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"And the LORD God made ... trees that were pleasing to the eye ..." Gen. 2:9, New International Version.

"Bonsai isn't just something I do; it's part of what I am." Remark to my wife and daughter.

Tuesday, March 26, 2013

"Exotic" works both ways.

     A local species of scale appears to have a sweet tooth for willow-leaf fig. It will attack other tropical species, too, like Ficus microcarpa. But if willow-leaf fig, Ficus salicaria, is available, it seems to go for that first, and with the greatest appetite. (Since Ficus salicaria is one of my favorites, that puts us very much at odds!)

One of my trees that came under attack.

I've suspected this for a couple of years, but a recent serious infestation of scale among my willow-leafs -- while other species in the Crate were only lightly bothered, or not at all -- has confirmed it. The infestation got started because of an oversight. I aim to treat all my trees annually with a systemic insecticide, but last year I ran out and somehow never bought more. It's an embarrassing mistake; but at least I learned something from it.

This tree suffered the most damage.

It's worth remembering that, as the title of this post says, the concept of "exotic" works both ways.  Ficus salicaria isn't native to this part of the world, so here it is an "exotic." But the scale, mealybugs, and other insect pests that are native to northern Indiana are "exotic" as far as Ficus salicaria is concerned!

Whenever we bring a tree or shrub species to an area where it is not a native, we expose it to pests and pathogens that are new to it. Some of those pests are going to find it appetizing; others are going to find it revolting. The tree's existing natural defenses are going to defeat some of those pests completely, while other pests are going to overwhelm those defenses without half trying. I'm over-generalizing a bit, but I hope my point is clear. And in the case of willow-leaf fig and the scale insects here, the tree's natural defenses almost might as well not exist!

Suspicious bumps -- orange arrows. Scale also attach to leaf surfaces.
A gentle scrape removes it, confirming that it's scale.

Besides being inordinately fond of Ficus salicaria, the scale insects here are quite difficult to detect when they are immature, even for those with some experience looking for them. By the time I confirmed that the trouble was with scale (there were other possibilities) one of my willow-leafs had suffered a good deal of damage. That damage will set the tree's development back by several months, but otherwise will not have any long-term effect. With one exception: the branch that I used in a graft last summer was killed, and the graft will have to be re-done. (The graft was doing well, too. :-( I referred to it most recently in this post .)
The grafted-in branch was killed.

Two days ago I sprayed all my willow-leafs, and a few other specimens too, with an insecticidal spray that I think of as "Carl's Soap Solution." I call it that because I got the recipe from Carl L. Rosner of New Jersey. Carl, however, while he recommends this spray enthusiastically, says that he learned it from someone else. I've found this solution to be effective against most non-boring beasties that attack the above-ground part of the tree.

Give me a few days, and I'll publish the recipe in a separate blog post, in both English and metric units.

I have a fresh supply of systemic insecticide, but I'm not going to use it indoors unless I must. Another thing worth remembering is that the research that led to many of our insecticides also led to the development of nerve gases! Best to use insecticides in a well-ventilated place or outdoors.

On the attack with the sprayer!

:-)  :-)  :-)


  1. That sucks. I've had some tiny bugs crawling in and out of the soil on a couple of my ficus and haven't been able to figure out what they are exactly. They don't look like spider mites, mealy bugs, or anything else I've seen people complain about. The trees don't really seem bothered by them either, but I knew they needed to be dealt with so I treated them with a mixture of of neem oil, dish soap, and alcohol diluted into water. That seems to have killed them with no ill effects to the trees. The recipe I saw didn't have the alcohol, but I didn't think it would hurt given it wasn't even a capful mixed into a liter sized bottle. If the trees had been more developed, or I had more money in them, I might have been a little less experimental. Thinking of it, it may have been related to Carl's Soap spray.

    1. Interesting, Charles. Carl Rosner recommends that the solution I used be kept off the roots, just to play it safe. But if your trees show no ill effects over time, we'll all have learned something!

      You may be seeing fungus gnats -- are they black? Fungus gnat larvae feed on plant roots, so it's a good idea to go after them.