The Citricola scale is a soft scale that is found primarily on citrus. Severe infestations can reduce tree vigor and reduce flowering and fruit set. The Citricola Scale Growing Degree Day Model can help to predict the timing of different life cycle stages.

Citricola Scale Life Cycle Stages

Citricola Scales overwinter as nymphs in twigs or branches, and adults emerge in late spring or early summer. Crawlers emerge later in summer and are active for a short time.

The periods of crawler emergence is key for insect prevention, if necessary. Researchers have created the Citricola Scale Emergence Growing Degree Day Model to better predict when the adults will emerge.

Calculating Growing Degree Day Units

The Citricola Scale Emergence Growing Degree Day model uses a lower threshold of 51.8F. It can be calculated with daily high and low temperatures, using the sine model to estimate growing degree day units, or the Pest Prophet app can be used to calculate GDD accumulation from hourly temperature data for a specific field.

Using Jan. 1st as a default “biofix” date, or starting point for accumulation. Peak crawler emergence occurs approximately at  636 GDD(F). This can be used an approximate target for beginning treatments.

Source:

Dreistadt, S.H. 1996. Citricola scale (Homoptera: Coccidae) abundance on Chinese hackberry and scale control with spray oil or acephate trunk implants. J. Econ. Entomol. 89: 481-487. “””,