Armyworms are voracious feeders of turfgrass / by Ganpati Jagdale

Interaction between entomopathogenic nematodes and armyworm caterpillars

All the larval (caterpillar) stages of armyworm feed on turfgrass leaves but their adult moths are not harmful to any plant species. Generally caterpillars feed on grass leaves during night time but during day time, they hide under thatch.

Armyworm Moth
Armyworm Moth

You will start noticing the presence of larvae of armyworm in your laws from June through August as they hatch from eggs during that period.

Armyworm Larva
Armyworm Larva

This is a right time to adopt effective control measures to target larval stages of armyworms. The effective control measures for armyworms can be chemical insecticides or biological control agents. However, most of the chemical insecticides have been restricted to use on home lawns, recreational parks and golf courses because of their deleterious effects on humans, both pet and wild animals, and the environment.

Biological control agents:

Therefore, the biological control agents including Nucleopolyhedrovirus, parasitoids(Braconid wasps, Apanteles spp. or Tachinid flies) and entomopathogenic nematodes (also called as beneficial nematodes) can serve as an alternative to chemical pesticides in controlling armyworms. Beneficial nematodes are also not harmful to animals, kids, pets, beneficial insects such as honeybees or the environment.

Beneficial Nematodes:

Three species of entomopathogenic nematodes including Steinernema carpocapsae, Heterorhabdtis indica and Heterorhabdtis bacteriophorahave showed a potential to manage armyworm infestation in the yards, parks and golf courses.

Steinernema carpocapsae infected Armyworm larval cadaver
Steinernema carpocapsae infected Armyworm larval cadaver

To protect from harmful UV light, it is advisable that the nematodes should applied early in the morning or late in the evening using Knapsack/backpack sprayers for the area over 5000 square feet and watering cans for the area less than 5000 square feet.

For the ideal control of armyworm larvae, Steinernema carpocapsae, Heterorhabdtis indica and Heterorhabdtis bacteriophora nematodes should be applied at the optimal rate of 1 billion infective juveniles/ acre in 100 to 260 gallons of water.

Literature

Andalo, V., Santos, V., Moreira, G.F., Moreira, C., Freire, M. and Moino, A. 2012.   Movement of Heterorhabditis amazonensis and Steinernema arenarium in search of corn fall armyworm larvae in artificial conditions.  Scientia Agricola 69: 226-230.

Ansari, M.A., Waeyenberge, L. and Moens, M. 2007.  Natural occurrence of Steinernema carpocapsae, Weiser, 1955 (Rhabditida: Steinernematidae) in Belgian turf and its virulence to Spodoptera exigua (Lepidoptera: Noctuidae). Russian Journal of Nematology 15: 21-24.

Kim, J. and Kim, Y. 2011.  Three metabolites from an entomopathogenic bacterium, Xenorhabdus nematophila, inhibit larval development of Spodoptera exigua (Lepidoptera: Noctuidae) by inhibiting a digestive enzyme, phospholipase A (2). Insect Science 18: 282-288.

Negrisoli, A.S., Garcia, M.S., Negrisoli, C.R.C.B., Bernardi, D. and da Silva, A. 2010.  Efficacy of entomopathogenic nematodes (Nematoda: Rhabditida) and insecticide mixtures to control Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) in corn crops. Crop Protection 29: 677-683.