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Mealy Bug, Humidifier Water & Garden Plague

The fungus Jeff is trying to control is actually an insect; using the water from dehumidifiers for plants; and what plague has hit this lady’s garden?
by Art Drysdale
by Art Drysdale

email: art@artdrysdale.com

Art Drysdale, a life-long resident of Toronto and a horticulturist well known all across Canada, is now a resident of Parksville, British Columbia on Vancouver Island, just north of Nanaimo. He has reno-vated an old home and has a new garden there. His radio gardening vignettes are heard in south-western Ontario over radio station Easy 101 FM out of Tillsonburg at 2 PM weekdays.

Art also has his own website at http://www.artdrysdale.com


July 15, 2007




Above, two shots of a particularly heavy infestation of mealy bugs on tropical plants in the southern U.S.; and, I’ve used photos of some of my oriental poppies here in other years, but never one of this delightful mauve colouration in double and semi-double form. Author photos. Below, the cankers of eastern filbert blight as seen on the plant’s branches. Photo by Jeff Stone, Oregon State University.

Jeff Reeves of the Toronto area (I believe) wrote on July 4th, “I would like to ask you a question about a problem I'm having with a Fukien Tea tree. I brought it in from outside (where it spent the summer) in October and shortly after noticed a powdery fungus that grows on the trunk and leaves and junctions of branches. It is white and sticky. It drops a sticky liquid around the base of the plant and on the table where it sits. I tried an organic fungicide and a gar-den sulfur fungicide that mentioned it controls powdery mildew (which seemed to describe it rather well). I sprinkled it on the plant as a powder and when that failed I tried it as a liquid that I fed to the roots. Someone at my bonsai meeting suggested using gin. I applied it with a toothbrush and two applications had no effect. So, I’m tapped. Any suggestions? The plant still grows new leaves but the older ones become sticky, dry out and then fall off. Hope this helps. I look forward to hearing from you. Thanks.”

I think the problem that Jeff has is not a fungus, but rather an insect, specifically mealy bug. I would try one of the Doktor Doom products, either ‘Botanics’ or the stronger ‘House & Garden Spray’. In any case, no fungicide is going to have any effect on what is obviously an insect problem. By the way, I would think Gin might well be a little strong although I know of no one who has actually tried it! An alternate ‘organic’ control is to spray the plant with as strong a jet of water (as the plant can stand) from the kitchen faucet. Use only cool water and do the spraying daily for several days, and then whenever there is further sign of new colonies.

On July 6th, Bill Faichnie wrote: “Well here it is summer and in Milton Ontario as in many communities there is a water restriction. My question--is the water from a dehumidifier good for watering plants? Does it have any nutritional value considering it is distilled water? I currently pour this down the drain, could I be making use of it?”

This is actually a controversial question Bill. But, generally it is fine to use dehumidifier distilled water for plants. There are some who say that such water could be contaminated with heavy metals, depending on the metal content of the ‘guts’ of the dehumidifier, but this should not be a consideration, at least not with flowers, only perhaps with vegetables. On the other hand, the use of this water may help guard against other water problems such as that which is high in soluble salts. It has no nutritional value.

Then on July 8th, Lyn Baskett, also from Milton, wrote about a serious problem that seems to be spreading, “Hi Art, hope you are well and enjoying the heat wave out west. I'm in Ontario (Milton) and have a Corkscrew Hazel with Eastern Filbert Blight. I read your comments to someone else where you mentioned this but didn't discuss the treatment. The tree is 20 - 25 years old, a beautiful tree (it was anyway), is there any way to save the tree?”

Unfortunately Lyn, it is not an easy undertaking. Eastern filbert blight (Anisogramma anomola) has been present in the eastern part of the North American continent for decades, and beginning about 1973 it turned up in Oregon here on the west coast. As far as I know, we are free of it here in British Columbia.

The first symptoms to appear on infected trees are elliptical black stomata. They are formed in longitudinal rows on infected branches, and appear only after extended cold periods, usually between May and August. The first stomata to appear erupt from branches 12-18 months after the initial infection. The infected area is known as a canker, and these cankers are perennial, adding both additional rows and more stomata to existing rows each year. Infected branches become girdled. Leaves on these branches die, remain attached, and flag the presence of the disease during the summer months. The tree declines, with many leafless, dead, and dying branches visible in the canopy. If no action is taken, in 5-12 years time the tree will die.

Extreme diligence is required to keep the disease under control. It is necessary to check the tree in the winter for cankers, and in the summer between July and August for flagging branches. Check these for cankers as well. In-fected branches should be pruned to at least .5 m (20”) below the lower edge of a canker (towards the trunk), as the fungus grows ahead of the area in which it produces its reproductive structures. The cut branches should be burned or chipped, because the fungus can continue to sporulate in the branch as long as it has moisture.

Unfortunately though there are chemicals available for commercial use (such as Copper hydroxide) they are not available for home use.

If the tree does die, it is advised not to re-plant the same genera as the spores produced can remain in the air for several years.

Colleen Lamont of Langley, B.C. wrote to Donna Dawson on July 12, saying, “Hi there - I am concerned about a problem in my garden. It is like a plague has gone through. I have lost 4 rose bushes, two have gone wild but I am most concerned about my wisteria tree and my hydrangea tree. The wisteria has been extremely prolific over the past 4 years with at least three bloomings every year. This year, nothing. Very small, very tight buds, no leaves, nothing. The hydrangea was really blooming the first two years I got it but has steadily declined until nothing this year. Again, very tight buds not very many and no leaves. What can I do? Can they be saved? I am especially concerned about the wisteria as it has been a focal point of the yard. Hope you can help.”

Something (at least one thing) strange here Colleen. When you say that two of your rose bushes went wild--just what happened? Rose bushes generally can be considered to have gone wild when the desirable cultivar that was budded onto a hardier rootstock dies, and the rootstock continues to grow. That should not be occurring to any extent in Langley, B.C. I need to know more to come up with an answer. Regarding the Wisteria, I am unclear what you mean that it had “at least three bloomings every year.” Wisteria shrubs/trees generally only bloom once, occasionally twice, in a year. When did these bloomings occur?

The description you give of the Wisteria and Hydrangea growth would indicate a total lack of water and possibly nutrition. Or, there could be something wrong with the soil--for example, too high a level of soluble salts. It will be easy to test both the pH and soluble salts level of the soil from a number areas of your garden. Try your nearest gar-den centre and they will either do the test for you, sell you a kit to do it, or direct you to a decent laboratory where the tests can be done. Note, only the pH and soluble salts tests are needed; the other tests for the level of specific nutrients (nitrogen, phosphorous and potash) are more complicated and unnecessary at this step.

Is it possible for you to send digital photos of the plants in question?

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