Erschoviella musculana
(Asian walnut moth)

Pictures

Top of page

Identity

Top of page

Preferred Scientific Name

• Erschoviella musculana Ershov

Preferred Common Name

• Asian walnut moth

Other Scientific Names

• Nycteola musculana Ershov
• Sarrothripus musculana Ershov

International Common Names

• English: walnut moth

EPPO code

• ERSHMU (Erschoviella musculana)

Taxonomic Tree

Top of page

• Domain: Eukaryota
•     Kingdom: Metazoa
•         Phylum: Arthropoda
•             Subphylum: Uniramia
•                 Class: Insecta
•                     Order: Lepidoptera
•                         Family: Noctuidae
•                             Genus: Erschoviella
•                                 Species: Erschoviella musculana

Notes on Taxonomy and Nomenclature

Top of page E. musculana attacks wild and cultivated varieties of Juglans regia (Pavlovskii and Shtakelberg, 1955; Degtyareva, 1964).

Description

Top of page Eggs

The egg is yellowish-grey to reddish-grey, spherical, 0.5 mm in diameter, strongly flattened from below and slightly flattened from the top, covered by small ribs. Both poles are covered by the net of hexagonal cells forming a star at the top (Vassiliev, 1912).

Larva

The neonate larva is cream-white to yellowish-white, 2-3 mm long with dark-brown head (0.5 mm in diameter) and with pronotum covered by a few long light hairs. The fully grown caterpillar before pupation is 15-20 mm long and approximately 5 mm wide at the first abdominal segment, light greenish-cream to greenish-brown or reddish-brown with pattern formed by small brown spots and specks. A light brownish pulsing dorsal vessel is visible through the middle of the dorsal part of the body. The body is covered by a few light brownish-cream hairs based on small dark-brown round scutella. These hairs are short on the head and rather long on the dorsal and lateral sides of the body. The anal plate is dark-brown. The pronotum is brown to greenish-brown. Thoracic legs are dark-brown and matt. Abdominal legs are of the same colour as the rest of the body. The head is brown and bright, 3-4 mm in diameter. The stigmata are very small (Vassiliev, 1912; Degtyareva, 1964; Dzhaparov, 1990).

Pupa

The pupa is 11-12 mm long and 3.5-3.6 mm wide. The head, antennae, legs and wings are light brownish-ochre. A wide, darker brown to black-brown longitudinal stripe runs along the dorsal side. The abdomen is mat, light greenish-brownish-ochre. The last two tergites have transverse wrinkles. The top of the abdomen is rounded and has no cremaster. The pupa is in a snow-white dense cocoon, which is 12-14 mm long and 4.5-5.2 mm wide (in the middle), and which is narrowed at both ends (Vassiliev, 1912; Degtyareva, 1964).

Adult

The adult wingspan is 18-23 mm. The length of the body is 8-9 mm. The fore wings are, in general, leaden-grey with transverse brown, white and black bands and lines. The wing fringe is grey with black points. The hind wings are monochrome grey. The thorax is grey or brownish-grey with dark transverse stripe. The antennae are thin, light brown to dark brown, covered by rare small hairs. The palpi are long and thin, grey with dark tops. The underside of wings and of the body is monochrome light grey (Vassiliev, 1912).

Distribution

Top of page In Central Asia, outbreaks of E. musculana occur in valley and mountain forests and orchards up to an altitude of 1900-2100 m.

Distribution Table

Top of page

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 10 Jan 2020

Risk of Introduction

Top of page E. musculana is considered as a serious walnut pest in many southern countries of the former USSR. It is very likely to be able to establish in the many European and Mediterranean countries of the south and east of the Europe where its host plants are important nut trees.

Host Plants and Other Plants Affected

Top of page

Symptoms

Top of page Damaged fruits are usually easily recognized by brown excrement accumulated at the entry hole of the caterpillar in the fruit or in the shoot. Aggregations of pest pupae are easily detected under loose bark and in other refuges. Damaged shoots often show yellowing and wilting (Vassiliev, 1912; Degtyareva, 1964).

List of Symptoms/Signs

Top of page

Biology and Ecology

Top of page In valleys and on southern slopes of mountains at altitudes of 1100-1300 m, the mass flight of the first generation of E. musculana usually occurs from the beginning of April until the end of May. The mass flight of the second generation occurs in June-July. The mass flight of the third generation occurs in August. At higher altitudes (1700-1900 m), the pest develops only two generations per year. In this case, the first generation flies in May and the second at the beginning of August. Above 1900 m, the pest develops only one generation per year and the flight is from the end of May until June. Adults feed on nectar and live for 21 days. The female lays 30-120 eggs, usually two or three together on young nuts (often where two nuts are touching) or on buds of one-year-old shoots of walnut. Neonate caterpillars usually enter the young nut through the petiole and feed there. After finishing one nut, a caterpillar passes into another and continues to feed. Infested nuts usually contains one caterpillar but it is possible to find nuts with two, and even three, caterpillars. The caterpillar moults four times. Development takes 25-40 days. When leaving the fruit before pupation, the caterpillar makes a round emergence hole, which is much larger than the entrance hole and is not filled with excrement. Caterpillars of the autumn generation cannot enter the nut, and so feed only in the pericarp. Caterpillars also often feed in the centre of young one-year-old shoots and even in leaf axils; this happens more often during years of low harvest of nuts. In this case, the entrance hole (usually at the base of leaf petiole) is also small and filled with excrement (easily seen from outside), whereas the round emergence hole (usually in the terminal bud) is much larger and free from excrement. Caterpillars usually spend all their life inside nuts and shoots, and they leave them only to find a place for pupation. They usually pupate in deep cracks in the bark or under loose bark in the butt part of the trunk up to several metres above the soil. It is possible sometimes to find large aggregations of cocoons (up to 170 specimens) in some refuges (usually under loose bark). Caterpillars of the first two generations may also pupate in the grass or on branches. Pupal development takes about 10 days. The pest overwinters at the larva or pupal stage inside the cocoon (Vassiliev, 1912; Degtyareva, 1964; Makhnovskii, 1955, 1970; Dzhaparov, 1990).

Natural enemies

Top of page

Means of Movement and Dispersal

Top of page E. musculana can spread by flight of the adult moths. All stages of the life cycle can be transported with walnut fruits (inside nuts) and on walnut plants moving in trade (inside shoots), particularly plants for planting and cut branches. Eggs, larvae and pupae (cocoons) may be associated with wood containing bark and may be present as contaminating pests on other products.

Impact

Top of page E. musculana is the most important pest of walnuts in the countries of its present distribution. It is first of all an important pest of walnut fruits. Young fruits damaged by the pest caterpillars fall. One caterpillar may destroy several fruits. Even in the case when caterpillars feed in the pericarp, fruits are deformed and do not usually produce normal nuts. In this way the pest considerably reduces the yield of nuts (by as much as 70-80%). This causes direct economic damage in commercial walnut orchards, and interferes with natural regeneration of walnut forests in mountains (causing erosion). In the years of low yield of nuts, the pest caterpillars feed inside young shoots causing them to wilt. In this case, the most important damage is observed on young trees. The pest may damage mountain walnut forests up to 1900-2100 m (Vassiliev, 1912; Degtyareva, 1964; Makhnovskii, 1970; Dzhaparov, 1990).

Assessment of the economic impact of the pest in 1986/1988 in Kyrgyzstan showed high losses of the walnut growing enterprise 'Arslanbob' due to E. musculana (Dzhaparov, 1990).

Prevention and Control

Top of page

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Possibilities for control of the pest are very limited. During almost all its life cycle, it is well protected against chemical and bacterial treatments. On young trees, trapping bands are used against pest caterpillars. Removing and destruction of fallen fruits may give good results. It is also possible to destroy aggregations of pest pupae under loose bark (Degtyareva, 1964; Makhnovskii, 1970; Dzhaparov, 1990).

The natural enemies of E. musculana may play an important role in regulation of its populations. Sixteen species belonging to Ichneumonidae, Braconidae, Pteromalidae, Torymidae, Trichogrammatidae, Carabidae, Raphidiidae and Formicidae are recorded as parasitoids and predators of the pest. The most frequent of these are Trichogramma sp. and Pimpla instigator. Sometimes, caterpillars are infected by the bacterium Bacillus thuringiensis or the fungus Beauveria bassiana (Degtyareva, 1964; Dzhaparov, 1990).

Phytosanitary Measures

E. musculana was added in 2003 to the EPPO A2 action list, and endangered EPPO countries are thus recommended to regulate it as a quarantine pest. Since the risk of introduction of E. musculana with fruits, cut branches or wood appears low enough to be acceptable, phytosanitary measures need concern only plants for planting of Juglans spp. Freedom from the pest can be ensured by a pre-export inspection.

References

Top of page

===, 2005. Erschoviella musculana. Bulletin OEPP/EPPO Bulletin, 35(3):425-428. http://www.blackwell-synergy.com/servlet/useragent?func=showIssues&code=epp

CABI/EPPO, 2005. Erschoviella musculana. Distribution Maps of Plant Pests, No. 673. Wallingford, UK: CAB International

Degtyareva VI, 1964. [The Main Lepidopteran Pests of Trees and Shrubs of the Central Part of Gissar Mountain Ridge and Gissar valley.] Izdatel’stvo Akademii Nauk Tadzhikskoi SSR, Dushanbe (TJ) (in Russian)

Dzhaparov EB, 1990. [Biology and ecology of Erschoviella musculana in walnut forests of Southern Kirgizia.] Doctoral Thesis, Leningrad Forest Technical Academy, Sankt-Peterburg, Russia (in Russian)

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm

Makhnovskii IK, 1970. The walnut moth. Zashchita Rastenii, 15(3):30-32

Vassiliev IV, 1912. [Oriental leaf beetle Agelastica orientalis Baly and walnut moth Sarrothripus musculana Ersch. - two pests of Turkestan horticulture.] Proceedings of the Bureau of Entomology v, IX, 7. Merkushev, Sankt-Peterburg, Russia (in Russian)

Yildiz, Y., Ayberk, H., 2019. The first parasitoid record of Garella musculana (Nolidae, Lepidoptera) from Turkey; Pimpla spuria (Ichneumonidae, Hymenoptera). Applied Ecology and Environmental Research, 17(2), 3427-3431. doi: 10.15666/aeer/1702_34273431

Yildiz, Y., Yildirim. I., Bostanci, C., Aydogan, O., 2018. Erschoviella musculana Erschoff 1874, a new record and a new walnut pest in Turkey. Journal of Bartin Faculty of Forestry, 20(2), 296-302. http://dergipark.gov.tr/download/article-file/475282

Distribution References

CABI, EPPO, 2005. Erschoviella musculana. [Distribution map]. In: Distribution Maps of Plant Pests, Wallingford, UK: CAB International. Map 673.

CABI, Undated. Compendium record. Wallingford, UK: CABI

CABI, Undated a. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI

EPPO, 2014. EPPO Global database (available online). Paris, France: EPPO. https://gd.eppo.int/

Yildiz Y, Yildirim I, Bostanci C, Aydogan O, 2018. Erschoviella musculana Erschoff 1874, a new record and a new walnut pest in Turkey. In: Journal of Bartin Faculty of Forestry, 20 (2) 296-302. http://dergipark.gov.tr/download/article-file/475282

Distribution Maps

Top of page