USE OF COVER CROPS FOR WEED SUPPRESSION IN HAZELNUT (CORYLUS AVELLANA L.) IN TURKEY.

Weed management is critical in hazelnut (Corylus avellana) production. Weeds reduce nutrient availability, interfere with tree growth, and reduce hand-harvesting efficiency. Field experiments were conducted to test effects of cover crops as alternative weed management strategies in hazelnut. The cover crop treatments consisted of Trifolium repens L., Festuca rubra subsp. rubra L., Festuca arundinacea Schreb., Vicia villosa Roth. And Trifolium meneghinianum Celmand fallow with no cover crop. Control plots such as weedy control, herbicide control and mechanical control were added as reference plots. The lowest weed dry biomass was obtained from Vicia villosa plots, and there were no significant differences among all other cover crop treatments. The highest cover crop dry biomass was measured in the Trifolium meneghinianum plots. Regarding the effect of cover crops on hazelnut yields, the lowest yield was ob- tained from weedy control plots, while the highest yield was obtained from F. arundinacea plots. This research indicated that cover crops could be used as living mulch in integrated weed management programs to manage weeds in the hazelnut orchards.

Exserohilum monoceras, Newly Reported on Late Watergrass in Turkey.

Echinochloa species are major weeds in rice-cropping systems and are among the most noxious weeds in the world. Throughout the world, Echinochloa oryzicola Vasing, (late watergrass) is one of the most important and serious weed species of this genus. In September 2010, punctiform, purplish dark brown leaf spots were observed on leaves and sheaths of Echinochloa oryzicola in a rice field in Terme, Turkey (41°13.412'N, 36°56.248'E). Individual lesions ranged from 1 to 3 mm in diameter. Infected leaf and sheaths were surface disinfected for 1 min in 1% NaOCl, plated on potato dextrose agar (PDA), and incubated at 25°C. Colonies of pure cultures on PDA turned to dark green colonies with increasing age. Conidia were 87 to 147 (120) × 15 to 21 (19) µm (n = 50), 6 to 10 pseudoseptate, straight or slightly curved, fusiform, tapering gradually toward the base, pale-to-dark straw colored, smooth, with a small protruding plenum-type hilum. The fungus was identified as Exserohilum monoceras (Drechsler) Leonard & Suggs based on its micromorphology and cultural features (1,2). Conidia were harvested from 3-week-old cultures grown on PDA by brushing the surface of the colonies with a small paint brush, suspending the conidia in sterile distilled water and filtering through cheesecloth for pathogenicity tests. Conidia were then diluted in sterile distilled water plus 0.1% polysorbate 20 to a concentration of 1 × 106 conidia/ml. Leaves and stems of Echinochloa oryzicola at the three-leaf stage were spray inoculated with 10 ml of this aqueous suspension per plant. Three inoculated plants and three noninoculated plants were placed in a dew chamber at 18 to 22°C with continuous dew, and after 48 h, plants were moved to a greenhouse bench. Symptoms, similar to those originally observed in the field, began to appear on the leaf and sheaths approximately 10 days later and E. monoceras was reisolated, successfully completing Koch's postulates. No symptoms developed on the control plants. E. monoceras has also been reported on Echinochloa oryzicola in Japan (3). To our knowledge, this is the first report of leaf spot on Echinochloa oryzicola caused by E. monoceras in Turkey where the fungus may have potential as a biological control agent. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute. Kew, Surrey, England, 1971. (2) M. Sisterna and R. Bezus. Plant Dis. 85:803, 2001. (3) H. Tsukamoton et al. Ann. Phytopathol. Soc. Jpn. 64:526, 1998.

The effects of cover crop on weed control in collard (Brassica olerecea var acephala) and lettuce (Lactuca sativa L.).

Leafy vegetables are not very competitive and weed interference can cause considerable yield losses in collard (Brassica olerecea var acephala) and lettuce (Lactuca sativa L.). Currently there are no pre or post emergence herbicides registered for weed control in these vegetables in Turkey. For this reason, alternative weed control strategies need to be developed. Cover crop residue could represent an alternative method of weed management in these crops. Field studies were conducted in 2004 at the Black Sea Agricultural Research Institute experimental field in Samsun, Turkey. The cover crop treatments consisted of Sorghum bicolor (L.) Moench, Sorghum vulgare Pers., Vicia villosa L., Amaranthus cruentus L., Pisum sativum L. and the bare ground with no cover crop. All cover crops were seeded by hand and incorporated into the soil on 11 May, 2004. Each plot was 10 m2 (2 x 5 m) and arranged in a randomized complete block design with four replications. All cover crops were incorporated into the soil by discing on 1 September 2004 at flowering stage of the cover crops. Broadleaved weed species were dominant in the experimental area. Most cover crops established well and S. bicolor biomass was the highest. The number of weed species emerging in all treatments was different at 14 DAD (days after desiccation). Similar results were observed at 28 and 56 DAD. Treatments with Vicia villosa residues had fewer weed species and lower total weed densities than other treatments.