How to Prevent Carrot Flies

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Carrots damaged by carrot fly maggots. Photo: gardening.which.co.uk

The carrot fly (Chamaepsila rosae, formerly Psila rosae) is a major annoyance for many home gardeners. The larva of this insect, the carrot fly maggot, pierces rusty-brown tunnels in the roots of carrots (Daucus carota) and then rot sets in, making them unusable. But fortunately there are ways of preventing this pest. Here are a few:

Note that the carrot also attacks other umbellifers (plants in the carrot family, Apiaceae), such as celery, parsley and parsnip. Most of the techniques shown here will help protect them as well.

Sow Late and Avoid the Rush

Adult carrot fly: it’s rarely seen, but its maggots are a major annoyance. Photo: Sarefo, Wikimedia Commons

First, you can simply delay sowing. The first generation of carrot fly is out early, in mid-May in most climate, and these flies lay their eggs in the soil near any carrot seedlings they can find. At first, the young larvae feed on the root hairs and secondary roots of the seedlings and only later do they start tunneling into the main root as it thickens.

However, if you sow your carrots late, about mid-June rather than in early May, by the time the seeds germinate, in about 2 weeks, there’ll no longer be any adult flies around to lay eggs near them, so you can avoid the problem! Of course, that will delay your carrot harvest, but still, should give them plenty of time to reach maturity.

Of course, there is a second generation of carrot fly that appears towards the end of July and into August and even a third generation in the fall in mild climates, but if the important first generation didn’t hatch in your garden, there will be very few latecomers around to even find your carrots. And even if a few flies do, this generation rarely causes any significant damage. It’s the first generation that’s the real problem.

Keep Wildlings Away
It is always wise to keep wild carrots (Daucus carota) away from any vegetable garden; otherwise there will always be carrot flies (and other carrot pests) right nearby. So, get out there and yank them out!

Pest Exclusion Barriers

A floating row cover will keep carrot flies at bay. Photo: http://www.amazon.ca

Another possibility is to sow your carrots early, as usual, but then set up an exclusion barrier by means of a sheet of floating row cover, also called pest-exclusion net or frost cover (in the latter case, because it can also protect against the cold). It’s a very light, translucent, whitish material that lets in rainwater, air and, of course, sunlight, but not insect pests.

For this barrier to be effective, though, you have to carry out crop rotation. It won’t work if you sow your carrots in the same place as the previous year, because the carrot fly overwinters as a pupa in the soil near the roots that it ate the previous summer. So, if you sow in the same spot and adult flies awaken and dig their way out of the ground, they’ll end up inside the barrier, ready to pounce on your carrots! However, if you sow your carrots in a new location, then protect with row cover, flies will find themselves outside of the barrier, unable to reach their favorite food.

No staking is required with floating row cover. Photo: wimastergardener.org

The idea is to loosely cover the row or spot where you sowed the carrots with floating row cover and to hold it in place with stakes, bricks, earth or stones so that it doesn’t blow away. No staking or other support is necessary: it’s called floating row cover because it “floats” above the leaves, rising with them as they grow. (That said, many gardeners do install stakes, hoops, etc., probably because it makes them feel more useful.) The border of the row cover, however, must, however, be pressed against the ground or even buried so it doesn’t open in the wind: if the flies find an opening, they will readily enter it.

You can remove the row cover, its work done, when the first generation of carrot flies dies at the end of June.

Skip a Year

Just don’t plant carrots in a given year and you’ll wipe out an entire generation of carrot flies. Photo: journeywithjill.net & clipart-library.com

Even more easily, if you had trouble with the carrot fly one year, simply avoid sowing them (and other umbellifers) the following year. When the flies emerge from the ground in late spring, they won’t find carrots nearby on which to lay their eggs. Since they’re poor fliers and rarely go very far, most will be unable to find a suitable host and will simply die.

That way, the following spring, there will be no overwintering pupae in the garden, so no flies, no maggots and no damage. Problem solved!

It often takes 4 to 7 years of carrot growing before the fly finds your vegetable garden again.

Make Your Carrots Indigestible … to Maggots, That Is

‘Resistafly’ carrot is just what it’’s name suggests: resistant to carrot flies. Photo: http://www.kingsseedsdirect.com

But the most laidback method of controlling the carrot fly is to grow carrots the flies don’t like.

Carrot flies find carrot plants through the smell of chlorogenic acid they give off. And moreover, maggots actually need this acid for their survival. Without the presence of chlorogenic acid, they soon die.

However, some carrots have a very low chlorogenic acid content or even contain none, like the following:

  • ‘Flyaway’
  • ‘Flyfree’
  • ‘Healthmaster’
  • ‘Ibiza’
  • ’Maestro F1’
  • “Paranoid”
  • ‘Resistafly’
  • ‘Sytan’

These carrots really don’t attract flies and even if they do find them, will suffer little damage, because the larvae die soon after hatching.

You will find carrot seeds resistant to the carrot fly in many seed catalogs, sometimes even in garden centers.

__________________

And there you go! By using the above methods, you can harvest delicious and healthy maggot-free carrots!

Nix Groundhogs in the Garden

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Groundhogs can do a lot of serious damage to a vegetable garden. Photo: http://www.farmersalmanac.com

Budding city gardeners are often shocked to discover that they may have to deal with groundhogs in their vegetable patch. I mean, aren’t groundhogs something you find way out in the country? 

Well, that may have been true in the distant past, but in regions where groundhogs (Marmota monax) live, they have long since adapted to suburbs and even the heart of the city, and seem particularly attracted to vegetable gardens. Just because a garden is urban doesn’t mean it will be spared their ravages. Community gardens and collective gardens—also known as all-you-can-eat-groundhog-buffets—appear to be an especially frequent target.

Meet the Neighbor

Distribution of the groundhog (Marmota monax). Ill.: Wikipedia

The groundhog is a large ground squirrel, one of 15 species in the marmot tribe (Marmotini). It’s found only in North America, mostly in the Eastern and Central United States, as well as all across Canada. (In the Western USA, it’s replaced by various smaller ground squirrels, such as prairie dogs.) There are marmots in Europe and Asia as well, although UK gardeners can relax; there are none in your country outside of zoos. Even so, the other marmot species are essentially alpine animals and people rarely garden on barren mountain tops. Only the American groundhog is a lowland species unfriendly to veggies.

The groundhog is a discrete little creature, often living mostly sight unseen in suburban yards and city green spaces. The landowner often only notices its presence in fall when the leaves drop from the trees, revealing its burrow entrance in a hidden corner, under a deck or tool shed or under shrubs. But if he has a vegetable garden, the presence of the groundhog is much more obvious, because, even if it eats a wide variety of plants in the wild, in town, it seems to have a clear preference for vegetables, including cabbages and other crucifers, lettuces, cucumbers, squash, beets, peas, beans and spinach. In addition, it’s quite the glutton: you may see an entire row of cauliflowers disappear in just one night!

Understanding Its Habits

To control a groundhog, you have to understand it.

Not a groundhog colony, but babies ready to leave their mother’s burrow. Mom is certainly not far away. Photo: http://www.pennlive.com.

First, it’s important to comprehend that the groundhog is largely a solitary animal. You’re not dealing with a colony, but just one animal. With the exception of mating season, males and females live separately and the young already leave their mother at about two months old to found their own burrow … which is why, in midsummer, you often suddenly find damage as the young settle into new territory and think your veggies belong to them. In the wild, a groundhog rarely lives long, only two to four years on average, but since each female produces about four pups a year, the population is easily maintained.

Typical groundhog burrow. Photo: wildlifecommandcenter.com

A groundhog lives in a burrow consisting of two to five entrances, long tunnels and at least two compartments: a nest filled with dry grass and a room that serves as a latrine. It will winter in the nest starting in late fall. Since you often see your neighborhood groundhog basking in the sun, rarely far from its burrow, that usually gives a good idea where it lives, often with entrances hidden under a tool shed, a patio or other garden structures. A groundhog will be active both day and night. It actually prefers the presence of humans, taking up residence near our homes, because it sees us as rather clumsy and stupid predators it can easily avoid, while its natural predators (wolves, coyotes, lynx, eagles, etc.) tend to stay away from us.

Groundhogs often chew vegetables (here squash) nearly to the ground. Photo: Diane Vautier

You can suspect a groundhog (or deer) when you find vegetables that are nibbled almost to the ground overnight. An insect simply doesn’t do that kind of damage. By observing what happens to the garden, you should be able to easily confirm if it’s a groundhog, as once it has found your vegetables, it inevitably comes back again and again.

Controls

One urban legend says that if you fill a plastic pop bottle with water and lay it on its side in the vegetable garden, the groundhog will see its image reflected in the side of the bottle and, thinking its territory invaded by a rival groundhog, will flee in panic. If only it were that easy!

A plastic owl may scare groundhogs away … for a while! Photo: http://www.aliexpress.com

However, there are other animal repellents that are more effective. By repellents, I don’t just mean odoriferous commercial products, but any item that scares the animal, whether by sound, sight or smell. So, you can place scented soap in the garden, attach aluminum plates or rags on a cord so that they move in the wind, apply repellents based on rotten eggs or coyote urine, apply blood meal, human hair, pet fur or mothballs to the soil (beware: mothballs are toxic to children!), place a plastic owl or snake in it, play a very loud radio, etc. (For a more complete list of repellents, see Do Animal Repellents Really Work?)

In fact, anything new will scare the groundhog and keep it away from your vegetable patch … for a while, usually no more than two weeks. When it realizes that there is no real danger, though, it will be back. So, the secret to success with repellents is to keep renewing them. If you change them every 10 or 12 days, the poor groundhog will keep feeling there is something new and dangerous each time and will stay away from your vegetables.

Most repellents are DIY household products or inexpensive sprays or granules, but to save you a lot of money, be aware that the ultrasonic devices that are supposed to keep groundhogs away (and indeed, almost any animal away) are no more effective than other repellents, yet are much more expensive. So, you might want forgo that category!

Fido has found a groundhog hole under the tool shed. His presence will make the groundhog very nervous. Photo: lifewithdogsandcats.com

A dog is also an effective groundhog repellent. Groundhogs are instinctively fearful of dogs and most dogs would make short work of a groundhog if ever they caught one, but for a dog to be an effective g-hog repellent, has to be able to roam freely near the garden 24 hours a day. If the dog is tied up or if you bring it indoors at night, the groundhog will quickly learn its limitations or its schedule and use your vegetable patch as smorgasbord when the dog is not around.

Plants That Groundhogs Don’t Like

Another possibility of living in harmony with a groundhog is to only grow plants that groundhogs don’t like to eat. You can find a list of such plants here: Plants Groundhogs Tend to Avoid.

Trap and Release

Sometimes you catch your groundhog without minutes of setting the trap. Photo: http://www.humanesociety.org

You can also catch your groundhog with a Havahart-type trap, a kind of cage with a one-way entrance pests can get into, but not out of. You can set up such a trap yourself or call in an exterminator. Or maybe the animal control department of your municipality can lend you one. For bait, use an apple slice coated with peanut butter. When you’ve caught the groundhog, release it at least 5 miles (8 km) from your home; otherwise it may return. 

The problem then is: where to release it? Farmers will not appreciate the addition of more groundhogs to their property and municipal parks won’t accept them. People have released (illegally!) so many groundhogs on the campus of my local university that, early in the morning, you sometimes see more groundhogs than students.

Fence Them Out

A fence with a bottom part buried underground will keep groundhogs out. Photo: Claire Tourigny

You can also fence in your vegetable patch. Groundhogs don’t jump nor are they really good climbers. A simple chicken wire fence attached to bargain basement wooden stakes is inexpensive and will offer good protection it as long as it is at least 3 feet (90 cm) high aboveground … and if another foot (30 cm) is buried at the bottom. Bend the buried part bend out (not in!) at a 45 ° angle away from the garden. That way, when the groundhog tries to dig, it will keep running into a barrier and soon give up. Of course, you’ll need a gate for your own access … but don’t leave it open by accident!

Hunt the ’Hog!

For a more “muscular” intervention, groundhog hunting is usually allowed in all seasons in areas where it is found … in the countryside, that is, but, of course, not in the city. You’ll probably need a small game hunting license to practice groundhog hunting. Groundhog meat is perfectly edible and quite delicious, tasting something like rabbit.

Drop a Bomb

You can also use a smoke bomb (or hire an exterminator to apply one). You’ll find this in hardware stores or online. This involves plugging all but one of the holes in the groundhog’s burrow, lighting the bomb and placing it inside, then plugging the last hole. If you see smoke, you’ve missed a hole!

The Most Effective Treatment

Motion-activated sprinkler. Photo: dealingwithdeer.com & jungledragon.com.

But the most effective treatment for most gardeners under most circumstances is a motion-activated sprinkler. You install it by connecting it to a garden hose and adjusting it so that it’s directed towards animal’s usual access point. When it makes a visit, day or night, it gets blasted with water. Water is, of course, harmless, but the shock of getting sprayed is terrifying. If there is one thing that a wild animal won’t tolerate, it’s being touched. It will give up any effort to visit your vegetable garden if it gets sprayed every time it tries to approach it.

A motion-activated sprinkler is also effective against deer, raccoons, skunks, cats, pigeons, crows, squirrels … and neighbors who cut through your yard. Any animal, in fact, larger than a chipmunk. If you can’t find this kind of sprinkler in your local garden center or hardware store, it’s easily accessible on the Internet.

So, there are ways of gardening even with a groundhog right next door. You just have to learn to think like one … and then put the proper controls into place.

Calla: June 2020 Houseplant of the Month

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The Story Behind the Calla 

Like the anthurium and the spathiphyllum, the calla—botanically known as Zantedeschia—is a member of the Arum family (Araceae) and is characterized by its pitcher-shaped bract (spathe), now available in a wide range of colors. The actual flowers, on the tubular spike in the centre of the inflorescence, are tiny and less eye-catching. 

Calla “lilies” (left) actually look nothing like true lilies (right). Photos: www.longfield-gardens.com

Although often called calla lily, it is not, of course, in any way related to the true lily (Lilium spp.) of the Lily family (Liliaceae). It’s also called the arum lily … but so are a half dozen other plants.

The white calla ((Zantedeschia aethiopica) covers vast territories in swampy areas. Photo: brisbane.qld.gov.au

Many arums have a preference for swamps. Zantedeschia species are also swamp plants that embed themselves firmly on river banks. The different species originate from southern Africa as far north as Malawi, and often grow in places where rainwater drainage is obstructed. These are periodically saturated swampy spots, but for relatively short periods, then they dry out. The plant can easily survive subsequent long periods of drought. 

Behind the Name

Zantedeschia was originally called Arum aethiopicum or Ethiopian arum lily, although it in fact grows nowhere near Ethiopia. At that time (18th century), Africa was largely unknown and Ethiopia was commonly thought to refer to the entire continent. The plant was later renamed Calla aethiopica, “calla” being Greek for beautiful, since the plant was believed to be a close relative of the bog arum, Calla palustris, but it turned out to be only a very distant relative. Even so, the name calla clung on as a common name for the genus.

Giovanni Zantedeschi. Photo: Rudolph Hoffmann, Wikimedia Commons

However, botanists now had to find a new name for the plant. Richardia africana was also used for a while, after the French botanist Louis Claude Richard (1754–1821), but it turned it had already been used for an obscure genus of New World plants, so yet another name was needed. Finally, botanists adopted the name Zantedeschia, after the Italian doctor and botanist Giovanni Zantedeschi (1773–1846) and that name stuck. 

The simple yet singular beauty of the white calla (Zantedeschia aethiopica). Photo: Alvesgaspar, Wikimedia Commons

The first calla grown was the white calla (Zantedeschia aethiopica) and it remains popular as a garden plant in mild climates, although, due to its large size, is rarely grown indoors. Its huge white flowers became very popular with florists and soon became particularly associated with mourning. Other calla colors, though, don’t have that negative connotation.

What to Look for When Buying a Calla

Callas come in a wide range of colors. Photo: Home Depot
  • Pricing is generally based on pot size, number of flowers per plant and the plant’s volume. 
  • It is also important to consider maturity. Avoid plants showing mostly green buds, particularly during the months with low light levels. Such flowers often struggle reach their full size and coloration due to lack of light.
  • Ensure that the plant is free of pests and diseases. This includes botrytis—a fungus that greatly detracts from the decorative value—on the leaves or flower. The tubers and the plant itself can also be infected with bacteria in the form of slimy stems and rapid decline of the plant. Yellow or drooping leaves are likewise not a good sign. 
  • Callas are stored cool during shipping (8–12°C), but only for short periods. After that, they need more warmth. Beware of plants stored too long in sleeves during the shipping and storage phase, as flowers and foliage can become damp due to excessive humidity and condensation inside the cellophane, leading to disease. Only the potting soil should be damp. 
  • If you buy tubers, look for large ones. The tuber’s diameter (given in cm) largely determines the number of flowers that will be produced by each plant.   

Not for Consumption

Obviously, callas are for decoration only and not for human consumption. Like most other arums, they are toxic to people and pets and should be kept out of the reach of small children.

Assortment

Callas make great gift plants. Photo: http://www.florastore.com

The calla is most widely available in the spring and summer months. Its range has expanded considerably in recent years, so that there are many flower colors and leaf markings available. Flowers can be white, pink, yellow, orange, red, purple, green and even nearly black. Bicolors are also available. They are usually single, but can also be double. The foliage can be narrow or arrow-shaped, green or spotted with white. The most popular varieties these days are the smaller-flowered hybrids, which produce more compact plants better suited to indoor growing. 

Besides being used as a gift plant and houseplant, callas also make great garden plants and as such are often sold as dry tubers for planting outdoors in the late spring or early summer. 

Care Tips

Callas come in various sizes with green or spotted leaves.

Callas are easy to care for and can be enjoyed for a long time. 

  • Indoors, the plant requires a bright spot which is as cool as possible. This will ensure the longest flowering. 
  • The plant is undemanding in the garden and, once in bloom, can be placed in either sun or shade. The temperature must remain above 5–8 °C (40–46 °F).
  • Indoors, callas can bloom for 2–12 weeks. The plants can flower for longer outdoors, particularly when the temperatures are cool.  
  • Make sure the soil never dries out by watering regularly. 
  • Apply fertilizer every two weeks to ensure lavish flowering. 
  • Most gardeners treat cannas as temporary plants and buy new ones each year. However, they can be rebloomed by giving them a rest period during the winter, when the plant is kept dry and the leaves are allowed to die back. The tubers will produce plenty of new flowers during the next growing season. 

Display Tips

Callas adapt to many indoor decors.

Their attractive often bright colors mean that callas work very well in cheerful ‘handmade’ interiors. The plant, which already appears to be a mixture of local and exotic, looks fabulous in artisanal pots with colorful ethnic patterns. 

The Calla Lily can also be placed in a simple earthenware pot, which looks attractive on the balcony or patio (a gift idea for Father’s Day). The attractive shape of the spathe makes it a fabulous eyecatcher anywhere.

The Calla Lily also combines readily with other foliage and flowering plants.

Start a trend and grow a calla today!

Text adapted from a press release by Thejoyofplants.co.uk
Unless otherwise mentioned, photos from Thejoyofplants.co.uk.
Styling by Elize Eveleens, Klimprodukties.

Instant Floating Solar Fountain

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Floating solar fountain. Photo: http://www.greenercountry.com

If you’ve always wanted a fountain in your garden, but figured you had neither the space nor the means, think again. There is a new generation of fountains running on integrated solar panels, therefore requiring no writing or electricity to install or hide. You can set yours up in just a minute and in any basin of water.

Three free-floating fountains in a water garden. Photo: smartsolarfountin.com

These fountains float on any source of water you want: a garden pool, a bird bath, even a bucket or basin of water you set on your deck. They come with changeable fountain heads for different spray heights and effects. Just set them in water on a sunny day and off they go. The better ones will work on cloudy days too!

Most come with an “anchor,” a sort of suction cup you with a cord so you can fix it to the bottom of your chosen basin and limit its movement. Otherwise, it will wander about as winds and currents push it. 

Splashing water attracts birds. Photo: http://www.nestneed.com

The sound of water splashing is a good way to attract birds to your garden, but just remember that birds need shallow water to bathe in, so you may want to add rocks to your basin so they’ll be able to take a shower.

And these fountains aren’t expensive. I’ve been seeing them in the $12 to $55 US range. The difference in price is often linked to whether the pump has a “battery backup” that will allow it to function on cloudy days and whether it has blocking and dry run protection (so it automatically turns off, thus preventing burn out, when the pump is blocked by a leaf or other debris or if the basin dries out).

Simple to install, simple to use. Photo: skytrendy.com

Are there any downsides to these fountains? Sure! They splash and splashing water is hard to control, especially in windy weather. So, don’t place yours near anything you want to keep dry.

Also, they will need sun and the more, the better. Don’t expect much of a show in shady areas!

Finally, keep that basin reasonably filled with water. The spraying effect means lots of water is lost to evaporation and has to be replaced. 

But an instant fountain you can actually afford: I think that’s pretty cool!

Look for one on Amazon and from other mail-order sources if not a local store specializing in water garden supplies.

Caterpillars Invading Birch Leaves

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Leafminer damage on birch leaves. Photo: http://www.peninsulaclarion.com

Question: My birch tree is being attacked by tiny caterpillars that live inside the leaf. What can I to do to prevent them?

L. Dionne

Answer: The larvae you see are leafminers. There are several species that affect birches, the most common of which are the birch leafminer (Fenusa pusilla) and the amber-marked birch leafminer (Profenusa thomsoni), both of European origin, but now well established in North America as pests.

They’re not real caterpillars (which are the larvae of moths and butterflies), but rather the young of sawflies, very small, inconspicuous and rarely noticed black flylike insects. But they’re not really flies either, but rather hymenoptera, four-winged insects, therefore closer relatives of bees and ants than to flies which, being diptera, have only two wings.

A Common Pattern

Although their timing varies, the different leafminer species follow the same pattern.

Adult birch leafminer. Photo: extension.unh.edu

The adult lays eggs under or inside the leaf and the larvae penetrate it, feeding on tissue from the inside of the leaf. All the adults are female, as the birch leafminers are parthenogenic (reproduce without fecundation).

If you peel open the leave, you can see the larvae and their frass (excrements) inside the leaf. Photo: http://www.exoticpests.gc.ca

At first, the damage is barely noticeable, at least from a distance, as the leaf remains green, but up close you can see small pale green or gray patches. If you hold the leaf up in front of a light at this point, you can see the larva, like a small white or translucent caterpillar, inside the leaf along with numerous black spots (its excrements). As it feeds, the patches grow in size.

Only in severe cases does the tree turn entirely brown. Photo: http://www.exoticpests.gc.ca

Later, after the larva has left the leaf, the patches turn brown and then become much more visible. There may have more than one larva per leaf, in which case it may turn completely brown. In extreme cases, the entire tree seems to turn an unhealthy bronze color.

The larvae drop to the ground after a few weeks of feeding and become pupae. Most species have one generation per year, but the birch leafminer (F. pusilla) follows this with a second one in summer, although only the spring infestation is very visible. In mild climates, there is sometimes even a third generation in the fall, but so insignificant it usually goes unnoticed.

The final generation of the season overwinters in the ground in the form of pupae, becoming adult sawflies in the early to late spring, depending on the species, and starting a new generation.

The damage caused by birch leafminers is mainly cosmetic, as the infestation is rarely severe enough to harm the health of the tree. Only occasionally are more than 40% of the leaves affected and even then, the tree can usually tolerate this as long as it only happens once every few years. Severe and repeated infestations, although quite unusual, can eventually weaken and kill a tree. 

Parasitic wasp. Photo: James K. Lindsey

You may have noticed that birch leafminers seem to be in decline. Certainly, you rarely see birches turn entirely brown as you would have 20 years ago. This seems largely due to predatory insects (tiny parasitic wasps, harmless to people), some of which are native and have learned to adapt to introduced leafminers, while others were introduced to various regions specifically to control them and are thriving. They prey on leafminers by laying their eggs inside in larvae and eating them alive (how charming!). As predatory wasp numbers increase, the severity of leafminer infestations has been decreasing.

Control

Since the leaf miner lives inside the leaf, most pesticides can’t reach it. Brian Kunkel, University of Delaware, Bugwood.org

Control of leafminers is difficult because the insect, living as it does inside the leaf, is naturally protected from pesticide sprays.

In the past, a systemic insecticide called Cygon, which penetrated the tissues of the tree, making the whole tree toxic, was used to control leafminers, but it has been banned almost everywhere, as have other most other systemic insecticides. 

Still, there are neem-based organic systemic insecticides, such as TreeAzin, that can be injected into the tree and thus control the pest, but the price of this treatment, which can only be applied by a specialist, may seem excessive.

If the infestation is minor, you can pull off the affected leaves on the most visible side of the tree one by one, but that can be quite a task and is certainly not one for a laidback gardener! Besides, even damaged leaves carry out some photosynthesis, and removing too many leaves may do more harm to the tree than the leafminers themselves.

Prevention

River birch (B. nigra) is one of the species that is rarely attacked by leaf miners. Photo: http://www.kb.jniplants.com

The most obvious prevention is to avoid planting susceptible species. Birch leafminers mainly attack white-barked birches, such as paper birch (Betula papyrifera), silver birch (B. pendula), gray birch (B. populifolia) and Japanese white birch (B. platyphylla). They rarely cause damage to other birches, including as river birch (B. nigra), yellow birch (B. alleghaniensis) and sweet birch (B. lenta).

Yellow sticky traps can help warn you of an impending infestation. Photo: http://www.urbanseedling.com

There also is the option of spraying the tree with an insecticide when adults emerge from the soil in the spring and before they lay their eggs. To find out when to spray, place yellow sticky traps in the tree just before it buds out and when you see small black flies accumulating on the trap, spray thoroughly with an insecticide. Few chemical insecticides are still available to home gardeners—and who these days even wants to hear of neonics, accused of destroying local populations of beneficial insects!—, but trained garden care specialists and arborists do have a few they’re allowed to use. 

Of course, even basic organic pesticides like insecticidal soap and neem will be effective if applied at just the right time. 

And prevention also includes treating your birch well, as strong trees will be more insect resistant. That includes watering during periods of drought and before the ground freezes in the fall, annual fertilization, the occasional application of compost and the use of mulch over the tree’s root zone.

Mostly, though, just apply the 15-pace rule. Before treating, step back 15 paces: if you can’t see the problem at 15 paces, it’s not worth treating!

’Nuff said!

New Product for White Grub Control

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White grubs proliferate in some lawns. Photo: http://www.the-scientist.com

If you’ve been dealing with white grubs in your lawn—and losing the battle more often than not!—there is a new biological control product you might want to consider: BTG (Bacillus thuringiensis galleriae). Yes, it has been sold to a limited degree for about 3 years now (and indeed, I’ve mentioned it in this blog in the past), but this year is seeing it on garden center shelves throughout North America. (Sorry, I’m not aware of its availability on other continents.)

How Do You Know If You Have White Grubs?

Usually, it’s pretty obvious! 

They’re essentially a lawn pest. They may be present in other types of garden, but rarely do any visible damage. But they cause lawns to turn brown and even die. 

Holes dug in a lawn by a skunk looking for white grubs. Photo: http://www.whygoodnature.com

Often, the first sign is when you notice holes dug in the lawn by mammals like skunks and raccoons, searching for the delicious grubs. Or hordes of birds like starlings and crows pecking at your turf.

Patches of turf lift right off and sometimes you even see the grubs. Photo: lawnsavers.com

Also, the lawn begins to turn yellow, then brown and will feel soft and spongy to walk on. If you take hold of a section of turf and try to lift it, it will come right off in your hands, its roots having been nibbled off by grubs. 

When you pull the turf up, you may see them just underneath. If not, dig a bit deeper into the soil under the lawn and you’ll find them, smiling lazily at you.

What Are White Grubs?

The various phases of one the white grub beetles: the Japanese beetle. Photo: ohioline.osu.edu

White grubs are the larval stage of various scarab beetles, like June beetles, chafers and Japanese beetles. They’re plump C-shaped whitish creatures with tan or brown heads and 3 pairs of shot legs. They can be tiny at hatching time, but grow over time, some reaching up to 1 inch (2.5 cm) in length. They live under the lawn until late spring of the following year (3 years in the case of June beetle larvae) before going into a short pupal stage, then maturing into adult beetles. 

The adults then dig their way out of the soil and feed on the foliage and flowers of nearby plants, often causing considerable damage (Japanese beetles and rose chafers, notably, are renowned for their destructiveness). Then, after a month or so, females return to lawns, especially low-mown ones, and lay the eggs of the next generation. They soon hatch … and the cycle begins anew.

What Is BTG?

This is the product I’m seeing in local garden centers. Photo: Scotts

Depending on where you live, you many find BTG (Bacillus thuringiensis galleriae) under various brand names. I’ve been seeing Grub B Gon Max locally, but you might find it under the names grubGONE!®, beetleGONE!®, BeetleJUS! or grubHALT!®, among others. (Don’t all those exclamation marks just drive you up the wall!!!)

Bacillus thuringiensis galleriae as seen under an electron microscope. Photo: http://www.sciencesource.com

BTG is a natural bacterium found in soils worldwide. It is specific to beetles in certain families: the Scarabaeidae, Buprestidae, Tenebrionidae and Curculionidae families, thus scarab beetles, wood-boring beetles (including emerald ash borers), darkling beetles and weevils. It will not harm other insects, such as pollinators (bees, butterflies, hoverflies) and predatory insects (wasps, lacewings, pirate bugs, etc.), nor even other beetles, like ladybugs. Nor is it harmful to humans, pets, mammals, birds, amphibians, fish or aquatic insects. 

Some of the Lawn Pests Controlled by BTG

Asiatic garden beetle
Japanese Beetle 
June Beetle (May beetle)
Oriental Beetle
Cupreous chafer
European chafer
Northern masked chafer
Southern masked chafer
Black turfgrass ataenius
Annual bluegrass weevil 

Obviously, BTG is not harmful to lawn grasses of any species, nor indeed plants of any type.

The variety used is a selected strain called BTG SDS-502, easier to produce commercially and more effective against lawn pests than other strains.

When the larva consumes the bacterium, it produces crystal proteins that poison its host, causing it to stop feeding. The grub gradually becomes paralyzed, then dies. The results are often noticeable within a week or so, as turf often recuperates quite quickly once its roots are no longer being eaten. 

Apply BTG with a spreader. Photo: murraylawnmowerparts.com

The product is usually applied to lawns with a spreader (the same type used for applying fertilizer and lawn seed), then watered in so the bacteria descend into the soil layer where the larvae live. Powdered forms can also be sprayed onto the foliage of susceptible plants to control adult insects, but they do not appear to be widely available at this time. 

Recommended application times according to grubGONE!®. Ill.: grubGONE!®

BTG can be applied to lawns at any time from spring through late fall. Usually, though, the best results are obtained by applications in July or August, timed to reach young larvae just emerging from eggs laid by adult females (they hatch in 10 to 30 days, depending on the species). However, many gardeners apply it in spring to control the damage animals cause as they search for larvae, in which case a second treatment will likely be needed in summer or fall to reach the grubs of the next generation.

Not to Be Confused With…

Beneficial nematodes. Photo: CSIRO

BTG is not the same thing as another grub treatment, beneficial nematodes. In fact, the two actually complement each other, each attacking grubs in different ways. Nor is it the same thing as milky spore disease (Paenibacillus popilliae), used specifically to control Japanese beetle larvae.

Is BTG Effective?

You tell me! I’m generally hearing very positive feedback about this product, but it’s fairly new. Time will probably tell. And I won’t be able to test it myself, as I’ve never had a white grub problem. 

Certainly, it would be worth trying if white grubs are ruining your lawn, especially if you’ve been using poisonous chemicals to control them or hiring lawn care companies to do the dirty work for you. And if enough neighbors use it, it might also bring down the damages from adult beetles, like Japanese beetles, to a more acceptable level.

Try it and see!