Biostatistics of Trissolcus vassilievi (Hym., Scelionidae) developed on sunn pest eggs cold-stored for different durations

摘要

 The common sunn pest (CSP) Eurygaster integriceps Puton is the most important pest of wheat and barley in Iran. A few egg pararsitoid from Trissolcus, Telenomus, Ooencyrtus, etc. attack CSP eggs. Often the host eggs are stored in cold temperatures for subsequent use with negative effects on the parasitoids which increases by time. This study focused on quantitative changes of biostatistics including parasitism rate, emergence rate, sex ratio, fecundity, immature development, longevity and body size of Trissolcus vassilievi (Mayr) reared on host eggs stored for different periods in 5?1?C. The results revealed that all above mentioned statistics were affected by storing with an increasing intensity by duration. Parasitism rate and sex ratio decreased more strongly than adult emergence rate. A maximum 35% decrease in fecundity was also observed with stronger effect in long term storages. An increasing effort to compensate the initial lag however was observed in first week of the reproductive life of those wasps that accessed to older eggs. Developmental time increased by a sigmoid trend by storage time. Head capsule width and hind tibia length as measurements of body size both decreased suddenly in those wasps that obtained from >2 week old eggs, but the width of the head capsule decreased more rapidly in females than males that may imply stronger fitness loss in females. As a conclusion host eggs stored < 1 month may use with negligible negative effects on the parasitoid efficacy, while longer storage times may cause serious negative syndromes