Mango seed and mango pulp weevil

Summary sheet

Introduction

Mango seed weevil (Sternochetus mangiferae)

Mango pulp weevil (Sternochetus frigidus)

Lifecycle and description

Equipment and technique

Equipment

Technique

Sample identification and reporting

Specimens for identification

Survey report

Further information

Appendix

1. References

2.  Further reading

3.  Data recording sheet

Summary sheet   Mango seed and pulp weevil

Introduction

This survey protocol will provide information supporting State freedom from two serious mango pests in Western Australia. These are mango seed weevil, Sternochetus mangiferae and mango pulp weevil, S. frigidus. A survey should be conducted as directed to maintain State freedom.

Mango seed weevil (Sternochetus mangiferae)

Mango seed weevil, also known as mango stone weevil is a pest specific to mangoes. This weevil has a pantropical distribution and has been recorded in Queensland and the Northern Territory. Although mango seed weevil infestations can degrade pulp and juice quality, this weevil is predominantly a pest of quarantine significance. The establishment and maintenance of State or Area Freedom from mango seed weevil allows Western Australian mango growers access to potential markets such as the United States and Japan which currently have restrictions on mango imports from countries with mango seed weevil.

Mango pulp weevil (Sternochetus frigidus)

Mango pulp weevil, also known as mango flesh weevil, is a pest specific to mangoes. This weevil has a distribution restricted to Southeast Asia and has not been reported in Australia. Mango pulp weevil infests mango pulp and causes fruit drop and renders the mango fruit unsaleable. The establishment and maintenance of State or Area Freedom from mango pulp weevil allows Western Australian mango growers access to potential markets such as the United States and Japan which currently have restrictions on mango imports from countries with mango seed weevil.

Life Cycle and Description

Mango seed weevil is considered to be a nocturnal insect, which feeds, mates and oviposits at dusk. Adult weevils usually remain in the vicinity of the original infestation until the following fruiting season. Mango sees weevil displays a clumping distribution with large infestations of mango seed weevil appear year after year at the same location and low infestations at other locations. In some areas, mango seed weevil infestations have been recorded at greater than 80% (Cunningham, 1991).

Long range dispersal of the weevil occurs primarily through the transport of infested fruit containing larvae, pupae or adults. The lifespan of the mango seed weevil is occurs over two seasons, sometimes separated by diapause (suspended larval development). The adult weevil is a dark brown weevil with paler patches. This small stout weevil has a small head and the body covered with papillate scales. It is between 6-9 mm in length.

Both mango seed weevil and mango pulp weevil larvae are white, legless grubs with a brown to black head. 1^st instar larvae can be up to 1.5 mm in length with final instar larvae up to 17 mm long. Pupae are white to pale red and can be 10 mm long.

Equipment and technique

Equipment list

• Banana/cane knife or large meat cleaver or hammer and multigrip pliers.
• Chopping block
• Waste container
• Specimen jars – 1 L plastic pickling jars and 50 ml disposable plastic jars
• Preserving solution of 80% alcohol and 5% glycerine

Technique

As both the mango seed and pulp weevil infests mango fruit at an early stage, any fruit is a viable sample. However, as infested fruit will ripen early, the sensitivity of the survey will increase by seeking out early ripening and fallen fruit prior to harvest. If the survey should coincide with the mango harvest, reject or fallen fruit should be inspected.

Pest	Kimberley	Southern Pastoral	Swan
Mango Seed Weevil Mango Pulp Weevil	October - December	December - February	February - March

Table 1. Survey windows for mango seed weevil and mango pulp weevil.
(Taken from Mango Growing in Western Australia, Agriculture W.A. Bulletin 4125)

 

Two weeks prior to the survey, the appropriate equipment needed should be collected and orchardists contacted for permission to do survey work. A list of orchardists should be available from local Agriculture WA offices.

 

Larvae or damage caused by mango seed weevil is not seen externally on the fruit. Fruit sampling is carried out by longitudinal dissection of fruit through the seed to expose the kernel. Pulp damage cause by the mango pulp weevil can also be surveyed in this manner. Alternatively, as it is difficult to dissect the seed within ripe fruit, removing the seed from the pulp and striking the fruit along the longitudinal axis with a hammer while holding the seed with suitable pliers (eg multigrips) will usually split the seed open. Mango fruit can be dissected on-site or taken to a more suitable location. If fruit are taken off-site to be dissected, the place of origin must be recorded to prevent a mix up of samples.

The random sampling of 600 fruits from randomly selected properties in each horticultural area will provide a 95% chance of detecting a 0.5% infestation of fruit.

Sample size has been determined using the following formula:

Probability of ³ 1 infested fruit) = 1 – Probability of no infected fruit in total sample)

= 1 - (1-0.5%) ⁶⁰⁰

= 1 - (1-0.005) ⁶⁰⁰

= 1 - (0.995) ⁶⁰⁰

= 95%

Sample identification and reporting

Seed or fruit suspected of either mango seed weevil or mango pulp weevil infestation are to be placed in a specimen container with a preserving solution of 80% alcohol and 5% glycerine and labelled with the following information:

• Collection site (Shire)
• Property name or owners name
• Name of collector
• Collection date

Specimens for identification send through internal mail ASAP to:

Andras Szito
Curator, Insect Collection
Plant Research and Development Services
Agriculture Western Australia
South Perth

Survey report send to:

Darryl Hardie
Surveillance Entomologist
Plant Research and Development Services
Agriculture Western Australia
South Perth

Further information contact:

Marc Poole
Surveillance Officer
Plant Research and Development Services
Agriculture Western Australia
South Perth

Phone: (08) 9368 3224
Fax: (08) 9367 2625
E-mail: mpoole@agric.wa.gov.au

 

 

Appendix 1. References

Cunningham, I.C. (1991) "Mango seed weevil in Queensland." ACTA Hort. 291: 413- 417.

Agriculture Western Australian (1996) "Mango growing in Western Australia" Bulletin No. 4125. Agdex 234/01

 

Appendix 2.  Further reading

EPPO/CABI (1997) "Sternochetus mangifera" In: Quarantine pests for Europe 2^nd edition (Smith, I.M., McNamara, D.G., Scott, P.R. Holderness, M. editors). CAB International Wallingford, UK

 

Appendix 3.  data recording sheet

Pest species: Mango seed weevil and mango pulp weevil

Locality:

Survey staff:

 

#Mango Pulp Weevil present or evidence (yes/no)	Comments
1
3
4
5
6
7
8
9
10
		Total sample size