediately to prevent spreading of the disease. It won’t get better!
• Composting: Some experts recommend against composting the plants, but others feel it’s OK if done correctly. The key is to make sure the material is completely dead. Infected plant material and spores will usually be killed in a hot compost pile (over 115° F). To make sure, you can solarize infected plants before composting. Potatoes are tougher, however, so you may want to cut them up and spread them on the ground where they’ll freeze, and plow them in next spring.
• Prevention: Use smart gardening practices to prevent fungal diseases. Water without wetting foliage, allow for plenty of air circulation, and make sure your veggie garden gets morning sun. Even though late blight doesn’t live in soil, practice crop rotation to prevent other diseases.

Further Information

• Late Blight of Potato and Tomato (Maryland Cooperative Extension)
• Late Blight: Frequently Asked Questions (Cornell University)
• Can I Compost Plants Killed By Late Blight? (Penn State Master Gardeners)

Related posts:

• Vegetable Garden: Crop Rotation Made Easy
• Vegetable Garden: Growing Cool-Season Vegetables
• How to Plant a Fall Vegetable Garden

Brown spots in lawns are frustrating to deal with! Just when you think you’ve done everything right, suddenly there’s a patch of grass that’s dead or dying. There are a number of causes of brown spots in lawns, from insects to disease to human error.

To get to the bottom of the situation, you’ll have to do a little old-fashioned investigating. Here’s a checklist to help you determine the cause of brown spots in your yard.

Human and Animal Damage

Unfortunately, it’s very easy for us (and our pets) to damage lawns. Some common causes of brown spots include:

• Dull Mower: Dull mower blades tear your grass, causing damage and gradual death to the grass.

  Remedy: Sharpen your blades in fall and spring. After mowing, examine your grass to see if the mower is cutting cleanly.

• Scalping: If your mower blade is set too low or there are lumps in the lawn, it can cut the grass too short and cause damage.

  Remedy: Practice proper mowing techniques by raising your mower blades, and smooth out high spots by digging up the sod, removing some of the soil underneath, and replacing the sod.



• Chemicals: Gasoline, fertilizer, herbicides, and pesticides can cause dead spots if spilled. If fertilizer is applied unevenly or incorrectly, it can burn the grass. Even insect repellents can burn your lawn when sprayed on the grass blades.

  Remedy: Pour chemicals, fuels, and sprays on your driveway, not on your lawn, and follow application directions.

• Animal Urine: Dogs are the most common culprit, but large birds and other animals can cause urine spots, too. Urine usually causes your lawn to turn yellow in spots, sometimes with a bright green ring around the edges where the diluted nitrogen in the urine acts as a fertilizer.

  Remedy: Check out our article on How to Keep Dogs From Damaging Your Lawn for tips.

Take a sample of stems, roots, and soil for analysis.

Poor Growing Conditions

The conditions in your yard may be unfavorable for grass to grow:

• Poor Soil: Soil quality can vary in your lawn, and poor soil can occur in patches, causing brown, bare areas or moss.

  Remedy: Take a screwdriver and push it into the soil. If it doesn’t go easily, your soil is likely compacted. Try aerating and top-dressing to incorporate organic matter in the soil. When you aerate, take a look at the plugs, to see how the quality and texture of your lawn varies in different spots. Keep this in mind as you amend and improve your soil.

• Buried Debris: I once puzzled over a brown patch for weeks before finding an old piece of buried lumber under the grass.

  Remedy: While you’ve got that screwdriver handy, poke around a little to see if anything is underneath the sod.


Compacted soil.

• Erosion: Water tends to run off slopes, taking grass seeds and young shoots with it, and leaving bare ground or dried out areas behind.

  Remedy: Aerate your lawn to increase water absorption. If the slope is steep, consider building terraces or planting groundcover.

• Roots: Large trees or shrubs usually win the battle for water and nutrients. The area under trees is notoriously difficult for growing grass.

  Remedy: Consider mulching or naturalizing areas under trees and shrubs.

• Drought: Lawns need one inch of water per week, either from rainfall or irrigation. Dry, compacted spots are more easily drought-damaged.

  Remedy: Keep an eye on dry, sunny spots, especially if your soil drains poorly. If you irrigate, make sure your entire lawn is watered evenly.

• Dormancy: Cool-season lawns can go dormant during the heat of summer while warm-season lawns go dormant during the winter. If your lawn has a mix of grasses, you’ll have curious brown patches as some areas go dormant while others stay green.

  Remedy: Seasonal dormancy is normal, but make sure your lawn is healthy and strong to prevent unnecessary browning.

Brown spots caused by dormant Bermuda grass mixed with green fescue.

Common Lawn Diseases and Pests

If you’ve eliminated all the above causes, it’s time to move on to some of the more serious diseases and pests that plague lawn grasses. Some of the most common culprits are:

• Thatch: Thatch is a buildup of decaying grass blades that can build up so thick that it chokes out healthy grass.

  Remedy: Remove thatch if it is more than ½” thick.

• Grubs: Grubs are a common problem in mid to late summer, and most easily identified when your sod easily pulls back from the ground like a carpet.

  Remedy: Pull back a section of sod and inspect for fat, white curved worms. More than ten per square foot can cause lawn damage. Grub control products are available at your garden center.

• Chinch bugs: Chinch bugs are a common summer pest in warm-season lawns, especially in hot sunny patches beside driveways and sidewalks.

  Remedy: Inspect your lawn closely, and look at your shoes as you walk through the grass – you should be able to spot the small black and white adults. They’re resistant to many pesticides, but there are products available to target them.



• Other insects: Caterpillars and other pests can live part of their life cycle in lawns.

  Remedy: Watch your lawn closely – look for crawling and munching insects and for grass blades that look eaten. Also watch for birds and wasps feeding on these pests in your lawn.

• Fungal Diseases: Brown patch and other fungal diseases thrive in moist conditions, most often in midsummer (when nights and days are hot and humid) and spring (as snow melts). They may show up as circular or irregular brown spots, or you may notice a spotting or infected pattern on the blades or a generally dying/thinning out.

  Remedy: Increase air circulation and sunlight as much as you can, to make your lawn less inviting to fungus. Note the size and shape of the damage as well as the frequency of watering, fertilizer, mowing habits, and sunlight in order to diagnose the disease correctly. Take a sample of the affected grass (blades, roots, and soil) to your local cooperative extension office for analysis.

Further Information

• Lawn Diseases (North Dakota State University)
• Common Lawn Diseases (Cornell University)
• What Kind of Lawn Diseases May I Have? (All About Lawns)
• Fall Lawn Care Guide
• Spring Lawn Care Guide
• Summer Lawn Care Guide

Related posts:

• How to Keep Dogs from Damaging Your Lawn
• Summer Lawn Care Guide
• Fall Lawn Care Guide

Mosquitoes are not only annoying, they can also carry serious diseases such as the West Nile virus. While spray on repellents work, they can be messy to use, have an odor, and bring strong chemicals in direct contact with your skin. To keep mosquitoes from ruining your time outdoors, consider an area mosquito repellent like those from ThermaCELL.

Related posts:

• When It Comes to Mosquitoes, Which Repellent Works Best?
• Mosquito Repellent for Your Yard
• (693) The Great Outdoors: Making the Most of Your Yard

ThermaCELL mosquito repellent provides an odorless 15’ x 15’ mosquito-free zone around you wherever you go. The butane cartridge inside the unit vaporizes the insecticide on the repellent pad to provide protection in a matter of minutes. ThermaCELL mosquito appliances are available at The Home Depot.

Related posts:

• When It Comes to Mosquitoes, Which Repellent Works Best?
• Mosquito-Free Yard
• (694) Room with a View, Part 1

Find out how household products from baby shampoo and corn syrup to sugar and soft drinks can be used to nurture plants and improve the soil in your garden.

Related posts:

• How to Clean Your Home Naturally Using Common Household Products
• Plants in Your Garden that Produce Seed for Birds