Friday, May 19, 2017

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 first instar larvae and egg mass
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 caterpillars third instar. Photo by Bill Ree.
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.

Friday, May 12, 2017

Stink bugs- have you seen me?

immature stink bug genus ChlorochroaYesterday as I was perusing the demo garden outside the office for insects (it's how I take a break...) when I came across a plethora of stink bugs.  There were adults. There were nymphs. There were even eggs!  I took photos and planned on using them for some future endeavor at the time unknown me to when.....

stink bug genus Chlorochroa seems to be the time for the photos.  I received an email this morning asking what the bug was that I had discovered in such high numbers yesterday.  I am assuming that since I'm now getting emails, it means that they are not only in East Austin, but in many other places as well.  Head out to your gardens and take a look to see if you can find stink bugs!

The stink bugs I found are in the genus Chlorochroa.  They can be from 8-19 mm (1/4-3/4") and can range in color from green to brown to black.  Around the edge of the body there is a white to yellow to reddish-orange stripe.  Nymphs and adults feed on plants.

stink bug eggs genus ChlorochroaIf you have these critters, you can try one of my favorite ways to manage stink bugs....the vacuum. You don't want to use your regular, household vacuum, but have one specifically for the garden.  I find that cordless, hand-held models are quick to grab and easy to use in the garden.  Don't buy a top of the line model with a lot of suction as they will also suck up a good bit of your plants.  Another option is to hand pick and dump the bugs into a bucket of soapy water.  If you find eggs, then either pluck off the leaf and throw it away or squish the eggs.

If you're not into vacuuming or hand picking, then you can try pesticides with active ingredients such as azadirachtin (neem), pyrethrins, lambda-cyhalothrin, beta-cyfluthrin, or imidacloprid.  If you have nymphs, you can try using an insecticidal soap.