Factors influencing mortality, fecundity and fertility of grape phylloxera (Daktulosphaira vitifoliae Fitch)

摘要

The movement, distribution and abundance of phylloxera populations are affected by environmental conditions (temperature, soil moisture, soil type), ability of establishing the feeding sites, grape variety and phylloxera strain. At temperatures below 15℃ phylloxera cannot establish new feeding sites (DAVIDSON AND NOUGARET 1921); according to TURLEY et al. (1996) temperature must even exceed 18℃ for phylloxera to establish feeding sites. As the soil temperature reaches 15℃ or lower, phylloxera larvae cease and only the newly hatched crawlers survive as hibernants. While in spring phylloxera is found primarily on the small feeder roots, during summer they are found mostly at mature older roots; in winter phylloxera stays at the mature roots (OMER et al. 1997). Once the stylet of phylloxera is inserted into the root cells, they inject saliva which activates the root cells to increase in size and number, and mobilize the stored nutrients so that the sugars and amino acids flow towards the feeding site. The phylloxera then sucks the liquid nutrients and grow (OMER et al. 2002). Since there is limited information on the relationship between gall formation and root size the aim of our study was to investigate the influence of various temperatures on survival, fecundity, fertility, and population of local phylloxera strains, and to determine whether the size of detached roots affects phylloxera longevity (oviposition period) and reproduction.