28 Plant Protection Quarterly Vol.7(1) 1992 three rows in each tray in a mixture of 6% pearlite and 94% sand. Trays were repli- Suitability of a new cultivar of perennial ryegrass as cated ten times for each line. After germi- a host for the Argentine stem weevil (Listronotus nation, seedlings were thinned to 20 plants per row. The plants were grown in a glass- bonariensis (Kuschel)) house (10°C–33°C temperature range), watered and fertilized regularly with S.C. ValentineA, G. CaonB, D.C. HopkinsB, P.G. AllenC and B.D. BartschA Aquasol (Arthur Yates and Co. Pty Ltd, 60 ASouth Australian Department of Agriculture, Flaxley Research Centre, Box Grand Junction Road, Wingfield, SA, 1571, Flaxley, SA 5153, Australia. 5084). Plants were trimmed regularly to a height of 60 mm to encourage tillering. BSouth Australian Department of Agriculture, Northfield Research Laborato- Adult Argentine stem weevils were col- ries, G.P.O. Box 1671, Adelaide, SA 5001, Australia. lected by vacuuming turf at a local golf C South Australian Department of Agriculture, Australian Quarantine and course in early December and 20 weevils Inspection Service, P.O. Box 63, Port Adelaide, SA 5015, Australia. were placed on each tray on 12th Decem- ber, 1990 (day one). Trays were covered with insect proof cages. Summary In Australia, the Argentine stem weevil On day seven, Argentine stem weevil Two lines of the New Zealand bred per- was first recorded in a bowling green in eggs were counted on plant tillers by ex- ennial ryegrass (Lolium perenne L.) New South Wales in 1962 (Chadwick 1963) amination under a binocular microscope cultivar, Ellett, having 88% and 1% of the and was subsequently found in a South of all tillers of 10 plants selected at random seeds infected with the fungal endophyte Australian golf course in 1972 (P. Allen, from each tray. The number of tillers dam- (Acremonium lolii (Latch, Christensen personal communication). The weevil is aged by adult feeding on these plants was and Samuels)) and a line of the Nether- now well established in most golf courses recorded. On day 27, larvae were similarly lands bred cultivar, Edgar with 1% endo- in South Australia and causes sufficient counted on the tillers of 10 plants in each phyte infected seeds were compared for damage to require annual control with in- tray. The diameters of tillers on two plants, suitability as hosts for the Argentine stem secticides. Records from the South Aus- selected at random from each tray, were weevil (Listronotus bonariensis tralian Department of Agriculture insect measured under a binocular microscope (Kuschel)). Plants from each cultivar were data base indicate that the weevil only oc- with a graduated eye-piece. These plants grown in trays in a glass house and the curs incidentally in pastures. Current sur- were dried at 100°C for 24 hours and the number of eggs, larvae and adult weevils vey data suggest most perennial ryegrass dry weight recorded. Each tray was vacu- supported by the cultivars were recorded. based pastures in southern Australia have umed on day 64 and the number of adult The proportion of leaves damaged by greater than 70% of the ryegrass plants weevils counted. adult feeding and the numbers of larvae infected with endophyte (Cunningham, Differences between cultivars in the pro- and adult weevils supported by the plants personal communication.) and this may be portion of damaged leaves and the were significantly (P<0.01) greater in the a major factor limiting the establishment number of larval and adult weevils were low endophyte cultivars compared to the of large numbers of the Argentine stem determined by analyses of variance. Due high endophyte cultivar. weevil in pastures in Australia. to heterogeneous error variance for the These data warn that the breeding and Perennial ryegrass cultivars bred in Eu- number of eggs per tiller, the number of introduction of new perennial ryegrass rope with a low or zero level of endophyte replicates with a zero or non-zero mean cultivars with a low level of endophyte infection are now available in Australia. number of eggs per tiller were counted for infection is likely to significantly in- These cultivars are likely to be more sus- each cultivar and differences between the crease the number of weevils which may ceptible than currently sown cultivars to observed and expected counts analysed be reflected in loss of ryegrass plants attack by the Argentine stem weevil and, by the Chi-squared heterogeneity test. from perennial pastures and consequent if sown in pasture mixtures, may result in production losses. significant increases in the number of wee- Results vils. However, the susceptibility of Mean plant dry weight was significantly Introduction cultivars to attack by and suitability as (P<0.05) higher for the cultivar, Edgar, and The Argentine stem weevil (Listronotus hosts for the Argentine stem weevil is in- the high endophyte line of Ellett compared bonariensis (Kuschel)) is a major pest of fluenced by many factors (Goldson 1982) to the low endophyte line of Ellett (Table perennial ryegrass (Lolium perenne L.) in including tiller diameter (Pilkington 1988). 1). The mean dry weight of tillers was sig- New Zealand causing annual pasture pro- This paper describes an experiment nificantly (P<0.05) less for Edgar and low duction losses of $NZ150-300M (Barker et which compared the suitability of a new endophyte Ellett than for high endophyte al. 1990). Prior to 1948 the Argentine stem low endophyte cultivar of perennial Ellett. weevil was considered a minor pest. How- ryegrass, bred in The Netherlands, and The proportion of leaves damaged by ever, since the introduction of a highly sus- high and low endophyte lines of Ellett per- adult feeding, the numbers of larvae per ceptible ryegrass, the weevil has become ennial ryegrass as hosts for the Argentine tiller and adult weevils per tray were sig- recognized as the second most important stem weevil. nificantly (P<0.01) greater for the cultivar, insect pest in New Zealand (Pottinger Edgar, and the low endophyte cultivar of 1977). Materials and methods Ellett compared to the high endophyte Plants infected with the fungal endo- Two lines of the New Zealand bred peren- cultivar of Ellett (Table 2). The percentage phyte Acremonium lolii (Latch, Christensen nial ryegrass (Lolium perenne L.) cultivar, of replicates in which eggs were present in and Samuels) are resistant to attack by the Ellett, having 88% and 1% of the seeds in- tillers was 60% for Edgar, 80% for low en- Argentine stem weevil (Prestidge et al. fected with the fungal endophyte dophyte Ellett and 30% for high endo- 1982, Barker et al. 1983) and the presence Acremonium lolii, and a line of the Nether- phyte Ellett. The Chi-squared value was of endophyte is considered essential for lands cultivar Edgar, with 1% endophyte significant at the 7% level of probability the persistence of perennial ryegrass infected seeds were sown in plastic trays suggesting a tendency towards a higher based pastures in New Zealand (Barker et measuring 440 mm × 320 mm × 120 mm number of eggs per tiller for low endo- al. 1981). on 1st October, 1990. Seeds were sown in phyte Ellett and Edgar compared with Plant Protection Quarterly Vol.7(1) 1992 29 Table 1. Mean plant dry weight, tiller dry weight, tiller diameter and number Pottinger, R.P. (1990). Role of of tillers per plant. Acremonium lolii in the population ecol- ogy of Listronotus bonariensis in New Ellett Edgar S.E. Zealand ryegrass pastures. Proceedings High endophyte Low endophyte of the International Symposium, on Acremonium/grass Interactions. Loui- Plant dry weight (mg) 499 b 375 a 519 b 55 A siana Agricultural Experiment Station. Tiller dry weight (mg) 41 b 26 a 31 a 3 pp. 7-11. Tiller diameter (mm) 2.3 b 2.2 ab 2.0 a 0.1 Chadwick, C.E. (1963). Occurrence of the Tillers per plant 12.5 a 15.0 b 17.4 b 1.8 Argentine stem weevil in N.S.W. Aus- A Calculated as plant dry weight/tiller number tralian Journal of Science 26, 91-2. Means in the same row followed by different letters are significantly (P < 0.05) different. Goldson, S.L. (1982). An examination of the relationship between Argentine Table 2. Mean proportion of damaged tillers, numbers of eggs and larvae per stem weevil (Listronotus bonariensis tiller, and adult weevils per tray. (Kuschel)) and several of its host grasses. New Zealand Journal of Agricul- Ellett Edgar S.E. tural Research 25, 395-403. High endophyte Low endophyte Pilkington, S. (1988). The effect of ryegrass tiller diameter and endophyte on Ar- Proportion of damaged tillers0.10 a 0.41 b 0.33 b 0.05 gentine stem weevil oviposition. Pro- -2A Eggs/tiller x 10 1.1 4.5 4.2 – ceedings of the 5th Australasian Confer- Larvae/tiller 0.03 a 0.24 b 0.21 b 0.03 ence on Grassland Invertebrate Ecology. Adults/tray 8.4 a 40.0 b 36.6 b 5.3 pp 221-8. AData analysed by Chi-squared test. See text for details. Pottinger, R.P. (1977). Argentine Stem Means in the same row followed by different letters are significantly (P<0.01) different. Weevil. Biology, damage and control. Aglink Farm Production and Practice high endophyte Ellett. endophyte infection. Although the Argen- No. 48, 4 pp. New Zealand Ministry of tine stem weevil has not yet been re- Agriculture and Fisheries, Research Di- Discussion corded as a major insect pest of pastures in vision. The results from this experiment show Australia, survey data currently being col- Prestidge, R.A., Pottinger, R.P.