Noctuid characteristics used in identification
The noctuid pests common in Washington orchards share many similar characteristics. Understanding the general characteristics of noctuids will allow growers to identify these pests based on specific differences.
Typical noctuid eggs are almost spherical with a slightly flattened top and tiny opening in the center called amicropyle. The egg has between 29 and 50 ribs, depending on species. Eggs are found on a variety of host plants in large batches (100-150), often in neat diagonal rows.
Noctuid larvae can change dramatically in appearance during their life cycle. Young larvae are generally green in color and move in a geometrid or inch-worm fashion. Noctuid larvae also have three stripes that run the length of their body. These stripes can range from obvious to somewhat indistinct in appearance. As larvae mature they can change color, often dramatically, and this base color can be different from individual to individual. The easiest way to distinguish between the main orchard pests is the marking on the last few segments of the larvae, rather than the coloring.
Noctuid adults of common orchard pests have generally nondescript coloring. However, identification is made easier by closer examination of the colorings and patterns of the reniform and obicular spots on the wings. These markings make distinguishing between bertha armyworm, spotted cutworm and Lacanobia subjuncta relatively easy.Back to Top
Spotted cutworm (Xestia c-nigrum)
The adult moth is a dark gray-black and has a distinct pyramid-shaped orbicular spot in white bordered with black and a brown reniform spot.
The mature larva turns brown, and black triangles appear on the seventh to ninth abdominal segments. There may be triangles on all abdominal segments, but they tend to be paler on the forward segments. Usually it has a light subspiracular stripe tinged with yellow or orange.
The spotted cutworm overwinters as a mature larva. The larva does not enter a diapause condition and thus is able to feed as soon as spring temperatures warm enough to allow for movement (>50F).
Spotted cutworm larvae spend the days sheltered in the ground cover and feed nocturnally on tree fruit hosts. The larvae will leave a chemical trail and often return to the same shoot to feed on successive days. In the spring overwintering larvae will feed on fruiting buds or fruitlets. Damage is often noted before the cover crop or fruit trees begin to grow, thus making fruiting buds particularly vulnerable. Since mature larvae are present in orchards through the entire fall season, spotted cutworm larvae can damage the latest maturing apples through harvest. Overwintering larvae are often found on mullein plants.
Bertha Armyworm (Mamestra configurata)
The adult moth is gray with a black-green background color. The green fades after it dies. The orbicular wing spot is gray or gray-brown with a black border and the reniform spot is white.
The egg is white when first laid, but turns purple prior to hatch. It has about 38 ribs. Eggs are laid on host plants, including apple and pear, in batches of 100 to 150 in neat diagonal rows.
The neonate larva has distinct black spots at the base of dark setae and the head capsule is dark brown to black. Young larvae can be gray, brown or green with five broken white stripes. The later instars generally turn brown with conspicuous yellow stripes often flushed with orange. No matter what the basic color, the larva always has black patches down the center back which help distinguish this species.
The Bertha armyworm overwinters as a pupa, thus there are no larvae present early in the season. Most damage to foliage or fruit is seen during late June and in late August.
Newly hatching larvae feed close to the egg mass, removing most of the green leaf tissue, leaving only a thin layer of the upper epidermis. This type of feeding is called "window pane". Older larvae can consume entire leaves, or excavate holes in fruit.
Bertha armyworm requires a weed host to complete its lifecycle. Poor weed control is often implicated in outbreak situations. This species is found often on pigweed and lamb's-quarter. The behavior and life history of this pest is closely associated with L. subjuncta. However, it appears that pear is a better host for bertha armyworm than Lacanobia subjuncta.
The L. subjuncta adult has characteristic wing patterns that range from light brown to black in color. The reniform and orbicular spots are light brown with a black border. These spots are relatively easy to identify.
Eggs are laid on the underside of fruit tree leaves. The eggs are pale gray when laid and turn a slightly purple color as they mature. Eggs are grouped together in masses of approximately 100 eggs. They are not as neatly grouped as bertha armyworm, and don't turn as dark purple.
The larvae are the most characteristic stage of L. subjuncta. Neonate larvae are similar in appearance to bertha armyworm, but do not have as dark a head capsule. Young larvae are green with broken white stripes. Larvae change both their color and pattern as they mature. Later instars generally change color and range from green to tan to a light red or brick color. It is the mature larvae that display the characteristic herringbone pattern on their dorsal side.
Newly hatched L. subjuncta larvae feed in a clustered group near the egg mass. Young larvae feed on the lower leaf surface removing most of the green leaf tissue between leaf veins. The upper epidermis of the leaf is left in tact creating a window-pane effect. As larvae mature, they generally move down the canopy. It appears that a majority of larvae leave the trees in favor of feeding on ground cover; however, a significant number of L. subjuncta remain in the tree.
L. subjuncta larvae feed on leaf tissue first causing holes in the leaf interior or on the periphery and then eating entire leaves. Fruit injury is incidental to foliage feeding but can be quite severe in high pressure areas. Larvae feed directly on fruit by excavating holes (Figs. 4, 8). These holes can be as large as a finger tip. Larvae are very mobile within the canopy and feeding appears to be evenly distributed throughout. Damage is most often associated with areas of the tree that have dense foliage in contact with clustered fruit.