Question
My bittersweet has scale - I think. I live in the Shenandoah Valley of Virginia (New Market). I believe it may be Euonymus Scale. They look like tiny, white grains of rice. They have covered the branches and leaves. I first noticed the leaves turning yellow the end of June then discovered the scale. I treated with Insecticidal soap the first and second week of July. This is what my local Ext. Co-op office suggested. Now it is Sept 11th and it appears to very active again. What do I do? Should I spray with soap? Wait until the leaves fall off from Autumn and prune? Use Oil during the winter? I've also planted 12 new "baby" bittersweet this spring and they are also showing signs of stress and infestation. Do I treat them too? Thank you in advance for your help.

Answer
Scale control can be challenging and may need to be repeated over several seasons. Proper timing of insecticide applications is a major key to success. Applications must target newly hatched scale crawlers which are active in May and again in June and July. They are very susceptible to control measures while moving over plant surfaces to find a feeding spot. Once settled, they begin to secrete a waxy covering that shields them from sprays.


Insecticidal soaps are long chain fatty acids that kill susceptible insects through direct contact. Like horticultural oils, they require thorough coverage. Soaps leave no residue so repeated applications may be needed.

Oil in the winter will control the scales overwintering. I would wait until the leaves fall off.

Imidacloprid (Bayer Advanced Garden Tree & Shrub Insect Control Concentrate) is applied as a drench around the root zone of infested plants. This water soluble insecticide is taken up by the roots and transported throughout the plant where it is ingested by sap feeding insects. This provides a means of scale control without reliance on sprays. Apply this in the early spring as the leaves are budding out.

Scales tend to thrive on stressed plants. Following a recommended fertility program and watering regime will promote plant health. However, over-fertilization favors scale buildup. If practical, improve plant sites to reduce stress and promote growth. Severely prune back heavily infested branches and protect new growth with insecticide applications.

I would treat the new plants the same as the older ones. The Bayer product works on scales without the repeated sprays.