Ownership of intellectual property rights

1.9Fiji ginger weevil

Very little is known of the developmental biology of Elytroteinus subtruncatus because it is difficult to rear under laboratory conditions (Mau and Martin Kessing 1992a). Adult weevils are dark brown to black, and 6–8 mm in length (Mau and Martin Kessing 1992a). The adult female lays a single egg in the corms, tubers, fruits or soft stems of a range of plants. The larvae are legless, and creamy-white in colour with a distinct brown head. They are about 12 mm long when full size (Miller 1923). The larva bores through the plant tissues, completing its development inside the host. Detailed information on the life history of Elytroteinus subtruncatus is lacking, but other species in the subfamily Cryptorhynchinae take from five to eight weeks to develop from egg to adult (Woodruff and Fasulo 2009).

On kava, the adult female oviposits into the stem after boring a hole. The entire development of the weevil takes place inside the stem, with the larva tunnelling through it, filling the tunnels with frass, and causing stem dieback, leaf wilt, and rotting. Damage can be recognised by stem holes, which are filled with black powdery matter and frass (Fakalata 1981). On begonias, larvae bore into the main stems, usually near the base (Simmonds 1928). In lemons, female weevils puncture the fruit stalks near the base and lay their eggs there. Upon hatching, the larvae attack the fruit at the base of the stalk, and work their way through the peel and tissue lying immediately underneath. Pupation takes place in the fruit, although the fruit may decay before the adult has developed (Miller 1923).

In the United States of America (USA), the Animal and Plant Health Inspection Service (APHIS) considers Elytroteinus subtruncatus to be a high-risk pest requiring mitigation for sweet potatoes exported from Hawaii to the mainland. This is the result of five weevil interceptions in 1995 and 1997 (nine sweet potato roots containing a total of eight larvae and two pupae) found in passenger baggage at Keahole International Airport, Hawaii (Follett et al. 2007).

1.9.1Probability of entry

The likelihood that Elytroteinus subtruncatus will arrive in Australia with the importation of fresh ginger from Fiji is: HIGH.

• 
  Weevil larvae burrow into the stems and rhizomes of ginger (Stout 1982) where they complete development. Pupation occurs within the feeding site (Mau and Martin Kessing 1992a).
  
• 
  Feeding gives rise to wilting, loss of vigour, and in severe infestations the affected plants die (Mau and Martin Kessing 1992a).
  
• 
  When disturbed, adult weevils in the subfamily Cryptorhynchinae typically feign death and drop to the ground (Lyal 1993). Such behaviour would reduce the chance of adult weevils being associated with ginger consignments.
  
• 
  The main risk would be from rhizomes in which eggs were laid late in the season, just before harvest, or after harvest during storage. The Fiji ginger weevil is noted as a long-term storage pest in other root crops such as yams (Dioscorea spp.) (Wilson 1987).
  
• 
  Adult weevils are dark brown to black, and 6–8 mm long (Mau and Martin Kessing 1992a). These would likely be found during pre-export processing or at quarantine inspection.
  
• 
  The larvae are legless, of a creamy-white colour, with a distinct brown head. They are about 12 mm long when full size, and rather plump (Miller 1923). Larvae may be imported inside the rhizomes, making detection difficult. However, affected rhizomes may show external signs of rot.
  
• 
  Ginger weevils have been intercepted in New Zealand in consignments of fresh ginger imported from Fiji. At least six ginger weevil specimens and a further two unidentified Elytroteinus spp. were found between 2000 and 2011 (interception data provided by NZMAF).
  
• 
  Ginger weevils have been intercepted in the United States in sweet potato tubers in interstate movements from Hawaii (Shea 2004). Elytroteinus subtruncatus is a regulated plant pest in the USA (APHIS 2000).
  
• 
  At least one Australian interception of this weevil has been noted, in Sydney, on unspecified goods from Fiji in 1963 (APPD 2011).
  

The likelihood that Elytroteinus subtruncatus will be distributed within Australia in a viable state to a susceptible part of a host, as a result of the processing, sale or disposal of fresh ginger from Fiji, is: MODERATE.

• 
  The weevil larva will remain within the ginger rhizome for some time, as pupation occurs at the feeding site inside the ginger (Mau and Martin Kessing 1992a). Emergence of adult weevils may not occur until some time after arrival in Australia.
  

• 
  Ginger will be distributed to many localities by wholesale and retail trade and by individual consumers.
  
• 
  Individual consumers could carry small quantities of ginger rhizomes to urban, rural and natural localities. Small amounts of ginger waste could be discarded in these localities.
  
• 
  Some ginger will be distributed to areas where ginger or other host species such as taro, lemons, avocado or sugarcane grow. Potential host plants are common in many populated areas of Australia.
  
• 
  Small amounts of ginger waste will be discarded into domestic compost.
  

• 
  Infested rhizomes that escaped detection during pre-export processing and importation are likely to be distributed in the wholesale and retail supply chain.
  
• 
  Elytroteinus spp. weevils are flightless (NZ MAF 2008) and have a limited ability to seek out new hosts once they leave the rhizome.
  
• 
  An infested ginger rhizome could be planted by a consumer, potentially providing a living host for the developing weevil. However, signs of weevil infestation such as tunnels, frass or rotting would lessen the likelihood that affected rhizomes would be used as planting material.
  
• 
  The adults of other species of Cryptorhynchinae are known to live for up to two years and to hibernate or aestivate when suitable host plants are not available (Woodruff and Fasulo 2009).
  

Probability of entry (importation × distribution)

1.9.2Probability of establishment

• 
  On lemons, Miller (1923) reported that only a single egg was laid in each fruit, so the fruit only contained a single larva. It is not known if this behaviour also occurs on ginger rhizomes, but it is considered likely.
  
• 
  For this pest to establish, it would need to complete its lifecycle. This could occur if several infested rhizomes remained together in the supply chain (or were planted together in the same garden), or if a single rhizome carried several eggs (oviposited by multiple females, as each female probably lays only a single egg in the rhizome), the pupae emerged, the adults survived and mated, and several females found suitable plants for their eggs. The combined probability of all these events happening is considered to be low.
  

1.9.3Probability of spread

• 
  Elytroteinus spp. weevils are flightless (NZ MAF 2008), so natural spread would be slow. Longer distance spread would only occur via movement of infested produce.
  
• 
  Climatic conditions in northern Australia are similar to that throughout the natural range of this weevil in the Pacific, so some spread could be anticipated.
  
• 
  Host plants such as avocado, lemon, sugarcane and taro are common in some parts of Australia.
  
• 
  The ginger weevil could be spread widely throughout Australia via the movement of other commodities such as lemon and avocado.
  
• 
  Elytroteinus subtruncatus has not spread widely in Hawaii since it was first reported in 1918, despite the presence of host plants such as avocado and taro (Follet et al. 2007).
  
• 
  The Fiji ginger weevil does not appear to be a particularly aggressive pest, and is likely to be limited in its spread by normal crop management techniques imposed as part of the growing cycle.
  

1.9.4Probability of entry, establishment and spread

1.9.5Consequences

1.9.6Unrestricted risk estimate

Unrestricted risk is the result of combining the probability of entry, establishment and spread with the outcome of overall consequences. Probabilities and consequences are combined using the risk estimation matrix shown in Table 2.5.

The unrestricted risk estimate for the Elytroteinus subtruncatus of ‘negligible’ achieves Australia’s ALOP. Therefore, specific risk management measures are not required for this pest.