Orchid Pests - By Mark Govan, Host “Florida Gardening” | ABC Pest Control Inc.

Some of my favorite flowering plants belong to the largest family of flowering plants, these are the Orchids. With as many as 35,000 species, everyone can pick their own favorite. Although many people think orchids are hard to grow, when properly grown under the shade of a tree or overhang, orchids can grow with minimal care. In fact, many people grow orchids indoors on trays filled with gravel and water. Because there are a few problems orchids get, let’s go over a few problems people seem to have when growing orchids.

I get many complaints from listeners of my radio program describing yellow leaves especially on the Cattleya orchids. This is a common problem due to too much light, too much water, or lack of nitrogen fertilizer. If you plant has been in the same place through the summer, look to see if the light the orchid receives has changed and move the plant accordingly. Too much sun can injure the leaves and cause them to turn yellow. Too much water can also cause the same problem. In some cases I have suggested removing the drip pan from beneath the orchid to allow the plant to drain through. Lengthening the time between watering can also prove to be an easy fix. Fertilizer should be applied every other week using a liquid fertilizer or fertilizer which is mixed with water and applied at one half the labeled rates. Orchids like to be fed sparingly but often. I like to use either Miracle Grow or Peters 15-15-15. Again, please use at half strength every other week!

Black spots on leaves or large blackened areas on the surface of the leaf are a sure case of sunburn. Try moving your plants to an area that does not get as much sun. Remember, as the seasons change so does the suns direction. By moving your plants to another area or maybe shading the plants with other hanging plants, your orchids can continue to grow in the same area for many years. If your plants already have been scorched, but there still is some green to the leaf, do not cut the leaf off until the plant produces additional leaves. Leaves which are completely yellow or dead may be removed at any time. Be sure to clip the leaf off with a sharp pair of pruning shears.

Blackened tips on an orchid leaf could be a sign of over fertilization. Plants that do not have good drainage or have a dense matting of roots tend to hold more water in the pot which can cause a salt build-up within the container. To correct this problem simply stop the fertilization process for a month and flush the plant with clean water several times allowing the plant to drain through completely. This process will wash the salts through the planting medium. You can continue fertilizing after one month.

Small brown or reddish black spots on the leaves may be a sign of a fungal problem. High humidity or poor light could be the cause. Increase light around the plant but only filtered light is recommended. Also, try to decrease the humidity by misting the plants less often. Sometimes, a fungicide such as Daconil is needed to control this fungus.

Scale insects and mealybugs can be troublesome on many orchid varieties. Scales look like small circular spots (1/16^th of an inch) on the leaves but if you push them with your fingernail they pop off the leaf. Mealybugs are a little larger than a scale insect and are white and hairy. Many small mealybugs can usually be seen crawling on your plant usually under the leaf. Control measures need to be taken if you can not simply wipe them off your plant with a small cloth. For people with many plants, spraying with an insecticide such as Talstar (the active ingredient is Bifenthrin) is much more effective in removing these pests permanently. Be sure to water your plants the night before your application and then only mix enough Talstar to use on your plants. Do not keep unused mixtures for later use. If you mixed extra use this mixture on other plants you have outside. Read the label to make sure you are mixing properly. For plants that are inside the home, I recommend you take the plants outside the home to treat then place them in the shade and return to the house after a few days.