Fall Webworms

Fall webworms are back.  They are really becoming more apparent as they grow and their webs get larger.

Fall webworms nests start to become apparent in late summer.

This is not the same caterpillar we saw in the spring; those were the Eastern Tent caterpillar.

Because fall webworms emerge in late summer, they don’t have a chance to do much damage to trees but their webs sure are ugly.

Fall webworms feed on a wide variety of trees. In our area this summer, I’ve been seeing them on walnuts, oaks, mulberries, cherries and other trees.

There are a couple of options available for controlling these pests.  The simplest method is to manually pull the webs down and destroy them.  For those you can’t reach, use a chemical pesticide sprayed up onto the web.  You don’t need much because they are easily killed by most chemical insecticides.

Some people recommend spraying the biological insecticide Bt. Bt works best when the worm are small.

Try to resist the urge to burn the webs in place on the tree.  You’ll end up scorching twig bark causing more damage to the tree than the webworms.

Paper wasps are a natural enemy of the fall webworm. If a paper wasp nest is located in a place on your property where they aren’t disturbing anyone, think about leaving them there to help control the webworms.




Koganemushi in the Garden

The first Japanese beetle of the season showed up in the garden several days ago.  The beetle actually landed on my arm. That was a big mistake on his part because I immediately tossed him to the chickens.

Those first beetles are forward scouts. Once they arrive, they release a pheromone that attracts other beetles. Before you know it, you have a real problem on your hands.

Sayaka Terada, a garden volunteer at Matthaei Botanical Gardens, told me that in Japan they are called koganemushi, or, in English, “gold bug.” Japanese farmers consider them somewhat of a nuisance because they do some damage on crops such as grapes and soybeans.

They are very beautiful insects if you look at them closely and ignore their destructive habits.

The beetles are emerging from the soil where they spend much of their lives as grubs.

Picking off the beetles and killing them whenever you find them is an adequate way of keeping their numbers down – if you are persistent.

Japanese beetles, like many other insects, have certain types of plants they prefer over others.  One of their favorites is evening primrose, a type of weed commonly found in and around gardens.  A good strategy is to let the beetles start feeding on the evening primrose; a large number of them will often congregate onto one plant.  You can then kill the beetles without having to spray your garden directly.

Two Japanese Beetles feeding on Evening Primrose. The green lighting effect is from the early morning sunlight.


Over the counter chemical sprays work well in controlling them but chemicals also kill beneficial insects.

There is promising research at Michigan State University that involves introducing naturally occurring microorganisms into the environment to infect the grubs and reduce their population.  This new method will be different from the milky-spore treatment that is currently available.






Cabbage Worms

Anyone who has ever planted a garden knows that it is almost impossible to grow cabbage without cabbageworms.

Here in my garden I have yet to see a cabbageworm in the cabbage patch.  The Imported Cabbage Worm is the easiest to identify.  Those little white butterflies you see fluttering around in the garden are the adult stage of the imported Cabbage Worm. If you look closely, you can spot the eggs they lay.  Every time a butterfly lands on a cabbage leaf it lays a single tiny white egg.

Cabbage Looper Butterfly on Kale.

The other cabbageworm that causes us trouble is the Cabbage Looper.  This worm moves across the plant by arching its body and moving its rear legs forward to the front of its body.  Then it stretches out to move its front legs forward, much like an inchworm.  You will not see the adult moth of the looper because it flies at night.

My cabbage patch is right next to the chicken run; just a wire fence separates the garden from thirty-five hens.  I think they may be intercepting the butterflies before they have a chance to reach my cabbage, although today the butterflies are out in full force.

Both species of cabbageworms chew large holes in the leaves and heads and leave behind large amounts of frass (droppings).  The control for them is the same too.

A biological insecticide Bt — sold under the trade name of Thuricide, Dipel and others, is a very effective and safe way to kill cabbageworms without harming beneficial insects.  Chemical insecticides easily and rapidly kill the worms but also kill any beneficial insects that happen to be in the garden.

You can try making a homemade cabbageworm killer by mixing two to three parts white baking flour with one part table salt.  Dust the cabbage plants with the mixture.

The smaller the cabbageworms, the easier they are to kill – no matter what insecticide you use. So, treat your cabbage plants early before the cabbageworms get a chance to grow.




New Threat to Walnut Trees

Another potential disease problem is over the horizon threatening our local trees.  This time it is the Black Walnuts that are at risk.

A fungal infection called Thousand Cankers has been killing Black Walnut trees in the western part of the United States for several years.  It has been confined to nine states in the Rocky Mountain area and westward until July of this year. Its range seemed to be associated with a different walnut called the Arizona Walnut.  Black Walnut is not native to that particular area but was brought in and planted by arborists, landscapers and others.

This summer it was confirmed that the disease had spread to at least one location in the Eastern USA,  Knoxville Tennessee.  Scientists now believe that it may have been present there for a number of years without anyone knowing about it.

At this time Thousand Canker disease is NOT present in Michigan.

The disease is caused by a fungus which is carried by a very tiny beetle called The Walnut Twig Beetle.  Despite its name the Twig Beetle  attacks larger branches or even the trunk of Black Walnut Trees by tunneling under the bark. They leave small “galleries” or tunnels in the wood caused by the beetle larvae feeding there.

When the larvae mature into adults they emerge from the branches out of small holes chewed through the bark. The fungus then infects the damaged area and causes a small lesion or “canker”.  These cankers spread very fast and merge together eventually moving from the outer bark into the cambium layer.  Each branch has a tremendous number of cankers which is how the disease got its name.

The cankers themselves are often difficult to see and identify.  A special lab test is needed for positive identification.

There is no cure or control for either the Twig Beetle or Thousand Cankers, plant pathologists are working on that though.

In the meanwhile we can help slow down the spread of this problem by not moving firewood just like we do to prevent Emerald Ash Borer from spreading.

There is no federal quarantine on moving wood products but the State of Michigan has issued its own quarantine against shipping articles made of wood from certain western states.

The USDA Forest Service has a good publication on this problem.

As I mentioned earlier, Thousand Cankers is not present in Michigan at this time. Keep in mind that there are a lot of other things that can cause a tree to show signs of  die-back  other than this disease.


Parasitized Tomato Hornworm

There seems to be an abundance of Hornworms in the garden this year.  A couple of posts ago I discussed picking the pests off of the plants by hand as one way of controlling them.

This morning while picking even more Hornworms off the tomatoes, I came across one that I though you should see. It had been parasitized by a small insect  known as a braconid wasp.

These tiny wasps  fly around the garden looking for likely victims. When they find a suitable host, they sting the caterpillar and lay their eggs inside its body.  The eggs hatch and the larvae feed on the innards the worm.  As the wasp larvae near the pupation stage, they chew through the caterpillar’s skin and spin small white  cocoons made of silk which remain stuck on the surface of their host. The cocoons are sometimes mistaken for eggs by some gardeners.

This Hornworm has 3 or 4 dozen cocoons on its back. Each cocoon contains one wasp that will emerge and begin hunting more caterpillars to parasitize.

Days later the new fully-developed adult wasps will emerge from the cocoons and  fly off to find new caterpillars to parasitize.  Needless to say the caterpillar does not survive the procedure, which is good news for us gardeners.

The adult flying wasp does get hungry but does not eat caterpillars instead it feeds on nectar from flowers

If you find a caterpillar with these cocoons on its body, leave it undisturbed where you found it so that you will have dozens more helpers in the battle against the Tomato Hornworm.


Tomato Hornworms Are Back

The week before last I saw the first few Tomato Hornworms in our garden. I was able to take care of them pretty quickly by picking off the first two or three.

Today they came back with a vengeance.  I found Hornworms all over our tomatoes. Here’s the first batch I “harvested” from the plants:

The first batch of today's Tomato Hornworms.

There are a few alternatives  you can use to get rid of Hornworms these include spraying chemical or biological insecticides, applying  insecticidal dusts or picking them off by hand, the method I prefer.

Whichever method you choose, do it quickly. They can grow from cute tiny caterpillars that hardly make a mark on a leaf to monsters like these  in just a few days. Once they reach this size, they can literally devour an entire plant overnight.

If you decide to use the hand pick method, here’s a tip that will help you find them.  Since Hornworms’ camouflage is so effective, they can be very difficult to detect. Go thorough your plants and pick off the ones you see right away. Then go do something else in another part of your garden for a while, even ten or twenty minutes will do.  This gives your eyes a chance to “re-set”.  When you come back to look for the worms, you can often spot the ones you missed the first time through.

It also helps to check them a couple times throughout the day. As the light changes, you may be able to spot the rest of them that are hiding.

In my first time through my plants I found this batch of worms.  After about a half an hour, I found eight more in the same spots I looked at the first time around!

You may be wondering what I was going to do with a bowl full of Tomato Hornworms. I took them over to our chickens and tossed the worms  in one at a time. This provides loads of entertainment for both the chickens and myself.  The chickens like to play several games with the worms like “Chicken Football” and ” Chicken Rugby” and my favorite “Tug of War”.

To avoid a lot of  disappointment,  check those tomato plants as soon as you can… before you head out to the beach.


Apple Codling Moth

Growing good apples is a little tricky because of all of the pests that feed on them and cause damage to the fruit.

We discussed the Curculio a couple of posts ago, this time we need to talk about another major pest on apples, the Codling Moth.  This is the proverbial “worm in the apple” that you see in those old-timey cartoons. It is not a worm as such but rather is the larva of a moth.

The Codling Moth is not a very attractive moth as seen in this photo taken by MSU Horticulturists.

Normally there are two generations of this pest in our area although in some years we see a third generation as well depending upon that season’s weather.

According to scientists who measure certain weather and other conditions, the Codling Moth larvae are hatching from their eggs right now.  After the larvae hatch, they will begin to burrow into the fruit.  Once they get inside the fruit they cannot be killed because  insecticides cannot reach them.

Codling Moth damage on apple. (MSU photo)

Timing is very critical for controlling Codling Moth effectively since the larvae begin to burrow into the fruit just hours after hatching. Large commercial orchards use sophisticated traps to monitor adult moths. With that information they can determine when egg laying happens  and apply their sprays accordingly.  For the rest of us we have to pretty much rely on our 10 day to two week spray schedule to do the trick.

Michigan State University Extension in Van Buren County has a very detailed web page regarding this pest.

Another generation of Codling Moth can be expected in August.



I decided to expand our vegetable garden this year by converting some of the wild area behind the existing garden into usable garden space.

While tilling and planting I found these subterranean dwelling insects known as “wireworms”.

You can see by the photo how they got their name, they sort of look like a piece of copper wire and have a hard, shiny exterior skin.

Wireworms found in the garden.

They are actually the larval form of the “click beetle”. These are beetles that make a “click” when they flip themselves up onto their  feet if they some how ended up on their back.

There are several species of wireworms out there and are commonly found in newly tilled sod, like my area, or in gardens that have not been weeded very thoroughly.

There  are also species that prefer garden crops, the potato is especially vulnerable to wireworm attack. Damage in potatoes shows up as reduced yield caused by the larvae  chewing on the roots and as holes burrowed into the potato tuber itself.

Years ago there were many insecticides that would eliminate wire worms in the garden, those have all been taken off the market due to environmental concerns.  Your best bet to reduce wire worms in the future  is to keep your garden free of weeds throughout the gardening season. There are also some biological products on the market that show some promising results in keeping wire worms in check.

Keeping wireworms away is another good reason to keep that garden weeded!


Dog Tick Season

We found our first Dog Tick (sometimes called Wood Tick) of the season this past Saturday. The warm weather has brought them out early this year.

On our property, this has been the only species of tick we have encountered. Fortunately the dog tick does not carry Lyme Disease.

Dog Ticks are about 3/16" long.

The experts at Michigan State University has this to say about the pests:

Their bites rarely result in serious disease in Michigan, but like other wood ticks, dog ticks are a known carrier of Rocky Mountain spotted fever and tularemia. The cases of Rock Mountain Spotted Fever reported in Michigan have been from primarily southern counties, particularly those located directly north of the Toledo Airport.

Hmmmm… that comment about Rocky Mountain Spotted Fever being found in the counties “directly north of the Toledo Airport” doesn’t give me too much comfort. I guess the lesson to be learned is that you need to check yourself and pets for ticks after spending a day walking or working in an area with tall grass or shrubs.  The ticks crawl up onto tall grass or shrubbery and wait for a likely host to walk by, usually a dog or cat (or raccoon or other wild animal). They don’t use trees for this purpose.

I spend a lot of time outside, sometimes in areas like those described, and do find a tick now and then. The most I’ve ever found on myself at one time was five ticks. That was several years ago. It was a bad tick year and  I spent the whole day working out in an area with tall grass.

If you find the ticks right away, they are easy to remove. The longer they stay on, the harder it is to get them off. The ticks have barbs on their mouth that they use to dig deeper and deeper into your skin until they find blood.  It takes them a few hours before they actually start “sucking blood” so usually you have plenty of time to get them off.

The recommended procedure for removing ticks is to use a pair of tweezers and grab them right at the surface of your skin then lift them straight out without twisting them. Avoid squeezing them to keep their “saliva” from being squirted back into your or your pet’s skin.

If left on too long, they will continue to feed on blood until they get “big and juicy” looking something like a disgusting, brown grape…yuk.  Don’t let them get to that point!  Sometimes you can find a tick starting to swell from feeding on a long-haired dog. This is  because when the ticks are small they are easily hidden under long fur.

Be aware that the ticks are out now and check your pets often.


Eastern Tent Caterpillars are Hatching

Those nasty tents of caterpillars that you see up in the trees in early summer have already begun to appear.  The above average temperatures we have been experiencing has caused our local population of  Eastern Tent Caterpillars to hatch from their egg masses during the last couple of days.

The egg were laid last fall by the adult tent caterpillar moth.

It is very easy to get rid of the caterpillars right now because they are only about one-eight of an inch long and very susceptible to sprays or even just squashing by hand.  Look for the masses near the ends of the twigs of apple, cherry, plum and other related trees. The egg masses are a little difficult to spot, but once you have see one, it’s a lot easier to recognize them.  Many times you can simply snip off the twig containing the egg mass and discard it.

This egg mass is already covered with a fine tent web spun by the caterpillars. The dark specks are frass (droppings) from the caterpillars.

The  egg masses look like a blob of foam that has dried out and hardened. The caterpillars spend the winter in these eggs then hatch out the same time the trees begin to leaf out in the spring.  These very tender newly “sprouting” leaves are like baby food to the newly hatched infant  caterpillars.

The tiny caterpillars are clearly visible in this photo.

Sometimes, if a severe rainstorm occurs during this stage, many of the caterpillars will be washed away.  Perfect timing of a storm doesn’t happen very often so I wouldn’t count on that to control your problem.

The “tent worms” will feed voraciously and devour a lot of leaves but generally won’t kill a tree or cause any  lasting damage.