For centuries we have been bringing a slice of outdoors into our homes and workplaces
with green and blooming plants… and for centuries we have had to deal with the insects
and diseases that accompany them. We ask plants to grow in an environment totally foreign to them and it can be a challenge to deal with their pests. The pests often the same ones that we have with our garden plants, but they can be a little more difficult to deal with indoors. The key to minimizing insect and disease problems indoors is to keep the plants as healthy as possible and try to duplicate their natural preferences. Even when we do everything we can, sometimes pests occur.  Almost every gardener, expert or not, has had a pest problem get out of control.

How do I know if it is an insect or disease? Some insects can be seen easily, but some take a magnifying glass. If the problem is not clearly identified as an insect, you have to determine the cause based on the type of damage to the plant.

What are some of the common signs of insects? Sticky spots, stunted or malformed growth and a rough feel to the leaves are all indicators of insect problems. And, of course, you might be able to see the bugs.

Are there common insects for indoors? Aphids, mealybugs, scale, whitefly and spider mites account for almost all of the insect problems indoors. Even though that sounds like a lot, you seldom have more than one problem at a time, and many plants are prone to problems from only one or two types of insects.

Are there cultural methods I can use to deal with insects instead of using chemicals? Keeping your plants as healthy as possible and unstressed will go a long way towards avoiding severe insect problems. Depending on what type of insect, you may be able to simply clip off the affected leaves and remove the pests. Whenever possible, a good shower washes off many of the pests, especially if you have a hand- held shower and can spray the underside of the leaves. This will minimize how much chemical spraying you might need to do.

If I need chemicals, what should I use? There are several options. First, make sure the chemical is labeled as safe for indoor use. Organic products that are effective include insecticidal soap, horticultural oil and pyrethrum. If all else fails, (or if you aren't going to be around to repeat applications) you can use insecticide granules. They are a systemic insecticide that you water into the soil. It is taken up by the roots and distributed throughout the plant, killing sucking and chewing insects.

How do I know what insecticide to use on my plant? Read the labels to make sure the insecticide will target your insect problem and that it is safe for your plant. Not all insecticides can be used on all varieties of plants. Whenever possible, start with insecticidal soap or pyrethrum before you resort to stronger chemicals.

How should I deal with aphids? Aphids multiply so quickly that they can be scary, but they are extremely susceptible to almost all insecticides. Start by giving the plant a good shower if possible. You'll notice almost all the aphids are on the most tender young tissue and you may want to just snip off those pieces and dispose of them. Then spray, especially the underside of the leaves, being sure to get all the surfaces. Watch for new aphids and spray again if needed in a week or so.

How about mealy bugs? They can be wiped off using a Q-Tip dipped in rubbing alcohol. Check over your plant on a regular basis and wipe off the mealy bugs as needed. You may also choose to use an insecticide to control the immature stages of mealybug that are not visible.

I think I have spider mites but I'm not sure. How can I tell and what can I do? Spider mites are so small you can't usually see them, but they leave the plants looking extremely rough, almost rusty; the foliage takes on a stippled appearance. If severe, you may see some webbing. Check by snipping off a piece and tapping it hard over a piece of white paper and watch for tiny, tiny specks to start moving. To rid a plant of spider mites, you will have to spray several times with a pyrethrum. Misting the plant frequently with
water reduces most spider mite problems: Spider mites prefer warm, dry conditions much like we have in our homes during the winter. Check your plants regularly — you might be able to control a spider mite problem before it gets out of hand.

I have a scaly growth on the stems of my plant, but it doesn't move. Is it an insect? What should I do? That scaly growth or brown bump is the immobile adult form of a scale insect. The only effective way to deal with scale is to gently rub them off and treat the plant with a horticultural oil or rubbing alcohol. Systemic insecticide can also be used. Scale, like mealybug, has an immature stage that is not visible to the naked eye. Insecticidal soap can be used to treat this 'crawler' stage.

How about whitefly? Whitefly is especially difficult to control because it is usually on your plant in several stages (adults, larvae and eggs) and not all stages are susceptible to insecticides. Spray with a gentle insecticide such as pyrethrum. You should repeat this process again in three days — and again in three days to make sure you get all the life stages. If you don't follow up, they will be back.

And what are those little things that look like fruit flies? Those are fungus gnats and they are a common pest in soil that is being kept too wet. To avoid fungus gnats, simply keep the soil drier. Insecticides are usually not warranted, and unless there are hundreds of gnats, they don't damage your plant. The adult gnats live only 48 hours.

What are the signs of disease? While some diseases are easy to detect, others look just like the damage caused by poor cultural conditions. Watch for large, irregular brown spots on the leaves, molds, mildews or rotting on the stem or roots.

Are there cultural methods to deal with diseases? Over-watering can allow many diseases to set in and damage a plant. Monitor your watering practices carefully and try to keep the plant as healthy as possible.  Generally speaking, the healthiest plant is grown lean (that is, with little fertilizer) and with only just enough water.

If cultural methods don't work, are there chemical treatments? Most diseases are caused by fungus and it is important to understand that fungicides are very effective preventatives, but are not good treatments. Once you have a disease in progress, you may minimize its spread by using a fungicide, but that won't help what is already damaged. Even when using fungicides, it is important to follow the cultural recommendations
at the same time. Usually, it is best to remove any badly affected parts of the plant.

Are the brown spots on my leaves caused by disease? Brown irregular spots on leaves are usually caused by a fungal disease and are almost impossible to treat. Remove and dispose of the leaves with spots. Keep your plant drier and well ventilated. When watering, be sure to water the soil surface and not the leaves.  Keeping the foliage dry will help prevent the spread of  fungus.

I've had problems with the stems rotting. Is this a disease? Stem, crown and root rots are all fungal diseases almost always caused by over-watering or poor drainage. As with most diseased plants, you will need to remove the affected portions. Unfortunately, with rots you often have to let the plant go and start over.

Recommended Products
Safer's Insecticidal Soap
Bonide All Season Oil
Sticky Yellow Traps
Gardening Tools and Gloves

 ©Bachman's 2008