Spodoptera ornithogalli, Yellow-striped Armyworm (Lepidoptera: Noctuidae)

Forest Huval, Reagan, Thomas E.

Bug Biz Pest Management and Insect Identification Series, LSU Ag Center, Research, Extension, Teaching

Authors: Sam des Bordes, Kaylee Deynzer, Forest Huval and T.E. Reagan

Description

The yellow-striped armyworm, Spodoptera ornithogalli, is a common pest of crops and home gardens in the eastern United States. Members of this species have a wide host range, causing fruit and foliar damage to over 17 plant families. Their eggs vary from pink to green in color, around 1/50 of an inch (0.5 mm) in diameter and slightly less in height. Larval coloration varies from tan to dark brown, with characteristic black triangular markings alongside a broad, dark-colored band running along the sides of the body. Mature larvae reach about 1 1/3 inches (35 mm) in length. The pupae are reddish-brown and up to ¾ of an inch (18 mm) in length and are similar to many other noctuid pupae in appearance. Adult moths have a wingspan of 1 1/3 to 1 2/3 inches (34-41 mm). The front wings are mottled with white, tan and brown colors. The hind wings are white and possess a light brown stripe along the edges.

Life Cycle

The yellow-striped armyworm undergoes three to four generations annually, with overwintered pupae emerging during March and April and adults initially becoming active from March through May. Successive broods of adult moths typically emerge during May and June, July and August, and August through November. The eggs are deposited in masses of roughly 500 individuals and are covered with scales from the mother’s body.

Egg masses are placed on foliage, trees and buildings. Approximately six days after being laid, the caterpillars hatch and begin feeding on green, tender foliage. Feeding occurs in groups and only takes place during the day. As they mature caterpillars isolate themselves, and after three weeks they burrow into the soil to pupate. After approximately two weeks in the soil, the pupae emerge as a new generation of adult moths. The last generation of the season overwinters as pupae and continues metamorphosis the following year. Members of this species have very little cold tolerance at all life stages and typically perish or overwinter when conditions get too cold. Development from egg to adult generally takes 40 days during warm-season weather.

Ecological Significance and Pest Status

The yellow-striped armyworm causes damage to plants predominantly through foliar feeding. Larvae strip the leaves to a lacelike appearance and often consume entire leaves. Larval feeding also occurs on plant fruits and roots and may cause damage to tomatoes, cotton and sweet potatoes in Louisiana. This insect pest has a wide host range and causes crop injury to many vegetables throughout its range, including asparagus, beans, beets, cabbage, cantaloupe, carrots, corn, cucumbers, lettuce, onions, peas, potatoes, sweet potatoes, tomatoes, turnips and watermelon. Row crops that may be damaged include cotton, sorghum, soybeans, sugarbeets, sunflowers, tobacco and wheat. Hemp (Cannabis sativa: Cannabaceae) is an emerging crop in Louisiana. and yellow-striped armyworms have been observed on hemp plants during both vegetative and reproductive stages of plant growth. While members of this species cause foliar damage, they do not appear to cause significant damage to the floral structures of hemp. The long-term impact of the species on hemp in Louisiana is unclear and the subject of ongoing research.

Management and Control

The proximity of crops to alfalfa fields and rangelands with susceptible weeds should be considered. After alfalfa is harvested yellow-striped armyworms may migrate to nearby vegetable crops, which serve as secondary host plants. Physical barriers, such as trenches and border plants, can help to mitigate pest pressure.

Several parasitoid wasps serve as natural predators to the yellow-striped armyworm. Rogas laphygmae, R. terminalis, Zele mellea, Chelonus insularis, Apanteles griffini (all Hymenoptera: Braconidae) and Euplectrus plathypenae (Hymenoptera: Eulophidae) may provide effective control if numbers are adequate. A number of tachinid flies have also been found to parasitize yellow-striped armyworm. These include Archytas spp., Choeteprosopa hedemanni Brauer and Bergenstamm, Euphorocera tachinomoides, E. omissa, Lespesia archippivora, L. aletiae, Omotoma fumiferanae, Winthemia quadripustulata and W. rufopicta (all Diptera: Tachinidae). Additionally, nuclear polyhedrosis viruses are highly pathogenic to larvae and reduce fecundity. Consult your parish extension agent for available biological control options in your area.

Insecticides can be applied to the foliage of plants to control actively feeding caterpillars. When larvae are young, the application of formulations with the microbial insecticide Bacillus thuringiensis can be an effective management tool. As always, applicators must follow label instructions. Please see the current Louisiana Pest Management Guide (LSU AgCenter publication No. 1838) for currently approved insecticides.

References

Bisabri-Ershadi B, and L. E. Ehler. 1981. Natural biological control of western yellow-striped armyworm, Spodoptera praefica (Grote), in hay alfalfa in northern California. Hilgardia 49: 1-23.

Capinera, J.L. “Common Name: Yellowstriped Armyworm Scientific Name: Spodoptera Ornithogalli (Guenée) (Insecta: Lepidoptera: Noctuidae).” Yellowstriped Armyworm - Spodoptera Ornithogalli, 2001, http://entnemdept.ufl.edu/creatures/veg/leaf/yellowstriped_armyworm.htm. Accessed 28 October 2020.

Hostetter, D.L., B. Puttler, A. H. McIntosh, R. E. Pinnell. 1990. A nuclear polyhedrosis virus of the yellowstriped armyworm (Lepidoptera: Noctuidae). Environmental Entomology 19: 1150-1154.

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Yellow-striped armyworm larva on hemp (Cannabis sativa: Cannabaceae) (Kaylee Deynzer).

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Young larva of yellow-striped armyworm on peanut (Arachis hypogaea: fabaceae) (Steve L. Brown, University of Georgia, Bugwood.org).

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Yellow-striped armyworm adult moth (Natasha Wright, Braman Termite and Pest Elimination, Bugwood.org).

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Characteristic triangular markings on yellowstriped armyworm larva (Whitney Cranshaw, Colorado State University, Bugwood.org).

11/9/2021 10:45:37 PM
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