Cutworms (Agrotis spp) are the larvae /caterpillars of several species of night-flying moths belonging to the Noctuidae family.
They mostly hide under litter or soil during the day and come out in the dark to feed on plants, where they attack and cut down the stem of seedlings, hence their names ‘cutworms’.
There are also climbing cutworm species that move up plants and feed on the foliage, buds and shoots.
Although they stay hidden during the day, they can feed throughout the day below the soil surface.
Cutworms can be confused with armyworm and African bollworm larvae. They are caterpillars, but are oftenly mistaken for grubs.
The adults are night-flying moths and do not cause damage.
Host Range
Cutworms attack all field crops.
Crops are at a higher risk of attack during the seedling and early vegetative growth stages.
Life Cycle
All cutworms have the same general life cycle although the length of stages may vary.
Some species lay a single egg or small/large groups of eggs in soil in lightly vegetated or bare areas, which hatch within 2-14 days depending on the species and temperature. The larvae (cutworms) are usually very active and feed on host plant until maturity. Pupation takes place in the soil. Adult moths emerge from overwintered or early-season pupae.
Generally, 3-4 generations per season are possible, although others may have only one generation per season.
Under favourable conditions, the life cycle takes 8-11weeks, depending on the species.
Identification
Cutworms can be quite distinct from one another. Their coloring vary from brown or tan to pink, green or gray and black. Some have a uniform color while others are spotted or striped, some are dull while others appear glossy or shiny.
These caterpillars are up to 50 mm long, curl up into a tight “C” when disturbed and remain still if picked up.
They can easily be found slightly below the soil level and around damaged plants during the day or on the soil level when it is cloudy or dark. Some cutworms may be easily overlooked because their body colors blend in with the soil.
Adult moths are moderate sized, brown or black insects showing various splotches, or stripes in shades of gray, brown, black or white. They generally have a body length of about one inch with wingspans up to 1.5 inches across. The forewings are darker than the hind wings and are patterned.
Feeding & Damage
The young caterpillars climb the young plants and skeletonize the leaves or create small holes as they feed. This is usually done during the night or on a cloudy day.
The older ones may also climb to cut off leaves, but they commonly cut through stems at ground level and feed on the top growth of felled plants. This happens late in the afternoon or at night. During the day, they hide under the soil or in debris.
Even if only the bottom of the plant is destroyed, the top will often shrivel and die. In most cases, entire plants gets destroyed.
Cutworms can cause a lot of damage in no time.
Management & Control
The following methods can be used to manage and/or control cutworms
Chemical methods
Cutworms are best controlled if the insecticide is drenched into the soil.
The following insecticides are effective in eradication of these insect pests.
- PROFILE 440EC 60ml/20l
- RANGER 480EC 60ml/20l
- PENTAGON 50EC 20ml/20l
- LOYALTY 700WDG 10g/20l
Note;
- Seed treatment can be done using SHIELD 600FS 3ml/1kg
- Drenching of the insecticide should be done late in the evening for effectiveness.
Non-chemical methods
They include the following;
- Use of beneficial parasites and natural enemies, e.g. fireflies, birds, parasitic wasps
- Early ploughing, which reduces the number of eggs deposition.
- Hand picking the cutworms
