Twospotted Lady Beetle (Adalia bipunctata) is an important insect used for biological control of aphids and other pests. Researchers have developed a growing degree day model for Twospotted Beetle that can help predict egg-hatch, pupation and adult emergence timing from when eggs or previous generation adults are observed, in order to improve pest management decisions.

Calculating Growing Degree Days

The Twospotted Lady Beetle model uses a lower threshold of 48.2F and an upper threshold of 86F. 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.

For this model, the “biofix” date, or date from which to start accumulating growing degree days, should be set to when Convergent Lady Beetle eggs or adults are first observed or introduced to field.

Egg hatch and larvae emergence occurs at approximately 78 GDD (F). Pupation begins at approximately 343 GDD(F) following the – date. First adult emergence occurs at approximately 469 GDD (F) after the biofix date.

Sources:

Obrycki, J. J., and M. J. Tauber. 1981. Phenology of three Coccinellid species: thermal requirements for development. Ann. Entomol. Soc. Amer. 74: 31-36.