Dan West Garden Center

August 2008 Newsletter©

Bugs!

This month we’re going to talk about a few of the insects we see in the garden this time of year.  First, one of my favorites…the aphid.

There are more than 1300 species of aphids in North America.  They can be black, brown, red, orange, yellow, green or cottony covered white.  Heavy infestations cause leaf curling, fruit loss and leaf drop.  Some are known to carry viruses. 

They feed by sucking plant juices from leaves, fruit, flower buds and tender stems.  Then they secrete a watery sticky substance called honeydew.  This is food for many insects and often you’ll find ants tending and protecting the herd to harvest the honeydew like the far left picture above.  Ants climbing your shrubs usually indicate the presence of aphids or scale insects (which also produce honeydew).  Honeydew drips down to the foliage below and to other plants on the ground.  Sooty mold then grows on the honeydew giving the foliage a black sooty appearance.   So, just like ants, sooty mold is an indication of insects.  Sooty mold is often found on crape myrtles, hollies, gardenias and citrus.

The really cool thing about aphids, is the way they reproduce.  In the fall, male and female aphids mate and the female lays eggs which overwinter.  In the spring, all the little hatchlings are female.  They mature quickly and instead of laying eggs, they give birth to 2 or 3 live young everyday.  The babies are  little xeroxed female copies of their mom. They in turn mature quickly and give birth to more little females.  This goes on all summer.  If the population gets too big, a few winged females are born and they fly off to start their own colony.  Some species, a little further south, skip the male segment entirely and females begat females which begat females and so on!

Lacebugs are another common problem in the Mid-South.   The azalea lacebug is quite common, but we have other species that attack pyracantha, quince, cotoneaster, eggplant, maple, birch and more.

In the pictures above you can see the typical damage on an azalea.  The upper side of the leaf has a salt and peppered appearance and the back side has the black droppings they leave behind.  Lacebugs, like aphids, feed by piercing the plant and sucking out the plant juices.  Eggs overwinter on the host plant, so make sure you apply a dormant oil spray in late fall and early spring.  Lacebugs more often attack a stressed plant.  That’s why you see them attack azaleas that get some sun, but not those in the shade.

The following are scale insects and they vary widely in appearance.

Some are armored, some are soft, some prefer stems, some prefer foliage. Eggs are laid under their protective waxy covering. The number varies among species, but some produce as many as 700 eggs.  The young are called scale crawlers.  They move to a place to feed and then become firmly attached for life.  Scale insects produce huge amounts of honeydew which, as we said earlier, leads to sooty mold.

Some of the more common types found around the Mid-South are:

Tea Scale  -  Found on the undersides of leaves on hollies and camellias.

Euonymus Scale  - If you’ve ever had a golden euonymus, you know this one.

Soft Brown Scale  - Common on English ivy, gardenias, begonias, ferns and many houseplants.

Lecanium Scale  - Attacks fruit trees and many shade trees.

Tortoise Scales  -  Often on magnolias, pines and tulip poplars.

Oystershell Scale  -  Found on dogwoods, maples and many other trees and shrubs.

San Jose Scale  -  Most commonly found on roses, apples, crabapples and pyracantha.

Another sucking insect we deal with is the leafhopper.  There are over 2500 species in North America.  Adults and young are quite mobile and move easily from plant to plant.

Leafhoppers seldom cause significant plant damage on ornamentals by feeding, but they can carry viruses and bacteria which can be very destructive.  They are the carrier for bacterial leaf scorch.

Sucking insects, like the ones above, are easily killed with a systemic insecticide that is absorbed into the plant.  The plant is protected for a couple of weeks to a year, depending on the product used.

Scale insects can be smothered with an oil spray anytime the temperature is between 40° and 90°.  Because sucking insects penetrate such a small area when feeding, insecticides that coat the surface of a leaf are not as effective as systemics.  Used frequently enough, most insecticides will work, but alternate often.  Aphids, in particular, that survive an application of some insecticides, whether organic or synthetic, develop an immunity that can be passed on to their daughters.

The next group of insects are the borers.  These are the larvae of moths, beetles, leafminers, wasps or weevils.  Some tunnel under the bark, some bore down through the new growth, some through twigs, some through the interior of leaves.

Above from left to right is a peach tree borer, an adult dogwood borer moth, leafminer damage and a flat headed borer. Below is a pine bark beetle, pine bark beetle damage, a squash vine borer larvae and adults and an oak gall.

These insects do significant damage to the plant when feeding.  If borers disrupt enough tissue in the trunk of a tree, food produced in the leaves cannot get back to the roots.  The roots begin to die off and then the top dies.  Plants you need to watch in the Mid-South for borers are dogwood, pines, plums, peaches, cherries, cherry laurel, apples, roses, iris, corn, squash and birch just to name a few. 

One of the more interesting boring insects is the oak gall wasp.  Eggs are laid in twigs which causes the gall to form. Most take two to three years to complete the life cycle.  Oak gall will not kill your tree.  I have seen mature trees heavily infested with hundreds and hundreds of  3 inch galls.  Often the small twigs break under the weight of the gall, so don’t park your new car under a heavily infested tree.  Imidacloprid will protect most trees, including some fruit trees, for a full year against boring insects.

The next major group of problem insects are the caterpillers.  From tiny cabbage loopers, to gigantic tomato hornworms, they come in all colors and sizes.

Above from left to right is the eastern tent caterpillar, tomato hornworm, bagworm and cutworm.

These are voracious eaters.  They can defoliate a plant virtually over night.  Many plants will resprout, but most needle evergreens do not recover when bagworms eat all the foliage. Check your junipers often.  Caterpillars are easily controlled with systemics or with B.T., a bacteria.

If that weren’t enough…there are always…

Whiteflies, thrips, thousands of types of leaf eating beetles and spider mites that are about ¼ the size of the period at the end of this sentence.

Also…below are flea beetles, a psyllid, an adelgid (I’m not making these names up!) and mealybugs.

And then there are these…

Root weevils, grasshoppers, earwigs, ants and plant bugs.

And more still…the twig girdler, the larvae of this cute little pair of flies is an apple maggot (there are lots of bad flies and maggots), the cicada and then roly-polys, sowbugs or pillbugs, what ever you want to call them. 

The cicada is summer music to some who like the sound and an annoyance to others, like me, who like peace and quiet.   Females lay eggs in the twigs of trees.  Nymphs emerge about 2 months later and fall to the ground where they bury in to feed on plant juices sucked from the roots.  One species takes 2-3 years to mature underground but the generations overlap, so we have some every year.  There are 2 species of periodical cicadas which take 13 or 17 years to mature.  There are 3 distinct broods of 13 year cicadas, each hatch after 13 years, but not in the same year.  There are 12 broods of 17 year cicadas, the largest of which is not due back until 2021.  When these broods hatch, it is not uncommon to have 50 to 100 climb the trunk of a tree and shed their skin…and then they start to sing.

Pillbugs are not insects.  They are crustaceans, related to crabs and lobsters.  They do not damage healthy plants.  They feed mostly on decomposing organic matter.

And there are more, but the bugs above are the most common.

So…can you buy just one insecticide to kill them all?  No.  The type of plant and its size, the insect, the urgency, the temperature, the time of year, the application method, is it prevention or curative?… all are factors to be considered when picking the right product.  That’s why there is Dan West.

This was last month’s mystery plant.  I told you I was going to make it easier, so I left the name on the picture.  I didn’t say it wouldn’t be tricky!  Hardy Gardenia is NOT a gardenia.  It is an azalea and only one person knew it.  So the one word answer had to be Rhododendron (the genus) or azalea.

Many, many, many people said gardenia. 

I just love this game! 

Here’s this month’s mystery plant.

The contest ends on Aug 15^th.  Drop by either store to enter or you can email your entry to questions@danwestonline.com.  One winner, selected from all correct entries, will receive a $25 Dan West Gift Certificate.

Next month we’ll talk about beneficial creatures in the garden…ladybugs, praying mantis, spiders, lizards, toads and snakes!  That’s right, snakes are beneficial!

Thanks again, for shopping with us at Dan West.