Hokkaido Elm with Scale bugs, yuk!

will*law

Hi,

Scale can be very tough to control. The best bet is a systemic, but I try to use least toxic things to, and some systemics are pretty nasty. Another related factor in my (little, perhaps!) head is that they generally persist in the environment for a while.

Anyway. I'd try a multipronged aproach, because you want to get rid of the boogers. Use a q-tip or a brush and apply rubbing alcohol to the trunk and branches. Don't get it on the foliage, it will destroy the leaves. This will kill any that it touches.

Consider using a pyrthrin spray. It's a contact insecticide made from a species of Chrysanthemum. It's really broad and toxic, but is organic and decomposes rapidly. Spray ALL your plants. Scale is tough. Be sure to follow the label instructions. And don't apply it once. Wait 3-7 days and reapply to kill whatever else has hatched.

After that, possibly immediately after it has dried, or mixed in, consider an oil of some sort. Really, either neem or a highly refined horticultural oil will do the job. Neem has additional properties that will help - depending on the species, it will kill, repel, or act as an appetitie suppresent. Generally, oils kill by smothering, and they are very effective with scale. The nice part about this is because it is a physical control, the pest won't develop resistance as is possible with a chemical poison. Be vary careful and follow the label instructions - oils can cause foliar damage pretty easily.

Good luck,

Will

Advertisement

rockm

Pyrethrin is pretty ineffective against mature scale, as are the vast majority of topical insecticides, including Neem oil. After a decade of battling scale on my bonsai (scale tends to favor hornbeam and beech in my nieghborhood for some reason, while other trees are left alone), I have found that simple hand removal of the mature insects is the most effective and least harmful to the plant. Spraying anything does little good and has a far steeper downside than any benefit. You don't need alcohol swabs. A simple short length of wire, a sharp eye and about ten minutes per tree is about all you really need. Once you recognize what the scale look like and their favorite places, removal time is cut to five or six minutes for a big tree...

october

Also, I used a pyrethrin based spray once and it killed about 60% of the foliage on my pyracantha. Just a warning.