To understand the effects of plant growth stage on the performance of grape phylloxera, Daktulosphaira vitifoliae (Fitch), demographic analyses were done using attached roots in a Vitis vinifera L. ‘Chardonnay’ vineyard during the vegetative, mid-ripening, and postharvest periods of grapevines. Survival of first instars was <30%. First instars coincide with the time of gall formation, and their survival was higher during postharvest than during the vegetative and mid-ripening periods. Survival after the second instar did not decrease with development but was stable, generally above 90% for the postharvest period and below 75% for the other experimental periods. Sucrose levels in root phloem parenchyma tissues were highest during postharvest compared with vegetative and mid-ripening periods and reflect a more rapid development during this period but only by a few days. The limiting step of grape phylloxera population growth appears to occur simultaneously with gall formation and is associated with survival. Survival and developmental rate of a virulent grape phylloxera strain were limiting with greenhouse vines of the resistant rootstocks 5C and SO4. Survival and developmental rates were more limiting for attached than detached roots.
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