Identification the Pest Attack on Centaurea Species in Transylvania Area

Abstract

SUMMARY The insect pests are considered to be very important as biological control agents, for horticulture and agriculture. Several insects pests considered are to be successful biological control agents for different knapweeds species, and especially for ones that can be very harmful in the natural grassland as: Centurea stoebe (Perju and Moldovan, 1990). During this year, were observed different attack caused by insect pests on Centaurea species, observed from spontaneous flora, in xero-mesophilic habitats from Transylvania region. Centaurea species have been observed and studied from different meadows, found in the following associations: Polygalo majoris-Brachypodietum Wagner 1941 from Faget Forest (CJ); Asperulo capitatae–Seslerietum rigidae Coldea 1997 from Cheile Turzii (CJ); Stipetum lessingianae Soo 1919 from Zackel Hill (SB), Loamnes (SB); Cariceto- Brachipodietum pinnati transsilvanicum Soo (1942) 1947 from Rosia de Secas (AB), Agrostetum stoloniferae Burdaja 1956 from Toparcea (SB). The knapweed plants from the xero-mexophilic habitats in Transylvania region recorded as host plants, according with our observations, are Centaurea scabiosa, C. atropurpurea W. et K., C. stoebe L., C. micranthos Gmel., C. jacea L., C. pseudophrygia C.A.M. and C. phrygia L. In addition were observed also Centaurea species from Natural History Museum garden as: C. cyanus L., C. phrygia L. and C. moschata L. Data regarding the Centaurea species, observed during the study, were determinate after Flora Romania (Ciocarlan, 2009). From each area were taken plant host samples and were determinate the insect pests form of attacks. The most vulnerable part of the plants was the flower-heads (capitulum) of Centaurea, especially the large inflorescence. Some of these insects’ pests were observed to be present also on another plants species from the investigated habitats, which migrate on Centaurea species when the food is limited.