Mango seed weevil Sternochetus mangiferae (Fabricius, 1775) Coleoptera:Curculionidae

Transcription

1 Islamic Republic Of Iran Ministry of Jihad-e-Agriculture Plant Protection Organization A Guide for Diagnosis & Detection Of Quarantine Pests Mango seed weevil Sternochetus mangiferae (Fabricius, 1775) Coleoptera:Curculionidae Edited by: Ahmad cheraghian Bureau of Plant Pest Surveillance and Pest Risk Analysis 2014

2 Sternochetus mangiferae (Fabricius, 1775) Coleoptera: Curculionidae Common name: Mango seed weevil, Mango stone weevil, Mango weevil Synonyms: Cryptorhynchus mangiferae (Fabricius), Acryptorhynchus mangiferae (Fabricius) Curculio mangiferae, Sternochetus ineffectus (Walker) Economic impact: All cultivars are susceptible to mango seed weevil attack but no external symptoms of attack are readily visible on infested fruits, apart from the brown hardened secretion remaining attached to them at the sites of oviposition. Marketability is not directly affected because the weevil resides inside the seed within a thick husk in mature mangoes and is rarely encountered. However, emerging adults cause post-harvest damage to the pulp of late-maturing cultivars in South Africa (Kok, 1979). The adults tunnel through the fruit, leaving scars on the outside which serve as sites for secondary fungal infection. Also, mango seed weevil infestation may increase fruit drop during early fruit development (Follett 2002), and may reduce the germination capacity of seeds. In Hawaii, germination rates for infested seeds were equal to that of uninfested control seeds in a polyembryonic cultivar ('Common'), whereas germination was significantly reduced for infested seeds of a monoembryonic cultivar ('Haden') compared with uninfested control seeds but germination of infested seeds was still >70% (Follett and Gabbard, 2000). Probably its greatest significance as a pest is to interfere with the export of fruit because of quarantine restrictions imposed by importing countries. In India, all cultivars are susceptible and levels of infestation vary from 48 to 87% (Bagle and Prasad, 1985). Hosts: Major hosts: Mangifera indica (mango) Minor hosts: Mangifera foetida (bachang) Geographic distribution: Asia: Bangladesh, Bhutan, China, Taiwan, India, Indonesia, Malaysia, Maldives, Myanmar,, Nepal, Oman, Pakistan, Philippine, Sri Lanka, Thailand, Vietnam, Yemen, Africa: British Indian Ocean Territory, Gabon, Ghana, Guinea, Kenya, Liberia, Madagascar, Malawi, Mauritius, Nigeria, Réunion, Seychelles, South Africa, Tanzania, Uganda, Zambia Australia and Pacific Island: Australia, Belau, Fiji, French Polynesia, Guam, New Caledonia, Northern Mariana Islands, Tonga, Wallis and Futuna. North America: U.S.A., Central America: Barbados, British Virgin Islands, Dominica, Grenada, Guadeloupe, Montserrat, Puerto Rico, Saint Lucia, Saint Vincent and the Grenadines, Trinidad and Tobago, United States Virgin Islands

3 World distribution map of Sternochetus mangiferae Morphology: Eggs When freshly laid the eggs are creamy-white. They are elliptical, mm (mean 0.79 plus or minus 0.20 mm) long and (mean 0.29 plus or minus 0.01 mm) wide. Larvae First instar larvae are elongate, cylindrical, legless and extremely slender; they are mm (mean 1.39 plus or minus 0.01 mm) long, and (mean 0.35 plus or minus 0.02 mm) wide. The body is white and the head is black. Final instar larvae (4th or 5th instar) are white and legless, they have a curved, typical curculionid form, and are mm (mean 16.7 plus or minus 0.28 mm) long, and mm (mean 8.0 plus or minus 0.32 mm) wide (Shukla and Tandon, 1985). The head is black, and is not retracted into the prothorax. The pronotal plate is strongly transverse. The typical abdominal segment is tripartite. The terga does not have coarse asperities, and the spiracles are annular biforous. A detailed description of the larva with diagnostic characters separating it from that of Sternochetus frigidus has not been published. The larva of S. frigidus was described by Gardner (1934) and Rahman and Ahmad (1972). Pupae The pupae are whitish when newly formed, but change to a very pale red colour just before eclosion. They are mm (mean 8.6 plus or minus 0.27 mm) long and mm (mean 6.95 plus or minus 0.22 mm) wide. The abdominal apex has paired urogomphi. Adults The adults have a compact body, mm long. They are black, and covered with black, greyish or yellowish scales. The pronotum is subparallel-sided in the basal third only. Interstices 3, 5 and 7 of the elytra are strongly carinate. There is an indistinct oblique pale humeral stripe on the elytra which is elongate (6:4) and gradually declivous behind. The femora have a single large tooth ventrally. The profemora are stout, and distinctly clavate. The tarsal claws are simple and free. The female has an elevated ridge at the pygidial apex, which is absent in the male.

4 Egg Larvae Pupae Adults Egg, Larvae, Pupae& Adults of Sternochetus mangiferae

5 Eggs Egg of Sternochetus mangiferae

6 Larvae Larvae of Sternochetus mangiferae

7 Pupae Pupae of Sternochetus mangiferae

8 Adults Adults of Sternochetus mangiferae

9 Adults Adults of Sternochetus mangiferae

10 Head Side Head Below Head Front Pronotum Rostrum Elytra Abdomen Leg Hind Adults of Sternochetus mangiferae

11 Biology and ecology: In Tamil Nadu, India, adult S. mangiferae feed on the leaves and tender shoots of mangoes during March and April (Subramanyam, 1926). They are nocturnal, fly readily and usually feed, mate and oviposit at dusk. After emergence, adults enter a diapause, which varies in duration with the geographic range. For example, in southern India, all adults emerging during June enter a diapause from July until late February of the following year (Shukla and Tandon, 1985). The onset and termination of diapause appear to be associated with long-day and short-day photoperiod, respectively (Balock and Kozuma, 1964). Adults are capable of surviving long, unfavourable periods. During non-fruiting periods, weevils diapause under loose bark on mango tree trunks and in branch terminals, or in crevices near mango trees (Van Dine, 1907; Balock and Kozuma, 1964). A few adults live through two seasons with a diapause period in between. Shukla and Tandon (1985) found that females began oviposition 3-4 days after mating, when the fruit was about marble-size. This occurred about mid-march and reached a peak during the first week of April. The oviposition period varies from 3 weeks (Subramanyam, 1926), 4 weeks (Hansen et al., 1989) to about 5 weeks (Shukla and Tandon, 1985). Females will oviposit on infested fruit (Hansen et al., 1989), and lay eggs mostly on the sinus of the fruit or sometimes on the stems (Shukla et al., 1985). The female makes a boat-shaped cavity in the skin (epicarp) into which an egg is deposited. She then covers each egg with a brown exudate and cuts a crescentshaped area mm in the fruit, near the posterior end of the egg. The wound creates a sap flow, which solidifies and covers the egg with a protective opaque coating. One female may lay 15 eggs per day, with a maximum of almost 300 over a 3-month period in the laboratory (Balock and Kozuma, 1964). Incubation requires 5-7 days, depending on the season and temperature (Balock and Kozuma, 1964). After hatching, the larva burrows through the flesh of the fruit and into the seed. As the fruit and seed develop, the tunnel and seed entry are completely obliterated, so that in time it is impossible to distinguish infested from non-infested seeds, unless they are cut open. The minimum time from hatching to seed penetration is one day. Larvae can penetrate the seed coat of younger fruit of all varieties, but apparently find entry impossible in the mature seed of the variety Itamaraca (Balock and Kozuma, 1964). Complete larval development usually occurs within the maturing seed, but also very occasionally within the flesh (Balock and Kozuma, 1964; Hansen et al., 1989; Follett and Gabbard, 2000). Nine early-instar weevils have been found in fruit (Follett, 2002). In southern India, larvae developed in the field between March and May and pupated in late May and early June, taking about a month to develop (Shukla and Tandon, 1985). In Hawaii, the larval period ranged from 22 days to 10 weeks (Balock and Kozuma, 1964; Hansen et al., 1989). There are five or seven larval instars (Balock and Kozuma, 1964; Seo et al., 1974; Shukla and Tandon, 1985; Hansen et al., 1989). Pupation usually occurs within the seed and rarely in the flesh. The pupal period lasts about a week (Subramanyam, 1926; Balock and Kozuma, 1964; Shukla and Tandon, 1985). In Hawaii, Hansen et al. (1989) found pupae from the end of May until about mid-july. Often only one adult will mature in each seed, but as many as six have been recorded (Balock and Kozuma, 1964; Follett, 2002). They cut their way out of the naked seed, usually via a small circular hole made in the concave edge of the endocarp, generally 4-8 weeks after the fruit falls and decays. Rarely, weevils emerge from the seed before fruit fall and eat their way through the flesh of the ripe fruit, ruining it

12 completely. They rapidly move out of the seeds and seek hiding places by crawling, rather than flying. In Bangalore, south India, adults of the new generation emerge during June (Shukla and Tandon, 1985). The estimated time required for development from egg to adult is days (Van Dine, 1907; Shukla and Tandon, 1985). Adults usually remain in the vicinity of the parent tree until the following fruiting season (Jarvis, 1946) and high infestations appear year after year in some locations, while low infestations occur in others nearby (Balock and Kozuma, 1964; Hansen et al., 1989).. Mango seed weevil life cycle - Northern Australia in Kensington Pride mango

13 Symptoms: Infected fruits are difficult to detect because usually no damage is visible externally. The incisions made by ovipositing females are small and generally soon heal (Kalshoven, 1981). Fruits are not adversely affected by infestation, except in rare instances where larvae feed and pupate within the pulp, or when they emerge from the seeds and tunnel up through the pulp (Balock and Kozuma, 1964; Follett and Gabbard, 2000). In South Africa, Kok (1979) showed that after harvest of latematuring varieties, adults tended to leave the seed and tunnel through the fruit, leaving a scar on the outside which served as a site for secondary fungal infection; this renders the fruit unfit for human consumption. Internally infected fruit rots from the outer surface of the stone. The stones also show holes and the cotyledons turn black and become a rotten mass. Seeds fail to germinate if the embryo is damaged and the reserve of food in the cotyledons is greatly reduced. Symptoms by affected plant part Fruits/pods: internal feeding. Seeds: internal feeding. Symptoms of damage of Sternochetus mangiferae

14 Symptoms of damage of Sternochetus mangiferae

15 Means of movement and dispersal: Plant parts liable to carry the pest in trade/transport - Bark: Adults; borne externally; visible to naked eye. - Fruits (inc. Pods): Eggs, Larvae, Pupae, Adults; borne internally; borne externally; invisible. - Growing Medium Accompanying Plants: Adults; borne externally; invisible. - Seedlings/Micropropagated Plants: Adults; borne externally; visible to naked eye. - Stems (above Ground)/Shoots/Trunks/Branches: Adults; borne externally; visible to naked eye. - True Seeds (inc. Grain): Larvae, Pupae, Adults; borne internally; borne externally; visible to naked eye. Transport pathways for long distance movement - Mail - Travellers And Baggage Phytosanitary significance: S. mangiferae Probably its greatest significance as a pest is to interfere with the export of fruit because of quarantine restrictions imposed by importing countries. In India, all cultivars are susceptible and levels of infestation vary from 48 to 87% (Bagle and Prasad, 1985). S. mangiferae is quarantine pest for Iran and some of other countries. Detection and inspection: Mango seeds should be opened with a knife to reveal the immature stages (larvae or pupae) and adults within the kernel. Shaking and / or beating mango tree branches to dislodge adult mango seed weevils. Detection and inspection hosts and seed for Sternochetus mangiferae

16 References: Abai, M. (1984).List of forest trees and shrubs of Iran. Plant pests and Diseases Rech. Inst.,Tehran, 147p. Barouti,S.,A.alavi,2004,Plant Nematology,Principles, Parasitic and Quarantine Nematode in Iran., p. Behdad,E.,1984.Pests of Fruit Crops in Iran,Sepehr pub,tehran,822p. Esmaile,M.1983, Pests of Fruit Crops in Iran, Sepehr pub,tehran,366p. CAB International Crop Protection Compendium Edition. CAB International. Wallingford, Oxon, UK. Modarres Awal, M.2012.List of Agricultural pests and Their Natural Enemies in Iran. Revised Edition, Ferdowsi university Prss,778p. Salavatean, Mer.1996, Plant quarantine in Iran, Research Institute,Ministey of Agriculture pub,279p. Cornelia Estelle Louw, BIOLOGY AND CONTROL OF THE MANGO SEED WEEVIL IN SOUTH AFRICA, Department of Zoology & Entomology, Faculty of Natural and Agricultural Sciences,University of the Free State, Bloemfontein,236p. www2.dpi.qld.gov.au/horticulture/18269.html flyaqis.mov.vic.gov.au/padil/s_magnif_diag.htm