Can scale insects disappear without treatment?
Written by
Liu Xiaohui
Reviewed by
Prof. Martin Thorne, Ph.D.Scale insects are rarely eliminated without treatment, even with optimistic thoughts. I have witnessed infestations go from a few scales to thousands of insects in a matter of months. These annoyances reproduce quickly, and female scales can lay 1,000 - 2,000 eggs. Natural predators seldom control established colonies effectively when left to their own devices.
Reproductive Capacity
- Single female produces 50-2,000 eggs
- Multiple generations per year accelerate spread
- Eggs protected under waxy covers resist elements
Protective Adaptations
- Waxy covers resist weather and pesticides
- Immobile adults avoid predator detection
- Overwintering eggs survive freezing temperatures
Environmental Limitations
- Natural predators need specific conditions
- Parasitic wasps require warm temperatures
- Heavy rains only wash off some crawlers
The magnitude of damage continues to rise if left untreated on the risk scale. Armored scales inject toxins that induce a yellow halo on leaves. Soft scales are sap feeders that excrete honeydew, which is the perfect food for sooty mold growth. Both types, armored and soft scales, can lead to leaf drop and branch dieback. Personally, I have seen completely healthy trees be killed within 2 seasons.
While natural enemies control relatively few scales under particular conditions, parasitic wasps only attack a few species of scales and only in the summer season. Lady beetles consume more than 50 scales daily, but they require a sufficient, ongoing population of scales to be effective. In my garden, natural predators reduced the scale problem by approximately 30%, but never eliminated it.
While the weather can affect but not solve infestations, some crawlers will be washed away with heavy rain. However, the eggs remain protected. Extreme cold can kill all but the overwintering forms. In contrast, exposed scales can be destroyed; however, documented scales survive Minnesota winters, insulated by bark.
Utilize integrated controls that incorporate both natural and mechanical techniques. Start with branches that have heavy infestations in the spring. Apply horticultural oil in the winter or spring during dormancy. Lady beetles can be introduced to control aphid populations when aphid crawlers emerge in the spring. This simple method has saved my magnolia trees from certain death.
Read the full article: Mastering Scale Insect Identification: A Complete Guide
