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Are we barking up the right tree?


Beautiful gardens by William Johnson

AS SPRING blossoms and summer approaches, I usually receive more questions about the plants and produce in homeowners’ landscapes. This year is no exception and here is a sample of recent queries.
Q: Clumps of some type of organism have suddenly appeared on the trunks of my crape myrtle and oak trees. They look like bark except that they move from one area on the trunk to another throughout the day. What might they be?
A: I have received distress phone calls and e-mails from many, many homeowners describing this problem. Although the clumps appear to be problematic, they are not. They are composed of insects known as barklice.
Most folks raise an eyebrow when they think of lice infestation. However, barklice are not the same as parasitic lice found on humans and animals. The scientific name for the type that occurs in our area is cerastipsocus venosus. A closely related species that forms silk webbing on tree trunks occurs in our growing area around mid to late summer.
Barklice move together as a family unit, somewhat like cattle in a pasture so, not surprisingly, they are also known as tree cattle. They do not pose any harm to humans, pets or trees and are beneficial insects that feed upon lichens, fungi, algae, dead plant tissue, pollen and other debris located on tree trunks.
Adult barklice are about a quarter-inch long and jet black in color with a few white stripes and a pair of very long antennae. The immature or teenage stages are known as nymphs and they are wingless with distinctive yellow and black bands on their body. The adults and nymphs feed in a group.
The wingless nymphs and winged adults form quarter-dollar-sized to hand-sized clusters and move about in “herds” over the tree trunk as they “graze” on its food.  Some county residents have noted that the clusters will temporarily scatter when suddenly disturbed, only to rejoin again as a “herd” shortly afterwards.
Although the local barklice species occurs on many different types of tree, it is most often noticed on crape myrtles, probably because it is so conspicuous on that tree’s smooth, light-colored bark. I have also seen the species on oaks and, in the master gardeners’ Discovery garden in Carbide Park, several fruit trees, including citrus and mayhaw, also have barklice this spring.
Q: The bark on my crape myrtles is peeling off and it looks like it has been shredded and just hangs off the trunk and some of the lower branches. Is this normal?
A: As crape myrtles age, their bark will begin to peel off. The horticultural term for this is exfoliating. It’s normal and there is no cause for alarm. After the gray bark peels away, you might notice a different shade of underbark.
Some of the newer crape myrtle varieties have underbark that is cinnamon to dark brown in color, adding to the tree’s beauty, especially in winter. Go ahead and peel any loose bark off once it starts shedding to hasten the exposure of the underbark.
Q: Why are there a lot of small holes in the leaves of my eggplants?
A: This damage is caused by insects known as flea beetles. Row covers will provide some protection. An insecticide – such as Sevin – containing carbaryl as an active ingredient can be used. Be sure to read and follow the manufacturer’s directions.
Q: When should I harvest my Irish potatoes?
A: New potatoes can be harvested as soon as they reach a suitable size. Fully-developed potatoes for storage can be harvested when the top growth turns yellow. Do not harvest potatoes when the soil is very wet as it will increase the chance of rotting.
Q: I have noticed that a lot of professional landscapers mulch trees with shredded pine-bark mulch in a cone formation around the base of trees. Is this a good idea?
A: Mulching around trees is recommended but allowing mulching materials to come into contact with the trunk can severely weaken or even kill the tree. The constant moist conditions created by the mulch will rot the bark layer and damage the tree’s cambium, or growth, layer.
It is recommended that mulch about four inches deep be spread around the tree but kept a few inches away from the trunk. The rule of thumb is to build donuts, not pyramids, around trees.
Q: Will pine needles used as a mulch help lower the soil’s pH?
A: It is true that pine needles help create an acidic soil in native forests after hundreds or even thousands of years of growth and decomposition. But in a home landscape there is not enough time or plant litter to substantially modify our slightly alkaline gumbo clay soils.
William Johnson is a horticulturist with the Galveston County office of Texas A&M AgriLife Extension Service. Visit his website at

Homeowners across the county have reported occurrences of clumps of insects appearing on trunks of trees in landscapes. The clumps are actually composed of insects known as Barklice which move together as a family unit somewhat like a herd of cattle in a pasture. Barklice are beneficial insects and do not pose any harm to humans, pets or to trees.William Johnson

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