The Sunflower Beetle is a beetle that feeds only on sunflowers . Typically adults feed on leaves, and can defoliate sunflowers very rapidly.

Sunflower Beetle Life Cycle Stages

Sunflower Beetles usually take one year to complete a generation. Sunflower Beetles overwinter as third instar larvae in the soil, and resume feeding activities spring or late winter. These larvae then pupate and adults emerge in late spring or early summer. Adults feed on leaves, before depositing eggs on the undersides of leaves.

The period of adult emergence is key for insect prevention, both for placing traps and for using insecticides, if necessary. Researchers have created the Sunflower Beetle Adult Emergence Growing Degree Day Model to better predict when the adults will emerge from the soil.

Calculating Growing Degree Day Units

The Sunflower Beetle Emergence Growing Degree Day model uses a lower threshold of 32F and an upper threshold of 90F. 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 Mar. 1st as a default “biofix” date, or starting point for accumulation, the first adult emergence occurs at approximately 419 GDD (F). However, it is recommended to place traps at approximately 712 GDD (F) in order to catch the first adult emergence. After adults are caught consistently, control measures should be taken.

Source:

Charlet, L. D. 1991. Overwintering survival and emergence pattern for the sunflower beetle (Coleoptera: Chrysomelidae) in the northern great plains. J. Econ. Entomol. 84: 132-135.