The Study On Pest Control And Occurrence Regularity Of Insect Pest In Yulin Grassland

Yulin city is located at the cross of five provinces,Shaanxi,Gansu,Ningxia,Inner Mongolia and Shanxi.The grassland distributes a wide range in Yulin as the north of Yulin is Wind-sandy Grass Shoal Area at southern end of Mu Us Desert while the south of Yulin is Loess Plateau,a transition zone from agricultural to pastoral area.Thus,it was enriched in grassland types and plants diversity and the natural environment be easily disturbed by human,causing a frequent outbreak of insect pests in Yulin grassland.The grassland health and cattle farming have been affected by insect pests for their species diversity and wide distribution and it's an important issue to control insect pests in Yulin.The major insect pest species,outbreak rules and pest control approaches based on biocontrol and were discussed in this thesis based on three years investigation and filed control trails.The major insect pest species were 26 species belonging to Orthoptera(14 species),Lepidoptera(5 species),Coleoptera(4 species)and Hemiptera(3 species).The locusts were the most frequent and severe insect pests in Yulin grassland while some Lepidopteran and Hemipteran species were widely distributed,such as Mythimna separata and Trigonotylus ruficornis.The insect pest was controlled by using UAV as the grassland with varied topography in mountain region.The mortality reached 72% for matrine and 100% for Beta cypermethrin.The virulence of two fungal strains,Beauveria bassiana GYS-13 and Metarhizium anisopliae QL-107 were evaluated in lab and were used as biocontrol agents for grassland locusts in Yulin.The bioassay showed strong virulence of both strains against Locusta migratoria manilensis under lab conditions.And then the biocontrol effects were tested in mountain grassland,which the control effects of two strains were all over 75% against the locusts included different species and instars.Especially the B.bassiana GYS-13 reached a strong biocontrol effect of 81.8% in total against all locusts in field.These findings indicated that the fungal strain B.bassiana GYS-13 had big potential to be bio-pesticides to control the locusts.Above finding presents the valuable reference to IPM of grassland insect pests.