While scouting sunflower for insects that may cause yield loss, you might spot some small red and gray beetles that are present on the head or close to it. These two insects are the red sunflower seed weevil and the gray sunflower seed weevil. It is common to observe both of these species on a single sunflower head. However, the populations of the red sunflower seed weevil are generally much greater than the populations for the gray sunflower seed weevil. For this reason, thresholds have been calculated for red sunflower seed weevils (4-6 red sunflower seed weevils per head) while the gray sunflower seed weevil is considered a non-economic pest.
Red Sunflower Seed Weevil
Like its name implies, the red sunflower seed weevil has an orange/red appearance due to small hairs that are present on its body (Figure 1). Often, these weevils will appear almost black due to these hairs being rubbed off. The red sunflower seed weevil has a black snout, with small bent antennae originating from it. The adults will also have black legs. Of the two species, the red sunflower seed weevil is smaller. When examining a plant, the red sunflower seed weevil will often be found down between the developing seeds in the head. It can also be observed climbing on the head or also on the leaves and stem of the plant. The red sunflower seed weevils are capable of flight, and drop from the plant when disturbed.
Figure 1. Red sunflower seed weevil adult. Credit: A. Varenhorst
Gray Sunflower Seed Weevil
Aptly named, the gray sunflower seed weevil adult is covered in small gray hairs that cover the majority of its body (Figure 2). The gray sunflower seed weevil is larger in size, and will have gray legs instead of black. It also has a black snout that has small antennae that originate from it.
Figure 2. Gray sunflower seed weevil adult. Credit: A. Varenhorst
The larvae of both species are small and live inside of the developing seeds. They are cream colored and take on a “C” shape when disturbed.