I n Australia this turfgrass weevil has been incorrectly referred to as the Billbug. This is primarily due to related Sphenophorus species in the United States known as Billbugs. The correct name of the pest is La Plata weevil and is regarded as a significant turfgrass pest in Australia where it occurs. This La Plata weevil is native to South America has been recorded in Argentina, Brazil, Bolivia and Chile.The genus Sphenophorus contains in excess of 70 species, most of which occur in North America where several species have become economic pests over a short period of time. Named by Ernst Germar in 1824, Sphenophorus brunnipennis is the only Sphenophorus species known to occur in Australia and New Zealand.
The weevil was identified in New Zealand in 1928 from where it was possibly introduced into Australia.
Research indicates the weevil is well established in Perth (WA) and Brisbane (Qld.) during the 1920's. The La Plata weevil was first recorded in New South Wales from Sydney in November 1931. Significant damage to Kikuyu ( Pennesitum clandestinum ) fairways was reported from several golf courses in Sydney during the summer of 1982 resulting in loss turf canopy.
Billbug Weevil Larvae
The billbug larvae cause the most damage to turf grass plants. The adults deposited their eggs in cavities made the feeding habits of the adult, which hollow out a grass stem. Young larvae begin to tunnel up and down the stem. Eventually the larvae become too large and fall to the surface where they start feeding on roots and crowns. This when severe damage occurs. Overseas literature indicates the larvae are fully grown between 35-50 days and pupates in the thatch where a tiny adult emerges 8-10days later.
Larvae can be up to 10mm long but as small as 2mm in the early instars. The larvae shed their skins (moult) upto six times, growing progressively larger with each moult. Overseas literature indicates the larvae are fully grown between 35-50 days and pupates in the thatch where a tiny adult emerges 8-10 days later.
The Adult Billbug
Adult billbugs are generally 10mm in length and their significant feature is their long snout and amour plated like body shell. A mature adult is larger than an Argentine Stem Weevil. Australian data on the life cycle of billbugs has not been fully carried out and is primarily based on similar Sphenophorus spp such as S . paravulus and S.minimus
Damage occurs primarily from November through to January. Infected turf will turn yellow initially and then brown as the larvae chew through stolons and rhizomes. The turf can easily be removed from the soil similar to scarab beetle damage. A second generation can occur in February if environmental conditions are favorable.
Biological using ENs
Spray at dusk when pests are evident and damaging sunlight is at a minimum. Air and soil temperatures must be within the range 12-32 o C. Area to be treated should be moist before applying to ensure environmental conditions are favourable for the nematodes activity and survival.
Apply nematodes uniformly to ensure that each square metre receives the same amount of nematodes. Use a two-way spraying pattern, applying half of the total solution in each direction.
Apply Turfnem 1 at a rate of 40 tubs per hectare this equates to applying 250,000 per sq. meter ( H.zelandica sp ). Post irrigation is essential following application.
To detect the presence of billbugs on your turf, a soil flushing method using a pyrethrum mixture will flush adults and larvae to the surface. Low lying areas, which stay moist usually, will exhibit symptoms first.
Flushing suspected sites using a pyrethrum and water at a rate of 25:1.