Question
Hi! I've brought some outdoor annuals inside, and I think they brought the pest in with them. They are itty bitty worm-like things that have made webs all over the plants. (I've looked up webworms and silkworms, neither of which look like these worms.) They've also burrowed inside the leaves; then that spot gets see-through and the worm seems to die? and turn black but the black string of it spreads. I've also noticed little black dots on the leaves - maybe their poop or their eggs? When I brought them in and planted them, I cleaned each leaf and removed the really bad ones. But they've reappeared. I'm kinda thinking they're leafminers, but I haven't seen any adult flies, which I assume I would've seen on the plants when I brought them in. Any other ideas?

Answer
Hi Heidi,
  I am not sure exactly what type of insect you are having a problem with. None of the signs you describe really fit any one type of insect. One possibility is there are more than one type of insect/mite on the plants. The most common insect/mite that produces webbing is spider mites but neither the larvae or adult stage of spider mites even remotely looks like worms. Spider mites also do not fit some of the other signs you described.
It could be problematic if you have both leaf-miners and spider mites on your plants. The best and most effective way to get rid of leaf-miners is to use a commercial systemic insecticide. However spider mites are very often resistant to chemical insecticides and the only effective treatment for them is either a commercial insecticidal soap spray or a homemade soap based treatment. Unfortunately, insecticidal soap sprays (commercial or homemade) will do little to effectively control leaf-miners. You will likely have to use both forms of treatment to rid your plants of pests.
Since the plants spent the summer outside, I would also recommend that you change the potting soil in case any soil dwelling pests took up residence in the potting soil your plants are in.

Here is some information about insect/mite control on houseplants. This information should help you effectively treat your plants for any and all insects or mites that are currently residing on your plants.

(The following information is copied from a guide I wrote on pest control on houseplants. If you would like to read the entire insect control guide or other guides I have written on plant care, you can find them on my Myspace page. The web address is  myspace.com/experthouseplants )

~ Spider Mites are tiny, spider like mites that can barely been seen with the naked eye. The most common Spider Mite is the Two-spotted Spider Mite, they have soft pear shaped bodies with 2 dark spots on their backs. The most visible sign of a Spider Mite presence is webbing on the undersides of leaves and between stems, however, webbing indicates a high population of Spider Mites. Although Spider Mites are very hard to see with the naked eye, their eggs can usually been seen easily, grouped together on the undersides of leaves. Looking at the underside of a leaf at a slight angle is also helpful in making the eggs (and adult spider mites) easier to see.
Spider Mites are very difficult to get rid of or control. Often they are resistant to chemical pesticides and many insecticides do not work for Spider Mites. If you are going to use a commercial pesticide be sure that it is listed on the label that the product is effective for Spider Mites.
The first step in getting rid of spider mites (and most crawling insects) is to spray the leaves, especially the undersides, with a strong spray of water. This will wash off as many of the insects as possible. Since Spider Mites are often resistant to most chemical pesticides it is best to use an insecticidal soap spray. Another good thing to use is pesticides made with neem oil. Be sure to cover all leaf surfaces completely. Repeat treatment every 5-7 days until there is no sign of Spider Mite presence.

There are several different types of commercial pesticides available. There are traditional chemical pesticides, insecticidal soap sprays and systemic pesticides. Always check the label of any pesticide you are thinking about using to make sure that the insect you want to get rid of is listed on the label. Also, as a general rule, always look for 'Houseplants' somewhere on the label of any product they want to use on houseplants.

~    A lot of people commonly use dishwashing liquid to make homemade insecticidal soap spray, but some dishwashing liquids contain a lot of perfumes, dyes and degreasers that can be harmful to plants. However I have used Dawn dishwashing liquid on plants for years and have never had a problem. Choose a dishwashing liquid that does not have all the perfumes and dyes if you can.
Be sure to rinse the plant thoroughly after spraying the plant with or dipping the plant in soapy water. Never leave soapy water to dry on a plant. Also never use any kind of liquid hand-soap, such as Softsoap, on plants.
To make a homemade soap spray, add several drops of dishwashing liquid to a spray bottle filled with distilled water. You can fill a large, deep container with soapy water or fill a sink with soapy water to make an insecticidal soap dip. Making insecticidal soap as a dip is especially helpful for soft leafed plants, such as African Violets and for small dense plants.
The drawback to insecticidal soap sprays is there is no lasting effect and you may have to repeat treatment several times.
To be effective, all leaf surfaces, especially the underside, needs to be wetted thoroughly with the insecticidal soap.

~ Of the commercial chemical pesticides, the one being used most these days is products containing Imidacloprid. Imidacloprid is not as toxic as most traditional pesticides and just as effective. However, it is still a toxic pesticide.
Pesticide products made with Neem oil are effective on most insects, including Spider Mites, and a lot less toxic than other chemical pesticides. Neem oil also has anti-fungal benefits, which is why most ' 3 in 1' products are made with neem oil. Neem oil is safe to use on most plants.
No matter what type of spray pesticide you use, always spray a ' test leaf' before spraying the entire plant with any pesticide product. Wait at least 24 hours then check the test leaf, if there is no damage to the test leaf then continue to treat the rest of the plant.

~ A systemic insecticide is a insecticide that works by getting absorbed into the plant and distributed throughout all parts the plant. When an insect feeds on the plant it is poisoned. Systemic insecticides are especially good for severe infestations or reoccurring insect problems. There are two forms of systemic insecticides, one is a granule that gets mixed into the soil and is taken up into the plant by the roots. This form of systemic takes time to take effect, often 5-10 days. The other form is spray systemics. This form of systemic is sprayed onto the plant's leaves and is absorbed into the plant. This form works like a spray insecticide, killing insects on contact, then works as a systemic for lasting control.

I hope this helps. If you have any questions or need additional information please don't hesitate to ask.
          Thanks
              Tracy