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Archive for January, 2014

Mealybugs on the underside of a basil leaf

I just noticed that the leaves of my Schefflera are sticky and so is the floor under the plant. What is going on?”

“Some of the leaves on my jade plant are covered with a black sooty film and the table it is sitting on is becoming sticky. Help!”

We get questions like these all the time – especially in the winter when many gardeners turn to indoor plants to satisfy their gardening itch. There are so many types of beautiful houseplants but they come with their own set of horticultural issues just like the outdoor plants do. Sometimes it’s environmental – low humidity causing brown edges or not enough light; sometimes it’s a watering issue – too much water or not enough; and sometimes it’s insect or disease problems.

Yellow stippling on leaves indicates damage from a sucking insect - in this case scale.

Yellow stippling on leaves indicates
damage from a sucking insect – in this
case Euonymus scale.

Sticky leaves, sooty mold, and discolored or misshapen foliage are all signs that some type of piercing and sucking insect like aphids, mealybugs, or scale is present on the plant. These insects have specialized, tubular mouth parts that penetrate the plant tissue and suck out the juices. Definitely not healthy for the plants! As they feed, they excrete a sugary liquid called honeydew that drips onto the foliage causing it to become sticky. Sometimes, with a heavier infestation, the honeydew can drip onto the ground under the plant. This happened to us once with a large Schefflera that was in our sunroom. When I walked near the plant, I discovered that the tile floor was very tacky. It turns out that the plant was infested with scale insects.

Mealybugs on the underside of a basil leaf.

Mealybugs on the underside of a leaf.

Mealybugs which are closely related to scale insects are one of the more common houseplant pests. These are slow-moving, soft-bodied insects that attack a wide variety of plants both indoors and out. They have flattened oval bodies that are usually covered with a waxy coating which gives them a white or grayish appearance. They look a little like the pillbugs (roly polies) that you find outdoors under logs except that they don’t roll up into a ball when you disturb them. Like most piercing, sucking insects, mealybugs are usually found on the underside of the leaves or on the stems of plants.

Sooty mold on laurel - Joseph O'Brien, USDA Forest Service, Bugwood.org

Sooty mold on California laurel

Their feeding can cause yellowing of the foliage, premature leaf drop, stunted growth, and if not controlled could eventually lead to the death of the plant. In addition, the honeydew they secrete provides the perfect growing medium for sooty mold, a black fungus that can spread over the leaves. A heavy coating of sooty mold can inhibit photosynthesis and further weaken the plant.

Female mealybugs lay large numbers of eggs which are often encased in a loose, waxy egg sac that resembles a cotton ball.

Adult mealybug and cottony egg case.

Adult female mealybug and egg case.

These egg cases are usually found on the stems and on the underside of leaves. When they first hatch, young mealybug nymphs (crawlers) move around actively and are likely to move from plant to plant. The adult females, while still mobile, are not nearly as active as the early nymphal stages.

Adult male mealybugs do not feed at all. Their sole purpose is to mate with the females and they survive only a day or two.

Mealybugs and cottony egg masses are easily seen on the underside of a leaf

Mealybugs and cottony egg masses are
easily seen on the underside of a leaf

Mealybugs and many other houseplant pests are sometimes inadvertently brought into the home when an infested plant is purchased. Because of this, it is very important to examine houseplants carefully for any sign of insect activity before you buy them. Look under the leaves and along the stem. Many insects, especially scale, are difficult to see because they really blend in with the plant. Mealybugs will hide in cracks and crevices along the stem and foliage but most of the time they are fairly visible upon inspection.

In spite of their soft-bodied appearance, mealybugs can be surprisingly hard to control because of their protective waxy covering and also their tendency to hide in places that are hard to reach with a spray.  If you find mealybugs on your houseplants, there are several products that you can try.

If there are just a few mealybugs on your houseplant, you can dab each one with a cotton swab soaked in rubbing alcohol. This will kill them right away. Be sure to keep checking on a daily basis for ones you may have missed.

If you have a heavier infestation, horticultural oil such as Bonide All Seasons Oil or PureSpray Green or an insecticidal soap will help control them if you can coat the insects with the spray. These products will also help control other houseplant pests such as scale, aphids, and whitefly. It is important to spray the underside of all the leaves.

Another good choice is Bayer Advanced 2-In-1 Insect Control plus Fertilizer Plant Spikes. These plant spikes contain a systemic insecticide that is taken up by the roots and transported to the stems and leaves. When insects feed on the plants, they ingest the pesticide and are killed. These plant spikes can only be used for ornamental houseplants – never on edibles.

Always read and follow the label directions when using any pesticides!

Enjoy your houseplants this winter! Here are more tips to keep them healthy!

Until next time – Happy Gardening!

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Ice accumulates on trees after a winter ice storm

Last night a period of freezing rain moved through the Shenandoah Valley. The temperature dipped just below freezing in the early morning but fortunately the ice didn’t accumulate much before it warmed up and everything began to melt off. We were lucky this time! Ice and snow buildup can sometimes cause major damage to trees and shrubs in the landscape, especially if the ice is thick or the snow is wet and heavy.

Heavy wet snow lay on the trees.

Heavy, wet snow lay on the trees.

While we were in Vermont over Christmas and New Year’s, we had two nice snow storms. The first came a few days after Christmas. The temperature was above freezing when it started so it began as rain. In the afternoon, the temperature began to drop and soon the rain shifted over to snow. The flakes were huge and wet and beautiful! This snow came down fast and accumulated quickly. Soon everything was covered with a blanket of heavy snow.

Glad my brother-in law brought the plow to dinner!

Glad my brother-in-law brought
the plow to dinner!

Because the snow started out very wet and the temperature dropped quickly, the snow became frozen to the branches of the trees. Generally, snow doesn’t accumulate heavily on deciduous trees because it typically falls through the branches to the ground below. This particular snow just seemed to stick tight to the branches which allowed even more snow to accumulate on them. My sister’s birch tree beside her house became so laden with snow that it bent almost to the ground. The hemlock off her deck was bowing pretty low as well. Luckily these trees were pretty resilient and they bounced back up when they were relieved of their burden of snow.

Snow accumulated on all the tree branches creating a beautiful winter wonderland. Thanks to my nieces for the pictures!

Snow accumulated on all the tree branches creating a beautiful
winter wonderland. Thanks to my nieces for the pictures!

The second snowfall was light and fluffy.

The 2nd snowfall was light and fluffy.

The second snowfall began on the evening of New Year’s Day and continued through the next day and night. It was really cold during this time with a high of 16oF and a low of -5oF. The contrast between this snow which was light and fluffy with tiny snowflakes and the previous snow was striking. This snow took a long time to accumulate because the flakes were so small. Even though it snowed steadily for more than 24 hours, we only got about 10″. It was beautiful!

This fine, light snow mostly fell right through the branches of the trees and what did accumulate was blown off in the slightest breeze. When the wind blew, we would see clouds of snow drifting through the woods. It reminded me of the yellow clouds of pine pollen blowing in the wind at our house in the spring! Cleaning off the cars was easy – Scott, my clever brother-in-law just fired up his leaf blower and voila – clear in a matter of seconds!!

A rhododendron droops under the weight of the snow.

A rhododendron droops under
the weight of heavy snow.

Most snowfalls in our area aren’t this light and fluffy and our landscape trees, shrubs, and woody perennials can at times suffer damage due to heavy snow or ice accumulation. One of the best ways to minimize storm damage to your trees and shrubs is to keep them properly pruned and thinned.

Even with that they can still become weighed down by ice and snow and we are often asked what to do for trees and shrubs in the aftermath of an ice storm or a heavy snow.

With snow accumulation, if it’s not too heavy, you can sometimes take a broom and gently brush the snow from the branches. It is best not to shake the branches as this can cause breakage.

Euonymus covered with a layer of ice.

Euonymus covered with a layer of ice.

In the case of ice accumulation, it is always better to let the ice melt off naturally. If you try to knock it off you will usually do more damage to your trees and shrubs and it’s also very dangerous. The same holds for a heavy, wet snow.

Most trees and shrubs will bounce back after the snow or ice melts off so it is usually safer to be patient and wait until they thaw out.

Once everything melts, you will be able to see if any permanent damage was done.

The most important thing is to be safe!

  • Ice buildup on a Japanese maple.

    Ice buildup on a Japanese maple.

    Don’t go near trees or branches that have fallen on power lines.

  • Watch for large broken branches that are hanging precariously and could fall in a gust of wind.
  • Assess the damage to determine if it is something that you can handle yourself or if you need to call in a professional tree service for help. Large limbs can be extremely heavy (hundreds of pounds) and dangerous!
  • Broken branches are one of the most common problems. Avoid any trimming or pruning that necessitates getting up on a ladder. This can be extremely dangerous especially if there is snow or ice on the ground.
  • When using a pole saw or trimmer, be mindful of any telephone or power lines and stay well away from these. It’s very easy to lose track of where they are in relation to where you are cutting! Better yet, leave this pruning to a professional.

Click for more tips on dealing with snow and ice damage.

Happy New Year everyone!

Until next time – Happy Gardening!

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