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Proceedings
THE OCCURRENCE OF WEEDS, DISEASES AND PESTS IN GRASSES GROWN FOR SEED IN THE CZECH REPUBLIC
J. Machác and B. Cagas
OSEVA PRO s.r.o. Grassland Research Station, 75654 Zubrí, Czech Republic
Weeds, diseases and pests are some of the important factors influencing the intensity and profitability of grass seed production. Based on our investigations they decrease the production by 33%, and another 28% of the monetary return from production is needed for their control or to reduce their negative influence. Nowadays, because of the relatively low importance of grass seed production here, it is not easy to find financial support for further investigation and research into new ways of control. Therefore, observations of the incidence and an evaluation of the importance of the most difficult weeds, diseases and pests could help in the choice of the best chemical and/or non-chemical control methods. Grass seed production is carried out on 14 000 ha in the Czech Republic. The incidence of weeds, diseases and pests during 1994-1997 was determined in three ways:
· Survey of 10% of that acreage before the control of weeds in spring;
· Survey of 20% of that acreage before seed harvest;
· Analyses of seed samples of 20% of the whole seed harvest performed in seed-testing laboratories
The depression of the whole agricultural sector in our country in the last years also had a negative influence on the production of grass seed. Reduced inputs (pesticides, fertilizers etc.) resulted in an increasing incidence in cultivated grasses of perennial and annual species of grass weeds such as quackgrass (Agropyron repens/L./P.B.), rough bluegrass (Poa trivialis L.), annual bluegrass (Poa annua L.), windgrass (Apera spica-venti /L./P.B.), common wild oat (Avena fatua L.), barnyard grass (Echinochloa crus-galli/L./P.B.), other minor grass species, and volunteer cereals. Of dicotyledonous species the most important are broad-leaved Rumex spp. (R. crispus L., R. obtusifolius L.), Matricaria and Anthemis species and Cirsium arvense (L.) Scop. Snow mold (Microdochium nivale /Fr./Samuels & Hallet), powdery mildew (Blumeria graminis /DC/E.O.Speer) and various leaf spots are the most common diseases. Rusts (Puccinia and Uromyces species) attack the grass canopy after the seed harvest and do not influence seed yield. Ergot (Claviceps purpurea /Fr./Tul.) is the most important fungal disease in Kentucky bluegrass, lowering both yield and quality of the seed. Silvertop (white spikedness), caused by the insect Leptopterna dolobrata L., causes considerable losses in bluegrass species, meadow and red fescue and yellow oat grass, mostly from the second harvest year on. The attached tables and graphs demonstrate the situation in the past 4 years. The results of these investigations should give an impulse to test and register appropriate pesticides for application on grasses grown for seed.