First Report of Longidorus breviannulatus Associated with Damage on Creeping Bentgrass Golf Greens in Québec, Canada

Creeping bentgrass, Agrostis stolonifera L., is the most important turfgrass species cultivated on golf greens in Canada. The needle nematode, Longidorus breviannulatus Norton & Hoffman, has several plant hosts including Gramineae such as corn, Zea mays L. (3), and creeping bentgrass (1). This large, plant-parasitic nematode is found most frequently in sandy soils and is encouraged by irrigation (2). In 2006, irregular, yellowish/chlorotic, and dead turfgrass patches were observed for the first time on several sand-based creeping bentgrass cv. Penncross greens on a golf course in Bromont, Québec (45°19'N, 72°39'W). Furthermore, a noticeable decline of the turfgrass root system was observed. Creeping bentgrass was grown with the following management practices: mowing height 3.18 mm, fertilization 2.27 kg N/0.45 kg P₂O₅/3.18 kg K₂O/92.9 m²/year, aeration two times per year with 9.53-mm-diameter hollow core. On 5 July 2006, soil (0.5 kg) was sampled from two damaged areas of green no. 11. Three plugs (5-cm diameter × 15 cm deep) were taken from each area with a soil probe and pooled to form two separate samples. Another set of soil samples was collected on 12 July from three golf greens (nos. 10, 11, and 16). One sample was taken from each of three damaged areas and two healthy areas of each green. Plant-parasitic nematodes were extracted from 100-ml volumes of each soil sample by the Baermann pan and funnel extraction methods. Numbers of L. breviannulatus from the soil sampled on 5 July were counted with a stereo-microscope after 4 days of extraction, while numbers of L. breviannulatus in the rest of the samples were counted after 7 days of extraction. Identification was determined by morphological examination of a small number of adult female nematodes (n = 7). Characteristics distinguishing these specimens as L. breviannulatus include: amphidial pouches (bilobed and extending to the guiding ring), length 5,115 μm (4,780 to 6,230 μm), distance of the guiding ring from the oral aperture 26 μm (24 to 30 μm), odontostyle length 83 μm (78 to 90 μm), and tail length 42 μm (37 to 50 μm). In the two soil samples collected on 5 July, 0 and 183 juveniles per kilogram of dry soil were recovered with the Baermann pan method. In samples collected on 12 July from damaged areas of three greens, averages of 16 (min 0 and max 60) and 22 (min 0 and max 80) juveniles per kilogram of dry soil were obtained with the Baermann pan and funnel methods, respectively. No L. breviannulatus was found in any sample from healthy areas. Although no damage threshold has been established for L. breviannulatus in creeping bentgrass, low numbers of needle nematodes can be damaging in other crops such as corn. In our study, the occurrence of the damage was related to populations of the needle nematode, and therefore, the nematode was the likely cause of the damage. In Canada, L. breviannulatus is reported from Ontario (4). To our knowledge, this is the first report of the occurrence of L. breviannulatus in Québec. References: (1) L. B. Forer. Plant Dis. Rep. 61:712, 1977. (2) R. B. Malek et al. Plant Dis. 64:1110, 1980. (3) D. C. Norton and J. K. Hoffmann. J. Nematol. 7:168, 1975. (4) W. Ye and R. T. Robbins. J. Nematol. 36:220, 2004.