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Elisabeth C. Miller Library

Keyword: Insect pests--Control

differentiating critter mounds

I live in Seattle and have, for the first time this fall, noticed dirt mounds on my property. These mounds tend to be located near patios/driveways, and are not in the sod. They are loamy, with no apparent holes, and are about three to five inches high. I wouldn’t call them conical. There are no mole tunnels, and, as far as I can see, no bugs. The mounds are bigger than the little fine-grain mounds I have noticed in years past with small black ants crawling in them. Is there someone I can ask about what is causing these mounds, and if it is something to be concerned about? Could it be ants or mice?

 

From your description of the dirt mounds, it sounds as though the critter in your yard may be either a mole or a gopher. The easiest way to tell the difference is by the type of mound you have. Here is information on moles and pocket gophers from Washington Department of Fish and Wildlife’s Living with Wildlife website.

Below is additional information from “Of Bugs and Blights” (in Balls and Burlaps, February 1988, pp. 4 and 14):

A gopher mound fans out from a hole near one edge of the mound. This hole remains plugged while the gopher is on the runway system. The gopher mound is relatively flat compared to the mole mound. Gopher mounds vary from 1 to 3 feet in diameter…several mounds often will be found together. They are not regularly found in a line as are mole mounds. The mole mound is somewhat conical and not much over a foot in diameter. The hole is not evident when you look at the mound. Push the soil aside and you will find it under the center of the mound. Each mound is connected with the other in a line by the moles’ runway system.

According to the article quoted above, moles are more likely to be found in gardens in Western Washington than are gophers. We have the journal Balls and Burlaps in the Miller Library. The article discusses the problems and benefits of moles, as well as control methods.

I also consulted the Western Garden Problem Solver (Sunset Books, 1998) to see if I could identify your mound-maker. Ground squirrels leave their burrows open, so if your mounds show no opening, you probably don’t have squirrels. Mole mounds appear volcano-like, with signs of soil excavation.

Here is a link to information on ants and their nests which you might look at to see if the images resemble the mounds of soil you are seeing.

Managing leaf gall on Arctostaphylos uva-ursi

My Arctostaphylos uva-ursi has suffered from galls caused by aphids. What approach would be best to combat the aphids and when is the best time in their life cycle to attack?

Kinnikinnick or Arctostaphylos uva-ursi sometimes suffers from galls caused by aphids, and is also susceptible to fungal diseases. If your plant has galls, you would see distorted, thickened, and often reddish leaves which almost don’t seem leaf-like. The aphids may also secrete honeydew which can then turn blackish with mold.

Douglas Justice, University of British Columbia Botanical Garden Associate Director offers these comments on Arctostaphylos uva-ursi:

The Arctostaphylos uva-ursi cultivar ‘Vancouver Jade’ — a UBC introduction and one of the most widely grown cultivars in temperate climates — is adapted to wetter conditions than many other cultivars, as it was selected from the Pacific Northwest. Nevertheless, like all kinnikinnicks, it is not a plant for poorly drained, shaded or high traffic areas. And unfortunately, it appears to be rather more susceptible to manzanita pod gall aphid than other cultivars. Populations of that insect pest can build up during “warm winter” periods (such as we’ve been experiencing in Vancouver over the past several years) and disfigure plants significantly.
Source: UBC Botanical Garden Forums

Oregon State University has information about leaf gall on Arctostaphylos uva-ursi in their Plant Disease management handbook online.

The following, from Pacific Northwest Insect Management Handbook (WSU, OSU and U. of Idaho, 2005) provides more information about the aphids.

Kinnikinnick Arctostaphylos – Aphids

Manzanita leafgall aphid, Tamalia coweni:

Pest description and crop damage – Manzanita leafgall aphids are grayish or greenish in color and prefer new growth. They feed on the leaves of kinnikinnick and other manzanita species (Arctostaphylos spp.). Aphid feeding causes the leaves to thicken and form bright red galls. Older galls turn brown. Severe infestations may slow the growth of the plant.

Nongall-forming aphids also may be seen occasionally on kinnikinnick. They are greenish, soft-bodied insects that may feed on leaves or stems. Honeydew, a sweet, sticky material, may be associated with aphid feeding. It may attract ants or become covered with a growth of dark, sooty mold. Severe infestations may result in leaf and twig dieback.

Management-biological control:
Syrphid fly larvae are important predators of leafgall aphids, and will feed on them inside the galls. Avoid use of broad-spectrum insecticides which kill these and other beneficial insects such as ladybird beetles and parasitic wasps.

Management-cultural control:
Prune off and destroy galls where seen. Avoid frequent shearing and overfertilization, which encourages succulent new growth favored by aphids. Wash other aphid pests from plants with a strong stream of water or by hand-wiping. Avoid excessive watering, and use slow-release or organic sources of nitrogen. Control ants, which “farm” aphids and protect them from predators in order to harvest their honeydew.

managing gall mites on fuchsias

My fuchsias have gall mites. Will a horticultural oil control them? I would prefer not to use a more toxic pesticide.

 

Several resources I consulted confirm what you thought about using horticultural oil to control the gall mite problem. The Organic Gardener’s Handbook of Natural Insect and Disease Control (ed. by Ellis and Bradley, 1996) says to spray dormant oil or lime-sulfur on dormant plants.

University of California, Davis’s Integrated Pest Management site has a page about this gall mite, recommending that gardeners “plant only resistant fuchsias and consider replacing susceptible plants. Prune or pinch off and destroy infested terminals. If damage cannot be tolerated, pruning may be followed with two applications of a miticide, applied 2 to 3 weeks apart. Soap or oil sprays provide some control, but cannot kill fuchsia gall mites enclosed in distorted plant tissue.”

According to a May 2004 article from the American Fuchsia Society, “to be effective, [horticultural oil] must come in contact with every live gall mite and smother every gall mite egg. The only way oil products can be effective in killing gall mites is for you to remove the leaves.” Link to this article.

managing fungus gnats indoors

I need advice on how to rid my house of fungus gnats which were introduced in a bag of potting soil I used when repotting my houseplants. One plant is difficult to repot because it has long branches that cascade down the side of the pot in an intertwined mass.

I always let the soil dry out completely before potting, and also in between waterings. Recently I added a bunch of sand to the top of the soil. Would repotting again help? Is there a no-pest strip that is safe for use indoors for this insect? (I’m chemically sensitive and also concerned about the soil’s fungus).

 

I’m sorry to hear of your struggle with fungus gnats. I consulted
University of California, Davis Integrated Pest Management online, and
here is a link to their page on this insect and methods of controlling it. Here are excerpts which may be relevant to your situation:

Purchase and use only pasteurized container mix or treat potting soil
with heat or steam before using it; this will kill flies as well as the
algae and microorganisms they feed on. Store pasteurized potting soil in
closed containers to prevent it from becoming infested before use.

Commercially available Steinernema nematodes, Hypoaspis mites, or the
biological insecticide Bacillus thuringiensis subspecies israelensis
(Bti) can be applied to control fungus gnat larvae in container media.

North Carolina State University Extension also has suggestions on indoor control of this pest. Excerpt:

Potted plants and other types of interiorscaping are often the culprits.
Check plants to see if the soil is excessively wet. Drain any excess
water from the dish below the pot. If the weather permits, move the
plants outdoors or allow the soil to dry down (not to the point where
plants wilt). You can also drench the soil as mentioned previously. Then,
increase the interval between regular watering and the problem should
abate.

If you can possibly repot the plant(s) which had the infested soil, and
use sterile potting soil, that should help. If this doesn’t work, the
Bacillus thuringiensis (Bt) or parasitic nematodes might be an option. I
think the Bt might present problems for your chemical sensitivity, as you
would need to avoid breathing it in, and prevent it from getting on your
skin and clothing. However, the Steinernema feltiae nematodes should not
be a problem at all. One example of a source for these is Peaceful Valley Farm Supply.

I don’t think adding sand on top of the potting soil will be effective.
It might actually create a kind of crust over the top of the soil,
causing a drainage problem. If you are concerned about fungus in the
soil, using sterilized or pasteurized potting soil is a good idea. You
can try using yellow sticky traps to catch the gnats; it can’t hurt,
although it won’t completely solve the problem unless you are willing to
repot with new soil. Most garden centers sell these traps, or you can
make your own as described by New Mexico State University Extension.

You can also employ trapping techniques using yellow sticky traps. These
may be purchased, or you can make them from yellow surveyors tape or
yellow plastic butter tubs, etc., coated with vegetable oil, Vaseline, or
other sticky material. Put these traps in a window or other well-lighted
location. The adult gnats are attracted to the yellow color and get stuck
on the trap. This removes them from the home environment and reduces
their ability to reproduce. (They die on the trap.) After you catch a lot
of gnats, just discard the whole trap or wipe the insects off and reapply
the sticky material mentioned above, and you are ready to catch more.

on managing weevils in the garden

What is the pest that eats little notches around my Bergenia
and Heuchera? What can I do to prevent this?

 

It is possible your Bergenia and Heuchera are being nibbled by black vine
weevils or strawberry root weevils. Usually you would begin to notice the
damage in mid-spring. The notches won’t kill your plants, but if you have
a lot of black vine weevils and plants appear to be wilting, you may want
to attempt to control the larvae. Spraying beneficial nematodes
(Steinernema) on the surrounding soil may also help.

Below are links to information about weevils:

Black Vine Weevil from UMass Extension

Black Vine Weevils from University of California’s Integrated Pest Management site

Strawberry Root Weevil from the Pacific Northwest Insect Management Handbook

A document about Black Vine Weevil (and other root weevils) from Ohio State University Extension

Excerpt:

“Adults that feed along leaf margins produce typical crescent shaped
notches. Careful searches should be made to try and locate specimens
since several other weevils and some caterpillars can produce this same
type of notching. Moderate to light notching seems to have little effect
on plant health.

“Black vine weevils are oblong oval in shape, about 1/2-inch long and have
a short, broad snout with elbowed antennae. The body is slate grey to
blackish brown and the wing covers have numerous small pits and short
hairs. This pest is difficult to distinguish from other Otiorhynchus
weevils. The strawberry root weevil is usually half the size of the black
vine weevil, and more brown in color. The rough strawberry root weevil is
only slightly smaller than the black vine weevil but the collar just
behind the head, the pronotum, is heavily pitted.

“Female weevils emerge from soil pupation chambers late May to early July.
These weevils must feed on plant material for 21 to 45 days before they
are ready to lay eggs. After the preoviposition period has passed, the
females place several eggs each day into the soil or leaf litter nearby
suitable host plants. The weevils hide during the daytime at the base of
plants or in mulch and leaf litter near food plants. Adults may live 90
to 100 days and usually lay 200 eggs during this time. The eggs hatch in
two to three weeks and the small C-shaped, legless larvae feed on plant
rootlets. The larvae grow slowly over the summer, molting five to six
times. By late fall the larvae have matured and are about 5/8-inch long.
The mature larvae enter a quiescent prepupal stage in an earthen cell and
pupate the following spring. A single generation occurs each year.

“Strategy 1: Habitat Modification – Egg and larval survival is helped when
soil moisture is moderate to high in July and August. Heavy mulches also
help maintain critical moisture levels. Remove excessive mulch layers and
do not water plants unless necessary. Excessively damp soils in the fall
also force larvae to move up the base of the plant where girdling can
occur. Properly maintain rain down spouts and provide for adequate
drainage of soil around plants.

“Strategy 2: Biological Control Using Parasitic Nematodes – The
entomopathogenic nematodes, Steinernema and Heterorhabditis spp., have
been effective for controlling black vine weevil larvae, especially in
potted plants. Sufficient water must be used during application to wash
the infective nematodes into the soil and root zone. If the nematodes are
to be used in landscape plantings, remove a much of the mulch as possible
and thoroughly wet the remaining thatch and soil before and after the
nematode application. Applications of the nematodes in landscapes has
produced variable results.”

problems affecting camellias

My camellia is potted and lives on an urban deck. In the spring, it was full of beautiful blooms and lush foliage. This summer it has been plagued with aphids and mealy bugs. I have sprayed two different times, 3 times each. My bush appears to continue to fail. It is dropping perfectly healthy-looking leaves and getting new growth, but it has few new buds and looks very “naked.” What is wrong with it? I have noticed small insects in the soil as well. I have added a watering of Safer-soap-with-water mixture but it seems to have had no improvement. Please help!

 

I wonder what kind of spray you have been using. Was it the Safer soap product?
Aphids seldom cause the demise of a mature plant. Aphids are attracted to lots
of leafy new growth, so it is best to avoid quick-release high-nitrogen
fertilizer. The best way to keep aphids in check is to encourage natural
predators like ladybugs, syrphid flies, lacewings, and parasitic wasps. Broad
spectrum pesticides will harm the helpful insects as well, so I would avoid use
of those. Mealy bugs are also a favorite of natural predators like those
mentioned above. Usually, regularly spraying jets of water to knock the aphids
and mealy bugs off the plant’s leaves should keep the damage in check. If
necessary, you can use insecticidal soap, but always test it on a small area of
the plant to make sure it does not cause any damage to the leaves.

It is possible there is something else going on with your camellia. Here is a
link to University of California, Davis’s Integrated Pest Management website,
with a list of problems affecting camellias. My own camellias do shed a certain number of healthy green leaves every year, but still manage to keep flowering. Excessive leaf drop may indicate overfertilizing, but it could also be a sign of too much or too little water.
Did buds drop from the plant, or did they simply not form? Failure to form buds
might be a result of cold injury (although since you had flowers in spring, this
seems to not be the problem), or it could also be a sign of overfertilizing with
a nitrogen-heavy product which encourages leafy growth at the expense of
flowers.

You may want to bring samples of the insect-affected leaves and the insects in
the soil to a Master Gardener Clinic for identification and diagnosis. You might
also mention the excessive leaf drop, which can be a symptom of Sudden Oak Death
(Phytophthora ramorum).

Jade plant care

I have been nursing a Jade plant cutting that dropped off an overwatered and rotting larger plant. It has been thriving in my windowsill for 6 months or so, and has grown a lot already.

In the last week or so, I have noticed a strange white speckling on the upper surface of almost all of its leaves. Upon close inspection, it does not look like insects; it looks sort of like a detergent residue, and if I scrape my nail against the surface of the leaf, a lot of it will come off, albeit with effort.

Do you know whether this is something I need to treat?

 

I wouldn’t assume the spots are a problem. As the following link to North Dakota State University Extension (now archived) mentions, it might be salt crystals that you are seeing:
“Those dots are salt crystals and can be wiped off with a damp cloth or just ignored because they are not causing any harm to the plant. All water (except distilled) contains some salt. When fertilizer is added to the root system, the plant takes up the nutrient salts with the water. As the water moves through the leaf pores during transpiration, the salts often are left behind on the surface.”

However, if you were to use a hand lens (not just the naked eye) and discover insects, there are resources with information on identifying and treating insect problems on indoor plants.

1. Pest and Diseases of Succulent Plants

2. Washington State University’s PestSense site lists several common houseplant pests, with information about treatment.

Always test any spray on one leaf before spraying the entire plant. Wait a few days after the test spray. Some plants are more sensitive to various soaps or oils.

3. The Northwest Center for Alternatives to Pesticides also has a guide to Growing Houseplants Without Using Pesticides.

repotting and caring for Jade plants

My 100-year-old Jade plant is about 5 feet tall and recently has been producing a sap from its leaves. White and sticky. Is there anything I can do to help this? Is it normal? Or is it endangering the plant? It is in kind of a cool spot; should I move it to a warmer place? It is a succulent, right? I would also like some information about repotting if necessary.

The pests most likely to cause a white, sticky substance are aphids, whiteflies, scale or mealybugs. These are known to affect jade plant, or Crassula ovata, which is indeed a succulent. They won’t destroy plants, but can weaken them and allow other problems to surface. If none of the pest descriptions below resemble what you are observing, you can take affected plant samples to a local county extension agent. Without knowing the specific pest, we can’t suggest specific treatments. Northwest Center for Alternatives to Pesticides has general information on caring for houseplants. Note their description of mealybugs, which do produce a sticky substance:
“These insects look like little bits of cotton that are greasy or waxy. They are oval in shape, have a segmented body, and are about 1/4 inch long. You’ll usually find them hidden between leaves and stems or under leaves. They move slowly. They make a sticky liquid called honeydew and also cause leaves to become distorted and spotted.”

As for temperature and repotting, The New House Plant Expert (by D. Hessayon, 1991, p. 212), says that succulents like a difference between day and nighttime temperatures. They like to be kept cool in the winter, with 50-55 degrees F ideal, but as low as 40 is alright. Jade plants should only be repotted when essential. Repotting should occur in the spring; shallow pots rather than deep ones are preferable.

Extensive care information can be found on Succulent-plant.com. There is also excellent general information on indoor care of succulents and cacti from Brooklyn Botanic Garden.

Powdery mildew and Euonymus

Have you heard about a problem with Burning Bush
(Euonymus alatus) getting a mildew this year? The
leaves have turned yellow green with small spots of
lighter yellow discoloration.

 

Powdery mildew is a common and usually not life-threatening
problem with Euonymus. Make sure the plant has good air
circulation, and be sure to clean up and destroy fallen
leaves which are infected. However, the symptoms of this
fungal problem would be whitish coating on the leaves, rather
than yellowed leaves. This makes me wonder if it is a
different problem such as scale (which is actually an
insect). Check and see if there are small bumps on the leaves
or stems. Scale can cause yellowed leaves. If your plant has
a small infestation, you can try scraping the scales off with
your fingernail, prune out the most infested parts of the
plant, and then apply dormant oil to the trunk and branches
before growth starts next spring, or apply superior oil
during the growing season. There are also other fungal and
bacterial problems that could be causing the spots.

See this fact sheet from Penn State for more on Euonymus scale.

Here is an archived link to additional information, which comes from
University of Illinois Extension. Excerpt:

Burning bush (also called Winged Euonymus): Euonymus alatus

Cold injury – Winter injury may be caused by very low
temperatures as well as drought stress. With excessively low
temperatures, the moisture in the cells freezes (due to
chemical compounds in plants, moisture freezes at various
degrees below freezing). Drought stress already has resulted
in limited moisture in the plant cells. Dry, freezing winds
during the winter reduces the moisture level even farther,
often resulting in dead plant tissue. Diseases can help
magnify or increase susceptibility to winter kill. Nectria
canker kills the sapwood tissue thus reducing or even cutting
off moisture to tissue further out on the plant. Winterkill
also makes plants more prone to infectious diseases and
insect problems.

Dieback/canker – See bridal wreath spirea. In addition
Botryosphaeria dothidea will infect and kill for similar
reasons.

Winged euonymus scale – Lepidosaphes yanagicola occasionally
occurs in the southern half of Illinois on burning bush. It
is an armored scale. And will attack several trees as well.
This scale can cause premature leaf drop, branch die back and
cause the plant to become more prone to winter injury. It is
found between the “wings” – the bark ridges. It does not move
to the plant’s leaves. The scale over winters as an adult and
lays its eggs in June. Eggs may be laid for up to a month.
Mating occurs before frost.

Euonymus scale – Unaspis euonymi – females are black and
males are white. The scale causes the foliage to develop
yellowish green spots. Heavy infestation results in early
foliage drop and often stems are killed. Eggs survive by over
wintering in the female body. The eggs hatch about early June
in Northern Illinois. Crawlers emerge and move onto new
growth or can be blown by wind to other plants.

Since I cannot diagnose the problem remotely, it makes sense
to take plant samples to a Master Gardener Clinic.