Black Worms on Sunflowers

Identifying Cutworms

• The name of the cutworm directly correlates with the damage they do to sunflower seedlings. More mature cutworm larvae will chew through the stalk entirely (usually near where it emerges from the soil), causing the plant to topple and die. The younger cutworm larvae will confine themselves to the leaves, causing notches, holes and "windows" (translucent see-through areas where the larvae was not mature enough to chew all the way through) in the leaves. Cutworms are actually caterpillars with spots and/or stripes and are predominately black or gray.

Identifying Sunflower Moth Larvae

• Sunflower moth larva (also a considered a caterpillar) is seen as a black or very dark brown worm on sunflowers in its older, more mature stage of development and will always have four yellow or creamy stripes running lengthwise down the body. When the larvae are younger, however, they will be yellowish. Unlike cutworms, the sunflower moth larvae will be found on the mature plant, as the sunflower moth lays its eggs during a sunflower's blooming period. Damage to the faces of the sunflower blossoms include stringy webbing and empty or bored seeds, and this will increase susceptibility to head-rot infection.

Treatment of Black Worms on Sunflowers

• Insecticide should be used to prevent the loss of plants and crop as soon as possible after the black worms are discovered on sunflowers. When treating for sunflower moth larvae, time is of the essence, as sunflower heads bloom rapidly and often concurrently. Treatment must proceed before all plants have bloomed to be the most effective, as this is when they are most vulnerable. Insecticide should also be applied for a cutworm problem, but only if the cutworms are no more than 1 1/4 of an inch long and the majority of them have not advanced to the pupal stage. After that point, the cutworm infestation is deemed to be so far advanced that the application of pesticide will be ineffective.

Prevention of Black Worms on Sunflowers

• The best method of treating black worms on sunflowers is to have sound preventative measures in place. When planting, sow your fields as consistently as possible to encourage the sunflower plants to come into bloom at the same time, as irregular blooming gives the sunflower moth a greater opportunity to spread its eggs. Plant to the same depth and ensure that all plants have good, moist soil. Install traps in your fields to better monitor pest levels. Apply preventative treatments of insecticide, but be sure to confine this application to the evening, to avoid killing helpful pollinators that are mainly active in the early hours.