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Cutworm

Classification and Description:  Several species of cutworms (Lepidoptera: Noctuidae) may be found in cotton.  Black cutworm (Agrotis ipsilon) and granulate, or subterranean cutworm (Feltia subterranea) are common, but variegated cutworm (Peridroma saucia) and other species may be present.  Moths of the black cutworm have a wingspan of about 1 ½ inches.  Each forewing has a characteristic dagger-shaped marking.  Cutworm larvae are relatively large, slick caterpillars that have a greasy appearance and feel. Larvae of the black cutworm (pictured) pass through 6-7 instars and reach a maximum size of about 1 ½ inches.  They are gray to black with five pairs of prolegs.

 

Hosts and Distribution:  Most cutworm species have a wide host range and may injure many cultivated plants including cotton and corn.  They are widely distributed throughout Tennessee and most of the United States.  However, the black cutworm rarely overwinters north of Tennessee because cold weather kills overwintering pupae.

 

Life History (Black Cutworm):  Females lay eggs singly or in groups of up to 30 in pastures, fence-row grasses or other weedy plants growing in fields.  Eggs are laid on stems of plants or plant debris near the soil surface.  Damp areas of the field are a preferred oviposition site.  Cutworms pupate in the soil. Most cutworm species have two or more generations per year in Tennessee.  Black cutworms may have as many as four generations per year.

 

Pest Status and Injury:  Cutworms are sporadic pests, typically causing economic injury to a small percentage of cotton fields each year.  However, severe infestations can reduce stands to the extent that replanting is necessary.  Only the larval stage is damaging and is almost always found hidden below ground during the day.  Larvae cut the stems of seedling cotton plants.  Smaller larvae may feed on leaves without cutting plants.

 

Management Considerations:  Economic damage is usually caused by larvae that are already present in the field at planting.  Maintaining a weed-free field for 3-4 weeks prior to planting by cultivation or use of herbicides will greatly reduce the chance of cutworm injury, effectively starving larvae from the field.  Besides destroying weed hosts in the field, cultivation will mechanically destroy larvae.  If a field is not kept weed free for at least three weeks prior to planting, preventative insecticides application are often used.  Pyrethroid insecticides applied in a narrow band behind the planter (5-7 inches) will typically prevent infestations of cutworm from causing economic damage.  Recommended treatments for cutworms are given in the Insect Control Recommendations for Field Crops (PB1768).  Because infestations may occur in isolated spots within fields, spot applications can sometimes be used.  Bt cotton will not effectively control large larvae that may be present at the time of planting.

Print-Ready PDF Publication (Cutworms W032)