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Where do armyworms come from?


February 13, 2024


The Searles Gardening Team

Lawns are often preyed upon by curl grubs and armyworms. Curl grubs are the offspring of beetles, and armyworms are caterpillars and the progeny of moths. In addition, there are several different types of armyworms, but today, we will concentrate on lawn armyworms.

They are easily distinguished by their dark bodies and the white or yellow striped patterns along the sides of the caterpillar. In the moth stage, they are light brown with their four wings in a V shape when resting, with a white spot in the centre of the front wings. Under the eaves of houses can be the perfect place for these moths to lay eggs, as the young drop from the eggs into the lawn or garden. They also lay their eggs on plants near food sources.

Throughout spring and autumn, 2-3 generations can occur; this depends on temperature so that it can vary from state to state. The moths lay their eggs that hatch within a ten-day period and then fall to the ground. Over the course of up to five weeks they can change into moths, that live for up to two weeks. The pupation occurs in tunnels in the ground. The number of small moths attracted to night lights may increase significantly when they emerge. The sheer number of caterpillars is the reason for the damage done to the lawns rather than how ravenous a few could be.

Insecticides to kill armyworms affect only those actively eating and do not kill the next generation's eggs; that is why re-applying is so important. The female can lay up to 1000 eggs in her lifetime. There are some natural predators for armyworms, but chemical controls are more effective in large numbers. Application of treatment in the late afternoon works well as they can be most active at this time or in the evening when the day's heat does not affect them. The caterpillar may also produce a fine thread; upon close inspection, you can see this on the lawn’s leaves.

Armyworms prefer well-kept lawns as they are watered and fertilised regularly and have plenty of green growth. Regular treatment when the pest is present is required if you want a pristine lawn. Nature does try to keep them in check with birds, frogs, wasps, etc., but since they are always in large numbers, chemical treatment is sometimes required to save the lawn from destruction.

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