Fall Armyworms

I have been getting questions on armyworms and consulting with other entomologists, they have been as well.  So, instead of me recreating the wheel, I am going to link you to a publication written by Dr. Allen Knutson.

Also, if you want to learn how to prepare your home to keep unwanted guest- in this case insects, not relatives- from entering your house, check out this month's All Bugs Good and Bad webinar provided by Janet Hurley.

Walnut caterpillars

An outbreak of walnut caterpillars has recently been reported in Fort Bend county.  These caterpillars can be found on pecan, walnut, and hickory as well as oak, willow and various woody shrubs. Walnut caterpillars have chewing mouthparts and can defoliate trees.

Walnut caterpillars live together in a group after hatching out of the eggs. As they grow, they are reddish-brown and become covered with long, white hairs. Larger larvae are covered in white hair and can grow up to 2 inches long.

Walnut caterpillar larvae first instar and egg mass. Photo by Bill Ree.

The way damage appears depends upon the stage of caterpillar you have.  Young caterpillars only feed on soft tissue of foliage, so you get skeletonized leaves.  Older larvae eat all parts of the leaf.  The majority of damage is caused by the last few instars of the caterpillar.  This leads to the conclusion that scouting for these insects early and often can help you control walnut caterpillars before too much damage occurs.

If you discover egg masses or newly hatched larvae in a cluster, you can remove the infested leaves by hand and dispose of them in a sealed plastic bag.  Groups of caterpillars found on the tree trunk or branches while they are molting can be squished or treated with insecticide.

Walnut caterpillar larvae third instar. Photo by Bill Ree.

If walnut caterpillars are found on your trees, then you can treat them with Bacillus thuringiensis var. kurstaki which is a product that targets caterpillars.  Other possible active ingredients that can be used include: spinosad, azadirachtin (neem), pyrethrins, or a pyrethroid product.

If you have an outbreak of walnut caterpillars, please contact Bill Ree as he is tracking this information.

Caterpillars- buck moth caterpillar, cankerworms and tent caterpillars

Cankerworm

The insects seemingly have arrived in our demogarden the past week.  I was out there with Master gardeners this morning and there was a lot to see....it makes me EXCITED (the Master Gardeners, not so much, as many of the insects are eating the plants they are tending so carefully).

So two items have already been covered recently in blog posts written by Dr. Mike Merchant in Dallas, so I'm going to direct to those pages and you can get all your information there.

Tent caterpillar

First are the tent caterpillars.  I had my neighbor find one last weekend and she sent me a picture for identification.  Mike's post on tent caterpillars.

Secondly, would be the cankerworms.  If you have oak trees in your area (and this is Texas, so who doesn't have oak trees, right?) then you probably have seen these or at least evidence of their activity.  Have you seen the silken threads hanging down from trees?  If so, then you have seen webbing from cankerworms.  Again, Mike has a great post on cankerworms here.

The last thing I want to cover is a caterpillar you DO NOT want to pick up.  This caterpillar has branching spines that can deliver a sting if touched.



Buck moth caterpillar

Buck moth caterpillars typically have a background color that is dark, but they can have varying coloration so some can be very light.  The body has white spots and the spines are double branched and form multiple rows along the body.  They can be almost 2 1/2 inches when fully grown.

Buck moth larvae are gregarious and will group together for the first three instars (smaller caterpillar stages).  After the third instar, they will wander off from the other caterpillars to feed on other plants until it is time to pupate.  And remember above how I was talking about oaks in Texas?  Well, that is the preferred food of buck moth caterpillars.

The adult buck moths are quite pretty and have a wingspan of 2-3 inches.  Wings are blackish in color with a white stripe running through the center with dark eyespots. Females have a solid black body while males have a black body with the tip of the abdomen being reddish-orange.

As mentioned previously, you DO NOT want to pick up the buck moth caterpillars.  The branching, urticating spines can deliver a sting when touched.  Reaction from the sting can vary but may include immediate pain, itching, swelling and redness.

 

Hornworms...sphingid larvae

A researcher asked me to pass the following along. He is researching sphingid larvae and would like to know the distribution of particular species.

Keep your eyes open for any Sphingidae larvae that look like the ones on the link below. They
feed mostly on mint, sage, Verbena, lantana and Monarda.
http://www.silkmoths.bizland.com/Lintneriaspecies.htm
If you know anyone else who has a garden who might grow those plants, please forward the link.

If you find the larvae, you can contact:

Bill Oehlke
155 Peardon Road
Montague PEI
C0A1R0
CANADA
oehlkew@islandtelecom.com

The Monarchs have returned!

Have you seen them? They're baaa-aack! It always warms my heart a bit when I go outside to look at my milkweed and find monarch caterpillars or their chrysalis dangling on the branches.

Monarch caterpillars are pretty distinct. Obviously, they are a caterpillar, so they have a worm-like body that is yellow, white and black striped. The caterpillars have two long, black projections that look similar to antennae towards the head region and then two black shorter projections near the end of the abdomen.

The pupa, or chrysalis, is usually formed on the milkweed plant and starts off bright green with metallic gold at the top. The chrysalis will change colors as time goes on and the caterpillar transforms into a butterfly. It eventually becomes transparent and you can kind-of see the butterfly inside.

After the adult (the butterfly) emerges from the chrysalis, it spreads it's wings and stays in place for several hours to allow it's exoskeleton to dry and harden before it can fly away.

It's not fall yet, so why do I have fall webworms?

While I haven't been getting many questions on them, I thought I would address fall webworms since I've been seen tons of webbing in trees all over town. Webworms can attack over 88 species of plants, but are often seen on pecan trees in Texas. We have 2-4 generations each year that start in the spring and continue into the fall. Fall populations are often the most damaging, giving the name fall webworms.

Caterpillars, the immature state, are very pretty in my opinion. They are about an inch long when fully mature and are pale greenish-yellow with long tufts of hair projecting from their body. Adult moths are somewhat drab with whitish coloring and small, dark spots on the front wings.

When caterpillars emerge from the egg, they immediately begin to spin the webbing that is expanded to cover the tree's foliage. The caterpillars use the webbing to protect them from predators. They enclose the foliage that they feed on and will expand the web size when they run out of foliage to eat.

So, options for managing webworms really depends on how annoyed you may be with the webbing, how large the tree is and what kind of effort you want to give to manage the caterpillars. Egg masses can be pruned or picked off the tree (egg masses are on the underside of leaves and typically covered with hairs). Pruning webs out of the tree or opening the webbing with a stick or stream of water can also help to manage populations. Pruned webbing should be disposed of in a sealed, plastic bag or dunked in a bucket of soapy water to kill the insects. Opening the webbing can allow predators to enter the web and help manage the pests. You do not want to burn the webbing out of the tree as this can often cause damage to the tree as well as being dangerous.

Of course, there are also chemical options. Less-toxic options include using active ingredients such as Bacillus thuringiensis variety kurstaki, also known as Bt. This variety of Bt specifically targets caterpillars, but will not differentiate between "good" and "bad" caterpillars, so avoid drift. Spinosad which comes from a soil microorganism is another option. Both of these chemicals must be consumed for them to work properly, so good coverage of the foliage is key (hence, you must open the webbing to get the chemical to where the caterpillars are feeding!). These options work best on smaller caterpillars (less than 1/3 inch).

For management of larger caterpillars, contact kill chemicals work best. Some active ingredients to look for include permethrin, cyfluthrin, carbaryl or acephate. Again, the chemicals have to get into the webbing where the caterpillars are located or they will not work very well.

Of course, you can always choose to let the caterpillars do their thing. The trees and caterpillars have been here living together for many, many years and nature always seems to find a balance of things on it's own.

Also, don't expect webbing to disappear from the tree once the caterpillars are gone. You will either have to wait for a heavy rain or use a high pressure water stream to knock the web out.

What are these holes in my plants?

The majority of questions that I fielded last weekend were regarding what could be chewing holes in the foliage of plants. Caterpillars, grasshoppers and leaf beetles come immediately to mind. Of course, everyone also wanted to know what they could do about the bugs.

First, look at the damage to determine if it's old or new damage. New damage will appear "fresh" and be green around the edge of the wound. Old damage will show browning around the area that has been chewed. If you have old damage, it's most likely too late to provide treatment as the bugs could have moved on to bigger and yummier plants. If it's new damage, first look for the bugs that could be doing the damage. This is where a bit of basic entomology comes in handy so you can properly identify what you're seeing. Try looking images up online (make sure to utilize a reliable resource such as a university or extension service). The TAMU entomology website hosts a variety of resources here:
http://insects.tamu.edu/websites/
If you can't find what you've got, you can always contact me for help.

With insect pests, it's usually better to try managing them early when they are still small. Why? Well, for one, they're small which is often easier to kill. Secondly, they are not as mobile as in the adult stage. Remember, adult insects have wings and can fly away, immatures have to hop, walk or crawl.

So for chewing insects, what are your options for control? Cover the plants with row cover to exclude the insects or hand pick the insects (wear leather gloves in case they try to bite you) from the plant and drop them in a bucket of soapy water. If you have a lot of insects or a lot of plants, you can try using a shop vac to suck the insects off the plants. Other options would be using products with active ingredients such as spinosad (get good coverage on foliage since insects have to consume this for it to work!), neem, d-limonene, pyrethroids (cyfluthrin, bifenthrin, deltamethrin, etc.) or carbaryl. Remember, when you choose pesticides, find ones that have the location you are treating on the label and follow all label instructions!