Beginner

Scientific Names
Various species of cutworm are commonly found in Ontario.  They include: Agrotis ipsilon (black cutworm), Euxoa messoria (dark-sided cutworm), Crymodes devastator (glassy cutworm) and Euxoa detersa (sandhill cutworm).

Identification

• Larvae are soft and fat, and they roll up when disturbed
• Early-season cutworms attack the seedling plants, usually cutting them below or at the soil surface
• A single larva may destroy several seedlings

Often Confused With
Common armyworm
Wireworm

Period of Activity
The first generation of cutworm larvae may be present in fields from early May through to mid-June.  Most species of cutworms feed at night, hiding during the day under loose stones or in the soil near the base of the plant. Plants at the seedling stage are most vulnerable to cutworm losses. Once plants have reached the mid-whorl stage, they are unlikely to suffer permanent damage due to cutworm feeding.

Scouting Notes
Check for cutworm damage by walking through the field and looking for wilted and/or fallen plants.  If any are found, dig around in the soil at the base of the plant.  The cutworm, if present, will be found 2- 3 cm (4/5- 1 1/5 in.) deep and within 10 cm (4 in.) of the damaged plant(s).  Make control decisions based on the number and size of larvae found.

Thresholds

Spray at 10% damage, if the plants have less than 4-5 leaves and if the cutworm larvae are less than 4 cm (1.5 in.) long.

Advanced

Scientific Names
Various species of cutworm are commonly found in Ontario.  They include: Agrotis ipsilon (black cutworm), Euxoa messoria (dark-sided cutworm), Crymodes devastator (glassy cutworm) and Euxoa detersa (sandhill cutworm).

Identification
Cutworm larvae are soft and fat, and they roll up when disturbed.  They can be as large as 3- 4 cm (1.5 to 2 in.) long. 

Early-season cutworms attack the seedling plants, usually cutting them below or at the soil surface.  A single larva may destroy several seedlings.  Cutworm larvae are commonly found burrowed 2- 3 cm (1 in.) into the soil at the base of damaged plants.

Often Confused With
Common armyworm
Wireworm

Biology
Most species of cutworm do not overwinter in Ontario.  In the early spring, adult moths are transported on the trade-winds from the overwintering sites.  Female moths are attracted to dense, green cover to lay their eggs.  Often, when they arrive in Ontario in early spring, the main source of habitat for the females are winter annual or perennial weeds. 

Eggs hatch and larval feeding often coincides with planting and crop emergence.  There are several generations per year; however, the first generation is most likely to cause economic damage in corn.

Once the larvae reach 2.5- 4 cm (1- 2 in.) in length, they cease feeding as they prepare to pupate.

Period of Activity
The first generation of cutworm larvae may be present in fields from early May through to mid-June.  Most species of cutworms feed at night, hiding during the day under loose stones or in the soil near the base of the plant. Plants at the seedling stage are most vulnerable to cutworm losses. Once plants have reached the mid-whorl stage, they are unlikely to suffer permanent damage due to cutworm feeding.

Scouting Notes
Check for cutworm damage by walking through the field and looking for wilted and/or fallen plants.  If any are found, dig around in the soil at the base of the plant.  The cutworm, if present, will be found 2- 3 cm (4/5- 1 1/5 in.) deep and within 10 cm (4 in.) of the damaged plant(s).  Make control decisions based on the number and size of larvae found.

 

Relationship between black cutworm development & potential damage in corn
Larval instar	Approx. size		Approx. feeding days	Potential number of plants that may be cut or tunneled
	cm	in.		1 leaf	2 leaf	4 leaf
4	<2.5	<1.0	25>	4	3	1
5	2.5	1.0	21	4	3	1
6	2.5-3.75	1.0-1.5	14	4	3	1
7	3.75-5	1.5-2	5	1	1	1
Reprinted from Ohio ICM newsletter, May 1994

Thresholds
Spray at 10% damage, if the plants have less than 4-5 leaves and if the cutworm larvae are less than 4 cm (1.5 in.) long.

Management Notes

• Control winter annual and perennial weeds in the fall to eliminate egg-laying habitat.
• If cutworms become a problem in rye cover crops, consider replacing the rye with a cover crop that is killed over winter, such as oats or oilseed radish.
• Cutworm control is most effective on small (less than 2.5 cm or 1 in.) larvae.  Larger larvae are difficult to control with insecticides.  At more mature stages (> 2.5 cm or 1 in. in length), they cease feeding as they prepare to pupate, and control becomes unnecessary.
• Apply insecticides in the early evening, as the cutworms come to the surface to feed at night.  Insecticides are more effective on moist soils.
• As this pest is sporadic in nature, and due to the relatively high threshold, preventative in-furrow or seed-treatments targeted at cutworms are usually unnecessary.