A Tale of Two Cutworms: Cutworm Control in Asparagus

Friday, May 5, 2023

Cutworm appearance and life cycle

Michigan asparagus is attacked by white cutworms, Euxoa scandens, and dark-sided cutworms, Euxoa messoria. Both species overwinter in Michigan, are present in many habitats and feed on many plants.

White cutworm moths fly from late June to mid-August. Females lay eggs singly or in small groups 0.25-0.5 inch deep in the soil, preferring sandy sites. Caterpillars hatch in August and have a translucent, milky white appearance. They feed on weeds and asparagus in the fall before burrowing into soil to overwinter as 0.5-0.75 inch long larvae. They emerge in early spring and pupate in late June, emerging in July as the next generation of moths. There is one generation per year.

Dark-sided cutworm moths are active from mid-August through October and lay eggs singly or in small groups 0.25-0.5 inch deep in the soil, including in asparagus fields. Eggs overwinter in the soil and hatch in April. Caterpillars are 1.5 inches when fully grown and are grayish with brownish, indistinct lines along their sides. They feed on weeds and volunteer asparagus from April through July before pupating in July or early August. There is one generation per year.

Cutworm damage

White cutworms can be active at near-freezing temperatures, emerging large and ready to feed at spear emergence. Caterpillars feed at night, climbing spears to damage tips or eat butts of harvested spears. This means damage is most severe during the first harvests when few butts are present, and generally lessens through the end of May. Feeding damage is also more severe during cool springs as slow-growing spears are exposed to cutworms for a longer time before harvest.

Dark-sided cutworms hatch in the spring as small larvae and are not large enough to cause significant damage until the second half of May through the end of harvest, with damage more severe as caterpillars grow. Unlike white cutworms, dark-sided cutworms do not climb spears. Instead, they feed at the base of spears at the soil surface. This causes the undamaged side of the spear to grow faster than the damaged side, resulting in crooked spears. Crooked spears may even be curled into partial spirals.

Source: msu.edu