If you bite into a sunflower seed and find a worm, it’s probably a sunflower moth.
Sunflower moths lay their eggs in sunflower heads. When those eggs hatch, tiny caterpillars begin feeding on developing seedheads and burrow into the seeds to feed. In doing so, they create wounds that allow diseases, such as Rhizopus head rot, to get in. And who wants to bite into a worm, even if it is tiny?
Each moth only lives for 7-10 days, but females quickly begin laying eggs on the underside of sunflower heads and the inner bracts. Larvae go through five instars as they feed on developing sunflower seeds. Then they fall to the ground, burrow into the soil, and overwinter in a cocoon. There are several sunflower moth species, but they are all prolific and destructive.
American sunflower moths
American sunflower moths (Homoeosoma electellum) are also found in South America. They have a ¾” wingspan and off-white, feathered wings with dark spots scattered along the forward and outer edges. American sunflower moth caterpillars feed extensively on canola and sunflowers. They also feed on cotton, orange blossoms, and yacón.
Banded sunflower moths
Banded sunflower moths (Cochylis hospes) are tiny, pale moths with a ½” wingspan. Those wings are tan with a dark triangular band on the forewings. Larva are off-white when they hatch but turn red or green as they grow. Their heads are dark. These moths are found in the eastern United States.
Cuban sunflower moths
Less is known about Cuban sunflower moths (Heterocampa cubana), which are also found in Florida. These stocky moths have dark forewings decorated with lines and patterns and lighter underwings. Cuban sunflower moth caterpillars are solid green with a yellow, red, or purple stripe along the top and pinhole dots on the sides. These caterpillars feed on sunflowers, mangrove flowers, and probably other plants.
Eurasian sunflower moths
Currently found in Anatolia, Europe, the Middle East, Russia, and West Africa, Eurasian sunflower moths (Homoeosoma nebulella) are darker and slightly larger than their American counterparts. They have wingspans of up to one inch. Eurasian moth caterpillars are gray with three stripes on top. Their heads are yellow. They feed heavily on sunflowers, ox-eye daisies, tansy, and thistle.
Larval feeding interferes with pollination as well as destroys your crop. You may see webbing on affected sunflower seedheads.
You can use pheromone traps to determine if these pests are present, but the traps will not eliminate the problem. One way to reduce the risk of sunflower moth damage is to delay planting sunflowers until slightly later in the season. This makes life more difficult for the moths, who will look elsewhere for egg-laying sites. Beneficial insects should also be encouraged with a variety of flowering plants. These predators and parasites will reduce the damage done by sunflower moths. Research is currently underway for resistant varieties of sunflowers, so be on the lookout.
If the caterpillars on your sunflowers are dark and have spines, it’s probably checkerspots.
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