All you need to know about cutworm control


The larvae of the moth (Agrotis segetum) are present all year round and overwinter in the ground and under weeds. They are usually dark, dirty gray or brown in color and have a smooth waxy appearance. When disturbed, the larva folds into a C-shape. It is usually located at a depth of 20 to 50 mm below the surface next to the cut seedlings. It feeds mainly at night and sheds six times, increasing with age. The larva usually attacks the stems of corn seedlings and "cuts" the plant, hence the name of the pest.

Life cycle

Cutworm moths are nocturnal and take flight at night, laying eggs singly or in groups on the soil surface, or on the leaves of weeds and maize plants that may occur in lands in the few weeks prior to planting. The eggs are small, white and round.
When the eggs are laid during autumn and winter, various sizes of larvae will be found in the soil until spring.

Feeding habits

Cutworms emerge from the soil at night and move from plant to plant, severing the stems of seedlings at the soil surface. They may consume only a small portion of a plant before moving on to the next, causing serious damage in the process.
In older maize plants (four-leaf stage), the larva chews a neat, round hole into the stem just below ground level.

Cutworm damage is easily distinguished from damage caused by the black maize
beetle or false wireworm. In the case of the latter, the edges of the feeding holes have a frayed appearance.

Above-ground symptoms of cutworm damage include wilting of the central whorl leaf, followed by wilting of the entire plant.
In cases of severe cutworm infestation, entire rows of seedlings in a land can be destroyed by these voracious feeders. This could happen as early as four days after the first emergence of the seedlings.

Weed control

Weed control is of vital importance in the fight against the pest, and pre-planting weed management is crucial. Weed species with aerial parts covering an extended surface area create an ideal habitat for cutworm larvae and accommodate many more of the pests than small or spindly weeds.

Between 20 and 30 larvae per plant in the case of Senecio species (ragwort) and 77 larvae per plant with Conyza bonariensis (fleabane) have been reported. Where practically possible, plough lands 35 days before planting and keep them free of weeds and volunteer plants until planting.

This will starve to death any small cutworms that may already be present in the soil.
If you have planted a herbicide-tolerant maize variety, you may need to apply herbicide after seedling emergence to kill off weeds, as well as insecticide to control the cutworm.
 If you see cutworm damage after plant emergence, apply a registered insecticide to control the larvae. Cutworm larvae remain below the surface when the soil is hot and dry. This inhibits the effectiveness of insecticides.
 

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