Lawn armyworm (Spodoptera mauritia) is a type of caterpillar which feeds mainly on lawns but can do damage to a few other plants like ornamental grasses and sweet corn. The caterpillar has a smooth body, dull brown/green in colour with black stripes or triangular markings along each side. They grow to approximately 4-5cm long and will curl up into a tight ball when disturbed. The adult is a grey/brown moth with a wingspan about 3-4cm wide.
Female moths can lay more than 1,000 eggs within 10 days and when hatched the caterpillars all stay together feeding on leaves, stems and seed heads. With so many hungry caterpillars altogether it’s not surprising that they can completely demolish a beautiful lawn in no time at all. Once they have devoured all food in one area they march off together to the next area just like an army.
Feeding occurs mainly in the evening and at night. During the day they hide under blades of grass and in the thatch. If you’re unsure if lawn armyworm are the cause of the damage then pour a bucket of soapy water over the area. They dislike the soap and will wriggle to the surface in a few minutes.
Mostly noticed on lawns but can also attack other ornamental grasses in garden beds, sweet corn and cereal crops.
Organic Control Methods for Lawn Armyworm
- Apply eco-neem at first sign of pest infestation and before lawn armyworm numbers build up to damaging levels. Apply with a watering can and ensure thorough coverage of treated areas.