Effects Of Grazing And Fencing On Diseases Of Grassland Plants

Grazing and fencing are the major management practices of grassland, which also affect incidence and development of grassland plants diseases. In this research, the disease incidence and severity of the dominant plant species were studied at a typical grassland with four different stocking rates at Tianshui Township, Huanxian country, Gansu Province, and at an alpine grassland with various periods of exclosure at Gannan Tibetan Autonomous Prefecture, Gansu Province. The survey was carried out in July, August and September of 2010, respectively. The relationship between grassland management practices and plant diseases was analyzed. The objectives of the study were to provide the information for grazing management and fencing practices. The major results are as follows:1、Nineteen diseases were found on the plants belong to 7 families 14 genera and 14 species in Huanxian grassland. Among those diseases found powdery mildew and rusts are the main ones. Twenty seven diseases were recorded from 11 families,16 genera and 19 plant species in Gannan alpine grassland. The most common diseases were rust and leaf spot. Four diseases may be the first disease records in Gansu Province. They are powdery mildew (Sphaerotheca elsholtziae) of Lamiophlomis otate, ring spot (Pestalotia sp.) of dandelion (Taraxacum mongolicum), rust (Puccina leveillei) of Geranium pretense, and rust (Phragmidium potentillae) of Potentilla fragarioides.2、The disease incidences of the hosts were decreased as sheep stocking rates increased in the paddocks with 0,2.7,5.3, and 8.7 sheep/hm2,respectively, in Huanxian grasslands. The incidences of leaf spot (Bipolaris stipicola) of Stipa bungeana, rust (Uromyces lespedezae-procumbentis) of Lespedeza davurica, powdery mildew (pathogen to be identified) of Gueldenstaedtia multiflora, rust (Uromyces sp.) of Euphorbia elusa, brown blotch (pathogen to be identified) of Potentilla bifurca,and powdery mildew (Sphaerotheca fusca) of Taraxacum mongolicum were significantly lower in the paddocks with 8.7 sheep/hm2 than those with 0 sheep/hm2 or 2.7 sheep/hm2.3、The disease incidence of four out of five major fungal diseases found in Gannan alpine grasslands decreased with the extension of fencing years except for Cares tristachya leaf spot which increased with fencing years.