Euscepes postfasciatus (West Indian sweet potato weevil)
Identity
- Preferred Scientific Name
- Euscepes postfasciatus (Fairmaire, 1849)
- Preferred Common Name
- West Indian sweet potato weevil
- Other Scientific Names
- Batatarhynchus destructor Hustache, 1933
- Cryptorhynchus batatae Waterhouse, 1850
- Cryptorhynchus postfasciatus Fairmaire, 1849
- Euscepes batatae (Waterhouse, 1850)
- Hyperomorpha squamosa Blackburn, 1885
- International Common Names
- Englishscarabee weevilsmall sweet potato weevil
- Spanishbroca del camotegorgojo de la batatapicudo de la batata de las Indias Occidentales
- Frenchcharançon de la patate douce
- Portuguesebroca do tuberculo da batata-doce
- Local Common Names
- Japanimozo-mushi
- EPPO code
- CRYPBA (Euscepes batatae)
- EPPO code
- EUSPPO (Euscepes postfasciatus)
Pictures
Distribution
Host Plants and Other Plants Affected
Host | Host status | References |
---|---|---|
Daucus carota (carrot) | Unknown | Muruvanda et al. (1986) |
Ipomoea (morning glory) | Other | |
Ipomoea acuminata | Wild host | |
Ipomoea aquatica (swamp morning-glory) | Other | |
Ipomoea batatas (sweet potato) | Main | Follett (2006) Kohama and Sugiyama (2000) Maeto and Uesato (2007) Nakamoto and Kuba (2004) Reddy et al. (2012) Sato et al. (2010) Fatiaki et al. (2017) Santos et al. (2021) |
Ipomoea indica (ocean blue morning-glory) | Unknown | Sato et al. (2010) |
Ipomoea pes-caprae (beach morning glory) | Unknown | Sato et al. (2010) |
Pharbitis nil (Japanese morning glory) | Main | |
Raphanus sativus (radish) | Unknown | Muruvanda et al. (1986) |
Symptoms
Under heavy infestation, the entire root is riddled and filled with faecal matter. It becomes dark in colour, light in weight and spongy in appearance (Sherman and Tamashiro, 1954). An unpleasant smell is characteristic of this damage and the affected roots taste bitter (Alleyne, 1982a). Larval damage is similar to that of Cylas formicarius and both cause the roots to produce furano-terpenoids and coumarins, making them unpalatable (Uritani et al., 1975). Larvae bore into the root just below the epidermis; the feeding tunnels are defined as sunken areas on the surface of the sweet potato (Sherman and Tamashiro, 1954). Heavily infested vines become enlarged, malformed and cracked (Sherman and Tamashiro, 1954). Adults emerge by chewing exit holes, so emergence holes are visible on the surface of roots or stems (Raman and Alleyne, 1991).
List of Symptoms/Signs
Symptom or sign | Life stages | Sign or diagnosis |
---|---|---|
Plants/Roots/internal feeding | ||
Plants/Stems/internal feeding |
Prevention and Control
Cultural Control and Sanitary Methods
Historically, weevil management has relied on cultural control measures such as the use of non-infested planting material, crop rotation, removal of volunteer plants and crop debris, prompt harvesting, removal of alternate wild hosts, planting away from weevil-infested fields, banking or planting in light soils that do not crack, and sufficient irrigation to reduce soil cracking (Sherman and Tamashiro, 1954; Chalfant et al., 1990).
Host-Plant Resistance
Host resistance to E. postfasciatus has only recently been studied. Field screening tests have been conducted in Tonga (Pole, 1988; Raman and Alleyne, 1991), Peru (Raman and Alleyne, 1991) and Barbados (Alleyne, 1982b).At the moment, no breeding programmes are being conducted to incorporate resistance to this weevil (Raman and Alleyne, 1991).
Biological Control
Very little information is available on biological control for E. postfasciatus. Raman and Alleyne (1991) assessed the potential of Beauveria sp. as a biocontrol agent and several parasites have been reported (Parasram, 1970).
Chemical Control
Yasuda (1991) showed that spot treatment of granulated carbosulfan on the ground around the stem was more effective at reducing infestation levels in the roots and stems than the conventional practice of spraying uniformly throughout the field.
Economic Threshold Levels
Yasuda (1997b) calculated the regression equation to express the relationship between the proportion of damaged sweet potato storage roots at harvest and the percentage of injured stems on day 75 after planting. Based on this equation, the threshold level of stems injured during the growing period for a tolerable damage level (13.6% of roots damaged at harvest) was estimated to be 5%. Insecticide application for this control threshold was as effective as the conventional application and required two rather than three applications.Sterile Insect Technique (SIT)An experimental eradication project for E. postfasciatus with SIT is currently in progress on Kume Island, Okinawa, Japan (Moriya, 1995; Kuba et al., 2000; Yamagishi and Shimoji, 2000).
Impact
E. postfasciatus is a major pest of sweet potato in the Pacific, Caribbean basin and some countries of South America (Raman and Alleyne, 1991). Even low-level infestations of this weevil reduce marketable yield because sweet potato roots produce furano-terpenoids in response to weevil feeding that make even slightly damaged roots unpalatable (Uritani et al., 1975). In the Caribbean, the weevil has caused extensive damage to roots both in the field and in storage for as long as sweet potato has been grown (Tucker, 1937; Parasram, 1970; Alleyne, 1982b).In Japan, the weevil is the most serious pest of sweet potato in the Ryukyu Islands (Kohama, 1990). Japanese phytosanitary regulations prohibit the transport of sweet potatoes from these islands to markets in mainland Japan.
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Copyright © CABI. CABI is a registered EU trademark. This article is published under a Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
History
Published online: 9 October 2023
Language
English
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