What is this white fuzzy stuff on the leaves of my orchid? Laura S.
'White fuzzy stuff' can describe anything from cotton balls to confectioner's sugar but horticulturalists know exactly what you mean. The dreaded insect, Mealy Bug, is at work here. Rarely fatal, this pest usually causes minor physical damage by sucking the juices from the leaves and flowers.
What makes this insect so exasperating and thoroughly despised amongst growers is the difficulty in getting rid of it 100%. It seems those 'critters' (highly scientific term) keep coming back regardless of treatment. We have found that it takes repeated applications of the correct pesticide to have a fighting chance of beating this formidable adversary.
One relatively people safe pesticide that is popular contains the active ingredient, pyrethrum (extracted from the Chrysanthemum daisy), and is sold premixed with water and packaged in a ready-to-use spray bottle. This product works by chemically poisoning the insects, then degrades very quickly into harmless compounds.
Another good option is a highly refined horticultural oil concentrate that when mixed with water in a 2% solution works effectively to physically smother the insects. This technique is attractive because there is no chance of chemical resistance. There are some strict application rules, however, such as keeping the oil and water constantly agitated and spraying only on cloudy days.
Treating mealy bugs, like growing orchids, requires patience and perseverance. The tops and bottoms of the leaves should be thoroughly sprayed every week for about a month outdoors. If the 'white fuzzy stuff' is on the blooms, there are too many hiding places within the petals and it is best just to cut off the flower stem.

I recently purchased a Phalaenopsis that had a bruise on a leaf. That leaf soon turned yellow and fell off. Now the other leaf is turning yellow. Can it survive without any leaves? Laura D.
No. Well, maybe. There is a chance, a slim chance. But don't hold your breath...
Every once in a while, a Phalaenopsis that has crown rot and has lost all it's leaves will make one last great effort to live by sending forth a new leaf from either the former center of the plant or from the side.
Amazingly, the leaf grows quite rapidly since it is using the existing root ball which is still alive in the pot. A second leaf may follow of equal size. Before long, the plant is full strength once more. The chance of this happening is 10%. Make that 5%.
Much better luck can be had by taking care of the plant initially rather than hoping for miraculous recoveries. Informed orchid buying goes along way to head off potential problems and involves more than just selecting 'pretty flowers'. The foliage should be plentiful and be a healthy medium green color with no bruises, cracks, or cuts where disease can set in.

My bark mixture looks dry even after I water it. Should I continue with my watering twice a week and spraying every day? Pat H.
Watering yes. Spraying no.
Orchids that are planted in bark chips are typically Cattleyas, Dendrobiums, and Oncidiums, and are quite happy with a regular twice a week watering regime.
The medium does indeed always seem dry so an easy to remember bi-weekly schedule is the most practical. A thorough watering consists of a good solid drenching so that every single root gets wet. When possible, choose sunny mornings.
Spraying, on the other hand, can be perilous since it invites disease. The water droplets of spray are too large to contribute to the humidity yet too small to evaporate quickly and can lead to spotting of the flowers and rotting of the tender new leaves. Sometimes in the summer, spraying of the foliage can be beneficial by cooling the plant. New root tips always enjoy a little spritz. But in general, exercise caution when spraying orchids.

Friday, July 1, 2005 - 18:15