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Sunflower Moths Present in South Dakota Sunflower

Tan moth present on a yellow sunflower head.
Figure 1. Sunflower moth adult. Courtesy: Phil Sloderbeck, Bugwood.org.

Written collaboratively by Adam Varenhorst, Amanda Bachmann, Ruth Beck and Patrick Wagner

The sunflower moth and its subsequent caterpillar are sunflower insect pests that need to be scouted for after the inflorescences begin to open (R4) through head maturity (R6).  Sunflower heads are most susceptible to damage caused by the caterpillars of the sunflower moth from the onset of anthesis (R5.1) to when the petals begin drying (R6). The adult sunflower moths are attracted to sunflowers during the early stages of blooming and will deposit eggs near the base of florets. Each female sunflower moth has the potential to lay as many as 400 eggs. In other states, populations of the caterpillars can range from 15-200 per head. In South Dakota, we generally will observe 1-5 sunflower moth caterpillars per head. However, there is still the potential for larger populations to occur. Therefore, it is important for South Dakota sunflower producers to scout for the moth.

Identification

Caterpillar with an orange head and black and white stripes on body, feeding on sunflower seeds.
Figure 2. Sunflower moth caterpillar. Courtesy: Adam Varenhorst.

The adult sunflower moths are relatively small, measuring approximately 3/8” in length with a wingspan of approximately ¾”. The moths are tan or light gray in color, and have their wings tucked tightly to their bodies when at rest (Figure 1).

The caterpillars of the sunflower moth have very distinctive coloration with bright orange heads and black bodies. They have white stripes that run the length of their bodies. The caterpillars range in size but reach approximately ¾” during their final developmental stage.

Scouting and Management

Light green sunflower florets covered by silken webbing.
Figure 3. Silken webbing that is spun by the sunflower moth caterpillar. Notice the accumulated debris in the webbing. Courtesy: Adam Varenhorst.

Sunflower moths do not overwinter in South Dakota and migrate north each year from southern states. They arrive in South Dakota when sunflowers begin flowering. The moths can be observed on sunflower heads during early flowering stages. During the first two instars, the caterpillars of the sunflower moth will initially feed on pollen and later transition to feeding on the seed. The caterpillars will feed directly on the seed and will also tunnel into the sunflower head tissue. This tunneling can lead to secondary infections of Rhizopus head rot, which is the main source of yield loss associated with this pest. A single caterpillar may feed on 3-12 seeds within a head. Additionally, the caterpillars of the sunflower moth spin silken threads that will bind drying florets and other materials to the head. This will give the head a trashy appearance (Figure 3).

Scouting for the sunflower moth should begin at the R4 growth stage. Moths are most active in early morning or evening. The best way to scout for sunflower moths is to use a flashlight and examine fields 1 hour after sunset, when moth activity peaks. Count the number of moths on the heads of 20 sunflowers from five random locations throughout the field. The threshold for sunflower moth is 1-2 moths per five sunflower heads.

When applying insecticides for management of insect pests on sunflower heads, be sure to orient the application so that maximum coverage reaches the head. Refer to the South Dakota Pest Management Guide: Alfalfa and Oilseeds for products labeled to control sunflower moths in sunflowers.

Related Topics

Sunflower, Oilseed