Spider mites

Do you have webbing covering plants in your landscape? Or maybe, you have webbing covering some of the leaves on your plants? Check the underside of the leaves for spider mites.

Spiders mites are not insects, but arachnids more closely related to spiders. They are very small, often looking like little dots running around on the leaf surface. If you look with a hand lens, you'll see that adults have eight legs and oval shaped bodies. Immatures resemble adults (except for the first stage out of the egg which only has six legs), but will be smaller in size.

Spider mites thrive and reproduce rapidly in hot weather, so conditions have been great for them lately. A generation can be completed within a week when conditions are favorable. Plants under water stress can become infested with spider mites.

Spider mites cause leaves to get a speckled appearance, called stippling, where the mites suck juices from the plant. Leaves may also turn a yellow or bronze color and eventually drop off. Leaves and other parts of the plant may also become covered with webbing.

So, what to do about spider mites?

• First off, check that you have an active infestation. Many times people see spider mite damage, but the mites are long gone.
• Ask yourself if you need to do anything or are beneficials doing the job for you.
• Avoid spider mites by reducing stress to your plants with planting in the proper location, watering and fertilizing properly.
• Try knocking spider mites off the plant using high pressure water spray.
• Be aware that sometimes pesticides may cause spider mites to become more of a problem after they are used.
• If you choose to use a pesticide, treat the underside of the leaves where spider mites like to hang out.

Juniper budworm & Spider mites

I've had a few people contact me late last week about their juniper trees (sometimes called cedar trees) turning brown and needles dropping off.  I was able to get a sample sent in from the Liberty Hill area and found webbing along with spider mites.  About 10 minutes after looking at the sample, I got an email from Pat Porter about another problem case with junipers in Central Texas, but this time the culprit was the juniper budworm and was in the Bee Caves area.



Juniper budworm. Photo by Steve Darnell.

You can find more information on spider mites here.

As for the juniper budworm, the caterpillar is the damaging stage.  It is small to medium in size (depending on the instar) and green with a brown head capsule.  The caterpillars, or larvae, feed on juniper foliage and construct silken tubes where they are protected.  The tube is also where the insect pupates.  Adults are small brown moths in the family Tortricidae (also known as leafrollers).

Branch with juniper budworm. Photo by Steve Darnell.

If trees are prized landscape trees that provide screening or shade, then control may be warranted.  For management without chemicals, try handpicking the infested branch tips.  You can place them in a bucket of soapy water or double bag them and throw them in the garbage.

There are natural controls by beneficials (birds, wasps, flies, etc.) that help to mange these insects, so if you choose a chemical control method, choose wisely.  You can target caterpillars only by using Bacillus thuringiensis var. kurstaki.  Other less-toxic active ingredients include spinosad or azadirachtin.  Other possible active ingredients include things such as lambda-cyhalothrin, imidacloprid, carbaryl or acephate.