Scarab found on city outskirts

Press, Volume CXVI, Issue 34106, 19 March 1976, Page 7

Scarab found on city outskirts

I he Adoryphorus scarab (Adoryphorus couloni), which was formerly known as the red-headed pasture cockchafer. has been found in a number of areas on the outskirts of Christchurch.

Dr K. G. Somerfield. a scientist with the plant health diagnostic station of the Ministry of Agriculture and Fisheries at Lincoln, and Mr W. P. Thomas, a scientist with the Entomology Division of the Department of Scientific and Industrial Research also at Lincoln, said this week that it occurred sporadically in at least 2000 hectares of counfy. It has been recorded as a sporadic pest of established pastures in Australia and can do damage of economic significance in some situations. The two scientists said it was closely related to the native grass grub and also the black beetle (Heteronychus arator). which is an introduced species originally from South Africa. The insect was first re-

a ported in a private garden t at Heathcote Valley in f 1963 by an amateur en- • tomologist. It was also then seen in a relative’s t garden about 100 yards - away and also on the ? Bridle Path one to one and c a half kilometres away. All 1 the e sightings were within s a radius of about a mile. " At the time it was 3 thought to be the black beetle. In the adult stage it a is very similar to the black :i beetle in Shape, size and i colour. c Then in October last year a student of Canterbun University living at t McCormicks Bay observed e some flying adults about o sunset one day. '■ The outcome was that s Dr Charles Watt, who is ‘ the head of the Entomology Division at the Mount Albert Research Centre of

t h e Department of Scientific and Industrial Research, identified it as Adoryphorous couloni, the first recording in New Zealand.

Mr R. J. Hardy, an entomologist with the Department of Agriculture in Tasmania, also confirmed its identity when he was here earlier in the year. .-1 insect of Australian origin it is known in parts of the mainland and also Tasmania. The final instar larvae are about three times the size of the native grass grub larvae. They are generally grey in colour with whitish areas around the breathing pores and with a reddish brown head. It can be identified by its tranverse anal spilt in contrast with the y-shaped and almost vertical split of the grass grub species. It is at this stage that the insect does damage to the pasture roots, like that done by the grass grub, and can leave bare patches of ground. The adult does not have the feeding capacity of its counterpart in the grass grub species relying on food reserves accumulated in the larval sta o e. Other than in October and November when it flies the adult beetle lives in the ground like the black beetle. The pest is found in older well established pastures not exposed to cultivation. The pasture would be al least three years old. It may also prefer loose friable type soils. In Australia it has a two-year cycle and is a slow breeder. Since the confirmation of the presence of the pest a numb'er of day-long searches have been made for it by from one to four persons.

Apart from at McCormicks Bay, it has been located in the Clifton beach area, Barnett Park, a third of the way up the Bridle Path on the Lyttelton side, on the side of the Avoca Valley road and also in a paddock near the tunnel road interchange near Horotane Valley. It has not been found on the opposite side of the Lyttelton harbour, or at Little River, New Brighton or at Taylors Mistake

In limited areas counts of from 10 to 20 per spade square have been recorded, but they have not been seen near the surface of the ground. Damage attributable to the pests has not been observed in the form of bare patches of ground. Ploughing and cultivation was one of the maim methods of control, Dr Somerfield said. Dr Somerfield said that the lucerne weevil (Sitona hum er al is) initially found on Banks Peninsula had now been found as far away as Palmerston in Otago and was widespread in Canterbury. Another possible minor pest of pastures has also been identified in New Zealand. It is the redheaded white grub (Dasygnathus dejeani). It has been found in a light trap of the Ministry of Agriculture and Fisheries at Kerikeri in the far north. It is an Australian pasture species not previously identified in New Zealand. It resembles an outsize black beetle.