Scale Insect Management on Ornamentals

We work on several species of scale insect to develop management tactics that are effective and pose less risk to natural enemies than conventional organophosphate and pyrethroid insecticides.

Reduced risk insecticides to control euonymus scale and protect natural enemies

We spent two years testing different conventional and reduced risk insecticides for

Euonymus scale

Euonymus scale on a heavily infested leaf. Photo S.D. Frank

efficacy against euonymus scale and effects on natural enemies.  Complete results are published in a recent paper.  In brief we found that some neonicotinoids provide excellent control of scale over the entire season.  Insect growth regulators also provide good control.   Of course excellent control was also achieved with horticultural oil but only for one generation.  Acute toxicity of these insecticides varies but was less than the pyrethroid bifenthrin.  However, chemicals had different effects on the number of parasitoids and predatory beetles present on plants.

 

Gloomy scale management on urban trees

Twice stabbed lady beetle on a maple branch infested with gloomy scale. Photo: S.D. Frank

We are in the second year of a project to determine how reduced risk and conventional insecticides affect gloomy scale abundance and natural enemies on street trees.  Many insecticides provided good control the first year. Now we are measuring scale abundance in the second year, parasitism rate and diversity, as well as the natural enemy community associated with trees in each treatment.  Many of the trees are in pretty bad shape so hopefully we will be able to quantify some improvement in tree growth and health after reducing the scale abundance.  We are also conducting research on the ecology of gloomy scale in urban areas to understand why they become so abundant in the first place. This work is conducted by Adam Dale.

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