Dynamics of pear psylla Caccapsylla pyri L. (Homoptera, Psyllidae) population in some wild and grown pear cultivars

Abstract

The dynamics of pear psylla populations was observed on P. communis, P. ussuriensis (b, and b, - control trees) and on five (b;, bo, b3, by and b;) grown cultivars: Bartlet, Passe Crassane, Gouyt, Highland and General Leclerc during 1994/95. The samples were taken once a month during the growing season. Counting different developmental phases of pear psylla helped establish the effect of year (season), cultivar and month on its population dynamics.

The presence of different developmental phases of pear psylla is established in all observed cultivars and control trees, as well as the disparity in its life cycle as a consequencoef a strongi nfluenceo f weatherb, eneficiali nsectsa ndt woi nterruptions in its growth dynamics (July and August 1994 and August 1995) due to absence of pear vigour growth.

It was found out that each factor highly influenced the total of hatched eggs; cultivars show different attractiveness to oviposition.

Nymph/egg ratio, as an indicator of preference in nymph nutrition, was equalized during individual growing season, somewhat higher in 1995, and nearly equal between cultivars and P. communis.

No differences in adults number existed in comparisons IJI-IX, IV-V, VII-VIII between the cultivars b₂, and b₄, b₅, b₆; b₃ and b₄; b₆ and b₄, b₅.