Time for a Tree Inspection

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When leaves have mostly fallen from your trees, it’s time to give them a good going over. Source: A melbournechapter.net & svgsilh.com, montage: laidbackgardener.blog

The disappearance of leaves from deciduous trees in the fall is often seen by home gardeners as the end of the horticultural season, but it’s also a golden opportunity to study your trees’ condition. Bare of foliage, their entire structure is visible, allowing you to see any flaws. So, a quick annual tree inspection tour, just to make sure everything is fine, is always a good thing.

Structural Problems

The most obvious problems usually have to do with weak, damaged or dead branches. Some branches may have snapped or bent and need removing. Others rub on neighboring branches, weakening and, eventually, killing both. Ideally, one or the other really ought to be removed.

Sometimes, you see clusters of weak branches all growing from about the same point, a probably as the result of an earlier poor choice in pruning. You’ll have to prune off all but one branch (probably the healthiest, straightest one) to give it a chance.

You can also remove any suckers (upright branches with no secondary stems) if you see any. Or there may have a very vigorous upright branch that is threatening to become a second trunk and that usually leads to a weak fork that can tear off and seriously damage the tree. So remove that as well.

Corrective Pruning

In all these cases, the solution is to do a little bit of pruning.

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If you can reach it, you can prune it! http://www.danskhusoghaveservice.dk

You can do the pruning yourself if the branches are near enough to the ground for you to be able to reach them, at least with a pole pruner. (Obviously, any time you remove a branch higher than your head, you should be wearing a safety helmet.) For out-of-reach or oversized branches, it’s better to have a certified arborist do the job. Avoid fly-by-night tree trimmers who often damage trees rather than helping them.

Also, over time, the lower branches of a tree sometimes start get in your way. Since you don’t want anyone to bump their head when walking under the tree, it is often better to “limb it up” (also called “raising the crown”) by removing the problematic lower branches and that’s something you can do yourself.

When to Prune?

To be completely honest, the time of year when you prune really doesn’t make a lot of difference. Yes, many experts say late winter or very early spring is the best time, while late fall/early winter is the second-best choice. In fact, the easiest thing to do is simply to prune when you first see the problem, before it gets any worse.

Two Typical Pruning Scenarios

When you simply want to shorten a branch for whatever reason, just cut it off slightly beyond a secondary branch pointing in the desired direction. The latter will take over and replace the original one, thus preserving the tree’s natural symmetry.

Removing a branch entirely, right back to the trunk, is a different situation. Doubly so if it’s a major branch. If you simply saw it off from above, the branch will likely tear loose as you near the end, pulling off a strip of bark as it falls, thus damaging the tree’s structure. Fortunately, there’s an easy way around this.

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Source: Claire Tourigny, from the book Les 1500 trucs du jardinier paresseux

First cut a notch under the branch, about 1 foot (30 cm) from the trunk and about ¼ to ⅓ of the way through. Then change position. Now saw from the top about 2 to 3 inches (5 to 7 cm) beyond the first cut until the branch breaks right off. It will now do so away from the trunk, thus avoiding any damage to it.

The final cut is the most important one, as you have to remove the stub. Cut as close to the trunk as possible, but without damaging the branch collar, the swollen bump seen at the base of the branch, because it’s from the collar that the new cells designed to cover the wound with fresh bark will form.

Finally, no, there is no need to cover the wound with pruning paint. It’s actually bad for the tree. Read Garden Myth: A Tree Wound Requires a Coat of Paint to understand why.

Bare Tree Leads to Other Discoveries

You may have other surprises when the leaves fall.

Often, you’ll find a bird’s nest, sometimes only a short distance from your front door, you never noticed in the summer, but that is visible now that the leaves have fallen. It will be empty in the fall and winter.

Or maybe you’ll discover a squirrel’s nest, which usually looks like a ball of dead leaves high up in the tree. In this case, the squirrel is likely still inside, as it’s a winter nest. You’ll discover that squirrels don’t actually hibernate. Although they spend much of the winter sleeping, they still come out from time to time to look for the nuts they buried in various hiding places earlier in the fall.

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Wasp nests are empty in the fall; the first frosts will have killed off their inhabitants. Source: USFWS Midwest Region, flickr.com

The other nest you’re likely to notice, looking like a greyish round ball in the branches, is a wasp nest. No need to panic: by mid-fall, the original queen and her workers will already be dead. The only survivor of the whole colony is the new queen and she’ll have left the nest, burying herself in the ground somewhere. She’ll wake up again in the spring and start building a new nest in another location. So, since the old nest is empty, if you want to recover it as a decoration, go for it! Otherwise, the nest will simply disintegrate over time.

Signs of Disease and Insects

So much for pleasant discoveries. Others are not so encouraging.

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Black knot disease is revealed when the leaves fall. Source: http://www.edmontonlandscapingoutdoorspace.com

Probably the most disagreeable discovery you make when a tree is free of leaves is black knot disease (Dibotryon morbosum, syn. Apiosporina morbosa). This disease of plums and cherries (and occasionally other stone fruits) attacks the tree’s branches: you’ll discover an elongated black mass covering part of a branch. Black knot acts much like a cancer, cutting off the flow of sap to the affected limb and eventually causing its death even as it spreads to other branches. Sadly, once you discover black knot in a tree, it’s probably doomed: at most you can extend the tree’s life by removing the nodules. Read The Cancer of Plums and Cherries to learn how pruning can be of some help.

Whether you decided to prune or not, I suggest you plant a replacement tree (and not a cherry or a plum!) in the spring. When your tree finally does die, its replacement will have already reached a decent size.

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These innocent-looking bumps are scale insects. Source: growingsmallfarms.ces.ncsu.edu

You may see other odd growths on the trunk and branches. Sometimes they’re harmless, like lichens and moss, sometimes they are serious diseases, such as crown gall disease (Agrobacterium tumefaciens), and sometimes the growths are caused by insects. Tiny bumps on the bark, for example, may well be scale insects.

Whatever causes the growths, you’ll have to identify the problem before appropriate treatment can be found.

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The perfect day for a tree inspection! Source: http://www.dpreview.com

Take your inspection tour on a beautiful late fall/early winter day, when you feel like taking a bit of a stroll outdoors anyway. And remember, this annual checkup is not only free, but often helps prevent very serious problems in years to come.

Scale Insects on Houseplants: A Nasty Surprise!

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Scale insects are quite visible on a green leaf, but often blend in with bark when they’re on a branch or trunk.

You find a strange growth on one of your houseplants, a sort of small brown bump. In fact, not just one brown bump, but several. Even many? Unfortunately, there’s a very good chance that what you’re seeing is an insect, a very sneaky one called a scale insect or just “scale”. If so, the faster you react, the faster than you can regain control!

Well Camouflaged

Detection of scale insects is difficult because they are so well camouflaged. The mature insect is covered with a shield-shaped shell that can be rounded or almost flat; brown, gray, green or transparent; or oval, comma-shaped or resembling an oyster shell. They often seem to be part of the plant’s bark or you may take them to be drops of dried sap. They can be especially confusing on ferns as the latter produce sporangia (spore-producing organs) that some scale insects are able to imitate!

Not sure if that small bump is part of the plant or not? Give it a flick with your finger. If it stays put, it’s part of the plant; if it comes off, it’s a scale insect.

Infestation usually begins out of sight on less visible parts of the plant (under leaves, at leaf axils, etc.) before spreading to cover much of the plant.

Often the first symptom you’ll notice is a clear, sticky substance that drips onto lower leaves and nearby objects. This is called honeydew and is excreted by scale insects. It is even more obvious when the honeydew becomes covered with sooty mold, looking much like black powder, and that can happen over time.

The infested plant usually continues to grow normally at first, but possibly with less vigor, then as the scale population increases, the leaves gradually turn yellow. It not treated, the plant will likely die.

Personal experience

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Cute, n’est-ce pas? But this little cycad caused me years of trouble!

A few years back, I found an adorable little cycad (Cycas revoluta) at a very reasonable price and I brought home without thinking too much about it. It seemed healthy and I placed it among my other houseplants. A few months later, I noticed some fronds turning yellow, then saw that the lower leaves were abnormally shiny and that there was a sticky substance in the saucer below. Upon closer inspection, I discovered it was full of scale insects: literally hundreds of them! And other plants in the area were too. After repeated treatments, I was able to save most of my plants, but I had to admit defeat and tossed the cycad and five other plants into the garbage: despite treatment after treatment, the scale insects kept coming back.

And now I have to inspect all my houseplants regularly because even 3 years later, I still occasionally find a plant I need to treat or toss. All because I brought home one plant without isolating it!

A Truly Weird Insect

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Brown soft scale (Coccus hesperidium).

Scale insects don’t look like insects. They have no antennae, wings or visible legs and live permanently attached to their host plant. The species most commonly seen on indoor plants is brown soft scale (Coccus hesperidium) which produces a brown to tan domed shell from 2.5 to 4 mm in length… and it’s one of the larger ones! This scale insect has a wide host range and can attack almost any houseplant. Other scale insects are specific to a single group of plants. Some are only found on orchids, others only on bromeliads, others only on ferns, etc.

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Mealybugs are close relatives of scale insects, but unlike the latter, are mobile.

A quick word about mealybugs, another houseplant insect. Scale and mealybugs are closely related, but the mealybugs are white and appear covered with cotton. Even more obviously, they have legs and move when disturbed, while a scale insect will not move when you touch it.

For more information on mealybugs, read Just Toss Plants Infested with Mealybugs.

How Can a Legless, Wingless Insect Get Around?

You must be wondering how an immobile, legless, wingless insect is capable of spreading from plant to plant. The secret is that scale insects are mobile… in their youth. Nymphs, called “crawlers”, are born from eggs hidden under their mother’s shell. Crawlers are so tiny they are rarely seen. In most species, they wander about for just two or three days, then settle down for the rest of their life on a new stem or leaf. Nymphs readily crawl from one plant to another and thus start a new colony. And there are several generations per year. One scale insect that escapes your treatment can result in to 20,000 scale insects in a single year!

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Outdoors, scale insects can be spread by ants.

In nature, as well as by wandering on their own, nymphs are often carried from plant to plant by the wind, by birds or by ants. In fact, some ant species even raise scale insects in order to harvest their sweet honeydew and carefully move them from one plant to another.

In our homes, though, we can’t blame wind, birds or ants. Scale insects inevitably arrive on infested plants we bring home. Then crawlers move on to new plants or the plant owner inadvertently carries them from plant to plant when watering or pruning or when he moves an infested plant.

If scale insect nymphs crawl, the males fly. They too are tiny and rarely seen. With no mouthparts, they live only a few days and their only role is to fecundate females. But they’re pretty much redundant, as the females of most species can produce eggs without fecundation through a process called parthenogenesis.

Controlling Scale Insects

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Always, always, always put new plants in quarantine.

It’s important to understand that, unless you live in the Tropics, the scale insects that infest your houseplants did not come from outdoors. The species of scale insects that infest houseplants are of tropical origin and can’t survive outdoors in temperate climates, at least not over the winter. Nor do scale insects spontaneously generate (although they may seem to!). The source of just about every infestation is always a plant that was already infested, brought home from somewhere else, often a nursery, but maybe too as a cutting offered by a friend.

Don’t do like I did: inspect every new houseplant before you buy it and then put it in isolation for a good month once you do bring it home. Did you know the word quarantine means 40 days? And that’s just about right as an isolation period for new houseplants.

If you have no separate room in which you can put your new purchase, just put it 6 feet (2 m) away from other plants or isolate it inside a transparent plastic bag.

If you do find scale insects, isolate the infested plant immediately if you already haven’t done so… and ask yourself seriously if it wouldn’t be better for you to simply discard it. Sometimes you can nip the infestation in the bud by cutting the plant right to the ground… but if so, do clean your pruning shears before using them on any other plant! Of course, not all plants will tolerate such a heavy pruning, so you’ll need other methods.

Insecticide sprays are not very useful. Adult scale insects are essentially immune to insecticides due to their protective shell. Moreover, even if the insecticide treatment did kill them, how would you know? The shell of a dead scale insect can remain on the plant for years, making you think the plant is still infested. The best treatment is to go over the whole plant with an old toothbrush dipped in an insecticidal soap solution to remove any shells. Yes, it’s tedious, but if it works, it may well be worthwhile! Then rinse the plant thoroughly to knock off any crawlers that may  be present… and watch it for a few weeks. If new shells appear, repeat the treatment… or toss the plant!

Outdoors

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There are literally hundreds of species of scale insects that can infest outdoor plants.

There are also many species of scale insects that attack outdoor plants, mostly woody plants like trees, shrubs and evergreens, but they are not the same ones that live on houseplants (again, if you live in a temperate climate).

The initial treatment for scale insects outdoors remains essentially the same: clean the trunk and branches with a brush dipped in a solution of insecticidal soap. Then spray the plant all over with insecticidal soap or horticultural oil. Also, a dormant oil treatment can be very helpful in reducing the population if you apply it at just the right time, and that is almost always just before the buds open in early spring, as that is when crawlers are active or when they have just settled down and therefore before their protective shell is fully formed. Even so, as with indoor plants, the shells of dead scale insects can remain attached to the bark for ages, so you still have go over the infested plant with a brush to be absolutely certain whatever treatment you used was effective.

Yes, scale insects are sneaky and hard to control, but if you’re persistent, you can succeed. Still, do remember they are much easier to prevent than cure… and prevention starts wit isolation!

Longer Days Awaken Pests

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Whiteflies may be in diapause in mid-January, but by March they’ll be wide awake and hungry!

You may not have noticed, but if you live in the Northern Hemisphere, many houseplant pests have been less visible of late than usual. That’s because many of them enter into diapause, a kind of semi-dormancy, starting in the fall. This is due to the influence of shorter day lengths. In fact, they are often so inconspicuous in late fall and early winter that you may even have thought you’d gotten rid of them entirely.

Other insects continue to remain active even when the days are short, but develop at a much lower rate than in summer and likewise may go sight unseen for a while. But when the days start to get longer and the increasing sun heats up your home or greenhouse just a bit more, the two groups are re-energized and begin to reproduce abundantly.

Even as early as late January, although it still feels like the middle of winter outdoors, days are getting perceptibly longer and gradually, depending on the species, the enemies of your plants will start get back to work. By early March, they are all active… and hungry.

The Culprits

Insects that are quiescent during short days (or almost so), but awaken as days lengthen include:

Aphids, fungus gnats and thrips, however, don’t seem to slow down much in winter. They are just about as active in January as in July! You have to keep your an eye open for these insects throughout the year.

What to Do?

  • 20160128C.jpgInspect your plants at the end of January, looking especially at leaf axils and leaf undersides. A magnifying glass may be needed to see red spider mites, as they are very tiny. Subsequently, an inspection every two weeks is never a bad idea.
  • Set out yellow sticky traps: often flying pests like whiteflies, fungus gnats and winged aphids will be caught before the infestation even begins, nipping it in the bud.
  • Isolate infested plants so the pests can’t spread.
  • Treat infested plants.

Treatments

20160129BInsecticidal soaps and horticultural oils are almost universal treatments against these creatures. Just follow the application details explained on their packaging. You can also spray infested plants with solutions of dishwashing liquid or other soaps, but make sure you test a few leaves first: they can be toxic de certain plants.

Another possible treatment is to spray a solution of 1 cup (250 ml) of rubbing alcohol in 1 quart (1 liter) of water to control scale insects, mealybugs, aphids and whiteflies. Warning: for your own protection, ventilate the room when applying rubbing alcohol on anything more than a limited scale. Its fumes can be toxic.

Keep an eye open and your finger on the spray bottle’s trigger. That way you ought to be able to stop pests in their tracks… and allow your plants to take full advantage of the lengthening days!