Phylloxera © 2001
Dr. Terry Bates

Concord roots infected with phylloxera (A-left) have less functional root surface area than healthy roots (A-right). Phylloxera form the characteristic nodosity hook on Concord roots (B) where the crawlers attatch to the inside of the hook (C and D).

New research is being conducted at the Fredonia Vineyard Lab with Dr. Greg English-Loeb that investigates the effect of phylloxera on Concord grapevine growth. The study also looks at the impact of irrigation and rootstocks in overcoming the negative effects of phylloxera infection. In 1999, nursery Concord grapevines were planted in 25 gallon pots of phylloxera-free soil. The experiment was set up as a factorial of phylloxera (+/- addition of eggs), irrigation (+/-), and rootstock (ownrooted/C.3309).

The interaction of phylloxera, irrigation, and rootstock on the total vine dry weight of young Concord vines.

Irrigation had the largest effect on vine biomass in young potted Concord grapevines. The dry weather in 1999 and the restricted root environment of the 25 gallon pots may have increased the irrigation effect.

In both irrigated and non-irrigated ownrooted vines, phylloxera decreased the total vine biomass. However, in non-irrigated/ownrooted vines phylloxera inhibited both root and shoot growth. In irrigated/ownrooted vines, phylloxera inhibited root biomass only and did not have an effect on shoot biomass (although phylloxera was present, there was enough water and nutrients available to sustain maximum shoot growth).

In a vineyard situation, there is currently no cost effective or environmentally sound way of keeping soil free of phylloxera. The other way of decreasing phylloxera nodulation is to use a phylloxera resistant rootstock. In the pot study, Concord vines grafted onto C.3309 rootstock had greater vine biomass than ownrooted/phylloxera vines. We speculate that the Concord/C.3309 vines were a bit smaller than the ownrooted vines in phylloxera-free soil because the grafted vines were significantly smaller going into the experiment.

Future experiments on the interaction of phylloxera and grape root biology will also include the factors of crop load and variety (Concord and Niagara).