Sunn pest population further declining

Abstract

For the second cosecutive year, the abundance of Sunn pest imagoes continued to decline. In the fall of 2006, the average density of Sunn pest imagoes at overwintering sites at the permanent sampling locations in Fruška gora and Deliblatska peščara was 9.4 specimens per m2 (6.7/m2 and 12.1/m2 at the respective sites) (Tab. 1), down from the average density of 12.5 imagoes per m2 in 2005. The decreasing trend in abundance in 2005 and 2006 indicates that Sunn pests will not be a threat for crops in Serbia in the 2007 growing season. For the first time, the dominant Sunn pest species were those of the genus Aelia (with 45.8% contribution), followed by Eurygaster austriaca Schrk. (35.3%) and E. maura L. (18.9%). Differences were observed between the locations, as had often been the case in prior years. At Fruška gora, E. austriaca (73,3%) was dominant, followed by E. maura (16.8%) and Aelia spp. (9.9%), whereas at Deliblatska peščara the most dominant group by far were Aelia spp. (63.0%), followed by E. maura (19.9%) and E. austriaca (17.1%). The female to male ratio was 1:1 in E. austriaca and 1:0.8 in E. maura (Tab. 2). In the fall of 2006, the natural mortality rate was determined only at the Deliblatska peščara overwintering site for E. austriaca, and was 0.6%.

Smanjenje brojnosti žitnih stenica, koje je počelo 2005, nastavljeno je i tokom 2006. godine. U jesen te godine, na mestima prezimljavanja, brojnost imaga na stalnim lokalitetima Fruške gore i Deliblatske peščare iznosila je 9,4 primeraka po m2 (Fruška gora 6,7 po m2, Deliblatska peščara 12,1 po m2) (Tab. 1). U odnosu na 2005. godinu, kada je brojnost, takođe, bila niska (12,5 imaga po m2), došlo je do daljeg smanjenja, te se pouzdano može reći da ove štetočine kod nas neće predstavljati opasnost ni u vegetaciji 2007. godine. Prvi put, u ukupnoj brojnosti, dominantne su vrste iz roda Aelia (zastupljene sa 45,8%), a slede ih Eurygaster austriaca Schrk. (35,3%) i E. maura L. (18,9%). Međutim, postoje razlike između lokaliteta, što je često i do sada bio slučaj. Na lokalitetu Fruške gore dominantna je E. austriaca (73,3%), ispred E. maura (16,8%) i Aelia spp. (9,9%), dok su na Deliblatskoj peščari ubedljivo dominantne Aelia spp. (63,0%), a slede ih E. maura (19,9%) i E. austriaca (17,1%). Odnos polova vrste E. austriaca bio je 1:1 (ženke:mužjaci), a vrste E. maura 1:0,8 (Tab. 2). Prosečan prirodni mortalitet imaga na mestima prezimljavanja, u jesen 2006. godine, bio je 0,6% (registrovan samo kod vrste E. austriaca na lokalitetu Deliblatske peščare).