Identification and Control of the Tea Tree Pest Nosophora semitritialis

Nosophora semitritialis (Lederer), belonging to the family Crambidae, subfamily Spilomelinae, order Lepidoptera, is a common leaf-feeding pest on tea plants.

The larvae of N. semitritialis primarily web leaves together with silk and hide within them, preferring to feed on young leaves and shoots that have grown in the current year. In the field, the damage resembles that caused by leaf-rolling moth pests. As the larvae grow older, the leaves they consume will show “window-pane” damage, notches, or only the main veins remaining. Severe infestations can result in the complete consumption of leaves and shoots, leaving bare twigs.

Before pupation, mature larvae of N. semitritialis will bite an elliptical leaf, roughly the length of their bodies, to use as a “blanket” covering their bodies. They then sew its edges to the underlying leaf to create a pupal chamber and pupate inside it (Fig. 1). The larvae of N. semitritialis, besides feeding on tea plants, also feed on plants such as oleifera Abel. and Schima superba Gardn. et Champ.

Fig. 1 Pupation of N. semitritialis with a “blanket”

1 Geographical Distribution

N. semitritialis is known to be distributed in , Jiangxi, Beijing, , Anhui, Hubei, , Guizhou, , Yunnan, Gansu, Guangdong, Hainan, and Fujian provinces in China; internationally, it is found in Japan, Myanmar, Indonesia, India, Bhutan, and the Philippines.

2 Morphological Characteristics

N. semitritialis is a holometabolous insect, undergoing four stages: adult, egg, larva, and pupa to complete one generation.

2.1 Adult

The adult of N. semitritialis is about 12 mm long with a wingspan of 22-30 mm. Its forehead is yellowish-white, and the top of its head is white. Its antennae are yellowish-brown and filiform. The labial palpi are yellowish-brown, with the ventral side of the base being white and the second abdominal segment having grayish-black, bristle-like long hairs in males. The dorsal side of the thorax and abdomen is yellowish-brown, and the legs are white, with the tibia of the forelegs being brown at the end. The basal half of the forewings is yellowish-brown, while the rest is tea-brown or yellowish-brown, with a semi-transparent white spot shaped like a long oval and a trapezoid joining at the end of the median cell. The outer side and below the spot are tea-brown. The inner and outer transverse lines are dark brown and wavy. The hindwings are tea-brown, with the base and the front edge being yellowish-white, and there is a large, semi-transparent square white spot outside the median cell. The fringes of both fore and hindwings are tea-brown (Fig. 2).

Fig. 2 Adult of N. semitritialis

2.2 Egg

The eggs of N. semitritialis are elliptical, about 0.75 mm long and 0.55 mm wide. Initially, they are milky white or light yellow and laid in clusters. Before hatching, they turn slightly red.

2.3 Larva

The larvae of N. semitritialis go through six instars and have a flattened, round body shape. Newly hatched larvae are white; as they grow, younger larvae show green food in the center of the thorax and abdomen and black feces at the tail (Fig. 3); later, the body color gradually turns uniform grass-green, with the head being yellowish-green with light brown patterns (Fig. 4); mature larvae are 18.6-23.5 mm long, with a head capsule width of 1.8-2.0 mm, pale yellow to reddish-brown, the head being brown, and the ocelli and the prothoracic shield being reddish-brown (Fig. 5). There are 1-3 black spots on the sides of each thoracic segment and the first, eighth, and tenth abdominal segments. Each abdominal segment has four setose tubercles, each bearing a bristle. The thoracic and abdominal legs are yellowish-green.

Fig. 3 Young larvae of N. semitritialis

Fig. 4 Older larvae of N. semitritialis

Fig. 5 Mature larvae of N. semitritialis (pre-pupal stage)

2.4 Pupa

The pupa of N. semitritialis is 8.5-13.0 mm long and 2.5-3.5 mm wide, reddish-brown, and spindle-shaped. It becomes brownish when close to eclosion, with six hook-like spines at the end of the abdomen (Fig. 6).

Fig. 6 Pupa of N. semitritialis

3 Occurrence Characteristics and Habits

N. semitritialis has about three generations per year, with young larvae overwintering by webbing leaves together and hiding within them.

Larvae mainly feed on the tender leaves and leaves grown in the current year located in the upper part of the tea plant. They often spin silk to web leaves into a cocoon and hide inside to feed. Young larvae have a small appetite, mainly hiding in the cocoons to feed on the mesophyll, forming “window-pane” damage and excreting feces inside the cococon (Fig. 7-A). After the third instar, their appetite increases significantly, and they often web adjacent leaves into an olive-shaped cocoon. Besides hiding inside to feed, they may also come out to feed on leaves, causing notched damage (Fig. 7-B), or find other leaves to web for continued feeding. Larvae have the habit of spinning silk to hang down and are usually inactive, staying quietly within the cocoons. When startled, bumped, or feeding, they can move quickly forward and backward, or even jump out of the cocoon or spin silk to hang down and escape, moving very agilely. Before pupating, mature larvae often transfer to another new leaf, biting an elliptical leaf similar in length to their bodies to use as a “blanket” to cover their bodies. They seal the edges with the leaf beneath to form a pupal chamber and pupate inside it (Fig. 1).

Adults have a strong phototaxis and remain hidden on the underside of leaves during the day without moving. When startled, they fly short distances rapidly and nimbly. Eggs are laid in clusters, primarily near the main veins on the underside of leaves.

Fig. 7 Damage caused by larvae of

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